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There are limited naturally derived protein biomaterials for the available medical implants. High cost, low yield, and batch-to-batch inconsistency, as well as intrinsically differing bioactivity in some of the proteins, make them less beneficial as common implant materials compared to their synthetic counterparts. Here, we present a milk-derived whey protein isolate (WPI) as a new kind of natural protein-based biomaterial for medical implants. The WPI was methacrylated at 100 g bench scale,95% conversion, and 90% yield to generate a photo-cross-linkable material. WPI-MA was further processed into injectable hydrogels, monodispersed microspheres, and patterned scaffolds with photo-cross-linking-based advanced processing methods including microfluidics and 3D printing. In vivo evaluation of the WPI-MA hydrogels showed promising biocompatibility and degradability. Intramyocardial implantation of injectable WPI-MA hydrogels in a model of myocardial infarction attenuated the pathological changes in the left ventricle. Our results indicate a possible therapeutic value of WPI-based biomaterials and give rise to a potential collaboration between the dairy industry and the production of medical therapeutics.

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.

Immune response is critical to tissue repair. Designing biomaterials with immunomodulatory functions has become a promising strategy to facilitate tissue repair. Considering the key roles of macrophages in tissue repair and the significance of the balance of M1 and M2, smart biomaterials, which can harness macrophage phenotypes dynamically to match the tissue healing process on demand, have attracted a lot of attention to be set apart from the traditional anti-inflammatory biomaterials. Here, we prepare a gold nanorod-contained shape memory polycaprolactone film with dynamic surface topography, which has the ability to be transformed from flat to microgrooved under near-infrared (NIR) irradiation. Based on the close relationships between the morphologies and the phenotypes of macrophages, the NIR-triggered surface transformation induces the elongation of macrophages, and consequently the upregulated expressions of arginase-1 and IL-10 in vitro, indicating the change of macrophage phenotypes. The sequential modulation of macrophage phenotypes by dynamic surface topography is further confirmed in an in vivo implantation test. The healing-matched modulation of macrophage phenotypes by dynamic surface topography without the stimuli of cytokines offers an effective and noninvasive strategy to manipulate tissue regenerative immune reactions to achieve optimized healing outcomes.

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.

Enzymatic cascade reactions in confined microenvironments play important roles in cellular chemical transformation. They also have important biotechnological and therapeutic applications. Here, enzymatic cascade microreactors (MRs) coupling glucose oxidase (GOx) and hemoglobin (Hb) (GOx-Hb MRs) were successfully fabricated by co-precipitation of GOx and Hb into a MnCO3 template, followed by the assembly of a multilayer film on a template surface, slight cross-linking, and final removal of MnCO3. In the presence of glucose with blood-relevant concentration, the GOx-Hb MRs exhibited a higher cascade reaction activity under mild acidic conditions than that under neutral conditions at physiological temperature. The GOx-Hb MRs effectively consumed glucose to generate HO· at pH = 5, which significantly inhibited bacterial growth and biofilm formation. This kind of enzymatic cascade microreactors might be useful for applications in biomedical fields.

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...

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.

The amphiphilic pyrene-containing random copolymers with light-responsive pyrene ester bonds were synthesized by copolymerizing 1-pyrenemethyl acrylate (PA) and N,N-dimethylacrylamide (DMA). The P(DMA-co-PA) copolymers formed spherical micelles in water, which were transformed into nanorods as a result of cleavage of the pyrene ester bonds under UV irradiation. In vitro culture with A549 cells and Raw cells showed that compared to the nonphotodegradable ones, the photodegradable P(DMA-co-PA) micelles caused significantly higher cytotoxicity under the same UV irradiation. The intracellular reactive oxygen species (ROS) level had a positive correlation with the cytotoxicity regardless of the cell types. The nonphotodegradable pyrene-containing micelles produced a lower level of ROS under UV irradiation. However, the photodecomposable P(DMA-co-PA) micelles produced a significant higher level of ROS under the same trigger of UV irradiation, which caused the shape transformation of micelles to nanorods and higher cytotoxicity simultaneously.

Selective enhancement of directional migration of endotheliocytes (ECs) over vascular smooth muscle cells (SMCs) plays a significant role for the fast endothelialization of blood-contacting implants, in particular for the antirestenosis of vascular stents. Herein, a complementary density gradient of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes and YIGSR peptide, a sequence specifically improving the mobility of ECs, was fabricated using a dynamically controlled reaction process. The gradients were visualized by fluorescent labeling and further quantified by X-ray photoelectron spectrometry (XPS) and quartz crystal microbalance with dissipation (QCM-d). The ECs exhibited preferential orientation and enhanced directional migration behavior on the gradient surface toward the region of lower PHEMA density and higher YIGSR density. The migration rate of the ECs was significantly enhanced to 5-fold, whereas the mobility of SMCs was not significantly influenced, leading to faster migration of ECs than SMCs. Therefore, the success of the complementary gradient relies on the appropriate interplay between the PHEMA brushes and the cell-specific ligands, enabling the selective guidance of EC migration.

