A Novel Electroactive Agarose-Aniline Pentamer Platform as a Potential Candidate for Neural Tissue Engineering

Hydrophobic Silk Fibroin-Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications

Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin-agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin-agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs' gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1-94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (-60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management.

Agarose amplification based sequencing characterization cell-free RNA in preimplantation spent embryo medium

BACKGROUND

The cell-free RNA (cf-RNA) of spent embryo medium (SEM) has aroused a concern of academic and clinical researchers for its potential use in non-invasive embryo screening. However, comprehensive characterization of cf-RNA from SEM still presents significant technical challenges, primarily due to the limited volume of SEM. Hence, there is urgently need to a small input liquid volume and ultralow amount of cf-RNA library preparation method to unbiased cf-RNA sequencing from SEM. (75) RESULT: Here, we report a high sensitivity agarose amplification-based cf-RNA sequencing method (SEM-Acf) for human preimplantation SEM cf-RNA analysis. It is a cf-RNA sequencing library preparation method by adding agarose amplification. The agarose amplification sensitivity (0.005 pg) and efficiency (105.35 %) were increased than that of without agarose addition (0.45 pg and 96.06 %) by ∼ 90 fold and 9.29 %, respectively. Compared with SMART sequencing (SMART-seq), the correlation of gene expression was stronger in different SEM samples by using SEM-Acf. The cf-RNA number of detected and coverage uniformity of 3' end were significantly increased. The proportion of 5' end adenine, alternative splicing events and short fragments (<400 bp) were increased. It is also found that 4-mer end motifs of cf-RNA fragments was significantly differences between different embryonic stage by day3 spent cleavage medium and day5/6 spent blastocyst medium. (141) SIGNIFICANCE: This study established an efficient SEM amplification and library preparation method. Additionally, we successfully described the characterizations of SEM cf-RNA in preimplantation embryo using SEM-Acf, including expression features and fragment lengths. SEM-Acf facilitates the exploration of cf-RNA as a noninvasive embryo screening biomarker, and opens up potential clinical utilities of small input liquid volume and ultralow amount cf-RNA sequencing. (59).

Conductive hydrogels based on tragacanth and silk fibroin containing dopamine functionalized carboxyl-capped aniline pentamer: Merging hemostasis, antibacterial, and anti-oxidant properties into a multifunctional hydrogel for burn wound healing

Hydrogels possessing both conductive characteristics and notable antibacterial and antioxidant properties hold considerable significance within the realm of wound healing and recovery. The object of current study is the development of conductive hydrogels with antibacterial and antioxidant properties, emphasizing their potential for effective wound healing, especially in treating third-degree burns. For this purpose, various conductive hydrogels are developed based on tragacanth and silk fibroin, with variable dopamine functionalized carboxyl-capped aniline pentamer (CAP@DA). The FTIR analysis confirms that the CAP powder was successfully synthesized and modified with DA. The results show that the incorporation of CAP@DA into hydrogels can increase the porosity and swellability of the hydrogels. Additionally, the mechanical and viscoelastic properties of the hydrogels are also improved. The release of vancomycin from the hydrogels is sustained over time, and the hydrogels are effective in inhibiting the growth of Methicillin-resistant Staphylococcus aureus (MRSA). In vitro cell studies of the hydrogels show that all hydrogels are biocompatible and support cell attachment. The hydrogels' tissue adhesiveness yielded a satisfactory hemostatic outcome in a rat-liver injury model. The third-degree burn was created on the dorsal back paravertebral region of the rats and then grafted with hydrogels. The burn was monitored for 3, 7, and 14 days to evaluate the efficacy of the hydrogel in promoting wound healing. The hydrogels revealed treatment effect, resulting in enhancements in wound closure, dermal collagen matrix production, new blood formation, and anti-inflammatory properties. Better results were obtained for hydrogel with increasing CAP@DA. In summary, the multifunctional conducive hydrogel, featuring potent antibacterial properties, markedly facilitated the wound regeneration process.

Structure-activity relationships of bioactive polysaccharides extracted from macroalgae towards biomedical application: A review

Macroalgae are valuable and structurally diverse sources of bioactive compounds among marine resources. The cell walls of macroalgae are rich in polysaccharides which exhibit a wide range of biological activities, such as anticoagulant, antioxidant, antiviral, anti-inflammatory, immunomodulatory, and antitumor activities. Macroalgae polysaccharides (MPs) have been recognized as one of the most promising candidates in the biomedical field. However, the structure-activity relationships of bioactive polysaccharides extracted from macroalgae are complex and influenced by various factors. A clear understanding of these relationships is indeed critical in developing effective biomedical applications with MPs. In line with these challenges and knowledge gaps, this paper summarized the structural characteristics of marine MPs from different sources and relevant functional and bioactive properties and particularly highlighted those essential effects of the structure-bioactivity relationships presented in biomedical applications. This review not only focused on elucidating a particular action mechanism of MPs, but also intended to identify a novel or potential application of these valued compounds in the biomedical field in terms of their structural characteristics. In the last, the challenges and prospects of MPs in structure-bioactivity elucidation were further discussed and predicted, where they were emphasized on exploring modern biotechnology approaches potentially applied to expand their promising biomedical applications.

Polysaccharide-based hydrogels for medical devices, implants and tissue engineering: A review

Hydrogels are highly biocompatible biomaterials composed of crosslinked three-dimensional networks of hydrophilic polymers. Owing to their natural origin, polysaccharide-based hydrogels (PBHs) possess low toxicity, high biocompatibility and demonstrate in vivo biodegradability, making them great candidates for use in various biomedical devices, implants, and tissue engineering. In addition, many polysaccharides also show additional biological activities such as antimicrobial, anticoagulant, antioxidant, immunomodulatory, hemostatic, and anti-inflammatory, which can provide additional therapeutic benefits. The porous nature of PBHs allows for the immobilization of antibodies, aptamers, enzymes and other molecules on their surface, or within their matrix, potentiating their use in biosensor devices. Specific polysaccharides can be used to produce transparent hydrogels, which have been used widely to fabricate ocular implants. The ability of PBHs to encapsulate drugs and other actives has been utilized for making neural implants and coatings for cardiovascular devices (stents, pacemakers and venous catheters) and urinary catheters. Their high water-absorption capacity has been exploited to make superabsorbent diapers and sanitary napkins. The barrier property and mechanical strength of PBHs has been used to develop gels and films as anti-adhesive formulations for the prevention of post-operative adhesion. Finally, by virtue of their ability to mimic various body tissues, they have been explored as scaffolds and bio-inks for tissue engineering of a wide variety of organs. These applications have been described in detail, in this review.

