Preparation and modeling of electrospun polyhydroxybutyrate/polyaniline composite scaffold modified by plasma and printed by an inkjet method and its cellular study

Polyhydroxyalkanoates: the natural biopolyester for future medical innovations

Polyhydroxyalkanoates (PHAs) are a family of natural microbial biopolyesters with the same basic chemical structure and diverse side chain groups. Based on their excellent biodegradability, biocompatibility, thermoplastic properties and diversity, PHAs are highly promising medical biomaterials and elements of medical devices for applications in tissue engineering and drug delivery. However, due to the high cost of biotechnological production, most PHAs have yet to be applied in the clinic and have only been studied at laboratory scale. This review focuses on the biosynthesis, diversity, physical properties, biodegradability and biosafety of PHAs. We also discuss optimization strategies for improved microbial production of commercial PHAs via novel synthetic biology tools. Moreover, we also systematically summarize various medical devices based on PHAs and related design approaches for medical applications, including tissue repair and drug delivery. The main degradation product of PHAs, 3-hydroxybutyrate (3HB), is recognized as a new functional molecule for cancer therapy and immune regulation. Although PHAs still account for only a small percentage of medical polymers, up-and-coming novel medical PHA devices will enter the clinical translation stage in the next few years.

Stem Cell Scaffolds for the Treatment of Spinal Cord Injury-A Review

Spinal cord injury (SCI) is a profoundly debilitating yet common central nervous system condition resulting in significant morbidity and mortality rates. Major causes of SCI encompass traumatic incidences such as motor vehicle accidents, falls, and sports injuries. Present treatment strategies for SCI aim to improve and enhance neurologic functionality. The ability for neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the investigation of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities including composite materials, natural polymers, synthetic polymers, and hydrogels have been explored. However, most trials remain largely in the preclinical stage, emphasizing the need to further develop and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation, including substrates and signaling pathways required for axonal regrowth post-injury, and provide an overview of current and emerging stem cell scaffolding platforms for SCI.

Polyhydroxybutyrate (PHB) Scaffolds for Peripheral Nerve Regeneration: A Systematic Review of Animal Models

Simple Summary

Currently, polymeric biomaterials are the choice for the design of scaffolds for the regeneration of peripheral nerves. Polyhydroxybutyrate (PHB) is a polymer belonging to the class of polyesters that are produced naturally in nature by microorganisms. To gain a better understanding of the efficacy of therapeutic approaches involving PHB scaffolds for peripheral nerve regeneration, we conducted a systematic review of the literature with the aim of discussing the current knowledge of PHB scaffolds applied to nerve regeneration. The use of PHB as a biomaterial to prepare tubular scaffolds for nerve regeneration was shown to be promising. The incorporation of additives appears to be a trend that improves nerve regeneration.

Abstract

In the last two decades, artificial scaffolds for nerve regeneration have been produced using a variety of polymers. Polyhydroxybutyrate (PHB) is a natural polyester that can be easily processed and offer several advantages; hence, the purpose of this review is to provide a better understanding of the efficacy of therapeutic approaches involving PHB scaffolds in promoting peripheral nerve regeneration following nerve dissection in animal models. A systematic literature review was performed following the “Preferred Reporting Items for Systematic Reviews and Meta-Analyses” (PRISMA) criteria. The revised databases were: Pub-Med/MEDLINE, Web of Science, Science Direct, EMBASE, and SCOPUS. Sixteen studies were included in this review. Different animal models and nerves were studied. Extension of nerve gaps reconnected by PHB scaffolds and the time periods of analysis were varied. The additives included in the scaffolds, if any, were growth factors, neurotrophins, other biopolymers, and neural progenitor cells. The analysis of the quality of the studies revealed good quality in general, with some aspects that could be improved. The analysis of the risk of bias revealed several weaknesses in all studies. The use of PHB as a biomaterial to prepare tubular scaffolds for nerve regeneration was shown to be promising. The incorporation of additives appears to be a trend that improves nerve regeneration. One of the main weaknesses of the reviewed articles was the lack of standardized experimentation on animals. It is recommended to follow the currently available guidelines to improve the design, avoid the risk of bias, maximize the quality of studies, and enhance translationality.