Combination of gene therapy with tissue engineering can enhance the interplay between cells and matrix, leading to better restoration and regeneration of tissues and organs in vivo. In this study the PLGA/fibrin gel hybrids were employed to load lipofectamine/pDNA-TGF-β1 complexes and mesenchymal stem cells (MSCs) (experimental group), acting as a cartilage-mimetic tissue platform. The gene complexes distributed more evenly in the hybrid scaffolds, whereas they adhered onto the pore walls of the PLGA sponges. The filled fibrin gel rendered gene release in a slower manner, too. Moreover, the fibrin gel entrapped MSCs and contributed to a higher cell loading density in the hybrid constructs. In vivo assay showed that in the defects implanted with the experimental constructs both gene and protein expression levels of TGF-β1 were significantly higher than those of the fibrin-free group at weeks 1, 3, and 6 after surgery. The full articular cartilage defects repaired by the experimental group for 12 w were resurfaced by neo-tissues with a similar thickness, cell arrangement, and color to the normal neighboring cartilage and abundant glycosaminoglycans.

Osteoarthritis (OA) is primarily characterized by focal cartilage destruction and synovitis. Presently, the pathogenesis of OA remains unclear, and an effective treatment methodology is an unmet need. To this end, a plethora of animal models and monolayer models have been developed, but they are faced with the limitation of high cost and inability to recapitulate a pure hyaline cartilaginous phenotype, which is important in studying the efficacy of therapeutic agents. We have previously developed a living hyaline cartilage graft (LhCG) that accurately presented a pure hyaline cartilage phenotype. Here, through the coculture of lipopolysaccharide (LPS)-activated macrophages with LhCG, we hypothesized that an accurate OA disease model may be developed. Subsequently, this model was evaluated for its accuracy for in vitro drug testing. Results indicated that chondrocyte proliferation and apoptosis were increased in the disease model. Additionally, extracellular matrix (ECM) synthesis increased as indicated by the increased anabolic gene expression levels, such as collagen type II and aggrecan. Up-regulation of matrix metalloproteinase-1 (MMP-1) and MMP-3 genes suggested increased degradative activity, while chondrocytic hypertrophic differentiation was observed. Furthermore, extensive degradation of collagen type II and glycosaminoglycans (GAGs) were also observed. The results of celecoxib treatment on our model showed inhibition of nitric oxide (NO) and prostaglandin E2 (PGE2) production, as well as down-regulation of MMP-1 and MMP-3 expression. Taken together, the results suggested that this coculture model was able to sufficiently mimic the native, diseased OA cartilage, while drug testing results confirmed its suitability as an in vitro model for predicting native cartilage response to drug treatment.

A novel sugar-functionalized amphiphilic pillar[5]arene containing galactose groups as the hydrophlic part and alkyl chains as the hydrophobic part was designed and synthesized. It self-assembles in water to produce nanotubes as confirmed by TEM, SEM, and fluorescence microscopy. These nanotubes, showing low toxicity to both cancer and normal cells, can be utilized as excellent cell glues to agglutinate E. coli. The existence of galactoses on these nanotubes provides multivalent ligands that have high affinity for carbohydrate receptors on E. coli.

Shrinking phenomenon of poly(allylamine hydrochloride) (PAH)/poly(styrene sulfonate, sodium salt) (PSS) multilayer microcapsules was observed when they were incubated in alkaline solutions containing Ca(2+). The shrinking was universal to those polyelectrolyte multilayer capsules regardless of the wall thickness and wall compositions suppose the conditions were proper. The shrinking extent increased along with the increase of solution pH and Ca(2+) concentration, and reached to a maximum value of 70% (from 7.4 to 2.3 μm). The shrunk capsules with a hollow structure and thick wall could well maintain their spherical shape in a dry state. During the capsule shrinking partial loss of the polyelectrolytes especially PSS took place, and the loss amount increased along with the increase of solution pH although the alteration patterns were different at lower Ca(2+) concentration. The complexation of PSS with Ca(2+), which is believed one of the major reasons governing the capsule shrinking, was demonstrated by X-ray photoelectron spectroscopy and turbidity experiment. The mechanism is proposed, which relies on the synergistic effects of deprotonation of PAH and screening of PSS by Ca(2+) leading to the thermodynamically favored-capsule shrinking.

