Molecular Architecture of Electroactive and Biodegradable Copolymers Composed of Polylactide and Carboxyl-Capped Aniline Trimer

Linear and star-shaped π-conjugated oligoanilines: a review on molecular design in syntheses and properties

Molecular Design and Synthesis of Linear and Star-shaped π-conjugated Oligoanilines with reversible optoelectrochemical properties.

In-Out Surface Modification of Halloysite Nanotubes (HNTs) for Excellent Cure of Epoxy: Chemistry and Kinetics Modeling

In-out surface modification of halloysite nanotubes (HNTs) has been successfully performed by taking advantage of 8-hydroxyquinolines in the lumen of HNTs and precisely synthesized aniline oligomers (AO) of different lengths (tri- and pentamer) anchored on the external surface of the HNTs. Several analyses, including FTIR, H-NMR, TGA, UV-visible spectroscopy, and SEM, were used to establish the nature of the HNTs’ surface engineering. Nanoparticles were incorporated into epoxy resin at 0.1 wt.% loading for investigation of the contribution of surface chemistry to epoxy cure behavior and kinetics. Nonisothermal differential scanning calorimetry (DSC) data were fed into home-written MATLAB codes, and isoconversional approaches were used to determine the apparent activation energy (E_α) as a function of the extent of cure reaction (α). Compared to pristine HNTs, AO-HNTs facilitated the densification of an epoxy network. Pentamer AO-HNTs with longer arms promoted an Excellent cure; with an E_α value that was 14% lower in the presence of this additive than for neat epoxy, demonstrating an enhanced cross-linking. The model also predicted a triplet of cure (m, n, and ln A) for autocatalytic reaction order, non-catalytic reaction order, and pre-exponential factor, respectively, by the Arrhenius equation. The enhanced autocatalytic reaction in AO-HNTs/epoxy was reflected in a significant rise in the value of m, from 0.11 to 0.28. Kinetic models reliably predict the cure footprint suggested by DSC measurements.

Hydroxypropyl cellulose enhanced ionic conductive double-network hydrogels

Ionic conductive hydrogels with both high-performance in conductivity and mechanical properties have received increasing attention due to their unique potential in artificial soft electronics. Here, a dual physically cross-linked double network (DN) hydrogel with high ionic conductivity and tensile strength was fabricated by a facile approach. Hydroxypropyl cellulose (HPC) biopolymer fibers were embedded in a poly (vinyl alcohol)‑sodium alginate (PVA/SA) hydrogel, and then the prestretched PVA-HPC/SA composite hydrogel was immersed in a CaCl₂ solution to prepare PVA-HPC_T/SA-Ca DN hydrogels. The obtained composite hydrogel has an excellent tensile strength up to 1.4 MPa. Importantly, the synergistic effect of hydroxypropyl cellulose (HPC) and prestretching reduces the migration resistance of ions in the hydrogel, and the conductivity reaches 3.49 S/ m. In addition, these composite hydrogels are noncytotoxic, and they have a low friction coefficient and an excellent wear resistance. Therefore, PVA-HPC_T/SA-Ca DN hydrogels have potential applications in nerve replacement materials and biosensors.

Biological Influence of Nonswelling Microgels on Cartilage Induction of Mouse Adipose-Derived Stem Cells

In cartilage tissue engineering, the target cells' functional performance depends on the biomaterials. However, it is difficult to develop an appropriate scaffold to differentiate mouse adipose-derived stem cells (mADSCs) into chondrocyte despite an increasing number of studies on biological scaffold materials. The purpose of this study was to create a novel scaffold for mADSC culture and chondrogenic differentiation with a new series of microgels based on polyethyleneimine (PEI), polyethylene glycol (PEG), and poly (L-lactic acid) (PLLA) and able to resist swelling with changes in temperature, pH, and polymer concentration. The biocompatibility and ability of the nonswelling microgels were then examined and served as scaffolds for cell culture and for cartilage differentiation. The results show that the new microgels are a novel biomaterial that both retains its nonswelling properties under various conditions and facilitates important scaffold functions such as cell adhesion, proliferation, and cartilage induction.

