The Impact of Polyethylene Glycol-Modified Chitosan Scaffolds on the Proliferation and Differentiation of Osteoblasts

The objective of this study was to investigate the influence of polyethylene glycol (PEG) incorporated chitosan scaffolds on osteoblasts proliferation and differentiation. The chitosan polymer was initially modified by the predetermined concentration of the photoreactive azido group for UV-crosslinking and with RGD peptides (N-acetyl-GRGDSPGYG-amide). The PEG was mixed at different ratios (0, 10, and 20 wt%) with modified chitosan in 96-well tissue culture polystyrene plates to prepare CHI-100, CHI-90, and CHI-80 scaffolds. PEG-containing scaffolds exhibited bigger pore size and higher water content compared to unmodified chitosan scaffolds. After 10 days of incubation, the cell number of CHI-90 (1.1 × 106 cells/scaffold) surpasses that of CHI-100 (9.2 × 105 cells/scaffold) and the cell number of CHI-80 (7.6 × 105 cells/scaffold) were significantly lower. The ALP activity of CHI-90 was the highest on the fifth day indicating the favored osteoblasts' early-stage differentiation. Moreover, after 14 days of osteogenic culture, calcium deposition in the CHI-90 scaffolds (2.7 μmol Ca/scaffold) was significantly higher than the control (2.2 μmol Ca/scaffold) whereas on CHI-80 was 1.9 μmol/scaffold. The results demonstrate that PEG-incorporated chitosan scaffolds favored osteoblasts proliferation and differentiation; however, mixing relatively excess PEG (≥20% wt.) had a negative impact on osteoblasts proliferation and differentiation.

Bio-inspired hemocompatible surface modifications for biomedical applications

When blood first encounters the artificial surface of a medical device, a complex series of biochemical reactions is triggered, potentially resulting in clinical complications such as embolism/occlusion, inflammation, or device failure. Preventing thrombus formation on the surface of blood-contacting devices is crucial for maintaining device functionality and patient safety. As the number of patients reliant on blood-contacting devices continues to grow, minimizing the risk associated with these devices is vital towards lowering healthcare-associated morbidity and mortality. The current standard clinical practice primarily requires the systemic administration of anticoagulants such as heparin, which can result in serious complications such as post-operative bleeding and heparin-induced thrombocytopenia (HIT). Due to these complications, the administration of antithrombotic agents remains one of the leading causes of clinical drug-related deaths. To reduce the side effects spurred by systemic anticoagulation, researchers have been inspired by the hemocompatibility exhibited by natural phenomena, and thus have begun developing medical-grade surfaces which aim to exhibit total hemocompatibility via biomimicry. This review paper aims to address different bio-inspired surface modifications that increase hemocompatibility, discuss the limitations of each method, and explore the future direction for hemocompatible surface research.

Fabrication of Low-Fouling Surfaces on Alkyne-Functionalized Poly-(p-xylylenes) Using Click Chemistry

A facial, versatile, and universal method that breaks the substrate limits is desirable for antifouling treatment. Thin films of functional poly-p-xylylenes (PPX) that are deposited using chemical vapor deposition (CVD) provide a powerful platform for surface immobilization of molecules. In this study, we prepared an alkyne-functionalized PPX coating on which poly (sulfobetaine methacrylate-co-Az) could be conjugated via click chemistry. We found that the conjugated polymers were very stable and inhibited cell adhesion and protein adsorption effectively. The same conjugation strategy could also be applied to conjugate azide-containing poly (ethylene glycol) and poly (NIPAAm). The results indicate that our method provides a simple and robust tool for fabricating antifouling surfaces on a wide range of substrates using CVD technology of functionalized poly (p-xylylenes) for biosensor, diagnostics, immunoassay, and other biomaterial applications.

Graphene oxide film guided skeletal muscle differentiation

Engineered muscle tissues can be used for the regeneration or substitution of irreversibly damaged or diseased muscles. Recently, graphene oxide (GO) has been shown to improve the adsorption of biomolecules through its biocompatibility and intrinsic π-π interactions. The possibility of producing various GO modifications may also provide additional functionality as substrates for cell culture. In particular, substrates fabricated from pristine GO have been shown to improve cellular functions and influence stem cell differentiation. In this study, we fabricated tunable GO substrates with various physical and chemical properties and demonstrated the ability of the substrate to support myogenic differentiation. Higher cellular adhesion affinity with unique microfilament anchorage was observed for GO substrates with increased GO concentrations. In addition, amino acid (AA)-conjugated GO (GO-AA) substrates were fabricated to modify GO chemical properties and study the effects of chemically modified GO substrates on myogenic differentiation. Our findings demonstrate that minor tuning of GO significantly influences myogenic differentiation.

