Electrospun polymer biomaterials

Mesenchymal stem cells for cartilage regeneration

Cartilage injuries are typically caused by trauma, chronic overload, and autoimmune diseases. Owing to the avascular structure and low metabolic activities of chondrocytes, cartilage generally does not self-repair following an injury. Currently, clinical interventions for cartilage injuries include chondrocyte implantation, microfracture, and osteochondral transplantation. However, rather than restoring cartilage integrity, these methods only postpone further cartilage deterioration. Stem cell therapies, especially mesenchymal stem cell (MSCs) therapies, were found to be a feasible strategy in the treatment of cartilage injuries. MSCs can easily be isolated from mesenchymal tissue and be differentiated into chondrocytes with the support of chondrogenic factors or scaffolds to repair damaged cartilage tissue. In this review, we highlighted the full success of cartilage repair using MSCs, or MSCs in combination with chondrogenic factors and scaffolds, and predicted their pros and cons for prospective translation to clinical practice.

Bowlin G. Characterization of Polydioxanone in Near-Field Electrospinning

Electrospinning is a popular method for creating random, non-woven fibrous templates for biomedical applications, and a subtype technique termed near-field electrospinning (NFES) was devised by reducing the air gap distance to millimeters. This decreased working distance paired with precise translational motion between the fiber source and collector allows for the direct writing of fibers. We demonstrate a near-field electrospinning device designed from a MakerFarm Prusa i3v three-dimensional (3D) printer to write polydioxanone (PDO) microfibers. PDO fiber diameters were characterized over the processing parameters: Air gap, polymer concentration, translational velocity, needle gauge, and applied voltage. Fiber crystallinity and individual fiber uniformity were evaluated for the polymer concentration and translational fiber deposition velocity. Fiber stacking was evaluated for the creation of 3D templates to guide the alignment of human gingival fibroblasts. The fiber diameters correlated positively with polymer concentration, applied voltage, and needle gauge; and inversely correlated with translational velocity and air gap distance. Individual fiber diameter variability decreases, and crystallinity increases with increasing translational fiber deposition velocity. These data resulted in the creation of tailored PDO 3D templates, which guided the alignment of primary human fibroblast cells. Together, these results suggest that NFES of PDO can be scaled to create precise geometries with tailored fiber diameters for biomedical applications.

Molecular recognition-directed site-specific release of stem cell differentiation inducers for enhanced joint repair

The remarkable difference in cell type and matrix composition between two connected parts of a joint (cartilage and subchondral bone) makes it challenging to simultaneously regenerate both parts for joint repair. Thus we chemically designed a biphasic hydrogel made of two well-bonded shape-tunable hydrogel phases, termed bone-regenerating hydrogel (BRH) and cartilage-regenerating hydrogel (CRH). The BRH and CRH, encapsulating stem cells, were produced by photo-crosslinking bone and cartilage matrix-mimicking biopolymers and a nanobox (β-cyclodextrin) in situ in the subchondral bone defect and cartilage defect, respectively. The nanoboxes in BRH and CRH were loaded with osteogenic and chondrogenic differentiation inducers (melatonin and kartogenin) by host-guest interactions, respectively. Such interactions directed the sustained phase- and defect site-specific release of the inducers and subsequent site-specific stem cell differentiation into cartilage and bone forming cells for joint repair. The strategy opens up a new chemical approach to biomaterials with phase-specific drug release for tissue repair.

Bisphosphonate-Functionalized Scaffolds for Enhanced Bone Regeneration

The local sustained release of bioactive substances are attracting increasing attention in bone tissue engineering, which is beneficial to bone tissue formation and helps to improve the bone ingrowth ability of a scaffold. Bisphosphonates (BPs), as a representative kind of osteoclast inhibitors, are proven to possess excellent osteogenic induction capability. Accordingly, various physical and chemical strategies are developed to functionalize bone tissue scaffolds with BPs to achieve controlled release profiles. Compared with traditional treatment modalities, local release of BPs from these composite scaffolds will contribute to continuous bone integration without the risk of many complications. This review explores the molecular mechanisms of BPs on bone metabolism and analyzes the appropriate concentrations of BPs that promote bone regeneration. The advanced BP loading strategies, implant modification technologies, and BP-loaded composite scaffolds based on different matrices are summarized. Finally, the latest advances and the future development of BP-modified scaffolds for enhanced bone regeneration are discussed. This article provides leading-edge design strategies of the BP-functionalized bone engineering scaffolds for improved bone repairability.