Electrospun Conducting and Biocompatible Uniaxial and Core-Shell Fibers Having Poly(lactic acid), Poly(ethylene glycol), and Polyaniline for Cardiac Tissue Engineering

Electroactive and biocompatible fibrous scaffolds have been prepared and characterized using polyaniline (PAni) doped with dodecylbenzenesulfonic acid (DBSA) combined with poly(lactic acid) (PLA) and PLA/poly(ethylene glycol) (PEG) mixtures. The composition of simple and core-shell fibers, which have been obtained by both uniaxial and coaxial electrospinning, respectively, has been corroborated by Fourier-transform infrared and micro-Raman spectroscopies. Morphological studies suggest that the incorporation of PEG enhances the packing of PLA and PAni chains, allowing the regulation of the thickness of the fibers. PAni and PEG affect the thermal and electrical properties of the fibers, both decreasing the glass transition temperature and increasing the electrical conductivity. Interestingly, the incorporation of PEG improves the PAni-containing paths associated with the conduction properties. Although dose response curves evidence the high cytotoxicity of PAni/DBSA, cell adhesion and cell proliferation studies on PLA/PAni fibers show a reduction of such harmful effects as the conducting polymer is mainly retained inside the fibers through favorable PAni···PLA interactions. The incorporation of PEG into uniaxial fibers resulted in an increment of the cell mortality, which has been attributed to its rapid dissolution into the culture medium and the consequent enhancement of PAni release. In opposition, the delivery of PAni decreases and, therefore, the biocompatibility of the fibers increases when a shell coating the PAni-containing system is incorporated through coaxial electrospinning. Finally, morphological and functional studies using cardiac cells indicated that these fibrous scaffolds are suitable for cardiac tissue engineering applications.

Degradable conductive self-healing hydrogels based on dextran-graft-tetraaniline and N-carboxyethyl chitosan as injectable carriers for myoblast cell therapy and muscle regeneration

Injectable conductive hydrogels have great potential as tissue engineering scaffolds and delivery vehicles for electrical signal sensitive cell therapy. In this work, we present the synthesis of a series of injectable electroactive degradable hydrogels with rapid self-healing ability and their potential application as cell delivery vehicles for skeletal muscle regeneration. Self-healable conductive injectable hydrogels based on dextran-graft-aniline tetramer-graft-4-formylbenzoic acid and N-carboxyethyl chitosan were synthesized at physiological conditions. The dynamic Schiff base bonds between the formylbenzoic acid and amine group from N-carboxyethyl chitosan endowed the hydrogels with rapid self-healing ability, which was verified by rheological test. Equilibrated swelling ratio, morphology, mechanical strength, electrochemistry and conductivity of the injectable hydrogels were fully investigated. The self-healable conductive hydrogels showed an in vivo injectability and a linear-like degradation behavior. Two different kinds of cells (C2C12 myoblasts and human umbilical vein endothelial cells (HUVEC)) were encapsulated in the hydrogels by self-healing effect. The L929 fibroblast cell culture results indicated the biocompatibility of the hydrogels. Moreover, the C2C12 myoblast cells were released from the conductive hydrogels with a linear-like profile. The in vivo skeletal muscle regeneration was also studied in a volumetric muscle loss injury model. All these data indicated that these biodegradable self-healing conductive hydrogels are potential candidates as cell delivery vehicles and scaffolds for skeletal muscle repair. STATEMENT OF SIGNIFICANCE: Injectable hydrogels with self-healing and electrical conductivity properties are excellent candidates as tissue-engineered scaffolds for myoblast cell therapy and skeletal muscle regeneration. The self-healing property of these hydrogels can prolong their lifespan. However, most of the reported conductive hydrogels are not degradable or do not have the self-healing ability. Herein, we synthesized antibacterial conductive self-healing hydrogels as a cell delivery carrier for cardiac cell therapy based on chitosan-grafted-tetraaniline hydrogels synthesized in our previous work. However, an acid solution was used to dissolve the polymers in that study, which may induce toxicity to cells. In this work, we synthesized a series of injectable electroactive biodegradable hydrogels with rapid self-healing ability composed of N-carboxyethyl chitosan (CECS) and dextran-graft-aniline oligomers, and these hydrogel precusor can dissolve in PBS solution of pH 7.4; we further demonstrated their potential application as cell delivery vehicles for skeletal muscle regeneration.

