Simultaneous dual syringe electrospinning system using benign solvent to fabricate nanofibrous P(3HB-co-4HB)/collagen peptides construct as potential leave-on wound dressing

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.

Dual-jet electrospun PDLGA/PCU nonwovens as promising mesh implant materials with controlled release of sirolimus and diclofenac

Dual-jet electrospinning was employed to produce two-component, partially degradable drug releasing nonwovens with interlacing of poly(D,L-lactide-co-glycolide) (PDLGA) and different poly(carbonate urethanes) (PCUs). Diclofenac sodium and sirolimus were released simultaneously from the copolyester carrier. The research focused on determining of release profiles of drugs, depending on the hydrophilicity of introduced PCU nanofibers. The influence of drugs incorporation on the hydrolytic degradation of the PDLGA and mechanical properties of nonwovens was also studied. Evaluation for interaction with cells in vitro was investigated on a fibroblast cell line in cytotoxicity and surface adhesion tests. Significant changes in drugs release rate, depending on the applied PCU were observed. It was also noticed, that hydrophilicity of drugs significantly influenced the hydrolytic degradation mechanism and surface erosion of the PDLGA, as well as the tensile strength of nonwovens. Tests carried out on cells in an in vitro experiment showed that introduction of sirolimus caused a slight reduction in the viability of fibroblasts as well as a strong limitation in their capability to colonize the surface of fibers. Due to improvement of mechanical strength and the ability to controlled drugs release, the obtained material may be considered as prospect surgical mesh implant in the treatment of hernia.

Biomedical Applications of Polyhydroxyalkanoate in Tissue Engineering

Tissue engineering technology aids in the regeneration of new tissue to replace damaged or wounded tissue. Three-dimensional biodegradable and porous scaffolds are often utilized in this area to mimic the structure and function of the extracellular matrix. Scaffold material and design are significant areas of biomaterial research and the most favorable material for seeding of in vitro and in vivo cells. Polyhydroxyalkanoates (PHAs) are biopolyesters (thermoplastic) that are appropriate for this application due to their biodegradability, thermo-processability, enhanced biocompatibility, mechanical properties, non-toxicity, and environmental origin. Additionally, they offer enormous potential for modification through biological, chemical and physical alteration, including blending with various other materials. PHAs are produced by bacterial fermentation under nutrient-limiting circumstances and have been reported to offer new perspectives for devices in biological applications. The present review discusses PHAs in the applications of conventional medical devices, especially for soft tissue (sutures, wound dressings, cardiac patches and blood vessels) and hard tissue (bone and cartilage scaffolds) regeneration applications. The paper also addresses a recent advance highlighting the usage of PHAs in implantable devices, such as heart valves, stents, nerve guidance conduits and nanoparticles, including drug delivery. This review summarizes the in vivo and in vitro biodegradability of PHAs and conducts an overview of current scientific research and achievements in the development of PHAs in the biomedical sector. In the future, PHAs may replace synthetic plastics as the material of choice for medical researchers and practitioners.

Dual-jet electrospun PDLGA/PCU nonwovens and their mechanical and hydrolytic degradation properties

A dual-jet electrospinning was used to mix a different hydrophilicity poly(carbonate urethanes) (PCUs) nanofibers with a biodegradable poly(D,L-lactide-co-glycolide) (PDLGA) copolyester microfibers. As a result, PDLGA/PCU partially degradable nonwovens consisting of an interlaced of both components fibers were obtained. In order to examine the hydrolytic degradation process of polyester fraction, as well as changes that occurred in the mechanical properties of the whole nonwovens, gel permeation chromatography, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry and scanning electron microscopy as well as static tensile test were performed. Obtained results showed that for the introduction of more hydrophobic PCU nanofibers (ChronoSil), the process of copolyester chain scission slowed down and the erosion mechanism proceeded in bulk. Unexpectedly, even greater deceleration of PDLGA fibers degradation was observed in case of more hydrophilic PCU (HydroThane), and erosion mechanism changed to surface. Enhancement the affinity of the whole nonwoven to the water, manifested by strong water uptake, facilitated the diffusion processes of both: water and acid degradation by-products, which limited autocatalysis reactions of the hydrolysis of ester bonds. On the other hand, strength tests showed the synergy in the mechanical characteristics of both components. Presented method allows influencing the mechanism and rate of polyester degradation without changing its chemical composition and physical properties, affecting only the physical interactions between the nonwoven and the degradation environment, and thus, on diffusion processes. Obtained partially degradable materials possessed also time prolonged functional properties, compared to the copolyester-only nonwoven itself, thus could be considered as promising for biomedical applications e.g. in drug release systems, implants or surgical meshes for supporting soft tissues.