Poly(lactic-co-glycolic acid)-bioactive glass composites as nanoporous scaffolds for bone tissue engineering: In vitro and in vivo studies

The aim of the present study was to investigate the feasibility of using composite scaffolds of poly(lactic-co-glycolic acid) (PLGA) and bioactive glass (BG) to repair bone defects. PLGA/BG composite scaffolds were prepared by thermally-induced phase separation. Scanning electron microscopy (SEM) was used to study the morphology, and liquid (absolute ethanol) replacement was used to calculate the porosity of the scaffold. The biocompatibility and degradation of the scaffold were determined using human osteosarcoma cell line MG-63 and animal experiments. SEM showed that the scaffold had a nanofibrous three-dimensional network structure with a fiber diameter of 160-320 nm, a pore size of 1-7 µm, and a porosity of 93.048±0.121%. The scaffold structure was conducive to cell adhesion and proliferation. It promoted cell osteogenesis and could be stably degraded in vivo.

Electroactive composite scaffold with locally expressed osteoinductive factor for synergistic bone repair upon electrical stimulation

Tissue engineering is a promising strategy for the repair of large-scale bone defects, in which scaffolds and growth factors are two critical issues influencing the efficacy of bone regeneration. Unfortunately, the broad application of growth factors is limited by their poor stability in the scaffolds. In the present study, the strictly controlled expression of human bone morphogenetic protein-4 (hBMP-4) in the presence of doxycycline is achieved by adding an hBMP-4 gene fragment into a non-viral artificial restructuring plasmid vector (pSTAR) to form the pSTAR-hBMP-4 plasmid (phBMP-4). Furthermore, the controlled release of phBMP-4 is obtained with an electroactive tissue engineering scaffold, generated by combining a triblock copolymer of poly(l-lactic acid)-block-aniline pentamer-block-poly(l-lactic acid) (PLA-AP) with poly(lactic-co-glycolic acid)/hydroxyapatite (PLGA/HA). This PLGA/HA/PLA-AP/phBMP-4 composite scaffold, with controlled gene release and Dox-regulated gene expression upon electrical stimulation, operating synergistically, exhibits an improved cell proliferation ability, enhanced osteogenesis differentiation in vitro, and effective bone healing in vivo in a rabbit radial defect model. Taking these results together, the proposed smart PLGA/HA/PLA-AP/phBMP-4 scaffold lays a solid theoretical and experimental basis for future applications of such multi-functional materials in bone tissue engineering to help patients in need.

Photocrosslinking maleilated hyaluronate/methacrylated poly (vinyl alcohol) nanofibrous mats for hydrogel wound dressings

Although electrospinning of nanofibrous scaffolds benefit to wound healing have been developed at a fast pace, achieving nanofibrous scaffolds with high absorptivity by green electrospinning and crosslinking techniques is still a great challenge. Here, we developed a maleilated hyaluronate/methacrylated poly (vinyl alcohol) (MHA) (MaPVA) composite nanofibers by electrospinning from pure water solvent and followed by photopolymerization to form crosslinking nanofibers network. Electrospinnability of MHA/MaPVA blend systems were investigated and the results shows that the morphology and diameter of the nanofibers were mainly affected by MHA/MaPVA weight ratios by changing viscosity and conductivity of the blend solutions. The crystalline microstructure of the electrospun fibers was not well developed due to intermolecular hydrogen bonding interaction between the molecules of MHA and MaPVA. The photocrosslinking MHA/MaPVA nanofibrous mats can swell to form fibrous hydrogels with high water absorption, meanwhile it is cytocompatible and capable of promoting the cell attachment, which render it great potential for wound dressings.

