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Both of the surface topographical features and distribution of biochemical cues can influence the cell-substrate interactions and thereby tissue regeneration in vivo. However, they have not been combined simultaneously onto a biodegradable scaffold to demonstrate the synergistic role so far. In this study, a proof-of-concept study is performed to prepare micropatterns and peptide gradient on the inner wall of a poly (D,L-lactide-co-caprolactone) (PLCL) guidance conduit and its advantages in regeneration of peripheral nerve in vivo. After linear ridges/grooves of 20/40 μm in width are created on the PLCL film, its surface is aminolyzed in a kinetically controlled manner to obtain the continuous gradient of amino groups, which are then transferred to CQAASIKVAV peptide density gradient via covalent coupling of glutaraldehyde. The Schwann cells are better aligned along with the stripes, and show a faster migration rate toward the region of higher peptide density. Implantation of the nerve guidance conduit made of the PLCL film having both the micropatterns and peptide gradient can significantly accelerate the regeneration of sciatic nerve in terms of rate, function recovery and microstructures, and reduction of fibrosis in muscle tissues. Moreover, this nerve conduit can also benefit the M2 polarization of macrophages and promote vascularization in vivo., Graphical abstract Dual gradient of nerve-affinitive CQAASIKVAV peptides and linear ridges/grooves on the inner surface of biodegradable guidance conduit synergistically promote the regeneration of sciatic nerve in terms of rate, function recovery and microstructures, and reduction of fibrosis in muscle tissues in vivo.Image 1, Highlights • CQAASIKVAV peptide gradient and micropatterns are integrated on inner surface of a nerve regeneration conduit. • Cell alignment and migration are promoted toward the region of a higher peptide density. • The peptide gradient and micropatterns can synergistically accelerate the regeneration of sciatic nerve in vivo.

The macrophages take significant roles in homeostasis, phagocytosis of pathogenic organisms, and modulation of host defense and inflammatory processes. In this study, the enantiomeric poly-D-lysine (PDL) and poly-L-lysine (PLL) were conjugated to gold nanorods (AuNRs) to study their influence on the polarization of macrophages. The AuNRs capped with cetyl trimethyl ammonium bromide (CTAB) (AuNRs@CTAB) exhibited larger toxicity to macrophages when their concentration was higher than 50 μg/ml, whereas the AuNRs@PDL and AuNRs@PLL showed neglectable toxicity at the same concentration compared with the control. The AuNRs@PDL and AuNRs@PLL were internalized into the macrophages with a higher value than the AuNRs@CTAB as revealed by transmission electron microscopy (TEM) and inductively coupled plasma mass spectrometry (ICP-MS) characterization. Unlike the grafted PDL/PLL on flat substrates, the AuNRs@PDL and AuNRs@PLL were not able to polarize M0 macrophages to any other phenotype after internalization as confirmed by ELISA, flow cytometry, and fluorescence microscopy analysis. Nonetheless, the expression of M1 phenotype markers was reduced after the internalization of AuNRs@PDL and AuNRs@PLL by M1 macrophages. The assays of ELISA, flow cytometry, and reactive oxygen species levels exhibited decrease in inflammation of the M1 macrophages.

Controlling the assembly of synthetic molecules in living systems is of significance for their adaptive applications. However, it is difficult to achieve, especially for composite self-assemblies, due to the complexity and dynamic change of the intracellular environment, and there exist technical difficulties for the direct visualization of organic and polymer self-assemblies. Herein, we demonstrate a novel strategy for the in situ formation of self-assembled micro-nano composite structures in a cell milieu using reduction-responsive microgels (MGs) as a platform. The MGs were prepared by a templating and crosslinking method using a synthetic amphiphlic polymer as the basic material and porous CaCO3 microparticles as the template. The aggregation-induced emission (AIE) tetraphenylethylene moieties and reduction-labile disulfide bonds in the MGs were employed as the self-assembly building blocks and triggering sites for the intracellular self-assembly, respectively. In the presence of reductive agents such as glutathione, nano-spikes were gradually formed on the MGs. After the MGs were internalized by cells, the in situ formation of microgel/nano-spike composite structures was evidenced by the enhanced fluorescence intensity and was further confirmed by direct transmission electron microscopy observation. This work provides an effective strategy to cope with the challenging task of achieving and probing controlled self-assembly in a cell milieu, leading to new insights into investigating biological self-assembly and promoting the development of micro-/nanomaterials by learning from nature.

Branched polyethylene (B-PE) elastomer was investigated for its potential medical application as a tarsus construct. The in vitro results showed that the B-PE and processed B-PE films or scaffolds did not exhibit noticeable cytotoxicity to the NIH3T3 fibroblasts and human vascular endothelial cells (ECs). The B-PE scaffolds with a pore size of 280–480 µm were prepared by using a gelatin porogen-leaching method. The porous scaffolds implanted subcutaneously in rats exhibited mild inflammatory response, collagen deposition and fast fibrovascularization, suggesting their good biocompatibility. Quantitative real-time PCR analysis showed low expression of pro-inflammatory genes and up-regulated expressions of collagen deposition and vascularization-related genes, validating the results of historical evaluation in a molecular level. The B-PE scaffolds and Medpor controls were transplanted in rabbits with eyelid defects. The B-PE scaffolds exhibited a similar elastic modulus and provided desirable repair effects with mild fibrous capsulation, less eyelid deformities, and were well integrated with the fibrovascular tissue compared with the Medpor controls.

Regeneration and functional recovery of peripheral nerves remain formidable due to the inefficient physical and chemical cues in the available nerve guidance conduits (NGCs). Introducing micropatterns and bioactive substances into the inner wall of NGCs can effectively regulate the behavior of Schwann cells, the elongation of axons, and the phenotype of macrophages, thereby aiding the regeneration of injured nerve. In this study, linear micropatterns with ridges and grooves of 3/3, 5/5, 10/10, and 30/30 μm were created on poly(d,l-lactide-co-caprolactone) (PLCL) films following with surface aminolysis and electrostatic adsorption of graphene oxide (GO) nanosheets. The GO-modified micropatterns could significantly accelerate the collective migration of Schwann cells (SCs) and migration of SCs from their spheroids in vitro. Moreover, the SCs migrated directionally along the stripes with a fastest rate on the 3/3-GO film that had the largest cell adhesion force. The neurites of N2a cells were oriented along the micropatterns, and the macrophages tended to differentiate into the M2 type on the 3/3-GO film judged by the higher expression of Arg 1 and IL-10. The systematic histological and functional assessments of the regenerated nerves at 4 and 8 weeks post-surgery in vivo confirmed that the 3/3-GO NGCs had better performance to promote the nerve regeneration, and the CMAP, NCV, wet weight of gastrocnemius muscle, positive S100β and NF200 area percentages, and average myelinated axon diameter were more close to those of the autograft group at 8 weeks. This type of NGCs thus has a great potential for nerve regeneration.

Selective adhesion and migration of urethral epithelial cells (HUCs) over fibroblasts (FIBs) are very important in the reconstruction of the urethral epithelial layer and prevention of ureteral scarring and stenosis. In this study, unsaturated polyurethane (PPFU-CO-SS) films were co-grafted with a cell-resisting poly(ethylene glycol) (PEG) layer and HUC-selective Cys-Ala-Gly (CAG) peptides, whose physicochemical changes were confirmed by X-ray photon spectroscopy, fluorescence spectroscopy and water contact angle measurements. The adhesion and activation of platelets on the PEG/CAG grafted surface were significantly reduced compared to those on the PPFU-CO-SS, resulting in a similar status as that on a PEG-grafted surface. The HUC-selective material could obviously promote the adhesion and migration of HUCs. The ratio of the urethral epithelial cells to fibroblasts on the PEG/CAG grafted surface was nearly 3-fold that on the unmodified PPFU-CO-SS in a co-culture competitive environment. The urethral epithelial cells cultured on the PEG/CAG grafted surface also had the highest migration rate, which was 2.24-fold compared to that on the PPFU-CO-SS control.