Electroconductive Nanofibrous Scaffolds Enable Neuronal Differentiation in Response to Electrical Stimulation without Exogenous Inducing Factors

Among the various biochemical and biophysical inducers for neural regeneration, electrical stimulation (ES) has recently attracted considerable attention as an efficient means to induce neuronal differentiation in tissue engineering approaches. The aim of this in vitro study was to develop a nanofibrous scaffold that enables ES-mediated neuronal differentiation in the absence of exogenous soluble inducers. A nanofibrous scaffold composed of polycaprolactone (PCL), poly-L-lactic acid (PLLA), and single-walled nanotubes (SWNTs) was fabricated via electrospinning and its physicochemical properties were investigated. The cytocompatibility of the electrospun composite with the PC12 cell line and bone marrow-derived mesenchymal stem cells (BMSCs) was investigated. The results showed that the PCL/PLLA/SWNT nanofibrous scaffold did not exhibit cytotoxicity and supported cell attachment, spreading, and proliferation. ES was applied to cells cultured on the nanofibrous scaffolds at different intensities and the expression of the three neural markers (Nestin, Microtubule-associated protein 2, and β tubulin-3) was evaluated using RT-qPCR analysis. The results showed that the highest expression of neural markers could be achieved at an electric field intensity of 200 mV/cm, suggesting that the scaffold in combination with ES can be an efficient tool to accelerate neural differentiation in the absence of exogenous soluble inducers. This has important implications for the regeneration of nerve injuries and may provide insights for further investigations of the mechanisms underlying ES-mediated neuronal commitment.

Nanoenzyme-Reinforced Multifunctional Scaffold Based on Ti3C2Tx MXene Nanosheets for Promoting Structure-Functional Skeletal Muscle Regeneration via Electroactivity and Microenvironment Management

The completed volumetric muscle loss (VML) regeneration remains a challenge due to the limited myogenic differentiation as well as the oxidative, inflammatory, and hypoxic microenvironment. Herein, a 2D Ti3C2Tx MXene@MnO2 nanocomposite with conductivity and microenvironment remodeling was fabricated and applied in developing a multifunctional hydrogel (FME) scaffold to simultaneously conquer these hurdles. Among them, Ti3C2Tx MXene with electroconductive ability remarkably promotes myogenic differentiation via enhancing the myotube formation and upregulating the relative expression of the myosin heavy chain (MHC) protein and myogenic genes (MyoD and MyoG) in myogenesis. The MnO2 nanoenzyme-reinforced Ti3C2Tx MXene significantly reshapes the hostile microenvironment by eliminating reactive oxygen species (ROS), regulating macrophage polarization from M1 to M2 and continuously supplying O2. Together, the FME hydrogel as a bioactive multifunctional scaffold significantly accelerates structure-functional VML regeneration in vivo and represents a multipronged strategy for the VML regeneration via electroactivity and microenvironment management.

Potential of graphene-based nanomaterials for cardiac tissue engineering

Cardiovascular diseases are the primary cause of death worldwide. Despite significant advances in pharmacological treatments and surgical interventions to restore heart function after myocardial infarction, it can progress to heart failure due to the restricted inherent potential of adult cardiomyocytes to self-regenerate. Hence, the evolution of new therapeutic methods is critical. Nowadays, novel approaches in tissue engineering have assisted in restoring biological and physical specifications of the injured myocardium and, hence, cardiac function. The incorporation of a supporting matrix that could mechanically and electronically support the heart tissue and stimulate the cells to proliferate and regenerate will be advantageous. Electroconductive nanomaterials can facilitate intracellular communication and aid synchronous contraction via electroactive substrate creation, preventing the issue of arrhythmia in the heart. Among a wide range of electroconductive materials, graphene-based nanomaterials (GBNs) are promising for cardiac tissue engineering (CTE) due to their outstanding features including high mechanical strength, angiogenesis, antibacterial and antioxidant properties, low cost, and scalable fabrication. In the present review, we discuss the effect of applying GBNs on angiogenesis, proliferation, and differentiation of implanted stem cells, their antibacterial and antioxidant properties, and their role in improving the electrical and mechanical properties of the scaffolds for CTE. Also, we summarize the recent research that has applied GBNs in CTE. Finally, we present a concise discussion on the challenges and prospects.

Fabrication, characterization and emulsifying properties of agarose microgel

Agarose microgels were prepared with bottom-up approach, and the emulsifying properties of agarose microgels were investigated. Physical properties of microgels are varied with agarose concentration, and further affect the emulsifying performance of microgels. Enhanced surface hydrophobicity index and decreased particle size of microgels was recorded with the increasing of agarose concentration, which was conducive to emulsifying properties of microgels. Improved interfacial adsorption of microgels was evidenced by Dynamic surface tension and SEM. However, microscopic morphology of microgel at O/W interface indicated that increasing agarose concentration could weaken the deformability of microgels. The influence of external conditions (pH and NaCl) on the physical properties of microgels were investigated, and their effects on the emulsion stability were evaluated. Compared with acidification, NaCl was appeared to be more destructive to emulsion stability. Results indicated acidification and NaCl could decrease surface hydrophobicity index of microgels, but there was differentiation in the variation of particle size. It was inferred that deformability of microgels could make contribution to the stability of emulsion. This study verified that microgelation was a feasible scheme to improve the interfacial properties of agarose, and the influence of agarose concentration, pH, and NaCl on the emulsifying performance of microgels was investigated.

Recent progress in the manipulation of biochemical and biophysical cues for engineering functional tissues

Tissue engineering (TE) is currently considered a cutting-edge discipline that offers the potential for developing treatments for health conditions that negatively affect the quality of life. This interdisciplinary field typically involves the combination of cells, scaffolds, and appropriate induction factors for the regeneration and repair of damaged tissue. Cell fate decisions, such as survival, proliferation, or differentiation, critically depend on various biochemical and biophysical factors provided by the extracellular environment during developmental, physiological, and pathological processes. Therefore, understanding the mechanisms of action of these factors is critical to accurately mimic the complex architecture of the extracellular environment of living tissues and improve the efficiency of TE approaches. In this review, we recapitulate the effects that biochemical and biophysical induction factors have on various aspects of cell fate. While the role of biochemical factors, such as growth factors, small molecules, extracellular matrix (ECM) components, and cytokines, has been extensively studied in the context of TE applications, it is only recently that we have begun to understand the effects of biophysical signals such as surface topography, mechanical, and electrical signals. These biophysical cues could provide a more robust set of stimuli to manipulate cell signaling pathways during the formation of the engineered tissue. Furthermore, the simultaneous application of different types of signals appears to elicit synergistic responses that are likely to improve functional outcomes, which could help translate results into successful clinical therapies in the future.

