The role of PGS/PCL scaffolds in promoting differentiation of human embryonic stem cells into retinal ganglion cells

Recent trends on polycaprolactone as sustainable polymer-based drug delivery system in the treatment of cancer: Biomedical applications and nanomedicine

The unique properties-such as biocompatibility, biodegradability, bio-absorbability, low cost, easy fabrication, and high versatility-have made polycaprolactone (PCL) the center of attraction for researchers. The derived introduction in this manuscript gives a pretty detailed overview of PCL, so you can first brush up on it. Discussion on the various PCL-based derivatives involves, but is not limited to, poly(ε-caprolactone-co-lactide) (PCL-co-LA), PCL-g-PEG, PCL-g-PMMA, PCL-g-chitosan, PCL-b-PEO, and PCL-g-PU specific properties and their probable applications in biomedicine. This paper has considered examining the differences in the diverse disease subtypes and the therapeutic value of using PCL. Advanced strategies for PCL in delivery systems are also considered. In addition, this review discusses recently patented products to provide a snapshot of recent updates in this field. Furthermore, the text probes into recent advances in PCL-based DDS, for example, nanoparticles, liposomes, hydrogels, and microparticles, while giving special attention to comparing the esters in the delivery of bioactive compounds such as anticancer drugs. Finally, we review future perspectives on using PCL in biomedical applications and the hurdles of PCL-based drug delivery, including fine-tuning mechanical strength/degradation rate, biocompatibility, and long-term effects in living systems.

Fortified electrospun collagen utilizing biocompatible Poly Glycerol Sebacate prepolymer (PGSp) and zink oxide nanoparticles (ZnO NPs) for diabetics wound healing: Physical, biological and animal studies

Collagen, a naturally occurring fibrous protein, is a potential resource of biological materials for tissue engineering and regenerative medicine because it is structurally biocompatible, has low immunogenicity, is biodegradable, and is biomimetic. Numerous studies have documented in the literature how Collagen nanofibers exhibit limited cell adhesion, poor viscosity, and no interior fibril structure. The biomedical industry is using Poly Glycerol Sebacate prepolymer(PGSp), a biodegradable and biocompatible polyester with high adhesion and very viscous appearance, more often. Here, unique electrospun Collagen/PGSp/ZnO/NPs blend nanofibers for skin tissue application were developed and described with varied PGSp percent. Additionally, when ternary blends of Collagen, PGSp, and Zink Oxide Nanoparticles (ZnO NPs) are used, the antibacterial properties of the scaffolds are improved. The bead-free electrospun nanofibers were produced by raising the PGSp concentration to 30%w/w. SEM, EDS, tensile, MTT, FTIR, SDS-page, swelling test, contact-angle, antimicrobial, biodegradation, XRD, and cell attachment procedures were used to characterize the crosslinked nanofibers. The ternary blend nanofibers with a weight ratio of Collagen/PGSp 30%/ZnONPs 1% had higher stress/strain strength (0.25 mm/mm), porosity (563), cell survival, and degradation time. Moreover, after applying for wound healing in diabetic rats, Collagen/PGSp 30%/could be show improving wound healing significantly compared to other groups.

Ciliary neurotrophic factor mediated growth of retinal ganglion cell axons on PGS/PCL scaffolds

Ciliary neurotrophic factor (CNTF) promotes survival and/or differentiation of a variety of neuronal cells including retinal ganglion cells (RGCs). Delivery of CNTF requires a suitable medium capable of mediating diffusion and premature release of CNTF within the target tissue. Polymeric tissue-engineered scaffolds have been readily used as substrates for cell transplantation, expansion, and differentiation and, as carriers of cell growth factors. Their functions to CNTF release for RGC proliferation have remained so far unexplored, especially to CNTF affinity to the scaffold and subsequent RGC fate. Electrospunpoly(glycerol sebacate)/poly(ϵ-caprolactone) (PGS/PCL) biopolymer scaffolds have recently shown promising results in terms of supporting regeneration of RGC neurites. This work explores covalent immobilization of CNTF on PGS/PCL scaffold and the way immobilised CNTF mediates growth of RGC axons on the scaffold. Anex-vivothree-dimensional model of rodent optic nerve on PGS/PCL revealed that RGC explants cultured in CNTF mediated environment increased their neurite extensions after 20 d of cell culture employing neurite outgrowth measurements. The CNTF secretion on PGS/PCL scaffold was found bio-mimicking natural extracellular matrix of the cell target tissue and, consequently, has shown a potential to improve the overall efficacy of the RGC regeneration process.