Collagen-Based Nanofibers for Skin Regeneration and Wound Dressing Applications

Skin regeneration after an injury is very vital, but this process can be impeded by several factors. Regenerative medicine is a developing biomedical field with the potential to decrease the need for an organ transplant. Wound management is challenging, particularly for chronic injuries, despite the availability of various types of wound dressing scaffolds in the market. Some of the wound dressings that are in clinical practice have various drawbacks such as poor antibacterial and antioxidant efficacy, poor mechanical properties, inability to absorb excess wound exudates, require frequent change of dressing and fails to offer a suitable moist environment to accelerate the wound healing process. Collagen is a biopolymer and a major constituent of the extracellular matrix (ECM), making it an interesting polymer for the development of wound dressings. Collagen-based nanofibers have demonstrated interesting properties that are advantageous both in the arena of skin regeneration and wound dressings, such as low antigenicity, good biocompatibility, hemostatic properties, capability to promote cellular proliferation and adhesion, and non-toxicity. Hence, this review will discuss the outcomes of collagen-based nanofibers reported from the series of preclinical trials of skin regeneration and wound healing.

Multifunctional, Robust, and Porous PHBV-GO/MXene Composite Membranes with Good Hydrophilicity, Antibacterial Activity, and Platelet Adsorption Performance

The limitations of hydrophilicity, strength, antibacterial activity adsorption performance of the biobased and biocompatible polymer materials, such as polyhydroxyalkanoates (PHAs), significantly restrict their wider applications especially in medical areas. In this paper, a novel composite membrane with high antibacterial activity and platelet adsorption performance was prepared based on graphene oxide (GO), MXene and 3-hydroxybutyrate-co-hydroxyvalerate (PHBV), which are medium-chain-length-copolymers of PHA. The GO/MXene nanosheets can uniformly inset on the surface of PHBV fibre and give the PHBV—GO/MXene composite membranes superior hydrophilicity due to the presence of hydroxyl groups and terminal oxygen on the surface of nanosheets, which further provides the functional site for the free radical polymerization of ester bonds between GO/MXene and PHBV. As a result, the tensile strength, platelet adsorption, and blood coagulation time of the PHBV—GO/MXene composite membranes were remarkably increased compared with those of the pure PHBV membranes. The antibacterial rate of the PHBV—GO/MXene composite membranes against gram-positive and gram-negative bacteria can reach 97% due to the antibacterial nature of MXene. The improved strength, hydrophilicity, antibacterial activity and platelet adsorption performance suggest that PHBV—GO/MXene composite membranes might be ideal candidates for multifunctional materials for haemostatic 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.

Peptide-Based Electrospun Fibers: Current Status and Emerging Developments

Electrospinning is a well-known, straightforward, and versatile technique, widely used for the preparation of fibers by electrifying a polymer solution. However, a high molecular weight is not essential for obtaining uniform electrospun fibers; in fact, the primary criterion to succeed is the presence of sufficient intermolecular interactions, which function similar to chain entanglements. Some small molecules able to self-assemble have been electrospun from solution into fibers and, among them, peptides containing both natural and non-natural amino acids are of particular relevance. Nowadays, the use of peptides for this purpose is at an early stage, but it is gaining more and more interest, and we are now witnessing the transition from basic research towards applications. Considering the novelty in the relevant processing, the aim of this review is to analyze the state of the art from the early 2000s on. Moreover, advantages and drawbacks in using peptides as the main or sole component for generating electrospun nanofibers will be discussed. Characterization techniques that are specifically targeted to the produced peptide fibers are presented.