Enhanced Osteoconductivity and Osseointegration in Calcium Polyphosphate Bioceramic Scaffold via Lithium Doping for Bone Regeneration

Calcium polyphosphate (CPP) is a novel bioceramic bone substitute, which is favored because its composition is highly similar to natural bone. According to previous studies, doping ions into CPP is an effective and convenient method for overcoming the shortcomings, such as poor osteoconductivity of CPP. Lithium (Li) is a fairly new additive to bone substitutes that brought attention due to its role in osteogenesis. The present study was conducted to assess whether doping Li into CPP could influence the microstructure, degradation, and osteoinductivity of CPP. The results found that both CPP and Li-doped CPP (LiCPP) had a single beta-CPP phase, indicating that Li did not affect the crystallized phase. SEM images revealed that both scaffolds were porous, while the surface of LiCPP was rougher and more uneven compared to CPP. Also, a better degradation property of LiCPP was observed via weight loss and ion release tests. In vitro study found that LiCPP extracts had advantages of promoting osteoblasts' proliferation and differentiation over CPP extracts. In vivo study on rabbit's cranial defects was also conducted. Microcomputed tomography and histological staining showed that LiCPP had better osteoconductivity than CPP. This study proved that doping Li into CPP is a feasible modification method, and LiCPP might be a suitable bioceramic for bone tissue engineering.

Smart Microneedles with Porous Polymer Coatings for pH-Responsive Drug Delivery

: This work demonstrates a simple approach for coating a porous polymer layer on stainless-steel (SS) microneedles characterized by a pH-responsive formulation for self-regulated drug delivery. For many drug-delivery applications, the release of therapeutic agents in an acidic microenvironment is desirable. Acid-sensitive polymers and hydrogels were extensively explored, but easily prepared polymeric microcarriers that combine acid sensitivity and biodegradability are rare. Here, we describe a simple and robust method of coating a porous polymer layer on SS microneedles (MNs) that release a model drug (lidocaine) in a pH-responsive fashion. It was constructed by packing the model drug and a pH-sensitive component (sodium bicarbonate) into the pores of the polymer layer. When this acid-sensitive formulation was exposed to the acidic microenvironment, the consequent reaction of protons (H+) with sodium bicarbonate (NaHCO3) yielded CO2. This effect generated pressure inside the pores of the coating and ruptured the thin polymer membrane, thereby releasing the encapsulated drug. Scanning electron micrographs showed that the pH-sensitive porous polymer-coated MNs exposed to phosphate-buffered saline (PBS) at pH 7.4 were characterized by closed pores. However, MNs exposed to PBS at pH 5.5 consisted of open pores and the thin membrane burst. The in vitro studies demonstrated the pH sensitivity of the drug release from porous polymer-coated MNs. Negligible release was observed for MNs in receiving media at pH 7.4. In contrast, significant release occurred when the MNs were exposed to acidic conditions (pH 5.5). Additionally, comparable results were obtained for drug release in vitro in porcine skin and in PBS. This revealed that our developed pH-responsive porous polymer-coated MNs could potentially be used for the controlled release of drug formulations in an acidic environment. Moreover, the stimuli-responsive drug carriers will enable on-demand controlled release profiles that may enhance therapeutic effectiveness and reduce systemic toxicity.

Low-Molecular-Weight Heparin-Functionalized Chitosan-Chondroitin Sulfate Hydrogels for Controlled Release of TGF-β3 and in vitro Neocartilage Formation