The Use of Biomaterials in Three-Dimensional Culturing of Cancer Cells

Cell culture is an important tool in biological research. Most studies use 2D cell culture, but cells grown in 2D cell culture have drawbacks, including limited cell and cell-extracellular matrix interactions, which make it inaccurate to model conditions in vivo. Anticancer drug screening is an important research and development process for developing new drugs. As an experiment to mimic the cancer environment in vivo, several studies have been carried out on 3-dimensional (3D) cell cultures with added biomaterials. The use of hydrogel in 3D culture cells is currently developing. The type of hydrogel used might influence cell morphology, viability, and drug screening outcome. Therefore, this review discusses 3D cell culture research regarding the addition of biomaterials.

Facile Capture of Recombinant Human Erythropoietin on Mesoporous Affinity Hydrogel Matrix Functionalized with Azoboronate

Boronate affinity ligands (BALs) have gained attention for glycoproteins capture and recognition due to their unique affinity interaction with glycans. In this paper, the effect of azo immobilization of phenylboronic acid on the reduction of adsorption pH of a recombinant glycoprotein (i.e., rhEPO) on hydrogel microparticles was investigated. To evaluate the influence of intraparticle porosity on protein adsorption, microporous (MicroBead) and mesoporous (MesoBead) agarose beads carrying two levels of amine densities were functionalized with azoboronate ligand. Affinity adsorption of the glycoprotein during static and dynamic adsorptions at relatively low pHs of 8 and 7 was studied. Results revealed successful adsorption of rhEPO at pH = 8 through affinity capture of glycans by azoboronate ligands. Increased amine density provided 1.1 and 1.5 times higher static adsorption capacities and dynamic performance efficiencies, respectively. In addition, adsorption capacities and initial adsorption rates of rhEPO on MesoBeads were respectively 1.4 and 2.5-2.8 times of MicroBeads. Also, at pH = 8, MesoBeads recorded higher dynamic recoveries (59 and 91%) compared with microporous ones (46 and 69%) since mesoporosity facilitates intraparticle mass transfer. Reduction of binding pH from 8 to 7 resulted in a sharp decrease in dynamic recovery (14%), indicating the appropriate binding pH of azoPBA to be above 7. The azoboronate affinity ligand is a leading candidate for capturing glycoproteins at relatively low pH. Also, mesoporous microparticles are appropriate tools in more efficient medium-sized protein binding applications.

Electrically conductive carbon-based (bio)-nanomaterials for cardiac tissue engineering

A proper self-regenerating capability is lacking in human cardiac tissue which along with the alarming rate of deaths associated with cardiovascular disorders makes tissue engineering critical. Novel approaches are now being investigated in order to speedily overcome the challenges in this path. Tissue engineering has been revolutionized by the advent of nanomaterials, and later by the application of carbon-based nanomaterials because of their exceptional variable functionality, conductivity, and mechanical properties. Electrically conductive biomaterials used as cell bearers provide the tissue with an appropriate microenvironment for the specific seeded cells as substrates for the sake of protecting cells in biological media against attacking mechanisms. Nevertheless, their advantages and shortcoming in view of cellular behavior, toxicity, and targeted delivery depend on the tissue in which they are implanted or being used as a scaffold. This review seeks to address, summarize, classify, conceptualize, and discuss the use of carbon-based nanoparticles in cardiac tissue engineering emphasizing their conductivity. We considered electrical conductivity as a key affecting the regeneration of cells. Correspondingly, we reviewed conductive polymers used in tissue engineering and specifically in cardiac repair as key biomaterials with high efficiency. We comprehensively classified and discussed the advantages of using conductive biomaterials in cardiac tissue engineering. An overall review of the open literature on electroactive substrates including carbon-based biomaterials over the last decade was provided, tabulated, and thoroughly discussed. The most commonly used conductive substrates comprising graphene, graphene oxide, carbon nanotubes, and carbon nanofibers in cardiac repair were studied.

Assessment of Binary Agarose-Carbopol Buccal Gels for Mucoadhesive Drug Delivery: Ex Vivo and In Vivo Characterization

Agarose (AG) is a naturally occurring biocompatible marine seaweed extract that is converted to hydrocolloid gel in hot water with notable gel strength. Currently, its mucoadhesion properties have not been fully explored. Therefore, the main aim of this study was to evaluate the mucoadhesive potential of AG binary dispersions in combination with Carbopol 934P (CP) as mucoadhesive gel preparations. The gels fabricated via homogenization were evaluated for ex vivo mucoadhesion, swelling index (SI), dissolution and stability studies. The mucoadhesive properties of AG were concentration dependent and it was improved by the addition of CP. Maximum mucoadhesive strength (MS) (27.03 g), mucoadhesive flow time (FT) (192.2 min), mucoadhesive time in volunteers (MT) (203.2 min) and SI (23.6% at 4 h) were observed with formulation F9. The mucoadhesive time investigated in volunteers (MT) was influenced by AG concentration and was greater than corresponding FT values. Formulations containing 0.3%, w/v AG (F3 and F9) were able to sustain the release (~99%) for both drugs till 3 h. The optimized formulation (F9) did not evoke any inflammation, irritation or pain in the buccal cavity of healthy volunteers and was also stable up to 6 months. Therefore, AG could be considered a natural and potential polymer with profound mucoadhesive properties to deliver drugs through the mucosal route.

Evaluating Novel Agarose-Based Buccal Gels Scaffold: Mucoadhesive and Pharmacokinetic Profiling in Healthy Volunteers

Agarose (AG) forms hydrocolloid in hot water and possesses a noteworthy gel strength. However, no reasonable scientific work on investigating the mucoadhesive character of AG has been reported. Therefore, the current study was designed to develop AG and carbopol (CP) based buccal gel scaffold for simultaneous release of benzocaine (BZN) and tibezonium iodide (TIB). Gels’ scaffold formulations (F1−F12) were prepared with varied concentrations (0.5−1.25% w/v) of AG and CP alone or their blends (AG-CP) using homogenization technique. The prepared formulations were characterized for solid-state, physicochemical, in vitro, ex vivo, and in vivo mucoadhesive studies in healthy volunteers. The results showed that mucoadhesive property of AG was concentration dependent but improved by incorporating CP in the scaffolds. The ex vivo mucoadhesive time reached >36 h when AG was used alone or blended with CP at 1% w/v concentration or above. The optimized formulation (F10) depicted >98% drugs release within 8 h and was also storage stable up to six months. The salivary concentration of BZN and TIB from formulation F10 yielded a Cmax value of 9.97 and 8.69 µg/mL at 2 and 6 h (tmax), respectively. In addition, the FTIR, PXRD, and DSC results confirmed the presence of no unwanted interaction among the ingredients. Importantly, the mucoadhesive study performed on healthy volunteers did not provoke any signs of inflammation, pain, or swelling. Clearly, it was found from the results that AG-CP scaffold provided better mucoadhesive properties in comparison to pure AG or CP. Conclusively, the developed AG based mucoadhesive drug delivery system could be considered a potential alternative for delivering drugs through the mucoadhesive buccal route.