Surface-Modified Highly Biocompatible Bacterial-poly(3-hydroxybutyrate-co-4-hydroxybutyrate): A Review on the Promising Next-Generation Biomaterial

Polyhydroxyalkanoates (PHAs) are bacteria derived bio-based polymers that are synthesised under limited conditions of nutritional elements with excess carbon sources. Among the members of PHAs, poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [(P(3HB-co-4HB)] emerges as an attractive biomaterial to be applied in medical applications owing to its desirable mechanical and physical properties, non-genotoxicity and biocompatibility eliciting appropriate host tissue responses. The tailorable physical and chemical properties and easy surface functionalisation of P(3HB-co-4HB) increase its practicality to be developed as functional medical substitutes. However, its applicability is sometimes limited due to its hydrophobic nature due to fewer bio-recognition sites. In this review, we demonstrate how surface modifications of PHAs, mainly P(3HB-co-4HB), will overcome these limitations and facilitate their use in diverse medical applications. The integration of nanotechnology has drastically enhanced the functionality of P(3HB-co-4HB) biomaterials for application in complex biological environments of the human body. The design of versatile P(3HB-co-4HB) materials with surface modifications promise a non-cytotoxic and biocompatible material without inducing severe inflammatory responses for enhanced effective alternatives in healthcare biotechnology. The enticing work carried out with P(3HB-co-4HB) promises to be one of the next-generation materials in biomedicines which will facilitate translation into the clinic in the future.

Elucidating the Surface Functionality of Biomimetic RGD Peptides Immobilized on Nano-P(3HB-co-4HB) for H9c2 Myoblast Cell Proliferation

Biomaterial scaffolds play crucial role to promote cell proliferation and foster the regeneration of new tissues. The progress in material science has paved the way for the generation of ingenious biomaterials. However, these biomaterials require further optimization to be effectively used in existing clinical treatments. It is crucial to develop biomaterials which mimics structure that can be actively involved in delivering signals to cells for the formation of the regenerated tissue. In this research we nanoengineered a functional scaffold to support the proliferation of myoblast cells. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] copolymer is chosen as scaffold material owing to its desirable mechanical and physical properties combined with good biocompatibility, thus eliciting appropriate host tissue responses. In this study P(3HB-co-4HB) copolymer was biosynthesized using Cupriavidus malaysiensis USMAA1020 transformant harboring additional PHA synthase gene, and the viability of a novel P(3HB-co-4HB) electrospun nanofiber scaffold, surface functionalized with RGD peptides, was explored. In order to immobilize RGD peptides molecules onto the P(3HB-co-4HB) nanofibers surface, an aminolysis reaction was performed. The nanoengineered scaffolds were characterized using SEM, organic elemental analysis (CHN analysis), FTIR, surface wettability and their in vitro degradation behavior was evaluated. The cell culture study using H9c2 myoblast cells was conducted to assess the in vitro cellular response of the engineered scaffold. Our results demonstrated that nano-P(3HB-co-4HB)-RGD scaffold possessed an average fiber diameter distribution between 200 and 300 nm, closely biomimicking, from a morphological point of view, the structural ECM components, thus acting as potential ECM analogs. This study indicates that the surface conjugation of biomimetic RGD peptide to the nano-P(3HB-co-4HB) fibers increased the surface wettability (15 ± 2°) and enhanced H9c2 myoblast cells attachment and proliferation. In summary, the study reveals that nano-P(3HB-co-4HB)-RGD scaffold can be considered a promising candidate to be further explored as cardiac construct for building cardiac construct.

Recent Development in the Fabrication of Collagen Scaffolds for Tissue Engineering Applications: A Review

Tissue engineering focuses on developing biological substitutes to restore, maintain or improve tissue functions. The three main components of its application are scaffold, cell and growthstimulating signals. Scaffolds composed of biomaterials mainly function as the structural support for ex vivo cells to attach and proliferate. They also provide physical, mechanical and biochemical cues for the differentiation of cells before transferring to the in vivo site. Collagen has been long used in various clinical applications, including drug delivery. The wide usage of collagen in the clinical field can be attributed to its abundance in nature, biocompatibility, low antigenicity and biodegradability. In addition, the high tensile strength and fibril-forming ability of collagen enable its fabrication into various forms, such as sheet/membrane, sponge, hydrogel, beads, nanofibre and nanoparticle, and as a coating material. The wide option of fabrication technology together with the excellent biological and physicochemical characteristics of collagen has stimulated the use of collagen scaffolds in various tissue engineering applications. This review describes the fabrication methods used to produce various forms of scaffolds used in tissue engineering applications.