Development of finasteride/PHBV@polyvinyl alcohol/chitosan reservoir-type microspheres as a potential embolic agent: from in vitro evaluation to animal study

Benign prostatic hyperplasia (BPH) is a prevalent urological disease affecting elders. Currently, the prostatic artery embolization (PAE) is considered as a minimally invasive and safe technique to treat BPH. However, various drug-loaded embolic agents have not been thoroughly investigated in BPH therapy. In this study, finasteride/poly(3-hydroxybutyrate-3-hydroxyvalerate)@polyvinyl alcohol/chitosan (FNS/PHBV@PVA/CS) reservoir-type microspheres were prepared via the solid-in-water-in-oil (S/W/O) emulsion crosslinking method with the aim to reduce the burst effect and control localized drug delivery. The structure and properties of the drug and resultant microspheres were characterized via field emission scanning electron microscopy (FESEM), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The results showed that the drug-loaded hybrid microspheres were well-dispersed and spherical with a mean diameter of 238.1 ± 27.3 μm. All samples exhibited excellent thermal stability. The FNS/PHBV microspheres were successfully encapsulated inside the PVA/CS polymeric matrix, which effectively suppressed the burst effect and prolonged the drug release up to 51 days. In vitro biocompatibility assessment indicated that the microspheres possessed excellent cytocompatibility and hemocompatibility. Furthermore, in vivo studies performed in the rabbit ear embolization model showed the formation of progressive ischemic necrosis after treatment for various periods. Histopathological studies revealed that the microspheres completely occluded the blood vessels with minimal foreign body response and formed the fibrotic area at the periphery of embolized arteries. Furthermore, the auricular vascular endothelial cells showed acute ultrastructural changes, associated with the ischemic necrosis induced by the embolization procedures. All these findings suggest that the FNS/PHBV@PVA/CS hybrid microspheres could be used as a promising drug delivery system for potential applications in BPH therapy.

Anti-biofouling and functionalizable bioinspired chitosan-based hydrogel coating via surface photo-immobilization

Zwitterionic polymer is a new generation of anti-fouling materials with its good resistance to protein and bacterial adhesion. Constructing the anti-fouling surfaces with zwitterionic polymer has been regarded as an effective approach for improving the biocompatibility and biofunctionality of clinic devices. Herein, we reported a facile approach to construct a biodegradable anti-biofouling and functionalizable hydrogel coating via photo-immobilization using commercial polyethylene terephthalate (PET) films as the substrate, based on zwitterionic glycidyl methacrylate-phosphorylcholine-chitosan (PCCs-GMA). The surface structure and physicochemical properties of zwitterionic PCCs-GMA hydrogel coating were investigated by X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) and static water contact angle measurement, and its functionalizable sites were detected by fluorescence labeling. Compared with the pristine PET and cationic chitosan - GMA and hydroxypropyltrimethyl ammonium chloride chitosan (HTCC) - GMA hydrogel coatings, zwitterionic PCCs-GMA hydrogel coating exhibited excellent biocompatibility, and significantly reduced protein adsorption for three model proteins of fibrinogen, immunoglobulin and lysozyme, repelled platelet adhesion, as well as showed a high resistance to bacterial attachment of Escherichia coli and Staphylococcus aureus and superior anti-fouling properties to MRC-5 cells. The results indicated that photo-immobilized zwitterionic PCCs-GMA hydrogel coating has perspective as a dual functional platform with integrated antifouling and further biofunctional properties for various biomedical applications.

Self-assembled, ellipsoidal polymeric nanoparticles for intracellular delivery of therapeutics

Nanoparticle shape has emerged as a key regulator of nanoparticle transport across physiological barriers, intracellular uptake, and biodistribution. We report a facile approach to synthesize ellipsoidal nanoparticles through self-assembly of poly(glycerol sebacate)-co-poly(ethylene glycol) (PGS-co-PEG). The PGS-PEG nanoparticle system is highly tunable, and the semiaxis length of the nanoparticles can be modulated by changing PGS-PEG molar ratio and incorporating therapeutics. As both PGS and PEG are highly biocompatible, the PGS-co-PEG nanoparticles show high hemo-, immuno-, and cytocompatibility. Our data suggest that PGS-co-PEG nanoparticles have the potential for use in a wide range of biomedical applications including regenerative medicine, stem cell engineering, immune modulation, and cancer therapeutics. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 2048-2058, 2018.