Inspired by natural hemin structure, the fabrication of metal organic framework (MOF) nanomaterials constructed by metal ions and iron porphyrin for peroxidase mimicking has attracted extensive attention recently due to their high concentration of active sites and great channeling for substrate diffusion. Herein, by using benzoic acid as capping agent, we fabricated uniform PCN-224 nanoparticles (NPs), which were composed of Zr6 cluster and tetrakis(4-carboxyphenyl)porphyrin (H2TCPP). Then Fe(Ⅲ) ions were incorporated into the center of H2TCPP producing iron porphyrin unit similar to hemin serving as catalytic active site. The procedure of iron incorporation didn't change the size and morphology of PCN-224 NPs. The newly formed Fe@PCN-224 NPs possessed peroxidase-like activity with much lower Km values and higher Kcat values than most of peroxidase-like nanozymes as well as natural horseradish peroxidase (HRP), indicating their enhanced catalytic activity. Taking advantage of the excellent peroxidase-like activity of Fe@PCN-224 NPs, we successfully developed a colorimetric method for simple and sensitive detection of hydrogen peroxide and glucose in combination with glucose oxidase.

Nanosize metal-organic frameworks (MOFs) are a class of promising porous nanomaterials for biomedical applications, in which their size control and surface modification are critical. Current approaches for fabrication of zeolitic imidazolate framework (ZIF-8) nanoparticles (NPs) with controlled size and poly(ethylene glycol) (PEG) surface modification are separated and time-consuming. Here, we report a simple and rapid synthetic method that combines the size control of ZIF-8 NPs and their surface modification of PEG at the same time. Monovalent amino PEG (PEG-NH2) was used as capping agent to control the size of ZIF-8 and simultaneously realize surface modification through coordination interaction. The size of ZIF-8 was tuned in a board range. The coated NPs showed intact crystalline structure with improved colloidal stability. By further adding the anticancer drug doxorubincin (DOX) into the reaction mixture, ZIF-8 NPs with encapsulated DOX and PEG surface modification (DOX@ZIF-8/PEG) can be synthesized in one-pot. They showed pH-responsive drug release property and efficacy in killing of cancer cells. Our facile one-pot process can be used to design MOFs NPs as multifunctional delivery systems for a variety of cargos such as therapeutic and imaging agents.

The increasing demands of surgical implantation highlight the significance of anti-infection of medical devices, especially antibiofilm contamination on the surface of implants. The biofilms developed by colonized microbes will largely hinder the adhesion of host cells, leading to failure in long-term applications. In this work, UV-responsive multilayers were fabricated by stepwise assembly of poly(pyrenemethyl acrylate- co-acrylic acid) (P(PA- co-AA)) micelles and chitosan on different types of substrates. Under UV irradiation, the cleavage of pyrene ester bonds in the P(PA- co-AA) molecules resulted in the increase of roughness and hydrophilicity of the multilayers. During this process, reactive oxygen species were generated in situ within 10 s, which destroyed the biofilms of Staphylococcus aureus, leading to the degradation of the bacterial matrix. The antibacterial rate was above 99.999%. The UV-irradiated multilayers allowed the attachment and proliferation of fibroblasts, endothelial cells, and smooth muscle cells, benefiting tissue integration of the implants. When poly(dimethylsiloxane) slices with the multilayers were implanted in vivo and irradiated by UV, the density of bacteria and the inflammatory level (judging from the number of neutrophils) decreased significantly. Moreover, formation of neo blood vessels surrounding the implants was observed after implantation for 7 days. These results reveal that the photoresponsive multilayers endow the implants with multifunctions of simultaneous antibiofilm and tissue integration, shedding light for applications in surface modification of implants in particular for long-term use.

Self-assembly in living systems is important for developing biological functional materials and regulating cellular processes, which have potential applications in disease diagnosis and treatment. However, the controllable fabrication of complex self-assemblies such as micro/nanocomposite structures and the direct observation of morphology-defined nanostructures in a cell milieu are still challenging. We report here a facile strategy for achieving the intracellular stimuli-responsive fabrication of micro/nanocomposite structures by using reduction-responsive microgels as a platform. Amphiphilic polymers (CSEG-g-Chol) that contained disulfide bonds in side chains and grafted cholesterol groups (Chol) were synthesized and used to prepare microgels (MGs) by a method based on a calcium carbonate template, in which the template was removed after the polymer was loaded and crosslinked. In the presence of reductants such as glutathione (GSH) and dithiothreitol (DTT), nanospikes gradually protruded from the surface of CSEG-g-Chol MGs. After internalization into cells, reduction-responsive self-assembly and the protrusion of nanospikes in the cell milieu were observed. No obvious influence on the cytoskeleton and endoplasmic reticulum was observed via light microscopy. However, co-incubation of the MGs caused a certain extent of cytotoxicity depending on the co-incubation concentration and stimulated the secretion of tumor necrosis factor-α (TNF-α), which was several times higher than in the control group. This work may serve as a paradigm for the study of intracellular and in vivo self-assembly and may also provide important insights for the investigation of biological self-assembly and interactions between micro/nanomaterials and cells.

The modulation of inflammation in tissue microenvironment takes an important role in cartilage repair and regeneration. In this study, a novel hybrid scaffold was designed and fabricated by filling a reactive oxygen species (ROS)-scavenging hydrogel (RS Gel) into a radially oriented poly(lactide-co-glycolide) (PLGA) scaffold. The radially oriented PLGA scaffolds were fabricated through a temperature gradient-guided phase separation and freeze-drying method. The RS Gel was formed by crosslinking the mixture of ROS-responsive hyperbranched polymers and biocompatible methacrylated hyaluronic acid (HA-MA). The hybrid scaffolds exhibited a proper compressive modulus, good ROS-scavenging capability, and cell compatibility.In vivotests showed that the hybrid scaffolds significantly regulated inflammation and promoted regeneration of hyaline cartilage after they were implanted into full-thickness cartilage defects in rabbits for 12 w. In comparison with the PLGA scaffolds, the neo-cartilage in the hybrid scaffolds group possessed more deposition of glycosaminoglycans and collagen type II, and were well integrated with the surrounding tissue.

Cellular metabolism plays a major role in the regulation of inflammation. The inflammatory macrophages undergo a wide-range of metabolic rewriting due to the production of significant amount of itaconate metabolite from cis-aconitate in the tricarboxylic acid cycle. This itaconate molecule has been recently described as a promising immunoregulator. However, its function and mode of action on macrophages and tissue repair and regeneration are yet unclear. Herein, the itaconate-derivative dimethyl itaconate (DMI) suppresses the IL-23/IL-17 inflammatory axis-associated genes and promotes antioxidant nuclear factor erythroid 2-related factor 2 target genes. The poly-e-caprolactone (PCL)/DMI nanofibers implanted in mice initially maintain inflammation by suppressing anti-inflammatory activity and particular inflammation, while at later stage promotes anti-inflammatory activity for an appropriate tissue repair. Furthermore, the PCL/DMI nanofiber patches show an excellent myocardial protection by reducing infarct area and improving ventricular function via time-dependent regulation of myocardium-associated genes. This study unveils potential DMI macrophage modulatory functions in tissue microenvironment and macrophages rewriting for proper tissue repair.

Tissue integration of orbital implants, following orbital enucleation treatment, represents a challenge for rapid fibrovascularization, long-time stability, anti-infection, and even induction of vascule regeneration. The objective of this study was to develop porous calcium-magnesium silicate materials, with good stability, bioactivity, and antibacterial potential as new orbital fillers. Three-dimensional (3D) diopside scaffolds (low dissolvability) were fabricated by direct ceramic ink writing assembly and then followed by one-step sintering at 1150 °C for 3 h. The pore wall of the scaffold was modified by another calcium-magnesium silicate, such as bredigite or akermanite, which dissolves quickly but shows greater angiogenic potential. These two Ca-Mg-silicates can be coated onto the pore strut, and the coating layers were observed to slowly dissolve in Tris buffer. The vascularization-favorable Cu ions, which had been doped into the bredigite or akermanite coating, could also be measured in the immersion medium. A primary angiogenic test in a panniculus carnosus muscle model in rabbit indicated that the Cu-doped bredigite and akermanite coatings were significantly beneficial for the neovascularization in the early stages. These results suggest that the diopside-based porous materials modified with functional coatings hold great potential for application in orbital reconstruction.