Preparation and characterization of conductive poly-dl-lactic-acid/tetra-aniline conduit for peripheral nerve regeneration

Defected peripheral nerve regeneration is still a challenge in clinical treatment. Conductive polymers show great potential in nerve tissue engineering because of their electrical property based on bioelectricity in vivo. In this study, conductive composite nerve conduit was synthesized with tetra-aniline and poly-dl-lactic acid. Their properties and the differentiation of rat pheochromocytoma 12 (PC12) cells in vitro stimulated with 200 mV for 1 h were investigated. Different amounts of tetra-aniline (0%, 5%, 10%, and 15%) were used to synthesize the conduits with different conductivities (0, 0.00625, 0.01, and 0.025 s/m, respectively), tensile strengths (2.45, 3.40, 4.45, and 5.50 MPa, respectively), and contact angles (80°, 78.5°, 62.5°, and 61.5°, respectively). The percentage of neurite-bearing cells and the median neurite length increased with an obvious raise of the content of tetra-aniline. In addition, the conduit with subcutaneous implantable experiments in vivo showed less inflammatory response. These promising results illustrated that this poly-dl-lactic acid/tetra-aniline conductive composite conduit had potential for nerve tissue engineering.

Oligoaniline-based conductive biomaterials for tissue engineering

The science and engineering of biomaterials have improved the human life expectancy. Tissue engineering is one of the nascent strategies with an aim to fulfill this target. Tissue engineering scaffolds are one of the most significant aspects of the recent tissue repair strategies; hence, it is imperative to design biomimetic substrates with suitable features. Conductive substrates can ameliorate the cellular activity through enhancement of cellular signaling. Biocompatible polymers with conductivity can mimic the cells' niche in an appropriate manner. Bioconductive polymers based on aniline oligomers can potentially actualize this purpose because of their unique and tailoring properties. The aniline oligomers can be positioned within the molecular structure of other polymers, thus painter acting with the side groups of the main polymer or acting as a comonomer in their backbone. The conductivity of oligoaniline-based conductive biomaterials can be tailored to mimic the electrical and mechanical properties of targeted tissues/organs. These bioconductive substrates can be designed with high mechanical strength for hard tissues such as the bone and with high elasticity to be used for the cardiac tissue or can be synthesized in the form of injectable hydrogels, particles, and nanofibers for noninvasive implantation; these structures can be used for applications such as drug/gene delivery and extracellular biomimetic structures. It is expected that with progress in the fields of biomaterials and tissue engineering, more innovative constructs will be proposed in the near future. This review discusses the recent advancements in the use of oligoaniline-based conductive biomaterials for tissue engineering and regenerative medicine applications.

STATEMENT OF SIGNIFICANCE

The tissue engineering applications of aniline oligomers and their derivatives have recently attracted an increasing interest due to their electroactive and biodegradable properties. However, no reports have systematically reviewed the critical role of oligoaniline-based conductive biomaterials in tissue engineering. Research on aniline oligomers is growing today opening new scenarios that expand the potential of these biomaterials from "traditional" treatments to a new era of tissue engineering. The conductivity of this class of biomaterials can be tailored similar to that of tissues/organs. To the best of our knowledge, this is the first review article in which such issue is systematically reviewed and critically discussed in the light of the existing literature. Undoubtedly, investigations on the use of oligoaniline-based conductive biomaterials in tissue engineering need further advancement and a lot of critical questions are yet to be answered. In this review, we introduce the salient features, the hurdles that must be overcome, the hopes, and practical constraints for further development.

Rapid thermal responsive conductive hybrid cryogels with shape memory properties, photothermal properties and pressure dependent conductivity

Stimuli responsive cryogels with multi-functionality have potential application for electrical devices, actuators, sensors and biomedical devices. However, conventional thermal sensitive poly(N-isopropylacrylamide) cryogels show slow temperature response speed and lack of multi-functionality, which greatly limit their practical application. Herein we present conductive fast (2 min for both deswelling and reswelling behavior) thermally responsive poly(N-isopropylacrylamide) cryogels with rapid shape memory properties (3 s for shape recovery), near-infrared (NIR) light sensitivity and pressure dependent conductivity, and further demonstrated their applications as temperature sensitive on-off switch, NIR light sensitive on-off switch, water triggered shape memory on-off switch and pressure dependent device. These cryogels were first prepared in dimethyl sulfoxide below its melting temperature in ice bath and subsequently put into aniline or pyrrole solution to in situ deposition of conducting polyaniline or polypyrrole nanoparticles. The continuous macroporous sponge-like structure provides cryogels with rapid responsivity both in deswelling, reswelling kinetics and good elasticity. After incorporating electrically conductive polyaniline or polypyrrole nanoaggregates, the hybrid cryogels exhibit desirable conductivity, photothermal property, pressure dependent conductivity and good cytocompatibility. These multifunctional hybrid cryogels make them great potential as stimuli responsive electrical device, tissue engineering scaffolds, drug delivery vehicle and electronic skin.