Development of Antifouling Hyperbranched Polyglycerol Layers on Hydroxyl Poly-p-xylylene Coatings

Antifouling surfaces that are resistant to protein adsorption and cell adhesion are desirable for many biomedical devices, such as diagnostic devices, biosensors, and implants. In this study, we developed an antifouling hyperbranched polyglycerol (hPG) surface on hydroxyl poly-p-xylylene (PPX-OH). PPX-OH was deposited via chemical vapor deposition (CVD), and an hPG film was then developed via the ring-opening reaction of glycidol. The hPG film greatly reduced the adhesion of L929 cells and platelets as well as protein adsorption. The addition of alkenyl groups in the hPG layer allows the conjugation of biomolecules, such as peptides and biotin, and elicits specific biological interactions. Since the CVD deposition of PPX-OH could be applied to most types of materials, our approach makes it possible to decorate an antifouling hPG film on most types of materials. Our method could be applied to biosensors, diagnostics, and biomedical devices in the future.

Photochemical coating of Kapton® with hydrophilic polymers for the improvement of neural implants

The polyimide Kapton® was coated photochemically with hydrophilic polymers to prevent undesirable cell growth on the polyimide surface. The polymer coatings were generated using photochemically reactive polymers synthesized by a simple and modular strategy. Suitable polymers or previously synthesized copolymer precursors were functionalized with photoactive arylazide groups by a polymer analogous amide coupling reaction with 4-azidobenzoic acid. A photoactive chitosan derivative (chitosan-Az) and photochemically reactive copolymers containing DMAA, DEAA or MTA as primary monomers were synthesized using this method. The amount of arylazide groups in the polymers was adjusted to approximately 5%, 10% and 20%. As coating on Kapton® all polymers effect a significantly reduced water contact angle (WCA) and consequently a rise of the surface hydrophilicity compared to the untreated Kapton®. The presence of the polymer coatings was also proven by ATR-IR spectroscopy. Coatings with chitosan-Az and the DEAA copolymer cause a distinct inhibition of the growth of fibroblasts. In the case of the DMAA copolymer even a strong anti-adhesive behavior towards fibroblasts was verified. Biocompatibility of the polymer coatings was proven which enables their utilization in biomedical applications.

Low-fouling and functional poly(carboxybetaine) coating via a photo-crosslinking process

Antifouling modification technology is developed for many biomedical applications such as blood-contact devices and biosensors.

Synthesis of polycarbonate urethane elastomers and effects of the chemical structures on their thermal, mechanical and biocompatibility properties

In this study, to obtain biomedical polyurethane elastomers with good mechanical properties and biocompatibility, a series of polycarbonate urethanes were synthesized via a two-step solution of polymerization method using the poly(1,6-hexanediol)carbonate diols (PCDL) as the soft segment, 4,4′-methylenebis(cyclohexyl isocyanate) (H₁₂MDI), 1,6-hexamethylene diisocyanate (HDI) and 1,4-butanediol (BDO) as the hard segment with dibutyltin dilaurate as the catalyst. In this article, we illustrated the physical behaviors were obviously influenced by synthetic routes. And their chemical and physical structures were investigated by gel permeation chromatograph (GPC), differential scanning calorimeter (DSC), fourier transform infrared spectrography (FT-IR) and mechanical properties tests. The surface wettability were studied by contact angle measurement (CA). As a kind of short-term implant biomaterial, the results of the hemolysis and platelet adhesive tests were recorded by spectrophotometer and scanning electron microscopy (SEM), indicating the materials have a great potential for developments and applications in biomedical field.

Evaluation of Electrospun PCL-PIBMD Meshes Modified with Plasmid Complexes in Vitro and in Vivo

Functional artificial vascular meshes from biodegradable polymers have been widely explored for certain tissue engineered meshes. Still, the foreign body reaction and limitation in endothelialization are challenges for such devices. Here, degradable meshes from phase-segregated multiblock copolymers consisting of poly(ε-caprolactone) (PCL) and polydepsipeptide segments are successfully prepared by electrospinning and electrospraying techniques. The pEGFP-ZNF580 plasmid microparticles (MPs-pZNF580) were loaded into the electrospun meshes to enhance endothelialization. These functional meshes were evaluated in vitro and in vivo. The adhesion and proliferation of endothelial cells on the meshes were enhanced in loaded mesh groups. Moreover, the hemocompatibility and the tissue response of the meshes were further tested. The complete tests showed that the vascular meshes modified with MPs-pZNF580 possessed satisfactory performance with an average fiber diameter of 550 ± 160 nm, tensile strength of 27 ± 3 MPa, Young's modulus of 1. 9 ± 0.2 MPa, water contact angle of 95° ± 2°, relative cell number of 122% ± 1% after 7 days of culture, and low blood platelet adhesion as well as weak inflammatory reactions compared to control groups.