Corneal chemical injury is a general but intractable ocular emergency, the sequelae of which are particularly challenging to treat. Human amniotic membrane (HAM) is one of the resources as a wound dressing for damaged corneal reconstruction, but the concerns related to the possible transmission of infectious diseases are the main drawbacks. Here we present a versatile method utilizing electrospinning and surface modification processes to develop optically highly transparent, microstructurally stable (>20 MPa in tensile strength in the wet state) biomimetic nanofibrous membranes. These membrane nanofibers, mainly consisting of a collagen–hyaluronate interior and a chitosan surface coating, showed superior mechanical and biological performances compared to HAM, and were favorable to the selective adhesion of epithelial cells (corneal, conjunctival) and fibroblasts. The alkali-burned corneal damage model in rats demonstrated that the biomimetic membranes could markedly improve re-epithelialization in corneal tissue within one week. Therefore, such bioactive multifunctional membranes may find widespread biomedical applications in wound healing and postoperative anti-adhesion in the near future.

Gypsum is a promising material for bone defect repair due to its osteoconductivity, whereas it is still limited in orthopedic and dental surgeries due to its low bioactivity and too rapid resorption so that one major concern is the significant loss in microstructural stability in vivo. In the present strategy some key features were significantly improved by introducing rapidly biodegradable but highly bioactive calcium silicate (CS) for regulating the physicochemical properties and biological performances of the gypsum-based cements at the same liquid/solid ratio. We demonstrated that introduction of 23% CS into β-calcium sulfate hemihydrate (CSH) could improve the physicochemical properties but would not compromise the mechanical strength of the composite. The surface bioactivity was significantly enhanced by introducing 23% CS, and these biphasic composites were favorable for decelerating the biodegradation rate by nearly 18.5% in 28 days in vitro. A mild bioresorption rate, with 39.6% of composite residual 4 weeks after operation, was determined when implanted in subcutaneous tissue of rats. 8 weeks after implantation, the composite cement containing 23% CS significantly enhanced new bone tissue regeneration with a much higher relative bone content (∼68.6%) than pure gypsum in critical size femoral defects in rabbits. The novel CSH–CS biocements represent promising candidates for rapid bone resconstruction and repair in trauma and pathological conditions.

A great number of stimuli-responsive particles have been developed and used for biomedical applications such as intracellular drug delivery. It is of paramount importance to study the intracellular responsive process of these particles, offering insight into the understanding of their structure variation and design criteria for better performance. In this study polyethyleneimine (PEI)-coated poly(lactide-co-glycolide) (PLGA) particles with a diameter of 430 nm were prepared via a one-step emulsion method. The amino groups in the PEI molecules allowed further covalent linking of fluorescein isothiocyanate (FITC), bifunctional coupling agents 3,3′-dithiobispropionimidate, amino-ended polyethylene glycol (NH2–PEG–NH2) and tetramethylrhodamine isothiocyanate (TRITC), resulting in fluorescence resonance energy transfer (FRET) pairs on the particles. The particles exhibited glutathione-responsive ability, and lost the FRET effect due to the separation of FITC/TRITC pairs from the particle surface as a result of the cleavage of disulfide bonds. The particles showed different FRET change rates in A549 cells and HEK293 cells depending on the intracellular GSH concentration. Moreover, a much slower degradation rate was found inside cells than in simulated buffer with a similar GSH concentration. The results suggest that the responsive behaviors of the particles obtained in simulated buffer may not match fully/correctly with the real situation in a complicated intracellular environment.

In this study, four kinds of TiO2 nanorods (TiO2 NRs), with similar aspect ratios but different surface functional groups, i.e. amines (–NH2), carboxyl groups (–COOH) and poly(ethylene glycol) (–PEG), were used to study their interaction with rat bone marrow stem cells (MSCs). The aspect ratios of the TiO2 NRs were measured (50 to 65 nm in length and 8 nm in width) under transmission electron microscopy (TEM). The cellular uptake of the TiO2 NRs was qualitatively studied by TEM and then quantified by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the MSCs ingested larger amounts of TiO2–core NRs and TiO2–NH2 NRs than those of TiO2–COOH NRs and TiO2–PEG NRs, with similar intracellular distribution patterns. TiO2–core NRs induced the highest cytotoxicity, as a result of the highest intracellular level of reactive oxygen species (ROS), which was lowered upon surface functionalization. The genotoxicity of the TiO2 NRs was neglectable at tested concentrations, studied by the comet assay. The adipogenic and osteogenic differentiation potentials of the MSCs were firstly evaluated in terms of lipid droplet formation and calcium deposition respectively in the presence of the TiO2 NRs. All of the TiO2 NRs did not show an obvious influence on the adipogenic differentiation potential of the MSCs. But TiO2–COOH NRs showed a significant impairment on the osteogenic differentiation behaviors. The influence of TiO2 NRs on the osteogenic differentiation of the MSCs was further quantitatively studied by the expression of osteogenic markers (collagen type I and osteocalcein), at both gene and protein levels. The results confirmed the strongest hindrance of the osteogenic differentiation of the MSCs by TiO2–COOH NRs, due to the up-regulation of transforming growth factor beta 1 (TGF-β1) and fibroblast growth factor (FGF-2). The results provide new information that the differentiation potential of the MSCs can be influenced by the presence of TiO2 NRs with different surface functionalities, suggesting a careful analysis of the biological impact of nanomaterials.

Poly(lactide-co-glycolide) (PLGA) is one of the most attractive biodegradable polymers for loading and delivering payloads, especially in the form of nanoparticles (NPs). In this work, NPs of PLGA with 3 different molecular weights were fabricated using bovine serum albumin (BSA) and polyethyleneimine (PEI) as dispersing agents. Elemental analysis revealed that the loading amounts of BSA and PEI were 40-60 μg mg-1 and 12-15 μg mg-1 in the BSA/PLGA NPs and PEI/PLGA NPs, respectively. About 13-18 μg mg-1 BSA was exposed onto the surface of the BSA/PLGA NPs. No degradation of the PLGA NPs was detected after being incubated in artificial lysosomal fluid or with macrophages in a culture medium for 7 days. The innate immune activation behavior of the BSA/PLGA and PEI/PLGA NPs was evaluated by co-incubation with RAW264.7 cells in vitro. PLGA NPs fabricated with different molecular weights of PLGA showed no difference in stimulating RAW264.7 cells. The PEI/PLGA NPs did not show significant immune activation in terms of secretion of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) too. By contrast, the BSA/PLGA NPs induced a significantly higher expression of TNF-α, likely due to the heterogeneous albumin and existence of endotoxin, and the synergistic role of larger uptake of the BSA/PLGA NPs by macrophages.

Engineering microstructures with bioactive molecules critically influences Schwann cell (SC) behaviors in terms of cellular spatial arrangement and directional migration, which are advantageous for expediting the repair of peripheral nerve defects. In this study, stripe micropatterns were fabricated on poly(D,L-lactide-co-caprolactone) (PLCL) films by thermo-pressing using polydimethylsiloxane (PDMS) stamps with ridges/grooves of 3/3 and 10/10 μm in width. Their surfaces were further entrapped with 0.7 μg cm−2 and 1.9 μg cm−2 gelatin by a facile swelling–shrinking entrapment technique using lower and higher concentrations of gelatin solutions, respectively. The surfaces entrapped with gelatin became more hydrophilic. On the micropatterned surfaces, the water droplet had an ellipse shape and exhibited an orientation along the stripes. The gelatin-entrapped and micropatterned PLCL surfaces could guide the adhered SCs to form an elongated shape with a higher length to width ratio along the stripes. The migration rate of the SCs was significantly enhanced parallel to the stripe direction, and was fastest on the 3/3 μm PLCL films entrapped with 1.9 μg cm−2 gelatin. The vinculin expression, adhesion force and expression of adhesion and migration-related genes such as integrin β1, Rac1, RhoA and Cdc42 revealed a stronger affinity of the SCs to the 3/3 μm PLCL films with a higher gelatin density.

