Surface engineering of PHBV by covalent collagen immobilization to improve cell compatibility

AK, Ramakrishna S, Amirul AAA. Surface Characterization and Physiochemical Evaluation of P(3HB-co-4HB)-Collagen Peptide Scaffolds with Silver Sulfadiazine as Antimicrobial Agent for Potential Infection-Resistance Biomaterial

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] is a bacterial derived biopolymer widely known for its unique physical and mechanical properties to be used in biomedical application. In this study, antimicrobial agent silver sulfadiazine (SSD) coat/collagen peptide coat-P(3HB-co-4HB) (SCCC) and SSD blend/collagen peptide coat-P(3HB-co-4HB) scaffolds (SBCC) were fabricated using a green salt leaching technique combined with freeze-drying. This was then followed by the incorporation of collagen peptides at various concentrations (2.5-12.5 wt.%) to P(3HB-co-4HB) using collagen-coating. As a result, two types of P(3HB-co-4HB) scaffolds were fabricated, including SCCC and SBCC scaffolds. The increasing concentrations of collagen peptides from 2.5 wt.% to 12.5 wt.% exhibited a decline in their porosity. The wettability and hydrophilicity increased as the concentration of collagen peptides in the scaffolds increased. In terms of the cytotoxic results, MTS assay demonstrated the L929 fibroblast scaffolds adhered well to the fabricated scaffolds. The 10 wt.% collagen peptides coated SCCC and SBCC scaffolds displayed highest cell proliferation rate. The antimicrobial analysis of the fabricated scaffolds exhibited 100% inhibition towards various pathogenic microorganisms. However, the SCCC scaffold exhibited 100% inhibition between 12 and 24 h, but the SBCC scaffolds with SSD impregnated in the scaffold had controlled release of the antimicrobial agent. Thus, this study will elucidate the surface interface-cell interactions of the SSD-P(3HB-co-4HB)-collagen peptide scaffolds and controlled release of SSD, antimicrobial agent.

Recycling of Chrome-Tanned Leather and Its Utilization as Polymeric Materials and in Polymer-Based Composites: A Review

Tanneries generate large amounts of solid and liquid wastes, which contain harmful chemical compounds in the environment, such as chromium, that is used in the tanning process. Until now, they have been almost completely dumped in landfills. Thus, finding eco-sustainable and innovative alternatives for the management and disposal of these wastes is becoming a huge challenge for tanneries and researchers around the world. In particular, the scientific and industrial communities have started using wastes to produce new materials exploiting the characteristics of leather, which are strongly connected with the macromolecular structure of its main component, collagen. None of the reviews on leather waste management actually present in the scientific literature report in detail the use of leather to make composite materials and the mechanical properties of the materials obtained, which are of fundamental importance for an effective industrial exploitation of leather scraps. This comprehensive review reports for the first time the state of the art of the strategies related to the recovery and valorization of both hydrolyzed collagen and leather waste for the realization of composite materials, reporting in detail the properties and the industrial applications of the materials obtained. In the conclusion section, the authors provide practical implications for industry in relation to sustainability and identify research gaps that can guide future authors and industries in their work.

Elucidation of Antimicrobial Silver Sulfadiazine (SSD) Blend/Poly(3-Hydroxybutyrate-co-4-Hydroxybutyrate) Immobilised with Collagen Peptide as Potential Biomaterial

The quest for a suitable biomaterial for medical application and tissue regeneration has resulted in the extensive research of surface functionalization of material. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] is a bacterial polymer well-known for its high levels of biocompatibility, non-genotoxicity, and minimal tissue response. We have designed a porous antimicrobial silver SSD blend/poly(3HB-co-4HB)-collagen peptide scaffold using a combination of simple techniques to develop a scaffold with an inter-connected microporous pore in this study. The collagen peptide was immobilised via -NH₂ group via aminolysis. In order to improve the antimicrobial performance of the scaffold, silver sulfadiazine (SSD) was impregnated in the scaffolds. To confirm the immobilised collagen peptide and SSD, the scaffold was characterized using FTIR. Herein, based on the cell proliferation assay of the L929 fibroblast cells, enhanced bioactivity of the scaffold with improved wettability facilitated increased cell proliferation. The antimicrobial activity of the SSD blend/P(3HB-co-4HB)-collagen peptide in reference to the pathogenic Gram-negative, Gram-positive bacteria and yeast Candida albicans exhibited SSD blend/poly(3HB-co-4HB)-12.5 wt% collagen peptide as significant construct of biocompatible antibacterial biomaterials. Thus, SSD blend/P(3HB-co-4HB)-collagen peptide scaffold from this finding has high potential to be further developed as biomaterial.