Current status and future direction of biodegradable metallic and polymeric vascular scaffolds for next-generation stents

Because of the increasing incidence of coronary artery disease, the importance of cardiovascular stents has continuously increased as a treatment of this disease. Biodegradable scaffolds fabricated from polymers and metals have emerged as promising materials for vascular stents because of their biodegradability. Although such stent framework materials have shown good clinical efficacy, it is difficult to decide whether polymers or metals are better vascular scaffolds because their properties are different. Therefore, there are still obstacles in the development of biodegradable vascular scaffolds in terms of improving clinical efficacy. This review analyzes the pros and cons of current stent materials with respect to five key factors for next-generation stent and discusses methods of improvement. Furthermore, we discuss biodegradable electronic stents with electrical conductivity, which has been considered unimportant until now, and highlight electrical conductivity as a key factor in the development of next-generation stents.

Electrospun conductive nanofibrous scaffolds for engineering cardiac tissue and 3D bioactuators

Mimicking the nanofibrous structure similar to extracellular matrix and conductivity for electrical propagation of native myocardium would be highly beneficial for cardiac tissue engineering and cardiomyocytes-based bioactuators. Herein, we developed conductive nanofibrous sheets with electrical conductivity and nanofibrous structure composed of poly(l-lactic acid) (PLA) blending with polyaniline (PANI) for cardiac tissue engineering and cardiomyocytes-based 3D bioactuators. Incorporating of varying contents of PANI from 0wt% to 3wt% into the PLA polymer, the electrospun nanofibrous sheets showed enhanced conductivity while maintaining the same fiber diameter. These PLA/PANI conductive nanofibrous sheets exhibited good cell viability and promoting effect on differentiation of H9c2 cardiomyoblasts in terms of maturation index and fusion index. Moreover, PLA/PANI nanofibrous sheets enhanced the cell-cell interaction, maturation and spontaneous beating of primary cardiomyocytes. Furthermore, the cardiomyocytes-laden PLA/PANI conductive nanofibrous sheets can form 3D bioactuators with tubular and folding shapes, and spontaneously beat with much higher frequency and displacement than that on cardiomyocytes-laden PLA nanofibrous sheets. Therefore, these PLA/PANI conductive nanofibrous sheets with conductivity and extracellular matrix like nanostructure demonstrated promising potential in cardiac tissue engineering and cardiomyocytes-based 3D bioactuators.

STATEMENT OF SIGNIFICANCE

Cardiomyocytes-based bioactuators have been paid more attention due to their spontaneous motion by integrating cardiomyocytes into polymer structures, but developing suitable scaffolds for bioactuators remains challenging. Electrospun nanofibrous scaffolds have been widely used in cardiac tissue engineering because they can mimic the extracellular matrix of myocardium. Developing conductive nanofibrous scaffolds by electrospinning would be beneficial for cardiomyocytes-based bioactuators, but such scaffolds have been rarely reported. This work presented a conductive nanofibrous sheet based on polylactide and polyaniline via electrospinning with tunable conductivity. These conductive nanofibrous sheets performed the ability to enhance cardiomyocytes maturation and spontaneous beating, and further formed cardiomyocytes-based 3D bioactuators with tubular and folding shapes, which indicated their great potential in cardiac tissue engineering and bioactuators applications.

Translational considerations in injectable cell-based therapeutics for neurological applications: concepts, progress and challenges

Significant progress has been made during the past decade towards the clinical adoption of cell-based therapeutics. However, existing cell-delivery approaches have shown limited success, with numerous studies showing fewer than 5% of injected cells persisting at the site of injection within days of transplantation. Although consideration is being increasingly given to clinical trial design, little emphasis has been given to tools and protocols used to administer cells. The different behaviours of various cell types, dosing accuracy, precise delivery, and cell retention and viability post-injection are some of the obstacles facing clinical translation. For efficient injectable cell transplantation, accurate characterisation of cellular health post-injection and the development of standardised administration protocols are required. This review provides an overview of the challenges facing effective delivery of cell therapies, examines key studies that have been carried out to investigate injectable cell delivery, and outlines opportunities for translating these findings into more effective cell-therapy interventions.