Repair of hyaline cartilage remains a huge challenge in clinic because of the avascular and aneural characteristics and the paucity of endogenous repair cells. Recently, tissue engineering technique, possessing unique capacity of repairing large tissue defects, avoiding donor complications and two-stage invasive surgical procedures, has been developed a promising therapeutic strategy for cartilage injury. In this study, we incorporated low-molecular-weight heparin (LMWH) into carboxymethyl chitosan-oxidized chondroitin sulfate (CMC-OCS) hydrogel for loading transforming growth factor-β3 (TGF-β3) as matrix of peripheral blood mesenchymal stem cells (PB-MSCs) to construct tissue-engineered cartilage. Meanwhile, three control hydrogels with or without LMWH and/or TGF-β3 were also prepared. The gelling time, microstructures, mechanical properties, degradation rate, cytotoxicity, and the release of TGF-β3 of different hydrogels were investigated. In vitro experiments evaluated the tri-lineage differentiation potential of PB-MSCs, combined with the proliferation, distribution, viability, morphology, and chondrogenic differentiation. Compared with non-LMWH-hydrogels, LMWH-hydrogels (LMWH-CMC-OCS-TGF-β3) have shorter gelling time, higher mechanical strength, slower degradation rate and more stable and lasting release of TGF-β3. After two weeks of culture in vitro, expression of cartilage-specific genes collagen type-2 (COL-2) and aggrecan (AGC), and secretion of glycosaminoglycan (GAG), and COL-2 proteins in LMWH-CMC-OCS-TGF-β3 group were significantly higher than those in other groups. COL-2 immunofluorescence staining showed that the proportion of COL-2 positive cells and immunofluorescence intensity in LMWH-CMC-OCS-TGF-β3 hydrogel were significantly higher than those in other groups. The LMWH-CMC-OCS-TGF-β3 hydrogel can slowly release TGF-β3 in a long term, and meanwhile the hydrogel can provide a biocompatible microenvironment for the growth and chondrogenic differentiation of PB-MSCs. Thus, LMWH functionalized CMC-OCS hydrogels proposed in this work will be beneficial for constructing functional scaffolds for tissue-engineered cartilage.

Localized controlled release of bevacizumab and doxorubicin by thermo-sensitive hydrogel for normalization of tumor vasculature and to enhance the efficacy of chemotherapy

In a malignant tumor, overexpression of pro-angiogenic factors like vascular endothelial growth factor (VEGF) provokes the production of pathologic vascular networks characterized by leaky, chaotically organized, immature, thin-walled, and ill-perfused. As a result, hostile tumor environment would be developed and profoundly hinders anti-cancer drug activities and fuels tumor progression. In this study, we develop a strategy of sequential sustain release of anti-angiogenic drug, Bevacizumab (BVZ), and anti-cancer drug, Doxorubicin (DOX), using poly (d, l-Lactide)- Poly (ethylene glycol) -Poly (d, l-Lactide) (PDLLA-PEG-PDLLA) hydrogel as a local delivery system. The release profiles of the drugs from the hydrogel were investigated in vitro which confirmed that relatively rapid release of BVZ (73.56 ± 1.39%) followed by Dox (61.21 ± 0.62%) at pH 6.5 for prolonged period. The in vitro cytotoxicity test revealed that the copolymer exhibited negligible cytotoxicity up to 2.5 mg ml^-1 concentration on HaCaT and HeLa cells. Likeways, the in vitro degradation of the copolymer showed 41.63 ± 2.62% and 73.25 ± 4.36% weight loss within 6 weeks at pH 7.4 and 6.5, respectively. After a single intratumoral injection of the drug-encapsulated hydrogel on Hela xenograft nude, hydrogel co-loaded with BVZ and Dox displayed the highest tumor suppression efficacy for up to 36 days with no noticeable damage on vital organs. Therefore, localized co-delivery of anti-angiogenic drug and anti-cancer drug by hydrogel system may be a promising approach for enhanced chemotherapeutic efficacy in cancer treatment.

ZnO Nanostructures and Electrospun ZnO-Polymeric Hybrid Nanomaterials in Biomedical, Health, and Sustainability Applications

ZnO-based nanomaterials are a subject of increasing interest within current research, because of their multifunctional properties, such as piezoelectricity, semi-conductivity, ultraviolet absorption, optical transparency, and photoluminescence, as well as their low toxicity, biodegradability, low cost, and versatility in achieving diverse shapes. Among the numerous fields of application, the use of nanostructured ZnO is increasingly widespread also in the biomedical and healthcare sectors, thanks to its antiseptic and antibacterial properties, role as a promoter in tissue regeneration, selectivity for specific cell lines, and drug delivery function, as well as its electrochemical and optical properties, which make it a good candidate for biomedical applications. Because of its growing use, understanding the toxicity of ZnO nanomaterials and their interaction with biological systems is crucial for manufacturing relevant engineering materials. In the last few years, ZnO nanostructures were also used to functionalize polymer matrices to produce hybrid composite materials with new properties. Among the numerous manufacturing methods, electrospinning is becoming a mainstream technique for the production of scaffolds and mats made of polymeric and metal-oxide nanofibers. In this review, we focus on toxicological aspects and recent developments in the use of ZnO-based nanomaterials for biomedical, healthcare, and sustainability applications, either alone or loaded inside polymeric matrices to make electrospun composite nanomaterials. Bibliographic data were compared and analyzed with the aim of giving homogeneity to the results and highlighting reference trends useful for obtaining a fresh perspective about the toxicity of ZnO nanostructures and their underlying mechanisms for the materials and engineering community.

