Human Fetal Osteoblast Response on Poly(Methyl Methacrylate)/Polystyrene Demixed Thin Film Blends: Surface Chemistry Vs Topography Effects

Surface Engineering of a Bioartificial Membrane for Its Application in Bioengineering Devices

Membrane technology is playing a crucial role in cutting-edge innovations in the biomedical field. One such innovation is the surface engineering of a membrane for enhanced longevity, efficient separation, and better throughput. Hence, surface engineering is widely used while developing membranes for its use in bioartificial organ development, separation processes, extracorporeal devices, etc. Chemical-based surface modifications are usually performed by functional group/biomolecule grafting, surface moiety modification, and altercation of hydrophilic and hydrophobic properties. Further, creation of micro/nanogrooves, pillars, channel networks, and other topologies is achieved to modify physio-mechanical processes. These surface modifications facilitate improved cellular attachment, directional migration, and communication among the neighboring cells and enhanced diffusional transport of nutrients, gases, and waste across the membrane. These modifications, apart from improving functional efficiency, also help in overcoming fouling issues, biofilm formation, and infection incidences. Multiple strategies are adopted, like lysozyme enzymatic action, topographical modifications, nanomaterial coating, and antibiotic/antibacterial agent doping in the membrane to counter the challenges of biofilm formation, fouling challenges, and microbial invasion. Therefore, in the current review, we have comprehensibly discussed different types of membranes, their fabrication and surface modifications, antifouling/antibacterial strategies, and their applications in bioengineering. Thus, this review would benefit bioengineers and membrane scientists who aim to improve membranes for applications in tissue engineering, bioseparation, extra corporeal membrane devices, wound healing, and others.

Atmospheric Pressure Plasma Surface Treatment of Polymers and Influence on Cell Cultivation

Atmospheric plasma treatment is an effective and economical surface treatment technique. The main advantage of this technique is that the bulk properties of the material remain unchanged while the surface properties and biocompatibility are enhanced. Polymers are used in many biomedical applications; such as implants, because of their variable bulk properties. On the other hand, their surface properties are inadequate which demands certain surface treatments including atmospheric pressure plasma treatment. In biomedical applications, surface treatment is important to promote good cell adhesion, proliferation, and growth. This article aim is to give an overview of different atmospheric pressure plasma treatments of polymer surface, and their influence on cell-material interaction with different cell lines.

Molecular Mechanisms of Topography Sensing by Osteoblasts: An Update

Bone is a specialized tissue formed by different cell types and a multiscale, complex mineralized matrix. The architecture and the surface chemistry of this microenvironment can be factors of considerable influence on cell biology, and can affect cell proliferation, commitment to differentiation, gene expression, matrix production and/or composition. It has been shown that osteoblasts encounter natural motifs in vivo, with various topographies (shapes, sizes, organization), and that cell cultures on flat surfaces do not reflect the total potential of the tissue. Therefore, studies investigating the role of topographies on cell behavior are important in order to better understand the interaction between cells and surfaces, to improve osseointegration processes in vivo between tissues and biomaterials, and to find a better topographic surface to enhance bone repair. In this review, we evaluate the main available data about surface topographies, techniques for topographies’ production, mechanical signal transduction from surfaces to cells and the impact of cell–surface interactions on osteoblasts or preosteoblasts’ behavior.

A facile surface modification of poly(dimethylsiloxane) with amino acid conjugated self-assembled monolayers for enhanced osteoblast cell behavior

Polydimethylsiloxane (PDMS) is a biocompatible synthetic polymer and used in various applications due to its low toxicity and tunable surface properties. However, PDMS does not have any chemical cues for cell binding. Plasma treatment, protein coating or surface modification with various molecules have been used to improve its surface characteristics. Still, these techniques are either last for a very limited time or have very complicated experimental procedures. In the present study, simple and one-step surface modification of PDMS is successfully accomplished by the preparation of hydrophilic and hydrophobic amino acid conjugated self-assembled monolayers (SAMs) for enhanced interactions at the cell-substrate interface. Synthesis of histidine and leucine conjugated (3-aminopropyl)-triethoxysilane (His-APTES and Leu-APTES) were confirmed with proton nuclear magnetic resonance spectroscopy (¹H NMR) and optimum conditions for the modification of PDMS with SAMs were investigated by X-ray photoelectron spectroscopy (XPS) analysis, combined with water contact angle (WCA) measurements. Results indicated that both SAMs enhanced cellular behavior in vitro. Furthermore, hydrophilic His-APTES modification provides a superior environment for the osteoblast maturation with higher alkaline phosphatase activity and mineralization. As histidine, leucine, and functional groups of these SAMs are naturally found in biological systems, modification of PDMS with them increases its cell-substrate surface biomimetic properties. This study establishes a successful modification of PDMS for in vitro cell studies, offering a biomimetic and easy procedure for potential applications in microfluidics, cell-based therapies, or drug investigations.