Hereditary Optic Neuropathies: A Systematic Review on the Interplay between Biomaterials and Induced Pluripotent Stem Cells

Hereditary optic neuropathies (HONs) such as dominant optic atrophy (DOA) and Leber Hereditary Optic Neuropathy (LHON) are mitochondrial diseases characterized by a degenerative loss of retinal ganglion cells (RGCs) and are a cause of blindness worldwide. To date, there are only limited disease-modifying treatments for these disorders. The discovery of induced pluripotent stem cell (iPSC) technology has opened several promising opportunities in the field of HON research and the search for therapeutic approaches. This systematic review is focused on the two most frequent HONs (LHON and DOA) and on the recent studies related to the application of human iPSC technology in combination with biomaterials technology for their potential use in the development of RGC replacement therapies with the final aim of the improvement or even the restoration of the vision of HON patients. To this purpose, the combination of natural and synthetic biomaterials modified with peptides, neurotrophic factors, and other low- to medium-molecular weight compounds, mimicking the ocular extracellular matrices, with human iPSC or iPSC-derived cell retinal progenitors holds enormous potential to be exploited in the near future for the generation of transplantable RGC populations.

A novel biomimetic nanofibrous cardiac tissue engineering scaffold with adjustable mechanical and electrical properties based on poly(glycerol sebacate) and polyaniline

Biomaterial tissue engineering scaffolds play a critical role in providing mechanical support, promoting cells growth and proliferation. However, due to the insulation and inappropriate stiffness of most biomaterials, there is an unmet need to engineer a biomimetic nanofibrous cardiac tissue engineering scaffold with tailorable mechanical and electrical properties. Here, we demonstrate for the first time the feasibility to generate a novel type of biocompatible fibrous scaffolds by blending elastic poly(glycerol sebacate) (PGS) and conductive polyaniline (PANI) with the help of a nontoxic carrier polymer, poly (vinyl alcohol) (PVA). Aligned and random PGS/PANI scaffolds are successfully obtained after electrospinning, cross-linking, water and ethanol wash. Incorporating of different concentrations of PANI into PGS fibers, the fibrous sheets show enhanced conductivity and slower degradation rates while maintaining the favorable hemocompatibility. The elastic modulus of the PGS/PANI scaffolds is in the range of 0.65-2.18 MPa under wet conditions, which is similar to that of natural myocardium. All of these fibrous mats show good cell viability and were able to promote adhesion and proliferation of H9c2 cells. Furthermore, the in vivo host responses of both random and aligned scaffolds confirm their good biocompatibility. Therefore, these PGS/PANI scaffolds have great potential for cardiac tissue engineering.

Effect of static tensile stress on enzymatic degradation of poly(glycerol sebacate)

Poly(glycerol sebacate) (PGS) is an excellent scaffold material in tissue engineering due to good biocompatibility and tunable mechanical properties. The degradation properties of PGS have been primarily explored in static phosphate buffer solution or enzyme solution. It is vital to understand how the tensile stress affect the degradation rate. In this study, PGS was synthetized by melt polycondensation and its properties were characterized. Then an in vitro degradation device which could provide different constant tensile stresses was carefully designed and established, and the enzymatic degradation of PGS was tested under 0-150 kPa at 37°C. It was found that holes of PGS surface arranged almost parallel to each other and perpendicular to the direction of tensile stresses at 100 kPa and 150 kPa after 2-4 days degradation. After 8 days degradation, the ultimate tensile strength (UTS) of PGS at 150 kPa was 0.28 MPa and the elastic modulus was 1.11 MPa, while the UTS of PGS was 0.44 MPa and the elastic modulus was 1.63 MPa before degradation, both of them have significant differences. Hence, the tensile stress and degradation time were proportional to the appear time and size of holes, leading to the decrease of mass loss, UTS and elastic modulus. The relationship between stress and PGS degradation rates was quantitatively described through our degradation experiments, providing guidance for suitable PGS applications in the future.