Data on the effect of electrospinning parameters on the morphology of the nanofibrous poly(3-hydroxybutyrate-co-4-hydroxybutyrate) scaffolds

Electrospinning is a promising approach to fabricate desirable electropsun nanofibrous scaffold that could be applied in the medical fields. In this study, bacterial copolymer poly(3-hydroxybutyrate-co-68 mol% 4-hydroxybutyrate) [P(3HB-co-68mol% 4HB)] copolymer produced was fabricated into electrospun nanofibers using various combination of electrospinning parameters including the polymer solution, applied voltage and injection speed. The morphology of the fabricated scaffolds were observed using scanning electron microscope (SEM). The SEM images were analysed for the fibre diameter distribution of the scaffolds using Image Analyser. The results revealed that the 8 wt% of polymer solution, 25 kV/cm of the applied voltage and 1.5 mL/h of the injection speed was the most suitable combination. This electrospinning parameters combination fabricated nanofibrous P(3HB-co-4HB) scaffold with smooth, beadles and uniform nanofibers with small fibre diameter distribution.

Recent Progress in Polyhydroxyalkanoates-Based Copolymers for Biomedical Applications

In recent years, naturally biodegradable polyhydroxyalkanoate (PHA) monopolymers have become focus of public attentions due to their good biocompatibility. However, due to its poor mechanical properties, high production costs, and limited functionality, its applications in materials, energy, and biomedical applications are greatly limited. In recent years, researchers have found that PHA copolymers have better thermal properties, mechanical processability, and physicochemical properties relative to their homopolymers. This review summarizes the synthesis of PHA copolymers by the latest biosynthetic and chemical modification methods. The modified PHA copolymer could greatly reduce the production cost with elevated mechanical or physicochemical properties, which can further meet the practical needs of various fields. This review further summarizes the broad applications of modified PHA copolymers in biomedical applications, which might shred lights on their commercial applications.

Collagen Type I: A Versatile Biomaterial

Collagen type I is the most abundant matrix protein in the human body and is highly demanded in tissue engineering, regenerative medicine, and pharmaceutical applications. To meet the uprising demand in biomedical applications, collagen type I has been isolated from mammalians (bovine, porcine, goat and rat) and non-mammalians (fish, amphibian, and sea plant) source using various extraction techniques. Recent advancement enables fabrication of collagen scaffolds in multiple forms such as film, sponge, and hydrogel, with or without other biomaterials. The scaffolds are extensively used to develop tissue substitutes in regenerating or repairing diseased or damaged tissues. The 3D scaffolds are also used to develop in vitro model and as a vehicle for delivering drugs or active compounds.

Designing Novel Interfaces via Surface Functionalization of Short-Chain-Length Polyhydroxyalkanoates

Polyhydroxyalkanoates (PHA), a microbial plastic has emerged as promising biomaterial owing to the broad range of mechanical properties. However, some studies revealed that PHA is hydrophobic and has no recognition site for cell attachment and this is often a limitation in tissue engineering aspects. Owing to this, the polymer is tailored accordingly in order to enhance the biocompatibilityin vivoas well as to suit the intended application. Thus far, these surface modifications have led to PHA being widely used in various biomedical and pharmaceutical applications such as cardiac patches, wound management, nerve, bone, and cartilage repair. This review addresses the surface modification on biomedical applications focusing on short-chain-length PHA such as poly(3-hydroxybutyrate) [P(3HB)], poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)].

Elicited ROS Scavenging Activity, Photoprotective, and Wound-Healing Properties of Collagen-Derived Peptides from the Marine Sponge Chondrosia reniformis

Recently, the bioactive properties of marine collagen and marine collagen hydrolysates have been demonstrated. Although there is some literature assessing the general chemical features and biocompatibility of collagen extracts from marine sponges, no data are available on the biological effects of sponge collagen hydrolysates for biomedical and/or cosmetic purposes. Here, we studied the in vitro toxicity, antioxidant, wound-healing, and photoprotective properties of four HPLC-purified fractions of trypsin-digested collagen extracts-marine collagen hydrolysates (MCHs)-from the marine sponge C. reniformis. The results showed that the four MCHs have no degree of toxicity on the cell lines analyzed; conversely, they were able to stimulate cell growth. They showed a significant antioxidant activity both in cell-free assays as well as in H₂O₂ or quartz-stimulated macrophages, going from 23% to 60% of reactive oxygen species (ROS) scavenging activity for the four MCHs. Finally, an in vitro wound-healing test was performed with fibroblasts and keratinocytes, and the survival of both cells was evaluated after UV radiation. In both experiments, MCHs showed significant results, increasing the proliferation speed and protecting from UV-induced cell death. Overall, these data open the way to the use of C. reniformis MCHs in drug and cosmetic formulations for damaged or photoaged skin repair.