Hypoxia, defined as inadequate oxygen supply at the tissue level, is a common pathological condition in the tumor microenvironment of certain solid tumors, leading to the limited efficiency of oxygen-dependent photodynamic therapy (PDT). To overcome this problem, tumor-targeting oxygen self-carrying nanoparticles are developed for photothermal therapy (PTT) and enhanced PDT to completely eradicate solid tumors. Hydrogen peroxide (H2O2) is a strong oxidant that can release oxygen in the presence of a catalyst or when being heated. The core-shell poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) are obtained by a double emulsion method: the hydrophilic H2O2/poly(vinylpyrrolidone) complex as an oxygen source and hydrophobic IR780 as a PTT/PDT agent are encapsulated into the core and shell of the NPs respectively. The tumor binding molecule, folic acid, is conjugated onto the surface of obtained PLGA NPs to enabling efficient cell uptake and tumor targeting. Once the PLGA-FA/IR780-H2O2 NPs are ingested by HepG2 cells, they can induce the photothermal effect and reactive oxygen species (ROS) are released to kill cancer cells under an 808 nm laser irradiation. The encapsulated H2O2 can supply additional oxygen and in turn significantly enhance the PDT effect. This innovative nanoplatform has exhibited excellent antitumor efficiency, verified vividly by the in vitro and in vivo assays, and may serve as a versatile platform for future cancer therapy.

Due to the poor self-repair capabilities of articular cartilage, chondral or osteochondral injuries are difficult to be recovered. In this study, an N-cadherin mimetic peptide sequence HAVDIGGGC (HAV) was conjugated to direct cell–cell interactions, and an aggrecanase-1 cleavable peptide sequence CRDTEGE-ARGSVIDRC (ACpep) was used to crosslink hyperbranched PEG-based multi-acrylate polymer (HBPEG) with cysteamine-modified chondroitin sulfate (Cys-CS), obtaining an aggrecanase-1 responsively degradable and HAV-conjugated hydrogel ((HAV-HBPEG)-CS-ACpep). A HBPEG-CS-ACpep hydrogel without the HAV motif was also prepared. The two hydrogels exhibited similar equilibrium swelling ratios, elastic moduli and pore sizes after lyophilization, indicating the negligible influence of conjugated HAV on the crosslinking networks and mechanical properties of the hydrogels. After being degraded in PBS, aggrecanase-1 (ADAMTS4) and trypsin, the HBPEG-CS-ACpep hydrogel exhibited significantly decreased elastic moduli with a much lower value when incubated in enzyme solutions. The two hydrogels could maintain the viability of encapsulated bone marrow-derived mesenchymal stem cells (BMSCs), and the (HAV-HBPEG)-CS-ACpep hydrogel better promoted the cell–cell interactions. After being implanted into osteochondral defects in rabbits for 18 weeks, the two cell-laden hydrogel groups achieved better repair effects than the blank control group. Moreover, hyaline cartilage was formed in the (HAV-HBPEG)-CS-ACpep/BMSCs hydrogel group, while a hybrid of hyaline cartilage and fibrocartilage was found in the HBPEG-CS-ACpep/BMSCs hydrogel group.

Bacterial infection is a major obstacle to the wound healing process. The hydrogel dressings with a simpler structure and good antibacterial and wound healing performance are appealing for clinical application. Herein, a robust hydrogel was synthesized from acrylamide (AM), acrylic acid (AA) and N,N′-methylene diacrylamide (MBA) via a redox initiating polymerization. The polymerization conditions were optimized to obtain the hydrogel with minimum unreacted monomers, which were 0.25% and 0.12% for AM and AA, respectively. The hydrogel had good mechanical strength, and could effectively resist damage by external forces and maintain a good macroscopic shape. It showed large water uptake capacity, and could post load a wide range of molecules via hydrogen bonding and electrostatic interaction. Loading of antibiotic doxycycline (DOX) enabled the hydrogel with good antibacterial activity against both Gram-positive bacteria and Gram-negative bacteria in vitro and in vivo. In a rat model of methicillin-resistant Staphylococcus aureus (MRSA)-infected full-thickness skin defect wound, the DOX-loaded hydrogel showed good therapeutic effect. It could significantly promote the wound closure, increased the collagen coverage area, down-regulate the expressions of pro-inflammatory TNF-α and IL-1β factors, and up-regulate the expressions of anti-inflammatory IL-4 factor and CD31 neovascularization factor.

Selective exhaustion of over-expressed reactive oxygen species (ROS) is of great significance in the therapy of osteoarthritis (OA) due to the inhibiting effect on oxidative stress and inflammation. Herein, a ROS-scavenging and drug-release platform was prepared via encapsulating dexamethasone acetate (DA)-loaded ROS erasable poly(ethylene glycol)-b-polythioketal-b-poly(ethylene glycol) (PEG-PTK-PEG) micelles (PDM) into an injectable hydrogel. The hydrogel (HDH@PDM) was constructed by Schiff base reaction between hydrazide-grafted hyaluronic acid (HA-ADH) and aldehyde-modified dextran (Dex-ALH), achieving a self-healing property for viscosupplementation. The PDM imparted enhanced antioxidant capability to the hydrogel, which in turn endowed the PDM with prolonged retention and sustained DA release. The intraarticularly administered multifunctional injectable hydrogel potently diminished inflammation via depleting ROS and suppressing inflammatory cytokines as well as downregulating pro-inflammatory M1 macrophages ratio in a rat OA model. The developed therapeutic system significantly alleviated OA symptoms, embodying in excellent capability of preventing cartilage extracellular matrix degeneration with negligible toxicity in vivo.

Cell migration plays an important role in many physiological and biological processes , which is influenced by both physicochemical properties of surrounding matrix and signal gradient generated by neighboring/remote cells. Here we aim to develop a co-culture system of immune cells and smooth muscle cells (SMCs) based on the combination of Transwell and cell-responsive hydrogels. This model can be used to study the cell invasion into hydrogels in dynamic physiological conditions , with better mimicking of the in vivo microenvironment . Methacrylic anhydride-modified hyaluronic acid (MA-HA) macromolecules were crosslinked by matrix metalloproteinases (MMPs) sensitive peptides (MMP SP) to fabricate a cell-degradable hydrogel mimicking dynamic extracellular matrix (ECM). The migration of SMCs into the MMP-sensitive hydrogel was investigated under the existence of U937 cells, a type of macrophage-like cells. The invasion distance of SMCs in the MMP-sensitive hydrogels was much longer than that in the MMP-insensitive ones both in vitro and in vivo. The impact of hydrogel degradability and inductive signal gradient generated by U937 cells on cell invasion was compared, revealing that the degradability plays a major role in regulating cell invasion into the 3D hydrogels. Further mechanism investigation revealed that the expressions of cell migration-related genes and proteins were significantly up-regulated in the MMP-sensitive hydrogels compared to those in the MMP-insensitive hydrogels.