A review about the role of additives in nerve tissue engineering: growth factors, vitamins, and drugs

Notably the integration of additives such as growth factors, vitamins, and drugs with scaffolds promoted nerve tissue engineering. This study tried to provide a concise review of all these additives that facilitates nerve regeneration. An attempt was first made to provide information on the main principle of nerve tissue engineering, and then to shed light on the effectiveness of these additives on nerve tissue engineering. Our research has shown that growth factors accelerate cell proliferation and survival, while vitamins play an effective role in cell signalling, differentiation, and tissue growth. They can also act as hormones, antioxidants, and mediators. Drugs also have an excellent and necessary effect on this process by reducing inflammation and immune responses. This review shows that growth factors were more effective than vitamins and drugs in nerve tissue engineering. Nevertheless, vitamins were the most commonly used additive in the production of nerve tissue.

Different methods of synthesizing poly(glycerol sebacate) (PGS): A review

Poly(glycerol sebacate) (PGS) is a biodegradable elastomer that has attracted increasing attention as a potential material for applications in biological tissue engineering. The conventional method of synthesis, first described in 2002, is based on the polycondensation of glycerol and sebacic acid, but it is a time-consuming and energy-intensive process. In recent years, new approaches for producing PGS, PGS blends, and PGS copolymers have been reported to not only reduce the time and energy required to obtain the final material but also to adjust the properties and processability of the PGS-based materials based on the desired applications. This review compiles more than 20 years of PGS synthesis reports, reported inconsistencies, and proposed alternatives to more rapidly produce PGS polymer structures or PGS derivatives with tailor-made properties. Synthesis conditions such as temperature, reaction time, reagent ratio, atmosphere, catalysts, microwave-assisted synthesis, and PGS modifications (urethane and acrylate groups, blends, and copolymers) were revisited to present and discuss the diverse alternatives to produce and adapt PGS.

Preparation and characterization of a new bio nanocomposites based poly(glycerol sebacic-urethane) containing nano-clay (Cloisite Na+ ) and its potential application for tissue engineering

Nanocomposites containing clay nanoparticles often present favorable properties such as good mechanical and thermal properties. They frequently have been studied for tissue engineering (TE) and regenerative medicine applications. On the other hand, poly(glycerol sebacate) (PGS), a revolutionary bioelastomer, has exhibited substantial potential as a promising candidate for biomedical application. Here, we present a facile approach to synthesizing stiff, elastomeric nanocomposites from sodium-montmorillonite nano-clay (MMT) in the commercial name of Cloisite Na⁺ and poly(glycerol sebacate urethane) (PGSU). The strong physical interaction between the intercalated Cloisite Na⁺ platelets and PGSU chains resulted in desirable property combinations for TE application to follow. The addition of 5% MMT nano-clay resulted in an over two-fold increase in the tensile modulus, increased the onset thermal decomposition temperature of PGSU matrix by 18°C, and noticeably improved storage modulus of the prepared scaffolds, compared with pure PGSU. As well, Cloisite Na⁺ enhanced the hydrophilicity and water uptake ability of the samples and accelerated the in-vitro biodegradation rate. Finally, in-vitro cell viability assay using L929 mouse fibroblast cells indicated that incorporating Cloisite Na⁺ nanoparticles into the PGSU network could improve the cell attachment and proliferation, rendering the synthesized bioelastomers potentially suitable for TE and regenerative medicine applications.