Biomimetic Properties of Force-Spun PHBV Membranes Functionalised with Collagen as Substrates for Biomedical Application

The force-spinning process parameters (i.e., spin speed, spinneret-collector distance, and polymer concentration), optimised and characterised in previous work by this group, allowed the rapid fabrication of large quantities of high surface area poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) (PHBV) polymeric fibre membranes. This paper examined the potential application for force-spun PHBV fibres functionalised with type I collagen for tissue regeneration applications. PHBV fibre scaffolds provide a biologically suitable substrate to guide the regeneration of dermal tissues, however, have poor cellular adhesion properties. The grafting of collagen type-I to PHBV fibres demonstrated improved cell adhesion and growth in Neo-NHDF (neonatal human dermal fibroblasts) fibroblasts. The examination of fibre morphology, thermal properties, collagen content, and degradability was used to contrast the physicochemical properties of the PHBV and PHBV-Collagen fibres. Biodegradation models using phosphate buffered saline determined there was no appreciable change in mass over the course of 6 weeks; a Sirius Red assay was performed on degraded samples, showing no change in the quantity of collagen. Cell metabolism studies showed an increase in cell metabolism on conjugated samples after three and 7 days. In addition, in vitro cytocompatibility studies demonstrated superior cell activity and adhesion on conjugated samples over 7 days.

Poly(3-Hydroxybutyrate-co-3-Hydroxyvalerate): Enhancement Strategies for Advanced Applications

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate), PHBV, is a microbial biopolymer with excellent biocompatible and biodegradable properties that make it a potential candidate for substituting petroleum-derived polymers. However, it lacks mechanical strength, water sorption and diffusion, electrical and/or thermal properties, antimicrobial activity, wettability, biological properties, and porosity, among others, limiting its application. For this reason, many researchers around the world are currently working on how to overcome the drawbacks of this promising material. This review summarises the main advances achieved in this field so far, addressing most of the chemical and physical strategies to modify PHBV and placing particular emphasis on the combination of PHBV with other materials from a variety of different structures and properties, such as other polymers, natural fibres, carbon nanomaterials, nanocellulose, nanoclays, and nanometals, producing a wide range of composite biomaterials with increased potential applications. Finally, the most important methods to fabricate porous PHBV scaffolds for tissue engineering applications are presented. Even though great advances have been achieved so far, much research needs to be conducted still, in order to find new alternative enhancement strategies able to produce advanced PHBV-based materials able to overcome many of these challenges.

Biomacromolecule immobilization: grafting of fish-scale collagen peptides onto aminolyzed P(3HB-co-4HB) scaffolds as a potential wound dressing

Polyhydroxyalkanoate (PHA) is a microbial polymer that has been at the forefront of many attempts at tissue engineering. However, the surface of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P(3HB-co-4HB)) is hydrophobic with few recognition sites for cell attachment. Various concentrations of fish-scale collagen peptides (FSCPs) were incorporated into P(3HB-co-4HB) copolymer by aminolysis. Later, FSCPs were introduced onto the aminolyzed P(3HB-co-4HB) scaffolds. Introduction of the FSCP groups was verified using Fourier transform infrared spectroscopy and the ninhydrin method. The effect of the incorporation of FSCPs on hydrophilicity was investigated using the water contact angle. As the concentration of FSCPs increased, the water contact angle decreased. In vitro study demonstrated that P(3HB-co-4HB)/FSCP scaffolds provided better cell attachment and growth of L929 mouse fibroblast cells and better cell proliferation. In vivo study showed that P(3HB-co-4HB)/1.5 wt% FSCPs had a significant effect on wound contractions, with the highest percentage of wound closure (61%) in 7 d.