Conductive and biodegradable scaffolds based on a five-arm and functionalized star-like polyaniline–polycaprolactone copolymer with a d-glucose core

The scaffolds demonstrated a porous structure with a large surface area and electrical conductivity, imitating the ECM to regulate cell attachment, proliferation, and differentiation.

Electro-Active Polymers (EAPs): A Promising Route to Design Bio-Organic/Bioinspired Platforms with on Demand Functionalities

Through recent discoveries and new knowledge among correlations between molecular biology and materials science, it is a growing interest to design new biomaterials able to interact-i.e., to influence, to guide or to detect-with cells and their surrounding microenvironments, in order to better control biological phenomena. In this context, electro-active polymers (EAPs) are showing great promise as biomaterials acting as an interface between electronics and biology. This is ascribable to the highly tunability of chemical/physical properties which confer them different conductive properties for various applicative uses (i.e., molecular targeting, biosensors, biocompatible scaffolds). This review article is divided into three parts: the first one is an overview on EAPs to introduce basic conductivity mechanisms and their classification. The second one is focused on the description of most common processes used to manipulate EAPs in the form of two-dimensional (2D) and three-dimensional (3D) materials. The last part addresses their use in current applications in different biomedical research areas including tissue engineering, biosensors and molecular delivery.

Catechin-Modified Polylactide Stereocomplex at Chain End Improved Antibiobacterial Property

Using different type of initiators, the antibacterial moieties are introduced at the chain end of poly(L,L-lactide) (PLLA) and poly(D,D-lactide) (PDLA), and the thermal properties are simultaneously improved using the stereocomplex approach. The physical interaction of polymers and antibacterial compounds is investigated. The double bonds at the chain end are utilized for the interaction of silver ion; however, the silver ions are not detected after stereocomplexation of PLLA and PDLA. On the other hand, catechin (CT) is selected as an initiator precursor of lactide polymerization, protecting the phenolic hydroxyl groups. The linear PLLA and PDLA are obtained by the initiator, resulting in CT conjugated PLAs at the chain end groups after deprotection of phenolic hydroxyl groups. The antibacterial properties are determined by proliferation tests of staphylococcus aureus. The results suggest that the antibacterial properties of CT modified PLAs are derived from the original CT parts.

Biocompatible, Biodegradable, and Electroactive Polyurethane-Urea Elastomers with Tunable Hydrophilicity for Skeletal Muscle Tissue Engineering

It remains a challenge to develop electroactive and elastic biomaterials to mimic the elasticity of soft tissue and to regulate the cell behavior during tissue regeneration. We designed and synthesized a series of novel electroactive and biodegradable polyurethane-urea (PUU) copolymers with elastomeric property by combining the properties of polyurethanes and conducting polymers. The electroactive PUU copolymers were synthesized from amine capped aniline trimer (ACAT), dimethylol propionic acid (DMPA), polylactide, and hexamethylene diisocyanate. The electroactivity of the PUU copolymers were studied by UV-vis spectroscopy and cyclic voltammetry. Elasticity and Young's modulus were tailored by the polylactide segment length and ACAT content. Hydrophilicity of the copolymer films was tuned by changing DMPA content and doping of the copolymer. Cytotoxicity of the PUU copolymers was evaluated by mouse C2C12 myoblast cells. The myogenic differentiation of C2C12 myoblasts on copolymer films was also studied by analyzing the morphology of myotubes and relative gene expression during myogenic differentiation. The chemical structure, thermal properties, surface morphology, and processability of the PUU copolymers were characterized by NMR, FT-IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and solubility testing, respectively. Those biodegradable electroactive elastic PUU copolymers are promising materials for repair of soft tissues such as skeletal muscle, cardiac muscle, and nerve.