Neuron-fibrous scaffold interfaces in the peripheral nervous system: a perspective on the structural requirements

The nerves of the peripheral nervous system are not able to effectively regenerate in cases of severe neural injury. This can result in debilitating consequences, including morbidity and lifelong impairments affecting the quality of the patient’s life. Recent findings in neural tissue engineering have opened promising avenues to apply fibrous tissue-engineered scaffolds to promote tissue regeneration and functional recovery. These scaffolds, known as neural scaffolds, are able to improve neural regeneration by playing two major roles, namely, by being a carrier for transplanted peripheral nervous system cells or biological cues and by providing structural support to direct growing nerve fibers towards the target area. However, successful implementation of scaffold-based therapeutic approaches calls for an appropriate design of the neural scaffold structure that is capable of up- and down-regulation of neuron-scaffold interactions in the extracellular matrix environment. This review discusses the main challenges that need to be addressed to develop and apply fibrous tissue-engineered scaffolds in clinical practice. It describes some promising solutions that, so far, have shown to promote neural cell adhesion and growth and a potential to repair peripheral nervous system injuries.

Advances in Electrospun Nerve Guidance Conduits for Engineering Neural Regeneration

Injuries to the peripheral nervous system result in devastating consequences with loss of motor and sensory function and lifelong impairments. Current treatments have largely relied on surgical procedures, including nerve autografts to repair damaged nerves. Despite improvements to the surgical procedures over the years, the clinical success of nerve autografts is limited by fundamental issues, such as low functionality and mismatching between the damaged and donor nerves. While peripheral nerves can regenerate to some extent, the resultant outcomes are often disappointing, particularly for serious injuries, and the ongoing loss of function due to poor nerve regeneration is a serious public health problem worldwide. Thus, a successful therapeutic modality to bring functional recovery is urgently needed. With advances in three-dimensional cell culturing, nerve guidance conduits (NGCs) have emerged as a promising strategy for improving functional outcomes. Therefore, they offer a potential therapeutic alternative to nerve autografts. NGCs are tubular biostructures to bridge nerve injury sites via orienting axonal growth in an organized fashion as well as supplying a supportively appropriate microenvironment. Comprehensive NGC creation requires fundamental considerations of various aspects, including structure design, extracellular matrix components and cell composition. With these considerations, the production of an NGC that mimics the endogenous extracellular matrix structure can enhance neuron–NGC interactions and thereby promote regeneration and restoration of function in the target area. The use of electrospun fibrous substrates has a high potential to replicate the native extracellular matrix structure. With recent advances in electrospinning, it is now possible to generate numerous different biomimetic features within the NGCs. This review explores the use of electrospinning for the regeneration of the nervous system and discusses the main requirements, challenges and advances in developing and applying the electrospun NGC in the clinical practice of nerve injuries.

Laminin-511 and recombinant vitronectin supplementation enables human pluripotent stem cell culture and differentiation on conventional tissue culture polystyrene surfaces in xeno-free conditions

Human pluripotent stem cells (hPSCs) are typically cultivated on extracellular matrix (ECM) protein-coated dishes in xeno-free culture conditions. We supplemented mixed ECM proteins (laminin-511 and recombinant vitronectin, rVT) in culture medium for hPSC culture on conventional polystyrene dishes. Three hPSC cell lines were successfully cultivated on uncoated polystyrene dishes in medium supplemented with optimal conditions of laminin-511 and rVT. Excellent colony shape and colony size as well as high expansion fold of hPSCs were found under these conditions, whereas the colony size was small and poor expansion fold was found solely on L-511-coated dishes. A small portion of L-511 in the culture medium supported hPSC adhesion and prevented the adhesion from being too strong on the uncoated dishes, and rVT in the culture medium further supported adhesion of hPSCs on the dishes by maintaining their pluripotency. Having the optimal composition of L-511 and rVT in the culture medium was important for generating good hPSC colony shapes and sizes as well as a high expansion fold. After long-term culture of hPSCs on uncoated dishes supplemented with the mixed proteins, the hPSCs successfully showed pluripotent markers and could differentiate into a specific lineage of cells, cardiomyocytes, with high efficiency.