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An approach to differentially modify the internal surface of porous silicon nanoparticles (pSiNPs) with hydrophobic dodecene and the external surface with antifouling poly- N -(2-hydroxypropyl) acrylamide (polyHPAm) as well as a cell-targeting peptide was developed. Specifically, to generate these core-shell pSiNPs, the interior surface of a porous silicon (pSi) film was hydrosilylated with 1-dodecene, followed by ultrasonication to create pSiNPs. The new external surfaces were modified by silanization with a polymerization initiator, and surface-initiated atom transfer radical polymerization was performed to introduce polyHPAm brushes. Afterward, a fraction of the polymer side chain hydroxyl groups was activated to conjugate cRGDfK─a peptide with a high affinity and selectivity for the α ν β 3 integrin receptor that is overexpressed in prostate and melanoma cancers. Finally, camptothecin, a hydrophobic anti-cancer drug, was successfully loaded into the pores. This drug delivery system showed excellent colloidal stability in a cell culture medium, and the in vitro drug release kinetics could be fine-tuned by the combination of internal and external surface modifications. In vitro studies by confocal microscopy and flow cytometry revealed improved cellular association attributed to cRGDfK. Furthermore, the cell viability results showed that the drug-loaded and peptide-functionalized nanoparticles had enhanced cytotoxicity toward a C4-2B prostate carcinoma cell line in both 2D cell culture and a 3D spheroid model.

We report a next-generation, biocide-free, and durable marine antifouling coating technology. To achieve this, we combined two different polymers previously developed by us. First, we synthesized well-defined 2-hydroxypropyl acrylamide (HPA) based bottlebrush polymers with concentrated polymer brush (CPB) structures, which exhibit excellent bioinertness, and second, we synthesized photoreactive copolymers of 2-hydroxypropyl acrylamide (HPA) and N -benzophenone acrylamide (BPA), which can be cross-linked by exposure to sunlight for 30 min. Simply mixing the bottlebrush polymers with the photoreactive copolymers and applying these as a coating provided a scalable method for achieving effective antifouling properties in one step on a broad range of polymer substrate materials. The resistance of bottlebrushes against acid and base hydrolysis was demonstrated in accelerated degradation experiments at 80 °C, and the coating thickness was found to be stable after 3 months of incubation in sea water. Optimized coatings prevented cypris larva attachment for up to 9 days and prevented the settling of marine organisms in the sea for up to 73 days. Due to the ease of application, long-term durability, and effective antifouling performance, our bottlebrush coating technology is expected to be exploited in biocide-free marine paints.

The generation of complex physicochemical signals on the surface of biomedical materials is still challenging despite the fact that a broad range of surface modification methods have been developed over the last few decades. Colloidal self-assembled patterns (cSAPs) are combinations of unique colloids differing in size and surface chemistry acting as building blocks that can be programmed to generate surface patterns with exquisite control of complexity. This study reports on producing a variety of pre-modified colloids for the fabrication of cSAPs as well as post-assembly modifications to yield complex surfaces. The surface of cSAPs presents hierarchical micro- and nanostructures, localized hydrophilic/hydrophobic characteristics, and tunable surface functionality imparted by the individual colloids. The selected cSAPs can control bacterial adhesion ( S. aureus , P. aeruginosa , and E. coli ) and affect the cell cycle of human bone marrow stem cells (hBMSCs). Moreover, in a mouse subcutaneous model, cSAPs with selective [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium (SBMA) modification can reduce the inflammatory response after being challenged with bacteria. This study reveals that functionalized cSAPs are versatile tools for controlling cellular responses at biointerfaces, which is instructive for biomaterials or biodevices.

Here, we have developed and evaluated a microfluidic-based human blood-brain-barrier (μBBB) platform that models and predicts brain tissue uptake of small molecule drugs and nanoparticles (NPs) targeting the central nervous system. By using a photocrosslinkable copolymer that was prepared from monomers containing benzophenone and N -hydroxysuccinimide ester functional groups, we were able to evenly coat and functionalize μBBB chip channels in situ , providing a covalently attached homogenous layer of extracellular matrix proteins. This novel approach allowed the coculture of human endothelial cells, pericytes, and astrocytes and resulted in the formation of a mimic of cerebral endothelium expressing tight junction markers and efflux proteins, resembling the native BBB. The permeability coefficients of a number of compounds, including caffeine, nitrofurantoin, dextran, sucrose, glucose, and alanine, were measured on our μBBB platform and were found to agree with reported values. In addition, we successfully visualized the receptor-mediated uptake and transcytosis of transferrin-functionalized NPs. The BBB-penetrating NPs were able to target glioma cells cultured in 3D in the brain compartment of our μBBB. In conclusion, our μBBB was able to accurately predict the BBB permeability of both small molecule pharmaceuticals and nanovectors and allowed time-resolved visualization of transcytosis. Our versatile chip design accommodates different brain disease models and is expected to be exploited in further BBB studies, aiming at replacing animal experiments.