Polydopamine Biomaterials for Skin Regeneration

Designing biomaterials capable of biomimicking wound healing and skin regeneration has been receiving increasing attention recently. Some biopolymers behave similarly to the extracellular matrix (ECM), supporting biointerfacial adhesion and intrinsic cellular interactions. Polydopamine (PDA) is a natural bioadhesive and bioactive polymer that endows high chemical versatility, making it an exciting candidate for a wide range of biomedical applications. Moreover, biomaterials based on PDA and its derivatives have near-infrared (NIR) absorption, excellent biocompatibility, intrinsic antioxidative activity, antibacterial activity, and cell affinity. PDA can regulate cell behavior by controlling signal transduction pathways. It governs the focal adhesion behavior of cells at the biomaterials interface. These features make melanin-like PDA a fascinating biomaterial for wound healing and skin regeneration. This paper overviews PDA-based biomaterials' synthesis, properties, and interactions with biological entities. Furthermore, the utilization of PDA nano- and microstructures as a constituent of wound-dressing formulations is highlighted.

Robust Silica–Agarose Composite Aerogels with Interpenetrating Network Structure by In Situ Sol–Gel Process

Aerogels are three-dimensional nanoporous materials with outstanding properties, especially great thermal insulation. Nevertheless, their extremely high brittleness restricts their practical application. Recently, although the mechanical properties of silica aerogels have been improved by regulating the precursor or introducing a polymer reinforcer, these preparation processes are usually tedious and time-consuming. The purpose of this study was to simplify the preparation process of these composite aerogels. A silicic acid solution treated with cation exchange resin was mixed with agarose (AG) to gel in situ, and then composite aerogels (CAs) with an interpenetrating network (IPN) structure were obtained by aging and supercritical CO₂ fluid (SCF) drying. Compared to previous works, the presented CAs preparation process is briefer and more environmentally friendly. Moreover, the CAs exhibit a high specific surface area (420.5 m²/g), low thermal conductivity (28.9 mW m⁻¹ K⁻¹), excellent thermal insulation properties, and thermal stability. These results show that these CAs can be better used in thermal insulation.

Sensitive and Low-Bias Transcriptome Sequencing Using Agarose PCR

Transcriptome sequencing has emerged as an important research tool for exploring the mysteries of life at the single-cell level. However, its wide application is limited by the bias associated with the amplification reactions which is essential for library building of trace RNA. In this study, low-melting-point agarose was added to the amplification reactions to take advantage of its molecular crowding effect and polymer cross-linked structure to improve the sensitivity of the reactions and reduce bias. To further evaluate the performance of the method, it was applied to transcriptome sequencing of microregion samples from brain tissue sections of mice with Parkinson's disease at the single cell level. The results showed that agarose PCR had better performance than in-tube PCR. Further application of agarose PCR to transcriptome library sequencing could obtain data closer to that of unamplified. With the addition of low melting point agarose, the sensitivity of the amplification reaction was significantly increased, while homogeneity was increased by approximately 2-fold. Not only that, but this work also provides 11% sensitivity improvement for spatial transcriptomic study on Parkinson's disease-associated gene detection. The agarose PCR provides a new tool for efficient and homogeneous amplification of trace samples and can be widely used for spatial transcriptome library sequencing and studies.

Regenerative rehabilitation with conductive biomaterials for spinal cord injury

The individual approaches of regenerative medicine efforts alone and rehabilitation efforts alone have not yet fully restored function after severe spinal cord injury (SCI). Regenerative rehabilitation may be leveraged to promote regeneration of the spinal cord tissue, and promote reorganization of the regenerated neural pathways and intact spinal circuits for better functional recovery for SCI. Conductive biomaterials may be a linchpin that empowers the synergy between regenerative medicine and rehabilitation approaches, as electrical stimulation applied to the spinal cord could facilitate neural reorganization. In this review, we discuss current regenerative medicine approaches in clinical trials and the rehabilitation, or neuromodulation, approaches for SCI, along with their respective translational limitations. Furthermore, we review the translational potential, in a surgical context, of conductive biomaterials (e.g., conductive polymers, carbon-based materials, metallic nanoparticle-based materials) as they pertain to SCI. While pre-formed scaffolds may be difficult to translate to human contusion SCIs, injectable composites that contain blended conductive components and can form within the injury may be more translational. However, given that there are currently no in vivo SCI studies that evaluated conductive materials combined with rehabilitation approaches, we discuss several limitations of conductive biomaterials, including demonstrating safety and efficacy, that will need to be addressed in the future for conductive biomaterials to become SCI therapeutics. Even so, the use of conductive biomaterials creates a synergistic opportunity to merge the fields of regenerative medicine and rehabilitation and redefine what regenerative rehabilitation means for the spinal cord. STATEMENT OF SIGNIFICANCE: For spinal cord injury (SCI), the individual approaches of regenerative medicine and rehabilitation are insufficient to fully restore functional recovery; however, the goal of regenerative rehabilitation is to combine these two disparate fields to maximize the functional outcomes. Concepts similar to regenerative rehabilitation for SCI have been discussed in several reviews, but for the first time, this review considers how conductive biomaterials may synergize the two approaches. We cover current regenerative medicine and rehabilitation approaches for SCI, and the translational advantages and disadvantages, in a surgical context, of conductive biomaterials used in biomedical applications that may be additionally applied to SCI. Furthermore, we identify the current limitations and translational challenges for conductive biomaterials before they may become therapeutics for SCI.

Biomaterial-based strategies for in vitro neural models

In vitro models have been used as a complementary tool to animal studies in understanding the nervous system's physiological mechanisms and pathological disorders, while also serving as platforms to evaluate the safety and efficiency of therapeutic candidates. Following recent advances in materials science, micro- and nanofabrication techniques and cell culture systems, in vitro technologies have been rapidly gaining the potential to bridge the gap between animal and clinical studies by providing more sophisticated models that recapitulate key aspects of the structure, biochemistry, biomechanics, and functions of human tissues. This was made possible, in large part, by the development of biomaterials that provide cells with physicochemical features that closely mimic the cellular microenvironment of native tissues. Due to the well-known material-driven cellular response and the importance of mimicking the environment of the target tissue, the selection of optimal biomaterials represents an important early step in the design of biomimetic systems to investigate brain structures and functions. This review provides a comprehensive compendium of commonly used biomaterials as well as the different fabrication techniques employed for the design of neural tissue models. Furthermore, the authors discuss the main parameters that need to be considered to develop functional platforms not only for the study of brain physiological functions and pathological processes but also for drug discovery/development and the optimization of biomaterials for neural tissue engineering.