Tazarotene Released from Aligned Electrospun Membrane Facilitates Cutaneous Wound Healing by Promoting Angiogenesis

Wound treatment is a long-lasting clinical issue. Poor angiogenesis leading to delayed wound closure causes huge challenges for healing. Functional electrospun membranes have been established as an efficient strategy to promote wound recovery by protecting and improving vascular regeneration. Here, we aimed to investigate the effect of tazarotene, an active drug for angiogenesis, loaded in aligned electrospun nanofibrous barrier on a soft tissue wound. This aligned membrane was arranged in a single direction, and tazarotene could be released from its nanofibers sustainably. The in vitro study demonstrated that compared with the random drug-loaded or other control groups, the aligned tazarotene-loaded membranes [poly-caprolactone (PCL)/AT] could stimulate proliferation, migration, angiogenesis, and vascular endothelial growth factor secretion and its gene expression of human umbilical vein endothelial cells. Furthermore, the in vivo model showed that the prepared tazarotene-loaded aligned membrane significantly accelerated the speed of healing, improved the neovascularization and re-epithelialization, and inhibited the inflammatory reaction in the wound area. All these results above indicated that the PCL/AT nanofibrous dressing, which could promote angiogenesis because of both stimulation of structure and chemical signals, is a promising wound-caring material.

Magnetic nanoparticle - indium phthalocyanine conjugate embedded in electrospun fiber for photodynamic antimicrobial chemotherapy and photodegradation of methyl red

ClIn(III) octacarboxy phthalocyanine (ClInOCPc) when alone or conjugated to magnetic nanoparticles (MNP-ClInOCPc) was employed for both photodynamic antimicrobial chemotherapy of an unknown water sample and Staphylococcus aureus, and for photo-degradation of methyl red (MR). The singlet oxygen quantum yields (Φ_Δ) in water using ClInOCPc and MNP-ClInOCPc embedded in polyacrylonitrile (PAN) electrospun fibers were 0.36 and 0.22, respectively. When in solution, MNP-ClInOCPc gave 90.6% photoinactivation of microbes in a water sample from the stream and of ClInOCPc resulted in 84.8 % photoinactivation. When embedded to the polymer, there was 48.0% clearance for ClInOCPc and 63.7% clearance for MNP-ClInOCPc for the microbes in the water sample from the stream. For the photo-degradation of MR, the rate of degradation increased with decrease of the MR concentration with the MNP-ClInOCPc having the fastest rate.

Electrospun fibers and their application in drug controlled release, biological dressings, tissue repair, and enzyme immobilization

Electrospinning is a method of preparing microfibers or nanofibers by using an electrostatic force to stretch the electrospinning fluid. Electrospinning has gained considerable attention in many fields due to its ability to produce continuous fibers from a variety of polymers and composites in a simple way. Electrospun nanofibers have many merits such as diverse chemical composition, easily adjustable structure, adjustable diameter, high surface area, high porosity, and good pore connectivity, which give them broad application prospects in the biomedical field. This review systematically introduced the factors influencing electrospinning, the types of electrospun fibers, the types of electrospinning, and the detailed applications of electrospun fibers in controlled drug release, biological dressings, tissue repair and enzyme immobilization fields. The latest progress of using electrospun fibers in these fields was summarized, and the main challenges to be solved in electrospinning technology were put forward.