Super stretchable electroactive elastomer formation driven by aniline trimer self-assembly

Biomedical electroactive elastomers with a modulus similar to that of soft tissues are highly desirable for muscle, nerve, and other soft tissue replacement or regeneration, but have rarely been reported. In this work, superiorly stretchable electroactive polyurethane-urea elastomers were designed based on poly(lactide), poly(ethylene glycol), and aniline trimer (AT). A strain at break higher than 1600% and a modulus close to soft tissues was achieved from these copolymers. The mechanisms of super stretchability of the copolymer were systematically investigated. Crystallinity, chemical cross-linking, ionic cross-linking and hard domain formation were examined using differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), nuclear magnetic resonance (NMR) measurements and transmission electron microscopy (TEM). The sphere-like hard domains self-assembled from AT segments were found to provide the crucial physical interactions needed for the novel super elastic material formation. These super stretchable copolymers were blended with conductive fillers such as polyaniline nanofibers and nanosized carbon black to achieve a high electric conductivity of 0.1 S/cm while maintaining an excellent stretchability and a modulus similar to that of soft tissues (lower than 10 MPa).

Ductile electroactive biodegradable hyperbranched polylactide copolymers enhancing myoblast differentiation

Myotube formation is crucial to restoring muscular functions, and biomaterials that enhance the myoblast differentiation into myotubes are highly desirable for muscular repair. Here, we report the synthesis of electroactive, ductile, and degradable copolymers and their application in enhancing the differentiation of myoblasts to myotubes. A hyperbranched ductile polylactide (HPLA) was synthesized and then copolymerized with aniline tetramer (AT) to produce a series of electroactive, ductile and degradable copolymers (HPLAAT). The HPLA and HPLAAT showed excellent ductility with strain to failure from 158.9% to 42.7% and modulus from 265.2 to 758.2 MPa. The high electroactivity of the HPLAAT was confirmed by UV spectrometer and cyclic voltammogram measurements. These HPLAAT polymers also showed improved thermal stability and controlled biodegradation rate compared to HPLA. Importantly, when applying these polymers for myotube formation, the HPLAAT significantly improved the proliferation of C2C12 myoblasts in vitro compared to HPLA. Furthermore, these polymers greatly promoted myogenic differentiation of C2C12 cells as measured by quantitative analysis of myotube number, length, diameter, maturation index, and gene expression of MyoD and TNNT. Together, our study shows that these electroactive, ductile and degradable HPLAAT copolymers represent significantly improved biomaterials for muscle tissue engineering compared to HPLA.

Facile Preparation of Water-Dispersible Graphene Sheets Stabilized by Carboxylated Oligoanilines and Their Anticorrosion Coatings

Dispersion of graphene in solvents is of crucial importance toward its practical applications. In this study, using a water-soluble carboxylated aniline trimer derivative (CAT(-)) as a stabilizer, the commercial graphene can be stably dispersed in water at high concentration (>1 mg/mL) via strong π-π interaction that was proved by Raman and UV-vis spectra. Moreover, the CAT(-)-functionalized graphene sheets (G-CAT(-) hybrid) exhibited high conductivity (∼1.5 S/cm), good electroactivity and improved electrochemical stability. The addition of well-dispersed graphene into waterborne epoxy system (G-CAT(-)/epoxy) remarkably improved corrosion protection compared with pure waterborne epoxy coating, based on a series of electrochemical measurements performed under 3.5% NaCl solution. This significantly enhanced anticorrosion performance is mainly due to the improved water barrier properties derived from highly dispersed graphene nanosheets in the epoxy coating.

Strong electroactive biodegradable shape memory polymer networks based on star-shaped polylactide and aniline trimer for bone tissue engineering

Preparation of functional shape memory polymer (SMP) for tissue engineering remains a challenge. Here the synthesis of strong electroactive shape memory polymer (ESMP) networks based on star-shaped polylactide (PLA) and aniline trimer (AT) is reported. Six-armed PLAs with various chain lengths were chemically cross-linked to synthesize SMP. After addition of an electroactive AT segment into the SMP, ESMP was obtained. The polymers were characterized by (1)H NMR, GPC, FT-IR, CV, DSC, DMA, tensile test, and degradation test. The SMP and ESMP exhibited strong mechanical properties (modulus higher than GPa) and excellent shape memory performance: short recovery time (several seconds), high recovery ratio (over 94%), and high fixity ratio (almost 100%). Moreover, cyclic voltammetry test confirmed the electroactivity of the ESMP. The ESMP significantly enhanced the proliferation of C2C12 cells compared to SMP and linear PLA (control). In addition, the ESMP greatly improved the osteogenic differentiation of C2C12 myoblast cells compared to PH10 and PLA in terms of ALP enzyme activity, immunofluorescence staining, and relative gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). These intelligent SMPs and electroactive SMP with strong mechanical properties, tunable degradability, good electroactivity, biocompatibility, and enhanced osteogenic differentiation of C2C12 cells show great potential for bone regeneration.