Photodynamic therapy is an effective alternative to traditional treatments due to its minimally invasive nature, negligible systemic toxicity, fewer side effects, and avoidance of drug resistance. However, it is still challenging to design photosensitizers with high singlet oxygen (1O2) quantum yields (QY) due to severe aggregation of the hydrophobic photosensitizers. Herein, we developed a discrete organoplatinum(II) metallacage using therapeutic cis-(PEt3)2Pt(OTf)2 as the building block to improve the 1O2 QY, thus achieving synergistic anticancer efficacy. The metallacage-loaded nanoparticles (MNPs) with tri-modality imaging capability allow precise diagnosis of tumor and real-time monitoring the delivery, biodistribution, and excretion of the MNPs. MNPs exhibited excellent anti-metastatic effect and superior anti-tumor performance against U87MG, drug resistant A2780CIS, and orthotopic tumor models, ablating the tumors without recurrence after a single treatment. Gene chip analyses confirmed the contribution of different therapeutic modalities to the tumor abrogation. This supramolecular platform holds potential in precise cancer theranostics., It is challenging to design photosensitizers (PS) with high quantum yields generating singlet oxygen due to severe aggregation between the hydrophobic PSs. Here they develop organoplatinum(II) metallatocage-based PS to overcome these challenges and show excellent antitumor effect.

Methicillin-resistant Staphylococcus aureus (MRSA) has been one of the major nosocomial pathogens to cause frequent and serious infections that are associated with various biomedical surfaces. This study demonstrated that surface modified with host defense peptide-mimicking β-peptide polymer, has surprisingly high bactericidal activities against Escherichia coli (E. coli) and MRSA. As surface-tethered β-peptide polymers cannot move freely to adopt the collaborative interactions with bacterial membrane and are too short to penetrate the cell envelop, we proposed a mode of action by diffusing away the cell membrane-stabilizing divalent ions, Ca2+ and Mg2+. This hypothesis was supported by our study that Ca2+ and Mg2+ supplementation in the assay medium causes up to 80% loss of bacterial killing efficacy and that the addition of divalent ion chelating ethylenediaminetetraacetic acid into the above assay medium leads to significant recovery of the bacterial killing efficacy. In addition to its potent bacteria...

Intelligent colloidal particles have been widely used as carriers for delivery of bioactive molecules due to the ability of controlled release. However, attention is mainly paid to the effects of their payloads, whereas the impacts of carriers are largely ignored. In this study, photo-responsive polyethylene glycol (PEG) microparticles were fabricated by using 8-arm-PEG with terminal amine groups (8-arm-PEG-NH2) and a photo-cleavable cross-linker. Due to the cleavable CO bond in the cross-linker, under UV irradiation the PEG particles could be decomposed gradually, leading to particle swelling and eventual disappearance. The PEG particles could be internalized by smooth muscle cells and HepG2 cells, and located in lysosomes. Their intracellular photo-response induced significant decrease of cell viability and increase of reactive oxygen species level.

Hypoxia, defined as an oxygen-deficient condition, is known to be a characteristic feature for most solid tumors that not only facilitates tumor metastasis but also jeopardizes the efficacy of therapies, especially photodynamic therapy (PDT) in which oxygen is essential in the treatment process. To overcome this problem, novel oxygen self-carrying nanoparticles (PMT NPs) have been developed for highly efficient and selective cancer treatment. Substituted diphenyl anthracene is designed as a more suitable 1O2 donor compared to diphenyl anthracene. Photooxidation in situ of diphenyl anthracene is achieved by introducing tetraphenyl porphyrin (TPP) into the polymer architecture. Micelles are obtained by a nanoprecipitation method and IR780 is encapsulated into the core of the micelles as a photosensitizer. Once the PMT NPs are ingested by HepG2 cells, they can induce the release of reactive oxygen species (ROS) to kill cancer cells with 808 nm laser irradiation. The micelles are about 60 nm in diameter with a narrow distribution, and are quite suitable for passive targeting to tumors via the enhanced permeability and retention (EPR) effect. In the presence of an 808 nm laser, the PMT NPs can release ROS and in turn significantly enhance the PDT effect. This innovative nanoplatform has exhibited excellent antitumor efficiency, was clearly verified by in vitro and in vivo assays, and may serve as a versatile theranostic platform for clinical tumor therapy.

Excessive reactive oxygen species (ROS) generated after myocardial infarction (MI) result in the oxidative injury in myocardium. Implantation of antioxidant biomaterials, without the use of any type of drugs, is very appealing for clinical translation, leading to the great demand of novel biomaterials with high efficiency of ROS elimination. In this study, a segmented polyurethane (PFTU) with a high density of ROS-scavenging backbone units is synthesized by the reaction of poly(thioketal) dithiol (PTK) and poly(propylene fumarate) diol (PPF) (soft segments), thioketal diamine (chain extender), and 1,6-hexamethylene diisocyanate (HDI). Its chemical structure is verified by gel permeation chromatography (GPC), 1 H nuclear magnetic resonance (1 H NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The electrospun composite PFTU/gelatin (PFTU/Gt) fibrous patches show good antioxidation capacity and ROS-responsive degradation in vitro. Implantation of the PFTU/gelatin patches on the heart tissue surface in MI rats consistently decreases the ROS level, membrane peroxidation, and cell apoptosis at the earlier stage, which are not observed in the non-ROS-responsive polyurethane patch. Inflammation and fibrosis are also reduced in the PFTU/gelatin-treated hearts, resulting in the reduced left ventricular remodeling and better cardiac functions postimplantation for 28 d.

Killing of cancer cells by applying mechanical disruption has been an appealing emerging strategy for cancer treatment in recent years. In this study, photoresponsive submicron particles based on diazo-resin that are able to release N2 under UV irradiation were prepared through a polyamine–salt aggregation method. After surface modification with hyaluronic acid, the particles could be internalized selectively by cancer cells and were mainly located in lysosomes after 6 h incubation. The viability of cancer cells decreased obviously after they were co-cultured with photoresponsive particles and UV irradiation due to the integrity damage of lysosomes by phototriggered N2 generation and the subsequent increased number of reactive oxygen species.

Multilayers incorporated with stimuli-responsive substances by means of layer-by-layer (LbL) self-assembly are much attractive due to the advantages of stimuli-responsiveness and potential applications in different fields. In this study, pyrenemethyl acrylate (PA) was synthesized, and was copolymerized with acrylic acid (AA) to obtain the amphiphilic and photodegradable P(PA-co-AA) polymers with a PA:AA molar ratio of 1.3:3, and an average molecular weight of 6.9 kDa and polydispersity index of 1.04. They formed micelles spontaneously when dispersed in aqueous solution with a size of 27.5 nm in a dry state and 136.6 nm in a wet state. The micelles were readily decomposed to form aggregates as a result of the cleavage of the pyrenemethyl ester bonds under UV-irradiation. UV-responsive micelles-containing multilayers were prepared by LbL self-assembly of the UV-responsive micelles and polyallylamine hydrochloride (PAH). UV-irradiation of the multilayers resulted in the decomposition of micelles, leading to larger surface roughness, and enhanced swelling ratio and wettability of the multilayers. In vitro culture of A549 and HepG2 cells showed significantly better adhesion at 4 h on the UV-illuminated multilayers, whereas the cell proliferation was not affected until 5 d. Fil: Zhang, Haolan. Zhejiang University; China Fil: Wang, Danyu. Zhejiang University; China Fil: Lin, Xue. Zhejiang University; China Fil: Politakos, Nikolaos. Centro de Investigación Cooperativa en Biomateriales; España Fil: Tuninetti, Jimena Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Centro de Investigación Cooperativa en Biomateriales; España Fil: Moya, Sergio Enrique. Centro de Investigación Cooperativa en Biomateriales; España Fil: Gao, Changyou. Zhejiang University; China