Effect of Polymer Demixed Nanotopographies on Bacterial Adhesion and Biofilm Formation

As the current global threat of antimicrobial resistance (AMR) persists, developing alternatives to antibiotics that are less susceptible to resistance is becoming an urgent necessity. Recent advances in biomaterials have allowed for the development and fabrication of materials with discrete surface nanotopographies that can deter bacteria from adhering to their surface. Using binary polymer blends of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polycaprolactone (PCL) and varying their relative concentrations, PS/PCL, PS/PMMA and PCL/PMMA polymer demixed thin films were developed with nanoisland, nanoribbon and nanopit topographies. In the PS/PCL system, PS segregates to the air-polymer interface, with the lower solubility PCL preferring the substrate-polymer interface. In the PS/PMMA and PCL/PMMA systems, PMMA prefers the air-polymer interface due to its greater solubility and lower surface energy. The anti-adhesion efficacy of the demixed films were tested against Pseudomonas aeruginosa (PA14). PS/PCL and PCL/PMMA demixed films showed a significant reduction in cell counts adhered on their surfaces compared to pure polymer control films, while no reduction was observed in the counts adhered on PS/PMMA demixed films. While the specific morphology did not affect the adhesion, a relationship between bacterial cell and topographical surface feature size was apparent. If the surface feature was smaller than the cell, then an anti-adhesion effect was observed; if the surface feature was larger than the cell, then the bacteria preferred to adhere.

Electrospun nanofibrous thermoplastic polyurethane/poly(glycerol sebacate) hybrid scaffolds for vocal fold tissue engineering applications

Vocal fold tissue engineering requires biomimetic scaffolds with an appropriate matrix stiffness closely matching that of the natural vocal folds to maintain function. Traditionally, poly(ɛ‑caprolactone) (PCL) and thermoplastic polyurethane (TPU) have been employed as the primary matrix materials for vocal fold electrospun scaffolds. However, not all of the scaffolds fabricated thus far matched the human vocal fold tissues. Poly(glycerol sebacate) (PGS) is a non-cytotoxic and biodegradable soft elastomer that has shown promising results for soft tissue engineering applications. However, no work has been done to employ this biomaterial to construct vocal fold scaffolds. In this study, PGS has been synthesized and blended with thermoplastic polyurethane (TPU) to produce vocal fold scaffolds with improved hydrophilicity and compliance by electrospinning. The resulting scaffolds were found to have mechanical properties mimicking those of the vocal fold lamina propria extracellular matrix (ECM). An unusual leaf-like structure was obtained when using 1,1,1,3,3,3‑hexafluoroisopropanol (HFIP) as the solvent. Other suitable fibrous scaffolds were also obtained when using acetic acid and 2,2,2‑trifluoroethanol (TFE) as binary solvents. A biological evaluation of these TPU/PGS scaffolds showed better cell spreading and significantly improved cell proliferation as compared to TPU-only scaffolds (p < 0.01), thereby suggesting potential applications for vocal fold tissue engineering.

Argon plasma improves the tissue integration and angiogenesis of subcutaneous implants by modifying surface chemistry and topography

BACKGROUND

Tissue integration and vessel formation are important criteria for the successful implantation of synthetic biomaterials for subcutaneous implantation.

OBJECTIVE

We report the optimization of plasma surface modification (PSM) using argon (Ar), oxygen (O2) and nitrogen (N2) gases of a polyurethane polymer to enhance tissue integration and angiogenesis.

METHODS

The scaffold's bulk and surface characteristics were compared before and after PSM with either Ar, O2 and N2. The viability and adhesion of human dermal fibroblasts (HDFs) on the modified scaffolds were compared. The formation of extracellular matrix by the HDFs on the modified scaffolds was evaluated. Scaffolds were subcutaneously implanted in a mouse model for 3 months to analyze tissue integration, angiogenesis and capsule formation.

RESULTS

Surface analysis demonstrated that interfacial modification (chemistry, topography and wettability) achieved by PSM is unique and varies according to the gas used. O2 plasma led to extensive changes in interfacial properties, whereas Ar treatment caused moderate changes. N2 plasma caused the least effect on surface chemistry of the polymer. PSM-treated scaffolds significantly (P<0.05) enhanced HDF activity and growth over 21 days. Among all three gases, Ar modification showed the highest protein adsorption. Ar-modified scaffolds also showed a significant upregulation of adhesion-related proteins (vinculin, focal adhesion kinase, talin and paxillin; P<0.05) and extracellular matrix marker genes (collagen type I, fibronectin, laminin and elastin) and deposition of associated proteins by the HDFs. Subcutaneous implantation after 3 months demonstrated the highest tissue integration and angiogenesis and the lowest capsule formation on Ar-modified scaffolds compared with O2- and N2-modified scaffolds.

CONCLUSION

PSM using Ar is a cost-effective and efficient method to improve the tissue integration and angiogenesis of subcutaneous implants.