Scaffolds the backbone of tissue engineering: Advancements in use of polyhydroxyalkanoates (PHA)

Our body is built to heal from inside out naturally but wide-ranging medical conditions necessitate the need for artificial assistance, and therefore, something that can assist the body to heal wounds and damaged tissues quickly and efficiently is of utmost importance. Tissue engineering technology helps to regenerate new tissue to replace the diseased or injured one. The technology uses biodegradable porous three-dimensional scaffolds for mimicking the structure and functions of the natural extracellular matrix. The material and design of scaffolds are critical areas of biomaterial research. Biomaterial-based three-dimensional structures have been the most promising material to serve as scaffolds for seeding cells, both in vivo and in vitro. One such material is polyhydroxyalkanoates (PHAs) which are thermoplastic biopolyesters that are highly suitable for this purpose due to their enhanced biocompatibility, biodegradability, thermo-processability, diverse mechanical properties, non-toxicity and natural origin. Moreover, they have tremendous possibilities of customization through biological physical and chemical modification as well as blending with other materials. They are being used for several tissue engineering applications such as bone graft substitute, cardiovascular patches, stents, for nerve repair and in implantology as valves and sutures. The present review overviews usage of a multitude of PHA-based biomaterials for a wide range of tissue engineering applications, based on their properties suitable for the specific applications.

Review of Hybrid Materials Based on Polyhydroxyalkanoates for Tissue Engineering Applications

This review is focused on hybrid polyhydroxyalkanoate-based (PHA) biomaterials with improved physico-mechanical, chemical, and piezoelectric properties and controlled biodegradation rate for applications in bone, cartilage, nerve and skin tissue engineering. PHAs are polyesters produced by a wide range of bacteria under unbalanced growth conditions. They are biodegradable, biocompatible, and piezoelectric polymers, which make them very attractive biomaterials for various biomedical applications. As naturally derived materials, PHAs have been used for multiple cell and tissue engineering applications; however, their widespread biomedical applications are limited due to their lack of toughness, elasticity, hydrophilicity and bioactivity. The chemical structure of PHAs allows them to combine with other polymers or inorganic materials to form hybrid composites with improved structural and functional properties. Their type (films, fibers, and 3D printed scaffolds) and properties can be tailored with fabrication methods and materials used as fillers. Here, we are aiming to fill in a gap in literature, revealing an up-to-date overview of ongoing research strategies that make use of PHAs as versatile and prospective biomaterials. In this work, a systematic and detailed review of works investigating PHA-based hybrid materials with tailored properties and performance for use in tissue engineering applications is carried out. A literature survey revealed that PHA-based composites have better performance for use in tissue regeneration applications than pure PHA.

Regulated Surface Morphology of Polyaniline/Polylactic Acid Composite Nanofibers via Various Inorganic Acids Doping for Enhancing Biocompatibility in Tissue Engineering

Conductive and degradable nanofibrous scaffolds have great potential in promoting cell growth, proliferation, and differentiation under an external electric field. Although the issue of inferior electrical conductivity in body fluids still exists, polyaniline (PANI)-based degradable nanofibers can promote cell adhesion, growth, and proliferation. To investigate whether the effect is caused by the PANI morphology, we selected three inorganic acids as dopants in the process of PANI in situ oxidative polymerization: hydrochloric acid, sulfuric acid, and perchloric acid. The obtained polyaniline/polylactic acid (PANI/PLA) composite nanofibers were characterized via SEM, FTIR, and XPS analysis, and we confirmed that the PLA nanofibers were successfully coated by PANI without any change to the porous structure of the PLA nanofibers. The in vitro mechanical properties and degradability indicated that the oxidation of acid dopants should be considered and that it was likely to have a higher oxidation degradation effect on PLA nanofibers. The contact angle test demonstrated that PANI/PLA composite nanofibers with different surface morphologies have good wettability, implying that they meet the requirements of bone tissue engineering scaffolds. The surface roughness and cell viability demonstrated that different PANI morphologies on the surface can promote cell proliferation. The higher the surface roughness of the PANI, the better the biocompatibility. Consequently, the regulated surface morphology of PANI/PLA composite nanofibers via different acids doping has positive effect on biocompatibility in tissue engineering.