Bio-Functional Textiles: Combining Pharmaceutical Nanocarriers with Fibrous Materials for Innovative Dermatological Therapies

In the field of pharmaceutical technology, significant attention has been paid on exploiting skin as a drug administration route. Considering the structural and chemical complexity of the skin barrier, many research works focused on developing an innovative way to enhance skin drug permeation. In this context, a new class of materials called bio-functional textiles has been developed. Such materials consist of the combination of advanced pharmaceutical carriers with textile materials. Therefore, they own the possibility of providing a wearable platform for continuous and controlled drug release. Notwithstanding the great potential of these materials, their large-scale application still faces some challenges. The present review provides a state-of-the-art perspective on the bio-functional textile technology analyzing the several issues involved. Firstly, the skin physiology, together with the dermatological delivery strategy, is keenly described in order to provide an overview of the problems tackled by bio-functional textiles technology. Secondly, an overview of the main dermatological nanocarriers is provided; thereafter the application of these nanomaterial to textiles is presented. Finally, the bio-functional textile technology is framed in the context of the different dermatological administration strategies; a comparative analysis that also considers how pharmaceutical regulation is conducted.

A Review on Porous Polymeric Membrane Preparation. Part I: Production Techniques with Polysulfone and Poly (Vinylidene Fluoride)

Porous polymeric membranes have emerged as the core technology in the field of separation. But some challenges remain for several methods used for membrane fabrication, suggesting the need for a critical review of the literature. We present here an overview on porous polymeric membrane preparation and characterization for two commonly used polymers: polysulfone and poly (vinylidene fluoride). Five different methods for membrane fabrication are introduced: non-solvent induced phase separation, vapor-induced phase separation, electrospinning, track etching and sintering. The key factors of each method are discussed, including the solvent and non-solvent system type and composition, the polymer solution composition and concentration, the processing parameters, and the ambient conditions. To evaluate these methods, a brief description on membrane characterization is given related to morphology and performance. One objective of this review is to present the basics for selecting an appropriate method and membrane fabrication systems with appropriate processing conditions to produce membranes with the desired morphology, performance and stability, as well as to select the best methods to determine these properties.

Development of Oxidized Polyvinyl Alcohol-Based Nerve Conduits Coupled with the Ciliary Neurotrophic Factor

Functionalized synthetic conduits represent a promising strategy to enhance peripheral nerve regeneration by guiding axon growth while delivering therapeutic neurotrophic factors. In this work, hollow nerve conduits made of polyvinyl alcohol partially oxidized with bromine (OxPVA_Br2) and potassium permanganate (OxPVA_KMnO4) were investigated for their structural/biological properties and ability to absorb/release the ciliary neurotrophic factor (CNTF). Chemical oxidation enhanced water uptake capacity of the polymer, with maximum swelling index of 60.5% ± 2.5%, 71.3% ± 3.6% and 19.5% ± 4.0% for OxPVA_Br2, OxPVA_KMnO4 and PVA, respectively. Accordingly, hydrogel porosity increased from 15.27% ± 1.16% (PVA) to 62.71% ± 8.63% (OxPVA_Br2) or 77.50% ± 3.39% (OxPVA_KMnO4) after oxidation. Besides proving that oxidized PVA conduits exhibited mechanical resistance and a suture holding ability, they did not exert a cytotoxic effect on SH-SY5Y and Schwann cells and biodegraded over time when subjected to enzymatic digestion, functionalization with CNTF was performed. Interestingly, higher amounts of neurotrophic factor were detected in the lumen of OxPVA_Br2 (0.22 ± 0.029 µg) and OxPVA_KMnO4 (0.29 ± 0.033 µg) guides rather than PVA (0.11 ± 0.021 µg) tubular scaffolds. In conclusion, we defined a promising technology to obtain drug delivery conduits based on functionalizable oxidized PVA hydrogels.

Synthesized of glucose-responsive nanogels labeled with fluorescence molecule based on phenylboronic acid by RAFT polymerization

We reported on the fabrication of sugar-responsive nanogels covalently incorporated with 3-acrylamidophenylboronic acid (AAPBA) as glucose-recognizing moiety, 2-(acrylamido)glucopyranose (AGA) as biocompatible moiety, and boron dipyrromethene (BODIPYMA) as fluorescence donor molecule. The p(AAPBA-AGA-BODIPYMA) nanogels were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization in the mixture solvents of H₂O/ethanol. Nanogels could respond to glucose and size of nanogels increased after treating with 3 mg/mL glucose medium. The fluorescent intensity of nanogels varied dependent on different glucose concentrations. Besides, insulin, a model drug, can be encapsulated into nanogels with the loading amount up to 8.2%. The drug release was dependent on the content of AAPBA moieties in nanogels and glucose concentrations in release medium. The investigation on the cytotoxicity of nanogels revealed that nanogels had good compatibility. Such glucose-responsive nanogels have potential in detection and treatment of diabetes.