Functionalized scaffolds to enhance tissue regeneration

Tissue engineering scaffolds play a vital role in regenerative medicine. It not only provides a temporary 3-dimensional support during tissue repair, but also regulates the cell behavior, such as cell adhesion, proliferation and differentiation. In this review, we summarize the development and trends of functional scaffolding biomaterials including electrically conducting hydrogels and nano-composites of hydroxyapatite (HA) and bioactive glasses (BGs) with various biodegradable polymers. Furthermore, the progress on the fabrication of biomimetic nanofibrous scaffolds from conducting polymers and composites of HA and BG via electrospinning, deposition and thermally induced phase separation is discussed. Moreover, bioactive molecules and surface properties of scaffolds are very important during tissue repair. Bioactive molecule-releasing scaffolds and antimicrobial surface coatings for biomedical implants and scaffolds are also reviewed.

In situ cross-linking of stimuli-responsive hemicellulose microgels during spray drying

Chemical cross-linking during spray drying offers the potential for green fabrication of microgels with a rapid stimuli response and good blood compatibility and provides a platform for stimuli-responsive hemicellulose microgels (SRHMGs). The cross-linking reaction occurs rapidly in situ at elevated temperature during spray drying, enabling the production of microgels in a large scale within a few minutes. The SRHMGs with an average size range of ∼ 1-4 μm contain O-acetyl-galactoglucomannan as a matrix and poly(acrylic acid), aniline pentamer (AP), and iron as functional additives, which are responsive to external changes in pH, electrochemical stimuli, magnetic field, or dual-stimuli. The surface morphologies, chemical compositions, charge, pH, and mechanical properties of these smart microgels were evaluated using scanning electron microscopy, IR, zeta potential measurements, pH evaluation, and quantitative nanomechanical mapping, respectively. Different oxidation states were observed when AP was introduced, as confirmed by UV spectroscopy and cyclic voltammetry. Systematic blood compatibility evaluations revealed that the SRHMGs have good blood compatibility. This bottom-up strategy to synthesize SRHMGs enables a new route to the production of smart microgels for biomedical applications.

Synthetic biodegradable functional polymers for tissue engineering: a brief review

Scaffolds play a crucial role in tissue engineering. Biodegradable polymers with great processing flexibility are the predominant scaffolding materials. Synthetic biodegradable polymers with well-defined structure and without immunological concerns associated with naturally derived polymers are widely used in tissue engineering. The synthetic biodegradable polymers that are widely used in tissue engineering, including polyesters, polyanhydrides, polyphosphazenes, polyurethane, and poly (glycerol sebacate) are summarized in this article. New developments in conducting polymers, photoresponsive polymers, amino-acid-based polymers, enzymatically degradable polymers, and peptide-activated polymers are also discussed. In addition to chemical functionalization, the scaffold designs that mimic the nano and micro features of the extracellular matrix (ECM) are presented as well, and composite and nanocomposite scaffolds are also reviewed.

Biodegradable electroactive polymers for electrochemically-triggered drug delivery

We report biodegradable electroactive polymer (EAP)-based materials and their application as drug delivery devices.

Oligoethylene-glycol-functionalized polyoxythiophenes for cell engineering: syntheses, characterizations, and cell compatibilities

A series of methyl- or benzyl-capped oligoethylene glycol functionalized 2,5-dibromo-3-oxythiophenes are synthesized and successfully polymerized by either Grignard metathesis (GRIM) polymerization or reductive coupling polymerization to yield the corresponding polymers in reasonable yields and molecular weights with narrow molecular weight distribution. These synthesized polyoxythiophenes exhibit high electroactivity and stability in aqueous solution when a potential is applied. Polyoxythiophenes from different polymerization approaches display different colors after purification and spectroelectrochemical studies confirm that the difference of color is from the difference of doping state. Little cytotoxicity is observed for the polymers by in vitro cell compatibility assay. NIH3T3 fibroblast cells are well attached and proliferate on spin-coated films. These results indicate that oligoethylene-glycol-functionalized polyoxythiophenes are promising candidates as conducting biomatierals for biomedical and bioengineering applications.