A novel bio electro active alginate-aniline tetramer/ agarose scaffold for tissue engineering: synthesis, characterization, drug release and cell culture study

Niobium-Treated Titanium Implants with Improved Cellular and Molecular Activities at the Tissue-Implant Interface

There have been several attempts to improve the cellular and molecular interactions at the tissue-implant interface. Here, the biocompatibility of titanium-based implants (e.g., Grade 2 Titanium alloy (Ti-40) and titanium-niobium alloy (Ti-Nb)) has been assessed using different cellular and molecular examinations. Cell culture experiments were performed on three substrates: Ti-40, Ti-Nb, and tissue culture polystyrene as control. Cells number and growth rate were assessed by cell counting in various days and cell morphology was monitored using microscopic observations. The evaluation of cells' behavior on the surface of the implants paves the way for designing appropriate biomaterials for orthopedic and dental applications. It was observed that the cell growth rate on the control sample was relatively higher than that of the Ti-40 and Ti-Nb samples because of the coarse surface of the titanium-based materials. On the other hand, the final cell population was higher for titanium-based implants; this difference was attributed to the growth pattern, in which cells were not monolayered on the surface. Collagen I was not observed, while collagen III was secreted. Furthermore, interleukin (IL)-6 and vascular endothelial growth factor (VEGF) secretion were enhanced, and IL-8 secretion decreased. Moreover, various types of cells can be utilized with a series of substrates to unfold the cell behavior mechanism and cell-substrate interaction.

Electrically Conductive Materials: Opportunities and Challenges in Tissue Engineering

Tissue engineering endeavors to regenerate tissues and organs through appropriate cellular and molecular interactions at biological interfaces. To this aim, bio-mimicking scaffolds have been designed and practiced to regenerate and repair dysfunctional tissues by modifying cellular activity. Cellular activity and intracellular signaling are performances given to a tissue as a result of the function of elaborated electrically conductive materials. In some cases, conductive materials have exhibited antibacterial properties; moreover, such materials can be utilized for on-demand drug release. Various types of materials ranging from polymers to ceramics and metals have been utilized as parts of conductive tissue engineering scaffolds, having conductivity assortments from a range of semi-conductive to conductive. The cellular and molecular activity can also be affected by the microstructure; therefore, the fabrication methods should be evaluated along with an appropriate selection of conductive materials. This review aims to address the research progress toward the use of electrically conductive materials for the modulation of cellular response at the material-tissue interface for tissue engineering applications.

Alginate/chitosan hydrogel containing olfactory ectomesenchymal stem cells for sciatic nerve tissue engineering

Regeneration and functional recovery after peripheral nerve damage still remain a significant clinical problem. In this study, alginate/chitosan (alg/chit) hydrogel was used for the transplantation of olfactory ectomesenchymal stem cells (OE-MSCs) to promote peripheral nerve regeneration. The OE-MSCs were isolated from olfactory mucosa biopsies and evaluated by different cell surface markers and differentiation capacity. After creating sciatic nerve injury in a rat model, OE-MSCs were transplanted to the injured area with alg/chit hydrogel which was prepared and well-characterized. The prepared hydrogel had the porosity of 91.3 ± 1.27%, the swelling ratio of 379% after 240 min, weight loss percentages of 80 ± 5.56% after 14 days, and good blood compatibility. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, 4',6-diamidino-2-phenylindole, and LIVE/DEAD staining were done to assay the behavior of OE-MSCs on alg/chit hydrogel and the results confirmed that the hydrogel can provide a suitable substrate for cell survival. For functional analysis, alg/chit hydrogel with and without OE- MSCs was injected into a 3-mm sciatic nerve defect of Wistar rats. The results of the sciatic functional index, hot plate latency, electrophysiological assessment, weight-loss percentage of wet gastrocnemius muscle, and histopathological examination using hematoxylin-eosin and Luxol fast blue staining showed that utilizing alg/chit hydrogel with OE-MSCs to the sciatic nerve defect enhance regeneration compared to the control group and hydrogel without cells.

Electroactive Composites with Block Copolymer-Templated Iron Oxide Nanoparticles for Magnetic Hyperthermia Application

Cancer has been one of the leading causes of human death for centuries. Magnetic hyperthermia is a promising technique to confine and control cancers. However, particles used in magnetic hyperthermia leaking from where the cancers are located could compromise human health. Therefore, we developed electroactive iron oxide/block copolymer composites to tackle the leakage problem. Experimental results show that oleylamine-modified magnetic iron oxide (Fe3O4) particles and electroactive tetraaniline (TA) could be templated in the self-assembled microstructures of sulfonated [styrene-b-(ethylene-ran-butylene)-b-styrene] (S-SEBS) block copolymers. Various amounts of Fe3O4 particles and TA oligomer were incorporated in S-SEBS block copolymer and their electroactive behavior was confirmed by exhibiting two pairs of well-defined anodic and cathodic current peaks in cyclic voltammetry tests. The heating performance of the resultant TA/Fe3O4/polymer composites improved on increasing the added amount of Fe3O4 particles and TA oligomers. Both Fe3O4 and TA can contribute to improved heating performance, but Fe3O4 possesses a greater contribution than TA does. Hence, the main source for increasing the composites' temperature is Neel relaxation loss from Fe3O4 magnetic particles.