Hyaluronic acid (HA)-based hydrogels have applied widely for biomedical applications due to its biocompatibility and biodegradability. However, the use of initiators or crosslinkers during the hydrogel formation may cause cytotoxicity and thereby impair the biocompatibility. Inspired by the crosslinking mechanism of fibrin gel, a novel HA-based hydrogel was developed via the in situ supramolecular assembly based on knob-hole interactions between fibrinogen and knob-grafted HA (knob-g-HA) in this study. The knob-grafted HA was synthesized by coupling knob peptides (GPRPAAC, a mimic peptide of fibrin knob A) to HA via Michael addition. Then the translucent fibrinogen/knob-g-HA hydrogels were prepared by simply mixing the solutions of knob-g-HA and fibrinogen at the knob/hole ratio of 1.2. The rheological behaviors of the fibrinogen/knob-g-HA hydrogels with the fibrinogen concentrations of 50, 100 and 200 mg/mL were evaluated, and it was found that the dynamic storage moduli (G′) were higher than the loss moduli (G″) over the whole frequency range for all the groups. The SEM results showed that fibrinogen/knob-g-HA hydrogels presented the heterogeneous mesh-like structures which were different from the honeycomb-like structures of fibrinogen/MA-HA hydrogels. Correspondingly, a higher swelling ratio was obtained in the groups of fibrinogen/knob-g-HA hydrogel. Finally, the cytocompatibility of fibrinogen/knob-g-HA hydrogels was proved by live/dead stainings and MTT assays in the 293T cells encapsulation test. All these results highlight the biological potential of the fibrinogen/knob-g-HA hydrogels for 3D cellular engineering., Graphical abstract Image 1, Highlights • Inspired by fibrin gel, a fibrinogen/knob-g-hyaluronic acid hydrogel was fabricated via “knob”-“hole” specific interaction. • The hydrogel showing good cytocompatibility was prepared under physiological condition without adding enzyme or crosslinker. • The “knob” - “hole” interaction gives it potential to prepare a hydrogel with good cytocompatibility in a mild and fast manner.

The adverse effect of airborne PM2.5 pollutes on human beings and the environment, most likely due to heavy metal leaching, has received extensive attention recently. It is urgently required to develop a simple and effective method to suppress the toxicity of PM2.5 pollutes. In this study, the heavy metal content of PM2.5 pollutes around Zhejiang university were firstly identified. Their cytotoxicity was confirmed, by inducing significantly enhanced intracellular reactive oxygen species level. Poly(N-isopropylacrylamide) (PNIPAM) submicron hydrogel particles with tunable crosslinking densities and thermo-responsive swelling/shrinking properties were then prepared by adjusting the crosslinking density. Anti-oxidant drug melatonin (MLT) was encapsulated into the obtained PNIPAM nanogel particles with the drug loading efficiency larger than 50%, achieving thermo-responsive drug release profile. The PNIPAM/MLT particles had a strong ability to reduce the cytotoxicity to Raw264.7 cells induced by the extractant of PM2.5 pollutes, as well as to suppress the intracellular reactive oxygen species (ROS) level and secretion of tumor necrosis factor alpha (TNF-α), especially when the cells were treated under 25°C for 3h after ingestion of the PNIPAM/MLT particles. This concept-proving study demonstrates the potential to use the thermo-responsive PNIPAM/MLT particles to suppress the toxicity of airborne PM2.5 pollutes, which is a paramount requirement for human health.

In order to improve neurite outgrowth on the in situ formed hyaluronic acid–based hydrogel, furan and methacrylate groups were grafted on hyaluronic acid successively. Furthermore, a laminin-derived peptide CQAASIKVAV was covalently immobilized via the Michael addition. The furan- and peptide-modified hyaluronic acid was then cross-linked in situ by mixing with bismaleimide poly(ethylene glycol) at 37 °C to obtain a bioactive hyaluronic acid–based hydrogel. The hyaluronic acid derivatives were characterized by 1H NMR and Fourier transform infrared spectroscopy. The gelation, swelling, and mechanical property of the hydrogels were analyzed. The modulus of the hydrogel could be tuned by changing furan substitution degree, while the peptide concentration could be changed by the ratio of furan- and peptide-modified hyaluronic acid with hyaluronic acid–furan. In vitro culture of PC12 cells showed that the longest neurite outgrowth appeared on the hyaluronic acid–poly(ethylene glycol) hydrogel with the highest peptide content (the substitution degree of peptide in furan- and peptide-modified hyaluronic acid was 23 %) and a lower threshold modulus of 4.5 kPa. The furan and methacrylate-functionalized hyaluronic acid provides a versatile platform for diverse functionalization and can be used for modulation of other cell behaviors as well.

Aligned fiber scaffolds can mimic the parallel aligned fibrils in the extracellular matrix (ECM) of bones, and thus regulate many cellular behaviors. The aligned scaffolds are usually prepared by a microplate micropatterned method, freeze casting, evaporation, slip casting, ice-templating, plain weaving, and fiber forming techniques. In this study, the melt spinning technology, which has the advantages of a higher spinning speed, solvent-free processing and readily scalable production, was used to prepare poly(l-lactide) (PLLA) melt spun fibers with an average diameter of 70.3 ± 11.4 μm. The fibers were further bonded by 5% PLLA tetrahydrofuran solution to prepare PLLA spun fiber-aligned scaffolds. Collagen and chitosan molecules were coated onto the fibers/into the scaffolds to obtain multiple biochemical and surface aligned topography cues, respectively. The collagen or chitosan-coated PLLA aligned scaffolds could effectively improve the viability, adhesion, length and migration behaviors of osteoblasts in vitro. In particular, the collagen coated aligned scaffold had the largest cell length and the fastest migration rate, with a preferential direction along the fibers. This type of scaffold provides a versatile substrate to control cell behaviors, having great potential for bone regeneration.

The extensive development and application of engineered nanoparticles (NPs) in various fields worldwide have been subjected to increasing concern due to their potential hazards to human health and the environment. Therefore, a simple, economical, and effective method for suppressing the toxicity of metal-based nanomaterials is needed. In this study, glutaraldehyde-crosslinked chitosan nanoparticles (CS NPs) were prepared and further modified with lysine (Ly-CS), glutamic acid (Glu-CS), or sodium borohydride reduction (R-CS), and used to suppress cytotoxicity induced by copper oxide NPs (CuO NPs) through chelation with intracellularly released copper ions. All three kinds of CS NPs had similar sizes of ∼100 nm in a dry state and ∼200 nm in cell culture medium, as determined by scanning electron microscopy, transmission electron microscopy, and dynamic light scattering. The chelating efficiency of different CS NPs followed the order Ly-CS > Glu-CS > R-CS. The CS NPs showed minimal or no toxicity to three different cell lines (HepG2, A549, and RAW264.7 cells) at 100 μg mL−1 with similar cell internalization and exocytosis processes. Comparatively, RAW264.7 cells exhibited higher endocytosis and exocytosis rates, as revealed by flow cytometry and confocal laser scanning microscopy. CS NPs were found as agglomerates inside A549 cells and RAW264.7 cells, with the amount of agglomerates inside RAW264.7 cells decreasing significantly with prolonged incubation. All three CS NPs, especially Ly-CS and Glu-CS NPs, efficiently suppressed the cytotoxicity induced by CuO NPs, and reduced the intracellular level of reactive oxygen species.

The development of antibiotic-loaded wound dressings is of great importance in wound healing and infection treatment. However, in traditional antibiotic-loaded wound dressings, antibiotics are released uncontrollably from the dressings primarily by passive diffusion. The overuse of antibiotics may lead to drug resistance and side effects, which could hinder the healing process. To overcome these shortcomings, a wound dressing with UV-responsive antibacterial property was developed in this study. Levofloxacin (LF) was first conjugated to amine-terminated poly(ethylene glycol) through a photolabile ortho-nitrobenzyl linker to obtain a photo-cleavable polyprodrug (LHP), which was then loaded into a poly(vinyl alcohol)/sodium alginate (PVA/SA) wound dressing. Compared to the PVA/SA dressing, the LHP-loaded dressing showed larger swelling capacity and retained good cytocompatibility. It was found that LF could be cleaved from LHP under UV irradiation at 365 nm and released gradually from the wound dressing with an increase in UV irradiation time. The antibacterial zone test proved that the LHP-loaded wound dressing possessed UV-responsive antibacterial properties against Staphylococcus aureus.