Application of Hybrid Electrically Conductive Hydrogels Promotes Peripheral Nerve Regeneration

Peripheral nerve injury (PNI) occurs frequently, and the prognosis is unsatisfactory. As the gold standard of treatment, autologous nerve grafting has several disadvantages, such as lack of donors and complications. The use of functional biomaterials to simulate the natural microenvironment of the nervous system and the combination of different biomaterials are considered to be encouraging alternative methods for effective tissue regeneration and functional restoration of injured nerves. Considering the inherent presence of an electric field in the nervous system, electrically conductive biomaterials have been used to promote nerve regeneration. Due to their singular physical properties, hydrogels can provide a three-dimensional hydrated network that can be integrated into diverse sizes and shapes and stimulate the natural functions of nerve tissue. Therefore, conductive hydrogels have become the most effective biological material to simulate human nervous tissue's biological and electrical characteristics. The principal merits of conductive hydrogels include their physical properties and their electrical peculiarities sufficient to effectively transmit electrical signals to cells. This review summarizes the recent applications of conductive hydrogels to enhance peripheral nerve regeneration.

Recent advances in industrial applications of seaweeds

Seaweeds have been generally utilized as food and alternative medicine in different countries. They are specifically used as a raw material for wine, cheese, soup, tea, noodles, etc. In addition, seaweeds are potentially good resources of protein, vitamins, minerals, carbohydrates, essential fatty acids and dietary fiber. The quality and quantity of biologically active compounds in seaweeds depend on season and harvesting period, seaweed geolocation as well as ecological factors. Seaweeds or their extracts have been studied as innovative sources for a variety of bioactive compounds such as polyunsaturated fatty acids, polyphenols, carrageenan, fucoidan, etc. These secondary metabolites have been shown to have antioxidant, antimicrobial, antiviral, anticancer, antidiabetic, anti-inflammatory, anti-aging, anti-obesity and anti-tumour properties. They have been used in pharmaceutical/medicine, and food industries since bioactive compounds from seaweeds are regarded as safe and natural. Therefore, this article provides up-to-date information on the applications of seaweed in different industries such as pharmaceutical, biomedical, cosmetics, dermatology and agriculture. Further studies on innovative extraction methods, safety issue and health-promoting properties should be reconsidered. Moreover, the details of the molecular mechanisms of seaweeds and their bioactive compounds for physiological activities are to be clearly elucidated.

A review on advances in the applications of spider silk in biomedical issues

Spider silk, as one of the hardest natural and biocompatible substances with extraordinary strength and flexibility, have become an ideal option in various areas of science and have made their path onto the biomedical industry. Despite its growing popularity, the difficulties in the extraction of silks from spiders and farming them have made it unaffordable and almost impossible for industrial scale. Biotechnology helped production of spider silks recombinantly in different hosts and obtaining diverse morphologies out of them based on different processing and assembly procedures. Herein, the characteristics of these morphologies and their advantages and disadvantages are summarized. A detailed view about applications of recombinant silks in skin regeneration and cartilage, tendon, bone, teeth, cardiovascular, and neural tissues engineering are brought out, where there is a need for strong scaffolds to support cell growth. Likewise, spider silk proteins have applications as conduit constructs, medical sutures, and 3D printer bioinks. Other characteristics of spider silks, such as low immunogenicity, hydrophobicity, homogeneity, and adjustability, have attracted much attention in drug and gene delivery. Finally, the challenges and obstacles ahead for industrializing the production of spider silk proteins in sufficient quantities in biomedicine, along with solutions to overcome these barriers, are discussed.

Cationic, anionic and neutral polysaccharides for skin tissue engineering and wound healing applications

Today, chronic wound care and management can be regarded as a clinically critical issue. However, the limitations of current approaches for wound healing have encouraged researchers and physicians to develop more efficient alternative approaches. Advances in tissue engineering and regenerative medicine have resulted in the development of promising approaches that can accelerate wound healing and improve the skin regeneration rate and quality. The design and fabrication of scaffolds that can address the multifactorial nature of chronic wound occurrence and provide support for the healing process can be considered an important area requiring improvement. In this regard, polysaccharide-based scaffolds have distinctive properties such as biocompatibility, biodegradability, high water retention capacity and nontoxicity, making them ideal for wound healing applications. Their tunable structure and networked morphology could facilitate a number of functions, such as controlling their diffusion, maintaining wound moisture, absorbing a large amount of exudates and facilitating gas exchange. In this review, the wound healing process and the influential factors, structure and properties of carbohydrate polymers, physical and chemical crosslinking of polysaccharides, scaffold fabrication techniques, and the use of polysaccharide-based scaffolds in skin tissue engineering and wound healing applications are discussed.

Human Organs-on-Chips: A Review of the State-of-the-Art, Current Prospects, and Future Challenges

New emerging technologies, remarkably miniaturized 3D organ models and microfluidics, enable simulation of the real in vitro microenvironment ex vivo more closely. There are many fascinating features of innovative organ-on-a-chip (OOC) technology, including the possibility of integrating semipermeable and/or stretchable membranes, creating continuous perfusion of fluids into microchannels and chambers (while maintaining laminar flow regime), embedding microdevices like microsensors, microstimulators, micro heaters, or different cell lines, along with other 3D cell culture technologies. OOC systems are designed to imitate the structure and function of human organs, ranging from breathing lungs to beating hearts. This technology is expected to be able to revolutionize cell biology studies, personalized precision medicine, drug development process, and cancer diagnosis/treatment. OOC systems can significantly reduce the cost associated with tedious drug development processes and the risk of adverse drug reactions in the body, which makes drug screening more effective. The review mainly focus on presenting an overview of the several previously developed OOC systems accompanied by subjects relevant to pharmacy-, cancer-, and placenta-on-a-chip. The challenging issues and opportunities related to these systems are discussed, along with a future perspective for this technology.