This study is focused on the uptake of PLGA particles with different coatings and its influences on the functions and toxicity of human endothelial cells. The PLGA particles coated with polyethyleneimine (PEI) or bovine serum albumin (BSA) were prepared via a one-step emulsion method, which had a similar diameter of ∼420 nm in water and ∼170 nm in a dry state but oppositely charged surfaces. Both types of the particles were readily internalized into cells within a short time regardless of their surface chemistry. Uptake of the positively charged particles caused apparently a decrease in cell viability, but did not significantly influence mitochondrial membrane potential and activity of caspase-3. The cell adhesion and migration were significantly affected, especially after uptake of the PLGA-PEI particles. The secretion levels of von Willebrand factor (vWF) and 6-k-PGF(1α) were not significantly influenced regardless of the surface coating.

The deformation and recovery behaviors of multilayer microcapsules were investigated after being forced to flow through a microchannel. The microchannel device with a constriction (5.7 μm in depth) in the middle was designed, and the multilayer microcapsules with different size and layer thickness (and thereby different mechanical strength) were used. Deformation in the microchannel was observed for all the capsules with a size larger than the constriction height, and its extent was mainly governed by the difference between capsule size and constriction height. The squeezed microcapsules could recover their original spherical shape when the deformation extent was smaller than 16%, whereas permanent physical deformation took place when the deformation extent was larger than 34%. The capsules filled with polyelectrolytes could greatly enhance their shape recovery ability due to the higher osmotic pressure in the capsule interior and could well maintain the preloaded low-molecular-weight dyes regardless of the squeezing.

Water-dispersible and fluorescent core–shell nanorods (NRs) consisting of covalently linked poly(allyamine hydrochloride)-pyrene (PAH-Py) were synthesized and used for fabricating hybrid organic–inorganic NRs. The reaction between 1-pyrenecarboxaldehyde (Py-CHO) nanorods and PAH was driven by Schiff base formation and followed by NaBH4 reduction, and caused 28% mass loss of Py molecules at the final stage (2 h). The final PAH-Py NRs contained 42% PAH, corresponding to a Py substitution ratio of 34.5%. They were uniform in size with a Py-CHO core (81.2 ± 16.4 nm) and PAH shell (45.0 ± 8.8 nm) fibrillar structure, and had a surface zeta potential of 53.7 ± 5.1 mV. The PAH-Py NRs could survive after annealed at 80 °C or dispersed in ethanol, and showed good suspension stability in water. Because of the functional amino groups, the nanorods could act as nanoanchors to immobilize either positively or negatively charged gold nanoparticles, or as nanoreactors to synthesize gold and platinum nanoparticles in situ...

A thorough understanding of the growth and surface properties of calcium−phosphate nanocrystals is essential for uncovering the mechanism by which their nanostructure interacts with other molecules. Herein, we reported a facile wet-chemical approach using cetyltrimethylammonium bromide (CTAB) for the oriented growth of octacalcium phosphate (OCP) nanobelts with a clean surface. The effect of various synthesis conditions, such as aging time, calcium salt species, CTAB, and/or other additive concentrations, on the growth of OCP nanobelts was examined. The results showed that the morphology of OCP nanobelts from a simple core to complex clusters was easily controlled by increasing aging time and CTAB concentration, whereas the nanobelt growth was heavily inhibited by a minor amount of polyaspartate (i.e., 0.03−0.12 μM). The postadsorption tests indicated the nanobelt surface was highly inert to CTAB, but had affinity to polyaspartate. Furthermore, the adsorption capability of therapeutic biphosphonate on OCP...

Poly(allylamine hydrochloride) (PAH) derivatives, that is, PAH-g-β-cyclodextrin (PAH-g-β-CD) and PAH-g-ferrocene with the same positive charges on their chains, were synthesized and employed as building blocks to obtain multilayer microcapsules by using a host−guest interaction between the β-CD and ferrocene. Alternative assembly of PAH-g-β-CD and PAH-g-ferrocene was conducted on sacrificial carbonate microparticles in a layer-by-layer (LbL) manner, followed by core dissolution with disodium ethylene diamine tetraacetate dihydrate (EDTA) to obtain the microcapsules. Step-wise increase of the layer thickness on silicone water was evidenced by ellipsometry, confirming the LbL growth mechanism. The hollow structure and morphology of the host−guest multilayer microcapsules were characterized by electron and scanning force microscopy. Owing to the charge interaction and host−guest interaction, the as-prepared microcapsules showed multiresponsiveness to pH, ionic strength, and host/guest molecules. For example,...

Hydrogen-bonded hollow microcapsules with a lightly cross-linked shell structure were fabricated by polymerization of acrylic acid in a solution containing surface-modified silica particles and pol...