The surface topology of nano/microparticles plays a significant role in modulating their interactions with cells, and may serve as a robust strategy for promoting cellular delivery. However, it is still an on-going challenge to achieve enhanced cellular delivery using surface-engineered organic-based particles. Herein, novel porphyrin micro–nanocomposite particles (MP–NPs), with poly(allylamine hydrochloride)-g-porphyrin MPs (PAH-g-Por MPs) as the core and porphyrin NPs as the protrudent structures on the surface, were prepared through a pH-responsive partial decomposition-induced self-assembly method. The porphyrin domains were less aggregated and easily exposed to cells, leading to significantly enhanced cellular uptake, stronger generation of intracellular reactive oxygen species (ROS), and a more effective photodynamic therapy effect compared with their smooth counterpart microparticles (MPs). The novel concept of turning therapeutics into biomimetic nanomaterials for enhanced cellular delivery and therapy may provide an inspiring horizon for the design of photosensitizers or other therapeutic delivery systems.

Stimuli-responsive biomaterials supply a promising solution to adapt to the complex physiological environment for different biomedical applications. In this study, a dynamic UV-triggered pH-responsive biosurface was constructed on titania nanotubes (TNTs) by loading photoacid generators, diphenyliodonium chloride, into the nanotubes, and grafting 2,3-dimethyl maleic anhydride (DMMA)-modified hyperbranched poly(l-lysine) (HBPLL) onto the surface. The local acidity was dramatically enhanced by UV irradiation for only 30 s, leading to the dissociation of DMMA and thereby the transformation of surface chemistry from negatively charged caboxyl groups to positively charged amino groups. The TNTs-HBPLL-DMMA substrate could better promote proliferation and spreading of rat bone mesenchymal stem cells (rBMSCs) after UV irradiation. The osteogenic differentiation of rBMSCs was enhanced because of the charge reversal in combination with the titania-based substrates.

Reactive oxygen species (ROS) play an important role in the pathogenesis of numerous diseases including atherosclerosis, diabetes, inflammation and myocardial infarction (MI). In this study, a ROS-responsive biodegradable elastomeric polyurethane containing thioketal (PUTK) linkages was synthesized from polycaprolactone diol (PCL-diol ), 1,6-hexamethylene diisocyanate (HDI), and ROS-cleavable chain extender. The PUTK was electrospun into fibrous patches with the option to load glucocorticoid methylprednisolone (MP), which were then used to treat MI of rats in vivo. The fibrous patches exhibited suitable mechanical properties and high elasticity. The molecular weight of PUTK was decreased significantly after incubation in 1 mM H2O2 solution for 2 weeks due to the degradation of thioketal bonds on the polymer backbone. Both the PUTK and PUTK/MP fibrous patches showed good antioxidant property in an oxidative environment in vitro. Implantation of the ROS-responsive polyurethane patches in MI of rats in vivo could better protect cardiomyocytes from death in the earlier stage (24 h) than the non ROS-responsive ones. Implantation of the PUTK/MP fibrous patches for 28 days could effectively improve the reconstruction of cardiac functions including increased ejection fraction, decreased infarction size, and enhanced revascularization of the infarct myocardium.

The design of hyaluronic acid (HA)-based and stimuli-responsive hydrogels to elicit highly controlled and tunable cell response and behaviors is a major field of interest in tissue engineering and regenerative medicine. The pH-responsive hydrogel can respond to pH variation during wound healing, which may in turn regulate the tissue regeneration process. In this study, a double-network hydrogel cross-linked with vinyl double bonds and Schiff base was prepared, whose properties were further adjusted by incubation in pH 7.4 and pH 5 buffers. The endothelial cells (ECs) migrated much deeper into the softer HA hydrogel pre-treated with pH 5 buffer than the stiffer hydrogel. By contrast, the mesenchymal stem cells (MSCs) migrated easily into the stiffer hydrogel. The ECs highly expressed RhoA and non-muscle myosin (NM) II genes in the softer hydrogel, which may facilitate amoeboid migration. Meanwhile, the MSCs were stiffer than the ECs, and highly expressed Rac1, RhoA, vinculin, NM II, hyaluronidase (HYAL) 2 and CD44 genes in the stiffer hydrogel, which facilitate mesenchymal migration. These results provide important clues for revealing the different migration strategies of the ECs and MSCs in HA hydrogels with different stiffness, and suggest that the mechanical properties and the network structure of hydrogels play an important role in regulating the three-dimensional migration process of these cells.

Conventional 3D porous scaffolds used as tarsal plate substitute may cause corneal irritation and conjunctival mucoid discharge, and even lead to blindness and cicatricial blepharon deformities. In this study, collagen/chitosan (Col/CS) sponges with thickness of 240 μm, 466 μm, and 724 μm were composited onto poly(propylene fumarate)-co-2-hydroxyethyl methacrylate (PPF–HEMA) polymer networks to obtain the corresponding biphasic scaffolds, which simulate the natural anatomy of posterior lamella of eyelid. These three scaffolds exhibited a porous structure with porosity of ∼90%, simulated elastic modulus, appropriate degradation rate and good biocompatibility. Composited with Col/CS sponge of difference thickness, the scaffolds induced different cellular behaviors such as proliferation, distribution and stratification, by regulating the mechanical properties cells sensed as effective modulus. In a rabbit tarso-conjunctival defect model, the grafted biphasic scaffolds promoted re-epithelization with functional regenerated conjunctiva. Hence, the biphasic composite scaffolds may be a promising substitute for tarso-conjunctival repair.

The recruitment of endogenous mesenchymal stem cells (MSCs), as an alluring approach for in situ tissue regeneration, always accompanies with other types of cells. Therefore, it is of enormous value to bestow a substrate with the property of selective capture to MSCs. However, it was reported that when MSCs are cultured on a substrate with excessive affinity, their stemness diminished. Therefore, constructing a substrate with the balanced ability of selective capture and stemness maintenance becomes a big challenge. In this study, an Aptamer 19S (Apt19S)-modified substrate was fabricated by grafting Apt19S on a PEGylated glass substrate. The X-ray photoelectron spectroscopy results verified that the antifouling poly(ethylene glycol) (PEG) layer was created. Tracking by ellipsometry, the thicknesses of PEG layers were proved to increase with PEG concentration. The results of the quartz crystal microbalance also validated that the Apt19S densities could be modulated by the concentrations of the Apt19S solution. The results of the cell adhesion assay indicated that the modification of Apt19S caused a significant increase in the adhesion ratio and area of rBMSCs. Selective adhesion was confirmed by coculture of rBMSCs with macrophages and NIH3T3 cells, demonstrating that a higher proportion of rBMSCs adhered to the Apt19S-modified substrate. The results of specific capture were further confirmed by a flow model to simulate the body fluid flow. The comprehensive results of reverse transcription polymerase chain reaction, immunofluorescence staining, proliferation capacity, and differentiation assay showed that the stemness of rBMSCs was maintained better on a substrate with the appropriate Apt19S density. All of these results indicated that Apt19S modification is an effective strategy to endow a substrate with the specific capture ability of MSCs, and the balance between selective capture and stemness maintenance can be achieved by the precise regulation of the aptamer density.