The development of antifibrotic materials and coatings that can resist the foreign body response (FBR) continues to present a major hurdle in the advancement of current and next-generation implantable medical devices, biosensors, and cell therapies. From an implant perspective, the most important issue associated with the FBR is the prolonged inflammatory response leading to a collagenous capsule that ultimately blocks mass transport and communication between the implant and the surrounding tissue. Up to now, most attempts to reduce the capsule thickness have focused on providing surface coatings that reduce protein fouling and cell attachment. Here, we present an approach that is based on the sustained release of a peptide drug interfering with the FBR. In this study, the biodegradable polymer poly(lactic- co -glycolic) acid (PLGA) was used as a coating releasing the relaxin peptide analogue B7-33, which has been demonstrated to reduce organ fibrosis in animal models. While in vitro protein quantification was used to demonstrate controlled release of the antifibrotic peptide B7-33 from PLGA coatings, an in vitro reporter cell assay was used to demonstrate that B7-33 retains activity against the relaxin family peptide receptor 1 (RXFP1). Subcutaneous implantation of PLGA-coated polypropylene samples in mice with and without the peptide demonstrated a marked reduction in capsule thickness (49.2%) over a 6 week period. It is expected that this novel approach will open the door to a range of new and improved implantable medical devices.

Gene silencing by RNA interference is a powerful technology with broad applications. However, this technology has been hampered by the instability of small interfering RNA (siRNA) molecules in physiological conditions and their inefficient delivery into the cytoplasm of target cells. Porous silicon nanoparticles have emerged as a potential delivery vehicle to overcome these limitations-being able to encapsulate RNA molecules within the porous matrix and protect them from degradation. Here, key variables were investigated that influence siRNA loading into porous silicon nanoparticles. The effect of modifying the surface of porous silicon nanoparticles with various amino-functional molecules as well as the effects of salt and chaotropic agents in facilitating siRNA loading was examined. Maximum siRNA loading of 413 μg/(mg of porous silicon nanoparticles) was found when the nanoparticles were modified by a fourth generation polyamidoamine dendrimer. Low concentrations of urea or salt increased loading capacity: an increase in RNA loading by 19% at a concentration of 0.05 M NaCl or 21% at a concentration of 0.25 M urea was observed when compared to loading in water. Lastly, it was demonstrated that dendrimer-functionalized nanocarriers are able to deliver siRNA against ELOVL5, a target for the treatment of advanced prostate cancer.

Thermal scanning probe lithography (t-SPL) is a nanofabrication technique in which an immobilized thermolabile resist, such as polyphthalaldehyde (PPA), is locally vaporized by a heated atomic force microscope tip. Compared with other nanofabrication techniques, such as soft lithography and nanoimprinting lithography, t-SPL is more efficient and convenient as it does not involve time-consuming mask productions or complicated etching procedures, making it a promising candidate technique for the fast prototyping of nanoscale topographies for biological studies. Here, we established the direct use of PPA-coated surfaces as a cell culture substrate. We showed that PPA is biocompatible and that the deposition of allylamine by plasma polymerization on a silicon wafer before PPA coating can stabilize the immobilization of PPA in aqueous solutions. When seeded on PPA-coated surfaces, human mesenchymal stem cells (MSC) adhered, spread, and proliferated in a manner indistinguishable from cells cultured on glass surfaces. This allowed us to subsequently use t-SPL to generate nanotopographies for cell culture experiments. As a proof of concept, we analyzed the surface topography of bovine tendon sections, previously shown to induce morphogenesis and differentiation of MSC, by means of atomic force microscopy, and then "wrote" topographical data on PPA by means of t-SPL. The resulting substrate, matching the native tissue topography on the nanoscale, was directly used for MSC culture. The t-SPL substrate induced similar changes in cell morphology and focal adhesion formation in the MSC compared to native tendon sections, suggesting that t-SPL can rapidly generate cell culture substrates with complex and spatially accurate topographical signals. This technique may greatly accelerate the prototyping of models for the study of cell-matrix interactions.

Stem cell injections for the treatment of articular cartilage damage are a promising approach to achieve tissue regeneration. However, this method is encumbered by high cell apoptosis rates, low retention in the cartilage lesion, and inefficient chondrogenesis. Here, we have used a facile, very low cost-based microfluidic technique to create visible light-cured microgels composed of gelatin norbornene (GelNB) and a poly(ethylene glycol) (PEG) cross-linker. In addition, we have demonstrated that the process enables the rapid in situ microencapsulation of human bone marrow-derived mesenchymal stem cells (hBMSCs) under biocompatible microfluidic-processing conditions for long-term maintenance. The hBMSCs exhibited an unusually high degree of chondrogenesis in the GelNB microgels with chondro-inductive media, specifically toward the hyaline cartilage structure, with significant upregulation in type II collagen expression compared to the bulk hydrogel and "gold standard" pellet culture. Overall, we have demonstrated that these protein-based microgels can be engineered as promising therapeutic candidates for articular cartilage regeneration, with additional potential to be used in a variety of other applications in regenerative medicine.