Synthesis of gold nanoparticles on surfaces has been accomplished by the incubation of poly(dimethylsiloxane) (PDMS) films in tetrachloroauric(III) acid and chitosan solution at room temperature and 4 degrees C. One important point in the present study is that the synthesis selectively occurred on the PDMS surface. These observations are substantially different from the reaction in solution, in which no particles can be formed at room temperature. Computation of surface plasmon bands (SPBs) based on Mie theory suggests that the particles are partially coated by chitosan molecules, and the experimental results confirm the theoretical calculations. The proposed mechanism is that chitosan molecules adsorbed or printed on the PDMS surfaces act as reducing/stabilizing agents. Furthermore, PDMS films patterned with chitosan could induce localized synthesis of gold nanoparticles in regions capped with chitosan only. In this way, colloidal patterns were fabricated on the surfaces with high spatial selectivity simultaneously with the synthesis of the particles. Surface-induced fluorescence quenching was observed in the regions capped with gold nanoparticles as well.

Stable weak polyelectrolyte microcapsules were prepared by assembly of branched poly(ethylenimine) (PEI) and sodium poly(acrylic acid) (PAA) followed by glutaraldehyde (GA) cross-linking. By assembly of the building blocks onto polystyrene (PS) latex particles, the variation of the zeta-potentials of the multilayers before and after cross-linking was measured as a function of pH. Charge reversal was observed for all multilayers regardless of their outmost layer composition and cross-linking during a change of pH. The phenomenon is explained by the penetration of the underlying layer. The cross-linked capsules could maintain their macroscopic topology at extreme low or high pH, while reorganizing their microstructure to enable selective permeation or rejection of macromolecules at lower ( pH 6), respectively. Using this property, dextran with a molecular weight of 2000 kDa was successfully encapsulated. Thus, it is possible to produce capsules that are at the same time pH responsive...

The stability of hollow microcapsules against environmental alterations such as pH, osmotic pressure, and temperature is a critical issue for practical applications. It is demonstrated here that multilayer capsules assembled from poly(allylamine hydrochloride) (PAH) and sodium poly(styrene sulfonate) (PSS) can be considerably stabilized by cross-linking of only the PAH component with glutaraldehyde (GA). Formation of a Schiff base between the aldehyde and the amine groups was evidenced by UV−vis spectroscopy. After cross-linking by 2% GA for 2 h, an apparently thicker capsule wall was obtained with higher folds, and no alteration of the macroscopic topology of the capsules was observed after incubation in 0.1 M NaOH for 24 h. The cross-linking significantly improved the mechanical strength of the capsules to resist osmotic pressure induced invagination. Consequently, both the critical pressure and the elasticity modulus (680 MPa) of the capsule wall were doubled compared with that of the control. The cros...

Loading and release behaviors of compressed polyelectrolyte multilayers composed of poly(styrenesulfonate sodium salt) and poly(diallyldimethylammonium chloride) were investigated using fluorescein and rhodamine 6G as indicators by confocal laser scanning microcopy, fluorescence spectroscopy, and UV-vis spectroscopy. Compression of the multilayers resulted in a more densely packed microstructure, leading to the decrease of fluorescence intensity of the incorporated probes to 80% of its initial value, and much slower releasing rate as well as smaller releasing amount regardless of the types of the probes and the presence of salt. Utilizing the difference of loading and release rates between the compressed and the uncompressed regions, arrays of dye reservoirs have been fabricated on a chemical homogeneous but physical heterogeneous multilayer film.

A thermal pressing method (TPM) has been developed to create physical-co-chemical multicomponent micropatterns on polymer surfaces. Rd-chitosan was spatially localized on the protuberant parts (red), while FITC-dextran was localized on the recessed parts (green) of the PCL film. The method endows convenient control of the pattern shape and results in biomacromolecule patterns with high stability against aqueous rinsing.

Capsules composed of poly(styrene sulfonate, sodium salt) (PSS)/poly(diallyldimethyl ammonium) chloride (PDADMAC) were prepared by layer-by-layer deposition of the polyelectrolytes on melamine formaldehyde colloidal templates followed by the decomposition of the cores by hydrochloride. A yield of more than 90% of intact capsules was achieved if (i) the core diameter was equal to or less than 3.8 μm and (ii) not more than five pairs of layers were adsorbed. When the cores were larger or the layers were thicker, the osmotic pressure difference caused by core dissolution led to an increased frequency of wall rupture. The elasticity modulus of a multilayer consisting of five pairs of PSS/PDADMAC was about 140 MPa as measured by osmotic pressure induced capsule deformation.

Ultrathin polyelectrolyte capsules fabricated by stepwise assembly of poly(styrenesulfonate sodium salt) and poly(diallyldimethylammonium chloride) are examined by confocal laser scanning microscopy and scanning force microscopy. The capsule surface is composed of grains of 124 ± 10 nm in diameter with a roughness of ∼13 nm. These grains are formed by laterally segregated polyelectrolyte complexes. Osmotically and annealing-induced capsule swelling facilitated further grain segregation together with a capsule surface area increase. Incubation in salt solution induced capsule shrinking and grain aggregation.