Entrapment of Autologous von Willebrand Factor on Polystyrene/Poly(methyl methacrylate) Demixed Surfaces

Human platelets play a vital role in haemostasis, pathological bleeding and thrombosis. The haemostatic mechanism is concerned with the control of bleeding from injured blood vessels, whereby platelets interact with the damaged inner vessel wall to form a clot (thrombus) at the site of injury. This adhesion of platelets and their subsequent aggregation is dependent on the presence of the blood protein von Willebrand Factor (vWF). It is proposed here that the entrapment of vWF on a substrate surface offers the opportunity to assess an individual’s platelet function in a clinical diagnostic context. Spin coating from demixed solutions of polystyrene (PS) and poly(methyl methacrylate) (PMMA) onto glass slides has been shown previously to support platelet adhesion but the mechanism by which this interaction occurs, including the role of vWF, is not fully understood. In this work, we report a study of the interaction of platelets in whole blood with surfaces produced by spin coating from a solution of a weight/weight mixture of a 25% PS and 75% PMMA (25PS/75PMMA) in chloroform in the context of the properties required for their use as a Dynamic Platelet Function Assay (DPFA) substrate. Atomic Force Microscopy (AFM) indicates the presence of topographical features on the polymer demixed surfaces in the sub-micron to nanometer range. X-ray Photoelectron Spectroscopy (XPS) analysis confirms that the uppermost surface chemistry of the coatings is solely that of PMMA. The deliberate addition of various amounts of 50 μm diameter PS microspheres to the 25PS/75PMMA system has been shown to maintain the PMMA chemistry, but to significantly change the surface topography and to subsequently effect the scale of the resultant platelet interactions. By blocking specific platelet binding sites, it has been shown that their interaction with these surfaces is a consequence of the entrapment and build-up of vWF from the same whole blood sample.

Arginine-leucine based poly (ester urea urethane) coating for Mg-Zn-Y-Nd alloy in cardiovascular stent applications

Selected from the family of self-designed biodegradable amino acid-based poly (ester urea urethane) (AA-PEUU) pseudo-protein biomaterials, arginine-leucine based poly (ester urea urethane)s (Arg-Leu-PEUUs) were used as protective and bio-functional coatings for bio-absorbable magnesium alloy MgZnYNd in cardiovascular stent applications. Comparing with poly (glycolide-co-lactide) (PLGA) coating, the Arg-Leu-PEUU coating had stronger bonding strength with the substrate; in vitro electrochemical and long-term immersion results verified a significantly better corrosion resistance. Acute blood contact tests proved a better hemocompatibility of Arg-Leu-PEUU coating. The immunofluorescent staining and cell proliferation test indicated that Arg-Leu-PEUU coating had a far better cytocompatibility. The Arg-Leu-PEUU coating stimulated human umbilical vein endothelial cells (HUVEC) to release reasonably increased amount of nitric oxide (NO), suggesting its potential in retarding thrombosis and restenosis. The superior corrosion resistance and biocompatibility as well as the indigenous NO production bio-functionality of the Arg-Leu-PEUU copolymer family indicate their capability to offer a far better protection of the magnesium-based implantable cardiovascular stent and bring their application closer to clinical reality.

Abrogated Cell Contact Guidance on Amino-Functionalized Microgrooves

Topographical and chemical features of biomaterial surfaces affect the cell physiology at the interface and are promising tools for the improvement of implants. The dominance of the surface topography on cell behavior is often accentuated. Striated surfaces induce an alignment of cells and their intracellular adhesion-mediated components. Recently, it could be demonstrated that a chemical modification via plasma polymerized allylamine was not only able to boost osteoblast cell adhesion and spreading but also override the cell alignment on stochastically machined titanium. In order to discern what kind of chemical surface modifications let the cell forget the underlying surface structure, we used an approach on geometric microgrooves produced by deep reactive ion etching (DRIE). In this study, we systematically investigated the surface modification by (i) methyl-, carboxyl-, and amino functionalization created via plasma polymerization processes, (ii) coating with the extracellular matrix protein collagen-I or immobilization of the integrin adhesion peptide sequence Arg-Gly-Asp (RGD), and (iii) treatment with an atmospheric pressure plasma jet operating with argon/oxygen gas (Ar/O₂). Interestingly, only the amino functionalization, which presented positive charges at the surface, was able to chemically disguise the microgrooves and therefore to interrupt the microtopography induced contact guidance of the osteoblastic cells MG-63. However, the RGD peptide coating revealed enhanced cell spreading as well, with fine, actin-containing protrusions. The Ar/O₂-functionalization demonstrated the best topography handling, e.g. cells closely attached even to features such as the sidewalls of the groove steps. In the end, the amino functionalization is unique in abrogating the cell contact guidance.

A novel biodegradable and biologically functional arginine-based poly(ester urea urethane) coating for Mg–Zn–Y–Nd alloy: enhancement in corrosion resistance and biocompatibility

Novel biodegradable and functional Arg-PEUU coating materials for MgZnYNd alloy stents may make drugs like sirolimus or paclitaxel unnecessary.