Preparation, properties and application of graphene-based materials in tissue engineering scaffolds

Tissue engineering has great application prospect as an effective treatment for tissue and organ injury, functional reduction or loss. Bioactive tissues are reconstructed and damaged organs are repaired by the three elements including cells, scaffold materials and growth factors. Graphene-based composites can be used as reinforcing auxiliary materials for tissue scaffold preparation because of their large specific surface area, and good mechanical support. Tissue engineering scaffolds with graphene-based composites have been widely studied. Part of research have focused on the application of graphene-based composites in single tissue engineering; The basic principles of graphene materials used in tissue engineering are summarized in some researches. Some studies emphasized the key problems and solutions urgently needed to be solved in the development of tissue engineering, and discussed their application prospect. Some related studies mainly focused on the conductivity of graphene, and discussed the application of electroactive scaffolds in tissue engineering. In this review, the composite materials for preparing tissue engineering scaffolds are briefly described, which emphasizes the preparation methods, biological properties and practical applications of graphene-based composite scaffolds. The synthetic techniques with stressing solvent casting, electrospinning and 3D printing are introduced in detail. The mechanical, cell-oriented and biocompatible properties of graphene-based composite scaffolds in tissue engineering are analyzed and summarized. Their applications in bone tissue engineering, nerve tissue engineering, cardiovascular tissue engineering and other tissue engineering are summarized systematically. In addition, this work also looks forward to the difficulties and challenges in the future research, providing some references for the follow-up research of graphene-based composites in tissue engineering scaffolds.

Conductive Polymeric-Based Electroactive Scaffolds for Tissue Engineering Applications: Current Progress and Challenges from Biomaterials and Manufacturing Perspectives

The practice of combining external stimulation therapy alongside stimuli-responsive bio-scaffolds has shown massive potential for tissue engineering applications. One promising example is the combination of electrical stimulation (ES) and electroactive scaffolds because ES could enhance cell adhesion and proliferation as well as modulating cellular specialization. Even though electroactive scaffolds have the potential to revolutionize the field of tissue engineering due to their ability to distribute ES directly to the target tissues, the development of effective electroactive scaffolds with specific properties remains a major issue in their practical uses. Conductive polymers (CPs) offer ease of modification that allows for tailoring the scaffold's various properties, making them an attractive option for conductive component in electroactive scaffolds. This review provides an up-to-date narrative of the progress of CPs-based electroactive scaffolds and the challenge of their use in various tissue engineering applications from biomaterials perspectives. The general issues with CP-based scaffolds relevant to its application as electroactive scaffolds were discussed, followed by a more specific discussion in their applications for specific tissues, including bone, nerve, skin, skeletal muscle and cardiac muscle scaffolds. Furthermore, this review also highlighted the importance of the manufacturing process relative to the scaffold's performance, with particular emphasis on additive manufacturing, and various strategies to overcome the CPs' limitations in the development of electroactive scaffolds.

Superior Technique for the Production of Agarose Dressing Containing Sericin and Its Wound Healing Property

Finding a simple and eco-friendly production technique that matches to the natural agent and results in a truly valuable natural scaffold production is still limited amongst the intensively competitive natural scaffold development. Therefore, the purpose of this study was to develop natural scaffolds that were environmentally friendly, low cost, and easily produced, using natural agents and a physical crosslinking technique. These scaffolds were prepared from agarose and sericin using the freeze-drying method (D) or freeze-thawing together with the freeze-drying method (TD). Moreover, plasticizers were added into the scaffold to improve their properties. Their physical, mechanical, and biological properties were investigated. The results showed that scaffolds that were prepared using the TD method had stronger bonding between sericin and other compounds, leading to a low swelling ratio and low protein release of the scaffolds. This property may be applied in the development of further material as a controlled drug release scaffold. Adding plasticizers, especially glycerin, into the scaffolds significantly increased elongation properties, leading to an increase in elasticity of the scaffold. Moreover, all scaffolds could activate cell migration, which had an advantage on wound healing acceleration. Accordingly, this study was successful in developing natural scaffolds using natural agents and simple and green crosslinking methods.

Biomaterial-Assisted Regenerative Medicine

This review aims to show case recent regenerative medicine based on biomaterial technologies. Regenerative medicine has arousing substantial interest throughout the world, with “The enhancement of cell activity” one of the essential concepts for the development of regenerative medicine. For example, drug research on drug screening is an important field of regenerative medicine, with the purpose of efficient evaluation of drug effects. It is crucial to enhance cell activity in the body for drug research because the difference in cell condition between in vitro and in vivo leads to a gap in drug evaluation. Biomaterial technology is essential for the further development of regenerative medicine because biomaterials effectively support cell culture or cell transplantation with high cell viability or activity. For example, biomaterial-based cell culture and drug screening could obtain information similar to preclinical or clinical studies. In the case of in vivo studies, biomaterials can assist cell activity, such as natural healing potential, leading to efficient tissue repair of damaged tissue. Therefore, regenerative medicine combined with biomaterials has been noted. For the research of biomaterial-based regenerative medicine, the research objective of regenerative medicine should link to the properties of the biomaterial used in the study. This review introduces regenerative medicine with biomaterial.

Use of electroconductive biomaterials for engineering tissues by 3D printing and 3D bioprinting

Existing methods of engineering alternatives to restore or replace damaged or lost tissues are not satisfactory due to the lack of suitable constructs that can fit precisely, function properly and integrate into host tissues. Recently, three-dimensional (3D) bioprinting approaches have been developed to enable the fabrication of pre-programmed synthetic tissue constructs that have precise geometries and controlled cellular composition and spatial distribution. New bioinks with electroconductive properties have the potential to influence cellular fates and function for directed healing of different tissue types including bone, heart and nervous tissue with the possibility of improved outcomes. In the present paper, we review the use of electroconductive biomaterials for the engineering of tissues via 3D printing and 3D bioprinting. Despite significant advances, there remain challenges to effective tissue replacement and we address these challenges and describe new approaches to advanced tissue engineering.

Alginate-Agarose Hydrogels Improve the In Vitro Differentiation of Human Dental Pulp Stem Cells in Chondrocytes. A Histological Study

Matrix-assisted autologous chondrocyte implantation (MACI) has shown promising results for cartilage repair, combining cultured chondrocytes and hydrogels, including alginate. The ability of chondrocytes for MACI is limited by different factors including donor site morbidity, dedifferentiation, limited lifespan or poor proliferation in vitro. Mesenchymal stem cells could represent an alternative for cartilage regeneration. In this study, we propose a MACI scaffold consisting of a mixed alginate-agarose hydrogel in combination with human dental pulp stem cells (hDPSCs), suitable for cartilage regeneration. Scaffolds were characterized according to their rheological properties, and their histomorphometric and molecular biology results. Agarose significantly improved the biomechanical behavior of the alginate scaffolds. Large scaffolds were manufactured, and a homogeneous distribution of cells was observed within them. Although primary chondrocytes showed a greater capacity for chondrogenic differentiation, hDPSCs cultured in the scaffolds formed large aggregates of cells, acquired a rounded morphology and expressed high amounts of type II collagen and aggrecan. Cells cultured in the scaffolds expressed not only chondral matrix-related genes, but also remodeling proteins and chondrocyte differentiation factors. The degree of differentiation of cells was proportional to the number and size of the cell aggregates that were formed in the hydrogels.