Safe and efficient membrane permeabilizing polymers based on PLLA for antibacterial applications

Highly active antibacterial poly(N,N-dimethylaminoethyl methacrylate)-block-poly(l-lactic acid)-block-poly(N,N-dimethylaminoethyl methacrylate) conjugated with poly(ethylene glycol) (D-PLLA-D@PEG) copolymers were synthesized.

In vitro evaluation and in vivo demonstration of a biomimetic, hemocompatible, microfluidic artificial lung

Despite the promising potential of microfluidic artificial lungs, current designs suffer from short functional lifetimes due to surface chemistry and blood flow patterns that act to reduce hemocompatibility. Here, we present the first microfluidic artificial lung featuring a hemocompatible surface coating and a biomimetic blood path. The polyethylene-glycol (PEG) coated microfluidic lung exhibited a significantly improved in vitro lifetime compared to uncoated controls as well as consistent and significantly improved gas exchange over the entire testing period. Enabled by our hemocompatible PEG coating, we additionally describe the first extended (3 h) in vivo demonstration of a microfluidic artificial lung.

Patterning of individual Staphylococcus aureus bacteria onto photogenerated polymeric surface structures

This manuscript describes the fabrication of bacterial surface arrays by using photolithographic techniques having in addition some particularly interesting features.

Modulation of the stemness and osteogenic differentiation of human mesenchymal stem cells by controlling RGD concentrations of poly(carboxybetaine) hydrogel

In vitro modulation of the differentiation status of mesenchymal stem cells (MSCs) is important for their application to regenerative medicine. We suggested that the morphology and differentiation states of MSCs could be modulated by controlling the cell affinity of a substrate. The objective of this study was to investigate the effects of surface bio-adhesive signals on self-renewal and osteogenic differentiation of MSCs using a low-fouling platform. Cell-resistant poly(carboxybetaine) hydrogel was conjugated with 5 μM or 5 mM of cell-adhesive arginine-glycine-aspartic acid (RGD) peptides in order to control the cells' affinity to the substrate. Human mesenchymal stem cells (hMSCs) were cultured on the RGD-modified poly(carboxybetaine) hydrogel and then the cells' states of stemness and osteogenic differentiation were evaluated using reverse-transcriptase polymerase chain reaction. The hMSCs formed three-dimensional spheroids on the 5 μM RGD substrate, while cells on the 5 mM RGD substrate exhibited spreading morphology. Furthermore, cells on the 5 μM RGD hydrogel maintained a better stemness phenotype, while the hMSCs on the 5 mM RGD hydrogel proliferated faster and underwent osteogenic differentiation. In conclusion, the stemness of hMSCs was best maintained on a low RGD surface, while osteogenic differentiation of hMSCs was enhanced on a high RGD surface.

Constructing robust and functional micropatterns on polystyrene surfaces by using deep UV irradiation

We report the preparation of different surface patterns based on the photo-cross-linking/degradation kinetics of polystyrene (PS) by using UV light. Upon exposure to UV light, PS can be initially cross-linked, whereas an excess of the exposure time or intensity provokes the degradation of the material. Typically photolithography employs either positive or negative photoresist layers that upon removal of either the exposed or the nonexposed areas transfer the pattern of the mask. Herein, we present a system that can be both negative and positive depending on several aspects, including the irradiation time, intensity, or presence of absorbing active species (photoinitiators) using a general setup. As a result of the optimization of the time of exposure and the use of an appropriate cover or the incorporation of an appropriate amount of photoinitiator (in this particular case IRG 651), different tailor-made surface patterns can be obtained. Moreover, changes of the chemical composition of the polystyrene using, for instance, block copolymers can lead to surface patterns with variable functional groups. In this study we describe the formation of surface patterns using polystyrene-block-poly(2,3,4,5,6-pentafluorostyrene) block copolymers. The introduction of fluorinated moieties clearly modifies the wettability of the films when compared with that of the same structures obtained with PS. As a consequence we present herein a patterning methodology that can simultaneously vary not only the morphology but also the surface chemical composition.