Aminoparticles – synthesis, characterisation and application in water purification

A convenient synthesis of processable aminoparticles is demonstrated with potential applications in water purification.

Biocompatibilities and biodegradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s produced by a model metabolic reaction-based system

Background

This study evaluated the biocompatibilities of random and putative block poly(3-hydroxybutyrate-co-3-hydroxyvalerate)s (PHBVs) produced by a metabolic reaction-based system. The produced PHBVs were fractionated, and the copolymer sequence distributions were analyzed using ¹H and ¹³C NMR spectroscopy. The thermal properties were analyzed using differential scanning calorimetry (DSC). Mechanical tests were conducted using a universal testing machine. The in vitro cytotoxicities of films composed of random PHBVs and putative block PHBVs were investigated against three types of mammalian cells. The surfaces of the copolymer films and the morphologies of the cells were qualitatively monitored using scanning electron microscopy (SEM) and atomic force microscopy (AFM).

Results

Films composed of poly(3-hydroxybutyrate) (PHB), random PHBVs, putative block PHBVs, polystyrene and polyvinylchloride were prepared and characterized. The diad and triad sequence distributions indicated that the PHBVs produced via the fed-batch cultivation using two different feed systems resulted in two types of copolymers: random PHBVs and putative block PHBVs. The monomer compositions and sequence distributions strongly affected the thermal and mechanical properties. The mechanical integrity and characteristics of the film surfaces changed with the HV content. Notably, the random PHBVs possessed different mechanical properties than the putative block PHBVs. The biocompatibilities of these films were evaluated in vitro against three types of mammalian cells: L292 mouse connective tissue, human dermal fibroblast and Saos-2 human osteosarcoma cells. None of the PHBV films exhibited cytotoxic responses to the three types of mammalian cells. Erosion of the PHA film surfaces was observed by scanning electron microscopy and atomic force microscopy. The production of transforming growth factor-β-1 and interleukin-8 was also examined with regards to the usefulness of PHB and PHBV as biomaterials for regenerative tissue. The production of IL-8, which is induced by PHB and PHBVs, may be used to improve and enhance the wound-healing process because of deficiencies of IL-8 in the wound area, particularly in problematic wounds.

Conclusion

Taken together, the results support the use of PHB and the random and putative block PHBVs produced in this study as potential biomaterials in tissue engineering applications for connective tissue, bone and dermal fibroblast reconstruction.

Improvement of the cytocompatibility of electrospun poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] mats by Ecoflex

Poly[(R)-3-hydroxybutyrate-co-(R)-3-hydroxyvalerate] (PHBV) is a nature-derived polyester with potential application in tissue engineering scaffolds. However, PHBV is associated with disadvantages including high brittleness, slow degradation, high hydrophobicity, and unsatisfactory biocompatibility. In this study, we sought to improve the properties of PHBV by blending it with Ecoflex, a synthetic biopolyester with a high flexibility, fast degradation, and comparatively higher hydrophilicity. PHBV was codissolved with Ecoflex in dichloromethane at different mass ratios (PHBV/Ecoflex: 100/0, 70/30, 50/50, and 30/70) and electrospun into mats. Compared with the pure PHBV mat, the Ecoflex-containing mats showed decreased contact angles with phosphate-buffered saline (PBS), accelerated weight loss in PBS, and increased strain at break with increasing Ecoflex mass ratios. In vitro cell culture also showed significantly improved adhesion and proliferation of human bone marrow stroma cells with the introduction of Ecoflex. Blending PHBV with Ecoflex is a simple and effective method to improve the chemical, mechanical, and biological properties of PHBV simultaneously and thereby to expedite its application in tissue engineering. To our knowledge, this is the first report showing the biocompatibility of Ecoflex-containing materials with human cells.