Engineering in vitro human neural tissue analogs by 3D bioprinting and electrostimulation

There is a fundamental need for clinically relevant, reproducible, and standardized in vitro human neural tissue models, not least of all to study heterogenic and complex human-specific neurological (such as neuropsychiatric) disorders. Construction of three-dimensional (3D) bioprinted neural tissues from native human-derived stem cells (e.g., neural stem cells) and human pluripotent stem cells (e.g., induced pluripotent) in particular is appreciably impacting research and conceivably clinical translation. Given the ability to artificially and favorably regulate a cell's survival and behavior by manipulating its biophysical environment, careful consideration of the printing technique, supporting biomaterial and specific exogenously delivered stimuli, is both required and advantageous. By doing so, there exists an opportunity, more than ever before, to engineer advanced and precise tissue analogs that closely recapitulate the morphological and functional elements of natural tissues (healthy or diseased). Importantly, the application of electrical stimulation as a method of enhancing printed tissue development in vitro, including neuritogenesis, synaptogenesis, and cellular maturation, has the added advantage of modeling both traditional and new stimulation platforms, toward improved understanding of efficacy and innovative electroceutical development and application.

Para-substituted sulfonic acid-doped protonated emeraldine salt nanobuds: a potent neural interface targeting PC12 cell interactions and promotes neuronal cell differentiation

Structural parameters, such as metal-like semiconductor and electrochemical properties of functionalized polyaniline, hold great potential especially for the development of the cell-substrate interface due to its ion/electron transfer ability. We report the one-step synthesis of sulfonic acid-doped polyaniline nanobuds (s-PANINbs) with controlled shape/size under various oxidation potentials. The different oxidation states of s-PANINbs are used to investigate the cell-specific platform for the induction of neuronal networks in PC12 cells, including the growth, proliferation, and differentiation of cells. The unique structure of one-dimensional (1-D) s-PANINbs enhances its intrinsic conductive properties, and facilitates the dispersibility and electrochemical activity via covalent bonding with dopants. The protonated emeraldine salt nanobuds of s-PANINbs synthesized at 0.18 V anodic potential demonstrated low resistivity (∼81.18 mΩ) and charge transfer resistance (∼3253 Ω). The most biologically compatible protonated emeraldine salt was used in vitro to induce PC12 cells associated with neurite outgrowth, contributing to the electrophysiology of neuronal cells under an external electrical stimulation. The western blotting analysis and qRT-PCR results show that β-III Tubulin, synapsin I, and TREK-1 are highly expressed in PC12 cells, confirming their successful differentiation into neural-specific cells. Our approach demonstrates the promising role of the self-standing framework based on the s-PANINbs of the protonated emeraldine salt in peripheral nerve repair for the future in vivo cell-interface.

A Green Composite Based on Gelatin/Agarose/Zeolite as a Potential Scaffold for Tissue Engineering Applications

Designing a novel platform capable of providing a proper tissue regeneration environment is a key factor in tissue engineering. Herein, a green composite based on gelatin/agarose/zeolite with pomegranate peel extract was fabricated as an innovative platform for tissue engineering. Gelatin/agarose was loaded with pomegranate peel extract-loaded zeolite to evaluate its swelling behavior, porosity, release rate, and cell viability performance. The composite characteristics were evaluated using XRD and DSC. The hydrogel performance can be adjusted for the desired aim by zeolite content manipulation, such as controlled release. It was shown that the green nanocomposite exhibited proper cellular activity along with a controlled release rate. Moreover, the hydrogel composite’s swelling ratio was decreased by adding zeolite. This study suggested a fully natural composite as a potential biomaterial for tissue engineering, which opens new ways to design versatile hydrogels for the regeneration of damaged tissues. The hydrogel performance can be adjusted specifically by zeolite content manipulation for controlled release.

Types of biomaterials useful in brain repair

Biomaterials is an emerging field in the study of brain tissue engineering and repair or neurogenesis. The fabrication of biomaterials that can replicate the mechanical and viscoelastic features required by the brain, including the poroviscoelastic responses, force dissipation, and solute diffusivity are essential to be mapped from the macro to the nanoscale level under physiological conditions in order for us to gain an effective treatment for neurodegenerative diseases. This research topic has identified a critical study gap that must be addressed, and that is to source suitable biomaterials and/or create reliable brain-tissue-like biomaterials. This chapter will define and discuss the various types of biomaterials, their structures, and their function-properties features which would enable the development of next-generation biomaterials useful in brain repair.

Polysaccharide-Based Biomaterials in Tissue Engineering: A Review

In addition to proteins and nucleic acids, polysaccharides are an important type of biomacromolecule widely distributed in plants, animals, and microorganisms. Polysaccharides are considered as promising biomaterials due to their significant bioactivities, natural abundance, immunoactivity, and chemical modifiability for tissue engineering (TE) applications. Due to the similarities of the biochemical properties of polysaccharides and the extracellular matrix of human bodies, polysaccharides are increasingly recognized and accepted. Furthermore, the degradation behavior of these macromolecules is generally nontoxic. Certain delicate properties, such as remarkable mechanical properties and tunable tissue response, can be obtained by modifying the functional groups on the surface of polysaccharide molecules. The applications of polysaccharide-based biomaterials in the TE field have been growing intensively in recent decades, for example, bone/cartilage regeneration, cardiac regeneration, neural regeneration, and skin regeneration. This review summarizes the main essential properties of polysaccharides, including their chemical properties, crosslinking mechanisms, and biological properties, and focuses on the association between their structures and properties. The recent progress in polysaccharide-based biomaterials in various TE applications is reviewed, and the prospects for future studies are addressed as well. We intend this review to offer a comprehensive understanding of and inspiration for the research and development of polysaccharide-based materials in TE.