Capture of endothelial progenitor cells (EPCs) in situ has been considered as a promising strategy for the rapid endothelialization and long-term patency of artificial blood vessels and implant devices. In this study, a CD133+ EPC capture surface was fabricated by grafting CD133 antibody (a more specific EPC surface marker than CD34) and Arg-Glu-Asp-Val (REDV) peptideon the methacrylate-grafted hyaluronic acid (MA-HA) and heparin-hybridized (MA-HA&Heparin) resisting layer. Vascular endothelial growth factor (VEGF) was further conjugated to the immobilized heparin. This engineered surface showed good hemocompatibility and significantly higher ability of capturing CD133+ EPCs from human peripheral blood mononuclear cells (PBMCs) and obviously upregulated the expression of endothelial cell (EC) marker genes of EPCs such as VEGF receptor 2 (VEGFR2), CD31, VE-cadherin, and von Willebrand factor (vWF), facilitating the differentiation of EPCs into ECs. The dramatically enhanced EPC proliferation on this surface was dependent on the integrin-VEGFR synergistic signaling, as ERK1/2 phosphorylation was only significantly enhanced on the REDV and VEGF co-immobilized surface. This study highlights a new surface coating strategy for blood-contact materials based on the specific EPC capturing and rapid endothelialization. STATEMENT OF SIGNIFICANCE: Capture of endothelial progenitor cells (EPCs) in situ is a promising strategy for the rapid endothelialization and long-term patency of artificial blood vessels and scaffolds. More specific capture of EPCs by targeting CD133 rather than CD34 can better reduce the risk of inflammation and restenosis. On the other hand, an appropriate microenvironment for EPC proliferation is equally important for endothelialization, which is rarely considered by the existing EPC capture strategies. In this study, the capture ratio of EPCs was significantly increased by simultaneously grafting CD133 antibody and VEGF on a MA-HA and heparin-hybridized antifouling layer. Further, proliferation of EPCs after capture was significantly promoted by grafting VEGF and REDV peptide through the integrin-VEGFR synergistic signaling. This study highlights a new strategy for the surface coating of blood-contact materials based on specific EPC capture and rapid endothelialization.

Cell migration in three-dimensional environment is extremely important for tissue regeneration and other biological processes. In this work, a model system was developed to study how endothelial cells (ECs) migrate into photo-responsive hydrogels under the presence of pro-inflammatory macrophages. The hydrogel was synthesized from hyaluronic acid grafted with coumarin and methacrylate moieties by both carbon–carbon covalent linking and coumarin dimerization under UV irradiation at 365 nm. The structure of the hydrogel was conveniently modulated by UV irradiation at 254 nm to decompose the coumarin dimers, leading to the significant decrease of modulus and increase of swelling ratio and mesh size. Under the presence of M1 macrophages, ECs were induced to migrate into the hydrogels with a different degree. A significant larger net displacement of ECs was found in the softer hydrogel obtained by irradiation with UV at 254 nm than in the stiffer original one at day 7.

The biodegradable polymer microparticles with different surface morphology and chemical compositions may influence significantly the behaviors of cells, and thereby further the performance of tissue regeneration in vivo. In this study, multi-stage hierarchical textures of poly(D,L-lactic-co-glycolide) (PLGA)/PLGA-b -PEG (poly(ethylene glycol)) microspheres with a diameter as large as 50–100 μm are fabricated based on interfacial instability of an emulsion. The obtained fuzzy structures on the microspheres are sensitive to annealing, which are changed gradually to a smooth one after treatment at 37 °C for 6 d or 80 °C for 1 h. The surface microstructures that are chemically dominated by PEG can be stabilized against annealing by dopamine deposition. By the combination use of annealing and dopamine deposition, a series of microspheres with robust surface topologies are facilely prepared. The fuzzy microstructures and dopamine deposition show a synergetic role to enhance cell-material interaction, leading to a larger number of adherent bone marrow-derived mesenchymal stem cells (BMSCs), A549 and MC 3T3 cells. The fuzzy microspheres with dopamine deposition can significantly promote bone regeneration 12 w post surgery in vivo, as revealed by micro-CT, histological, western blotting and RT-PCR analyses.

Differentiation of stem cells is influenced by many factors, yet uptake of the magnetic particles with or without magnetic field is rarely tackled. In this study, iron oxide nanoparticles-loaded bovine serum albumin (BSA) (Fe 3 O 4 /BSA) particles were prepared, which showed a spherical morphology with a diameter below 200 nm, negatively charged surface, and tunable magnetic property. The particles could be internalized into bone marrow mesenchymal stem cells (MSCs), and their release from the cells was significantly retarded under external magnetic field, resulting in almost twice intracellular amount of the particles within 21 d compared to that of the magnetic field free control. Uptake of the Fe 3 O 4 /BSA particles enhanced significantly the osteogenic differentiation of MSCs under a static magnetic field, as evidenced by elevated alkaline phosphatase (ALP) activity, calcium deposition, and expressions of collagen type I and osteocalcin at both mRNA and protein levels. Therefore, uptake of the Fe 3 O 4 /BSA particles brings significant influence on the differentiation of MSCs under magnetic field, and thereby should be paid great attention for practical applications. Statement of Significance Differentiation of stem cells is influenced by many factors, yet uptake of the magnetic particles with or without magnetic field is rarely tackled. In this study, iron oxide nanoparticles-loaded bovine serum albumin (BSA) (Fe 3 O 4 /BSA) particles with a diameter below 200 nm, negatively charged surface, tunable Fe 3 O 4 content and subsequently adjustable magnetic property were prepared. The particles could be internalized into bone marrow mesenchymal stem cells (MSCs), and their release from the cells was significantly retarded under external magnetic field. Uptake of the Fe 3 O 4 /BSA particles enhanced significantly the osteogenic differentiation of MSCs under a constant static magnetic field, while the magnetic particles and external magnetic field alone do not influence significantly the osteogenic differentiation potential of MSCs regardless of the uptake amount. The results demonstrate a potential magnetic manipulation method for stem cell differentiation, and also convey the significance of careful evaluation of the safety issue of magnetic particles in real an application situation.

Selective cell adhesion and migration, which mimics the natural biological events in vivo, is very important for the right repair of damaged tissues. In this study, glycosylated hyperbranched polymers (LA-HPMA) were synthesized, and were grafted on glass slide through dopamine deposition with different densities adjusted by co-grafting of poly(ethylene glycol) (PEG). The LA-HPMA and PEG molecular brushes were characterized by X-ray photoelectron spectroscopy (XPS), quartz crystal microbalance with dissipation (QCM-d) and ellipsometry. The adhesion of human hepatoma (HepG2) cells was promoted on the surface of a higher LA-HPMA density, and the migration rate was accelerated from 6.4μm/h on PEG surface to 12.7μm/h on 75% LA-HPMA surface. By contrast, the density and spreading area of mouse embryonic fibroblast (NIH3T3) cells were not significantly influenced by the LA-HPMA density, and the migration rate did not change significantly on all types of surfaces either. Therefore, the specific interactions of carbohydrate-protein can be used to modulate cell behaviors in vitro, for example the selective adhesion and migration of HepG2 cells.

Submicron-sized poly(lactide-co-glycolide) nanoparticles (PLGA-NPs) stabilised with bovine serum albumin (BSA) are dual radiolabelled using gamma emitters with different energy spectra incorporated into the core and coating. PLGA core is labelled by encapsulation of 111In-doped iron oxide NPs inside PLGA-NPs during NP preparation, while the BSA coating is labelled by electrophilic substitution using 125I. After intravenous administration into rats, energy-discriminant single-photon emission computerised tomography (SPECT) resolved each radioisotope independently. Imaging revealed different fates for the core and coating, with a fraction of the two radionuclides co-localising in the liver and lungs for long periods of time after administration, suggesting that NPs are stable in these organs. The general methodology reported here represents an excellent alternative for visualising the degradation process of multi-labelled NPs in vivo and can be extended to a wide range of engineered NPs.

Chirality is one of the most fascinating and ubiquitous features in nature, especially in biological systems. The effects of chiral surfaces, especially in combination with degradable materials of good biocompatibility, on stem cell behaviors has not yet been tackled. In this communication, the chiral monomers N-acryloyl-l(d)-valine (l(d)-AV) are synthesized and are polymerized to obtain chiral (l(d)-PAV-SH) oligomers, which are covalently immobilized onto electron-deficient poly(propylene fumarate) polyurethane (PPFU) via Michael addition. The PPFU-l-PAV can interact more strongly and actively with bone marrow stem cells (BMSCs) than PPFU-d-PAV, leading to a larger cell spreading area, faster migration velocity, and stronger osteodifferentiation tendency.