The effects of PHBV electrospun fibers with different diameters and orientations on growth behavior of bone-marrow-derived mesenchymal stem cells

Microenvironments in which cells live play an important role in the attachment, growth and interactions of cells. To mimic the natural structure of extracellular matrices, electrospinning was applied to fabricate biomaterials into ultrafine fibers. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a biocompatible and biodegradable polyester, has been shown to be an excellent biomaterial candidate for tissue engineering. In this study, five types of PHBV fibrous scaffolds with different diameters and orientations were obtained by changing solvents, concentration of electrospun solution and collector. Three kinds of scaffolds with good continuity and suitable mechanical properties, selected according to the morphology and mechanical properties of the scaffolds, were used for studying the influence of fiber diameter and orientation on growth behavior of bone-marrow-derived mesenchymal stem cells (MSCs). The results indicated that the random-oriented nanofibrous scaffold is most favorable for cell growth compared to other scaffolds, while the microfibrous scaffold resulted in the lowest viability of MSCs. The orientation of nanofibers showed a distinct effect on cell morphology by guiding cell skeleton extension. Both the random-oriented and aligned PHBV nanofibrous scaffolds showed to be good candidates for applications in tissue engineering.

Bioactive surface modification on amide-photografted poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Collagen was chemically immobilized on poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) films via hydrophilic polyacrylamide spacers, aiming to establish the bioactive surface and the inner surface models. The inner surface modified films presented higher wettability than the surface modified films. Wide-angle x-ray diffraction results showed that the d-spacing values of the inner surface model increased compared with those of the surface model, but there was no significant difference between the amide- and collagen-modified PHBV films. The peak melting temperatures of PHBV and the special endotherm around 70 °C were following the order: PHBV > amide-modified PHBV > collagen-modified PHBV. The weight loss of the collagen-modified PHBV (inner surface model) might involve hydrolyzation and mineralization during 360 days of incubation, with a maximum value of 18.24%, while PHBV films did not show significant weight loss. The pH value of the degradation fluids fluctuated in the range of 6.86-7.22, as the initial pH was recorded at 7.20. Based on the surface model, collagen-modified PHBV scaffolds were prepared, which enhanced chondrocyte adhesion and spread on the biomimetic surface. Two surface modification models might develop a protocol with a view to generating a biocompatible and biomechanical scaffold for use in meniscus regeneration.

A Novel Biocompatible Poly (3-hydroxy-co-4-hydroxybutyrate) Blend as a Potential Biomaterial for Tissue Engineering

Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) P(3HB-co-4HB) biopolymer was subjected to a depyrogenation treatment followed by blending with vitamin E (P(3HB-co-4HB)/Vit E blend), collagen (Col blend) or both (P(3HB-co-4HB)/Vit E/Col hybrid blend) to improve its biological performance. The cytocompatibility and pro-inflammatory response to the biopolymer after the treatment and blending were evaluated by cellular responses in vitro. Cell attachment and spreading of murine NIH 3T3 fibroblasts seeded on the films were found to be the highest on the hybrid P(3HB-co-4HB)/Vit E/Col blend film. The P(3HB-co-4HB) blends showed increased cell proliferation and negligible cytotoxicity. The pro-inflammatory cytokines, IL6 and TNF α expression in the murine macrophage cell line J774 A-1 monocyte/macrophage cells cultured on the biopolymer films were assessed by immunoblotting and RT-PCR analyses which revealed that the combined blending strategy was the most effective in reducing the pro-inflammatory activity. The depyrogenated P(3HB-co-4HB) blends significantly extend the range of biomaterials suitable for tissue engineering.

PHBV microspheres--PLGA matrix composite scaffold for bone tissue engineering

Polymer scaffolds, particularly in the form of microspheres, have been employed to support cells growth and deliver drugs or growth factors in tissue engineering. In this study, we have established a scaffold by embedding poly (beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV) microspheres into poly (L-lactic-co-glycolic acid) (PLGA) matrix, according to their different solubility in acetone, with the aim of repairing bone defects. PLGA/PHBV scaffolds had good pore parameters, for example, the porosity of PLGA/30% PHBV scaffold can reach to 81.273 +/- 2.192%. Besides, the pore size distribution of the model was evaluated and the results revealed that the pore size mainly distributed between 50 mum and 200 mum. With increasing the amount of PHBV microspheres, the compressive strength of the PLGA/PHBV scaffold enhanced. The morphology of the hybrid scaffold was rougher than that of pure PLGA scaffold, which had no significant effect on the cell behavior. The in vitro evaluation suggested that the model is suitable as a scaffold for engineering bone tissue, and has the potential for further applications in drug delivery system.