Development of an Electroactive Hydrogel as a Scaffold for Excitable Tissues

For many cells used in tissue engineering applications, the scaffolds upon which they are seeded do not entirely mimic their native environment, particularly in the case of excitable tissues. For instance, muscle cells experience contraction and relaxation driven by the electrical input of an action potential. Electroactive materials can also deform in response to electrical input; however, few such materials are currently suitable as cell scaffolds. We previously described the development of poly(ethyelene glycol) diacrylate-poly(acrylic acid) as an electroactive scaffold. Although the scaffold itself supported cell growth and attachment, the voltage (20 V) required to actuate these scaffolds was cytotoxic. Here, we describe the further development of our hydrogels into scaffolds capable of actuation at voltages (5 V) that were not cytotoxic to seeded cells. This study describes the critical next steps towards the first functional electroactive tissue engineering scaffold.

Nanotechnology-assisted microfluidic systems: from bench to bedside

With significant advancements in research technologies, and an increasing global population, microfluidic and nanofluidic systems (such as point-of-care, lab-on-a-chip, organ-on-a-chip, etc) have started to revolutionize medicine. Devices that combine micron and nanotechnologies have increased sensitivity, precision and versatility for numerous medical applications. However, while there has been extensive research on microfluidic and nanofluidic systems, very few have experienced wide-spread commercialization which is puzzling and deserves our collective attention. For the above reasons, in this article, we review research advances that combine micro and nanotechnologies to create the next generation of nanomaterial-based microfluidic systems, the latest in their commercialization success and failure and highlight the value of these devices both in industry and in the laboratory.

Hydrogels and Dentin-Pulp Complex Regeneration: From the Benchtop to Clinical Translation

Dentin-pulp complex is a term which refers to the dental pulp (DP) surrounded by dentin along its peripheries. Dentin and dental pulp are highly specialized tissues, which can be affected by various insults, primarily by dental caries. Regeneration of the dentin-pulp complex is of paramount importance to regain tooth vitality. The regenerative endodontic procedure (REP) is a relatively current approach, which aims to regenerate the dentin-pulp complex through stimulating the differentiation of resident or transplanted stem/progenitor cells. Hydrogel-based scaffolds are a unique category of three dimensional polymeric networks with high water content. They are hydrophilic, biocompatible, with tunable degradation patterns and mechanical properties, in addition to the ability to be loaded with various bioactive molecules. Furthermore, hydrogels have a considerable degree of flexibility and elasticity, mimicking the cell extracellular matrix (ECM), particularly that of the DP. The current review presents how for dentin-pulp complex regeneration, the application of injectable hydrogels combined with stem/progenitor cells could represent a promising approach. According to the source of the polymeric chain forming the hydrogel, they can be classified into natural, synthetic or hybrid hydrogels, combining natural and synthetic ones. Natural polymers are bioactive, highly biocompatible, and biodegradable by naturally occurring enzymes or via hydrolysis. On the other hand, synthetic polymers offer tunable mechanical properties, thermostability and durability as compared to natural hydrogels. Hybrid hydrogels combine the benefits of synthetic and natural polymers. Hydrogels can be biofunctionalized with cell-binding sequences as arginine-glycine-aspartic acid (RGD), can be used for local delivery of bioactive molecules and cellularized with stem cells for dentin-pulp regeneration. Formulating a hydrogel scaffold material fulfilling the required criteria in regenerative endodontics is still an area of active research, which shows promising potential for replacing conventional endodontic treatments in the near future.

Carbon Nanomaterials for Electro-Active Structures: A Review

The use of electrically conductive materials to impart electrical properties to substrates for cell attachment proliferation and differentiation represents an important strategy in the field of tissue engineering. This paper discusses the concept of electro-active structures and their roles in tissue engineering, accelerating cell proliferation and differentiation, consequently leading to tissue regeneration. The most relevant carbon-based materials used to produce electro-active structures are presented, and their main advantages and limitations are discussed in detail. Particular emphasis is put on the electrically conductive property, material synthesis and their applications on tissue engineering. Different technologies, allowing the fabrication of two-dimensional and three-dimensional structures in a controlled way, are also presented. Finally, challenges for future research are highlighted. This review shows that electrical stimulation plays an important role in modulating the growth of different types of cells. As highlighted, carbon nanomaterials, especially graphene and carbon nanotubes, have great potential for fabricating electro-active structures due to their exceptional electrical and surface properties, opening new routes for more efficient tissue engineering approaches.

Biomaterials in Valvular Heart Diseases

Valvular heart disease (VHD) occurs as the result of valvular malfunction, which can greatly reduce patient's quality of life and if left untreated may lead to death. Different treatment regiments are available for management of this defect, which can be helpful in reducing the symptoms. The global commitment to reduce VHD-related mortality rates has enhanced the need for new therapeutic approaches. During the past decade, development of innovative pharmacological and surgical approaches have dramatically improved the quality of life for VHD patients, yet the search for low cost, more effective, and less invasive approaches is ongoing. The gold standard approach for VHD management is to replace or repair the injured valvular tissue with natural or synthetic biomaterials. Application of these biomaterials for cardiac valve regeneration and repair holds a great promise for treatment of this type of heart disease. The focus of the present review is the current use of different types of biomaterials in treatment of valvular heart diseases.

Regeneration of the peripheral nerve via multifunctional electrospun scaffolds

Over the last two decades, electrospun scaffolds have proved to be advantageous in the field of nerve tissue regeneration by connecting the cavity among the proximal and distal nerve stumps growth cones and leading to functional recovery after injury. Multifunctional nanofibrous structure of these scaffolds provides enormous potential by combining the advantages of nano-scale topography, and biological science. In these structures, selecting the appropriate materials, designing an optimized structure, modifying the surface to enhance biological functions and neurotrophic factors loading, and native cell-like stem cells should be considered as the essential factors. In this systematic review paper, the fabrication methods for the preparation of aligned nanofibrous scaffolds in yarn or conduit architecture are reviewed. Subsequently, the utilized polymeric materials, including natural, synthetic and blend are presented. Finally, their surface modification techniques, as well as, the recent advances and outcomes of the scaffolds, both in vitro and in vivo, are reviewed and discussed.

Agarose-based biomaterials for advanced drug delivery

Agarose is a prominent marine polysaccharide representing reversible thermogelling behavior, outstanding mechanical properties, high bioactivity, and switchable chemical reactivity for functionalization. As a result, agarose has received particular attention in the fabrication of advanced delivery systems as sophisticated carriers for therapeutic agents. The ever-growing use of agarose-based biomaterials for drug delivery systems resulted in rapid growth in the number of related publications, however still, a long way should be paved to achieve FDA approval for most of the proposed products. This review aims at a classification of agarose-based biomaterials and their derivatives applicable for controlled/targeted drug delivery purposes. Moreover, it attempts to deal with opportunities and challenges associated with the future developments ahead of agarose-based biomaterials in the realm of advanced drug delivery. Undoubtedly, this class of biomaterials needs further advancement, and a lot of critical questions have yet to be answered.