Acute and repeated dose 28-day oral toxicity of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) nanoparticles in Sprague-Dawley rats

This study aimed to investigate the oral acute and subacute toxicity of Poly [3-hydroxybutyrate-co-4-hydroxybutyrate], P(3HB-co-4HB) in the form of nanoparticles in Sprague-Dawley rats. Acute oral administration of P(3HB-co-4HB) nanoparticles was performed as a single dose up to 2000 mg/kg in six female rats for 14 days. Subacute toxicity study via oral administration for 28 days at doses of 0 (control), 500, 1000 and 2000 mg/kg in rats (10 rats in each group, female:male = 1:1) was conducted. The estimated lethal dose (LD₅₀) of P(3HB-co-4HB) nanoparticles was >2000 mg/kg. No mortality, unusual changes in behaviour, adverse clinical signs, abnormal changes in body weights or food consumption were observed on all animals treated with P(3HB-co-4HB) nanoparticles during 14 days of the acute toxicity study. In the subacute test, there was no mortality and toxicologically significant changes in clinical signs, body weights, food consumption, hematology, clinical biochemistry, urinalysis, macroscopic findings, organ weights as well as histopathological examination were observed.

En route to economical eco-friendly solvent system in enhancing sustainable recovery of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) copolymer

Separation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] from bacterial cell matter is a critical step in the downstream process with respect to material quality and eco-balance as P(3HB-co-4HB) is widely used for biomedical applications. Therefore, an efficient and eco-based extraction of P(3HB-co-4HB) using a combination of NaOH and Lysol in digesting the non-polymeric cell material (NPCM) digestion is developed. The NaOH and Lysol show synergistic influence on the copolymer extraction at a high purity and recovery of 97 and 98 wt% respectively. The optimized cell digestion method was found applicable to a vast batch of cells containing copolymers from various 4HB monomer compositions. At the largest extraction volume of 100 L, P(3HB-co-4HB) with a purity of 89 wt% was extracted with a maximum recovery of 90 wt%. The method developed has also eliminated the cell pretreatment step. The extraction method developed in this research has not only produced an economic and efficient copolymer recovery but has also retained the copolymer quality, in term of its molecular weight and thermal properties. It demonstrates a practical and promising downstream processing method in recovering the copolymer effectively from the bacterial biomass.

Manufacture and property research of heparin grafted electrospinning PCU artificial vascular scaffolds

PCU (polycarbonate polyurethane) is supposed to be an ideal elastomer for manufacturing artificial vessel scaffold with perfect mechanical strength and biocompatibility. Surface grafting by heparin sodium can increase its anticoagulant hemorrhagic, achieving a better application in artificial vessels. Artificial vessels were preliminarily prepared by electrostatic spinning, treated by NH₃ plasma and cross-linked with the anticoagulant heparin sodium chemically. Performances of the PCU-Hep (heparin sodium grafted purethane artificial vessels) artificial vessel were calculated through the physical and chemical property tests, evaluation of blood and biocompatibility. Results manifested that heparin sodium was successfully grafted to the vascular surface, porosity, pore diameter and water permeability of the vascular prosthesis fitted the requirements of artificial vessels, the blood test results demonstrated that the vascular material had a low hemolysis, in vitro cytotoxicity experiment and animal experiments proved an excellent biocompatibility. Thus the heparin sodium grafted electrospinning vessels could reduce intravascular thrombus and had potential clinical application.

A Review of the Latest Advances in Encrypted Bioactive Peptides from Protein-Rich Waste

Bioactive peptides are considered the new generation of biologically active regulators that not only prevent the mechanism of oxidation and microbial degradation in foods but also enhanced the treatment of various diseases and disorders, thus increasing quality of life. This review article emphasizes recent advances in bioactive peptide technology, such as: (i) new strategies for transforming bioactive peptides from residual waste into added-value products; (ii) nanotechnology for the encapsulation, protection and release of controlled peptides; and (iii) use of techniques of large-scale recovery and purification of peptides aiming at future applications to pharmaceutical and food industries.