A new surface based on self-assembly of two colloids into well-defined nanostructures, so-called binary colloidal crystals (BCCs), was fabricated for stem cell culture. The facile fabrication process are able to cover large surface areas (>3 cm-diameter, i.e. > 7 cm(2)) with ordered surface nanotopographies that is often a challenge particularly in biomaterials science. From our library, four different combinations of BCCs were selected using mixtures of silica, polystyrene and poly(methyl methacrylate) particles with sizes in the range from 100 nm to 5 μm. Cell spreading, proliferation, and surface-induced lineage commitment of human adipose-derived stem cells (hADSCs) was studied using quantitative real time polymerase chain reaction (qRT-PCR) and immunostaining. The results showed that BCCs induced osteo- and chondro- but not adipo-gene expression in the absence of induction medium suggesting that the osteochondral lineage can be stimulated by the BCCs. When applying induction media, higher osteo- and chondro-gene expression on BCCs was found compared with tissue culture polystyrene (TCPS) and flat silica (Si) controls, respectively. Colony forming of chondrogenic hADSCs was found on BCCs and TCPS but not Si controls, suggesting that the differentiation of stem cells is surface-dependent. BCCs provide access to complex nanotopographies and chemistries, which can find applications in cell culture and regenerative medicine.

Ordered surface nanostructures have attracted much attention in biotechnology and biomedical engineering because of their potential to modulate cell-surface interactions in a controllable manner. However, the ability to fabricate large area ordered nanostructures is limited because of high costs and low speed of fabrication. Here, we have fabricated ordered nanostructures with large surface areas (1.5 × 1.5 cm(2)) using a combination of facile techniques including colloidal self-assembly, colloidal lithography and glancing angle deposition (GLAD). Polystyrene (722 nm) colloids were self-assembled into a hexagonally close-packed (hcp) crystal array at the water-air interface, transferred on a biocompatible tantalum (Ta) surface and used as a mask to generate an ordered Ta pattern. The Ta was deposited by sputter coating through the crystal mask creating approximately 60-nm-high feature sizes. The feature size was further increased by approximately 200-nm-height respectively using GLAD, resulting in the fabrication of four different surfaces (FLAT, Ta60, GLAD100, and GLAD200). Cell adhesion, proliferation, and osteogenic differentiation of primary human adipose-derived stem cells (hADSCs) were studied on these ordered nanostructures for up to 2 weeks. Our results suggested that cell spreading, focal adhesion formation, and filopodia extension of hADSCs were inhibited on the GLAD surfaces, while the growth rate was similar between each surface. Immunostaining for type I collagen (COL1) and osteocalcin (OC) showed that there was higher osteogenic components deposited on the GLAD surfaces compared to the Ta60 and FLAT surfaces after 1 week of osteogenic culture. After 2 weeks of osteogenic culture, alkaline phosphatase (ALP) activity and the amount of calcium was higher on the GLAD surfaces. In addition, osteoblast-like cells were confluent on Ta60 and FLAT surfaces, whereas the GLAD surfaces were not fully covered suggesting that the cell-cell interactions are stronger than cell-substrate interactions on GLAD surfaces. Visible extracellular matrix deposits decorated the porous surface can be found on the GLAD surfaces. Depth profiling of surface components using a new Ar cluster source and X-ray photoelectron spectroscopy (XPS) showed that deposited extracellular matrix on GLAD surfaces is rich in nitrogen. The fabricated ordered surface nanotopographies have potential to be applied in diverse fields, and demonstrate that the behavior of human stem cells can be directed on these ordered nanotopographies, providing new knowledge for applications in biomaterials and tissue engineering.

Anionic ring-opening polymerization of glycidol was initiated from activated glass, silicon, and porous silicon substrates to yield thin, ultralow-fouling hyperbranched polyglycerol (HPG) graft polymer coatings. Substrates were activated by deprotonation of surface-bound silanol functionalities. HPG polymerization was initiated upon the addition of freshly distilled glycidol to yield films in the nanometer thickness range. X-ray photoelectron spectroscopy, contact angle measurements, and ellipsometry were used to characterize the resulting coatings. The antifouling properties of HPG-coated surfaces were evaluated in terms of protein adsorption and the attachment of mammalian cells. The adsorption of bovine serum albumin and collagen type I was found to be reduced by as much as 97 and 91%, respectively, in comparison to untreated surfaces. Human glioblastoma and mouse fibroblast attachment was reduced by 99 and 98%, respectively. HPG-grafted substrates outperformed polyethylene glycol (PEG) grafted substrates of comparable thickness under the same incubation conditions. Our results demonstrate the effectiveness of antifouling HPG graft polymer coatings on a selected range of substrate materials and open the door for their use in biomedical applications.