Electrospun Nanomaterials for Energy Applications: Recent Advances

Electrospinning is a simple, versatile, cost-effective, and scalable technique for the growth of highly porous nanofibers. These nanostructures, featured by high aspect ratio, may exhibit a large variety of different sizes, morphologies, composition, and physicochemical properties. By proper post-spinning heat treatment(s), self-standing fibrous mats can also be produced. Large surface area and high porosity make electrospun nanomaterials (both fibers and three-dimensional fiber networks) particularly suitable to numerous energy-related applications. Relevant results and recent advances achieved by their use in rechargeable lithium- and sodium-ion batteries, redox flow batteries, metal-air batteries, supercapacitors, reactors for water desalination via capacitive deionization and for hydrogen production by water splitting, as well as nanogenerators for energy harvesting, and textiles for energy saving will be presented and the future prospects for the large-scale application of electrospun nanomaterials will be discussed.

Fabrication of Electrospun Polymer Nanofibers with Diverse Morphologies

Fiber structures with nanoscale diameters offer many fascinating features, such as excellent mechanical properties and high specific surface areas, making them attractive for many applications. Among a variety of technologies for preparing nanofibers, electrospinning is rapidly evolving into a simple process, which is capable of forming diverse morphologies due to its flexibility, functionality, and simplicity. In such review, more emphasis is put on the construction of polymer nanofiber structures and their potential applications. Other issues of electrospinning device, mechanism, and prospects, are also discussed. Specifically, by carefully regulating the operating condition, modifying needle device, optimizing properties of the polymer solutions, some unique structures of core⁻shell, side-by-side, multilayer, hollow interior, and high porosity can be obtained. Taken together, these well-organized polymer nanofibers can be of great interest in biomedicine, nutrition, bioengineering, pharmaceutics, and healthcare applications.

New Alginate/PNIPAAm Matrices for Drug Delivery

This paper deals with a comparative study on the interpolymeric complexes of alginate poly(N-isopropyl acryl amide (PNIPAAm) and corresponding graft copolymers with various compositions in respect to their toxicity, biocompatibility and in vitro and in vivo release of theophylline (THP). Loading of the various matrices with theophylline and characterization of loaded matrices was studied by near infrared spectroscopy⁻chemical imaging (NIR⁻CI) analysis, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). It was appreciated that THP loading is higher than 40% and the drug is relatively homogeneous distributed within all matrices because of some specific interactions between components of the system. All samples have been found to be non-toxic and biocompatible. It was established that graft copolymers having a good stability show a better drug carrier ability, a higher THP loading, a prolonged release (longer release duration for graft copolymers of 235.4⁻302.3 min than that for IPC 72/28 of 77.6 min, which means approximately four times slower release from the graft copolymer-based matrices than from the interpolymeric complex) and a good bioavailability. The highest values for THP loading (45%), prolonged release (302.3 min) and bioavailability (175%) were obtained for graft copolymer AgA-g-PNIPAAm 68. The drug release mechanism varies with composition and architecture of the matrix.

The emerging field of pancreatic tissue engineering: A systematic review and evidence map of scaffold materials and scaffolding techniques for insulin-secreting cells

A bioartificial endocrine pancreas is proposed as a future alternative to current treatment options. Patients with insulin-secretion deficiency might benefit. This is the first systematic review that provides an overview of scaffold materials and techniques for insulin-secreting cells or cells to be differentiated into insulin-secreting cells. An electronic literature survey was conducted in PubMed/MEDLINE and Web of Science, limited to the past 10 years. A total of 197 articles investigating 60 different materials met the inclusion criteria. The extracted data on materials, cell types, study design, and transplantation sites were plotted into two evidence gap maps. Integral parts of the tissue engineering network such as fabrication technique, extracellular matrix, vascularization, immunoprotection, suitable transplantation sites, and the use of stem cells are highlighted. This systematic review provides an evidence-based structure for future studies. Accumulating evidence shows that scaffold-based tissue engineering can enhance the viability and function or differentiation of insulin-secreting cells both in vitro and in vivo.