Injectable PNIPAM/Hyaluronic acid hydrogels containing multipurpose modified particles for cartilage tissue engineering: Synthesis, characterization, drug release and cell culture study

Novel injectable thermosensitive PNIPAM/hyaluronic acid hydrogels containing various amounts of chitosan-g-acrylic acid coated PLGA (ACH-PLGA) micro/nanoparticles were synthesized and designed to facilitate the regeneration of cartilage tissue. The ACH-PLGA particles were used in the hydrogels to play a triple role: first, the allyl groups on the chitosan-g-acrylic acid shell act as crosslinkers for PNIPAM and improved the mechanical properties of the hydrogel to mimic the natural cartilage tissue. Second, PLGA core acts as a carrier for the controlled release of chondrogenic small molecule melatonin. Third, they could reduce the syneresis of the thermosensitive hydrogel during gelation. The optimum hydrogel with the minimum syneresis and the maximum compression modulus was chosen for further evaluations. This hydrogel showed a great integration with the natural cartilage during the adhesion test, and also, presented an interconnected porous structure in scanning electron microscopy images. Eventually, to evaluate the cytotoxicity, mesenchymal stem cells were encapsulated inside the hydrogel. MTT and Live/Dead assay showed that the hydrogel improved the cells growth and proliferation as compared to the tissue culture polystyrene. Histological study of glycosaminoglycan (GAG) showed that melatonin treatment has the ability to increase the GAG synthesis. Overall, due to the improved mechanical properties, low syneresis, the ability of sustained drug release and also high bioactivity, this injectable hydrogel is a promising material system for cartilage tissue engineering.

Stimuli-Responsive Drug Release from Smart Polymers

Over the past 10 years, stimuli-responsive polymeric biomaterials have emerged as effective systems for the delivery of therapeutics. Persistent with ongoing efforts to minimize adverse effects, stimuli-responsive biomaterials are designed to release in response to either chemical, physical, or biological triggers. The stimuli-responsiveness of smart biomaterials may improve spatiotemporal specificity of release. The material design may be used to tailor smart polymers to release a drug when particular stimuli are present. Smart biomaterials may use internal or external stimuli as triggering mechanisms. Internal stimuli-responsive smart biomaterials include those that respond to specific enzymes or changes in microenvironment pH; external stimuli can consist of electromagnetic, light, or acoustic energy; with some smart biomaterials responding to multiple stimuli. This review looks at current and evolving stimuli-responsive polymeric biomaterials in their proposed applications.

Differentiation of human olfactory system-derived stem cells into dopaminergic neuron-like cells: A comparison between olfactory bulb and mucosa as two sources of stem cells

Cell transplantation has become a possible therapeutic approach in the treatment of neurodegenerative diseases of the nervous system by replacing lost cells. The current study aimed to make a comparison between the differentiation capacity of the olfactory bulb neural stem cells (OB-NSCs) and olfactory ectomesenchymal stem cells (OE-MSCs) into dopaminergic-like neurons under the inductive effect of transforming growth factor β (TGF-β). After culturing and treating with TGF-β, the differentiation capacities of both types of stem cells into dopaminergic neuron-like cells were evaluated. Quantitative real-time polymerase chain reaction analysis 3 weeks after induction demonstrated that the mRNA expression of the dopaminergic activity markers tyrosine hydroxylase (TH), dopamine transporter (DAT), paired box gene 2 (PAX2), and PAX5 in the neuron-like cells derived from OB-NSCs was significantly higher than those derived from OE-MSCs. These findings were further supported by the immunocytochemistry staining showing that the expression of the tyrosine hydroxylase, DAT, PAX2, and paired like homeodomain 3 seemed to be slightly higher in OB-NSCs compared with OE-MSCs. Despite the lower differentiation capacity of OE-MSCs, other considerations such as a noninvasive and easier harvesting process, faster proliferation attributes, longer life span, autologous transplantability, and also the easier and inexpensive cultural process of the OE-MSCs, cumulatively make these cells the more appropriate alternative in the case of autologous transplantation during the treatment process of neurodegenerative disorders like Parkinson's disease.

Chitosan/polyvinyl alcohol nanofibrous membranes: towards green super-adsorbents for toxic gases

Removal of hazardous gases from the atmosphere has become a big challenge for scientists and engineers alike. Eco-friendly nature of biopolymers has given a new dimension to the debate within the environmental science area but attempts mainly failed to cleanse the air stream of toxic gases as a consequence of design imperfections. In this work, green electrospun nanofibrous membranes based on chitosan (Cs)/polyvinyl alcohol (PVA) composite with a very high carbon monoxide adsorption capacity (much higher than the values one may expect from activated carbon and zeolite adsorbents, and also higher than that of the metal-organic framework) are developed. 2^k−1 factorial design, response surface and desirability function analyses are merged to optimize the electrospinning parameters for functional-based carbon monoxide elimination. The best Cs/PVA adsorbent obtained through multi-objective optimization has a very high desirability value level of 0.953. Optimized electrospinning parameters are: Voltage = 17 kV, spinning distance = 13 cm, flow rate = 0.2 mL/h, and PVA concentration = 6 wt.%; and optimized properties are: maximum thermal stability = 329 °C, minimum fiber diameter = 9.8 nm, and maximum surface area = 2204 m²/g. This work opens a new era for taking the next steps towards the design and optimization of green super-adsorbents for gaseous contaminations.

Electric field-responsive nanoparticles and electric fields: physical, chemical, biological mechanisms and therapeutic prospects

Electric fields are among physical stimuli that have revolutionized therapy. Occurring endogenously or exogenously, the electric field can be used as a trigger for controlled drug release from electroresponsive drug delivery systems, can stimulate wound healing and cell proliferation, may enhance endocytosis or guide stem cell differentiation. Electric field pulses may be applied to induce cell fusion, can increase the penetration of therapeutic agents into cells, or can be applied as a standalone therapy to ablate tumors. This review describes the main therapeutic trends and overviews the main physical, chemical and biological mechanisms underlying the actions of electric fields. Overall, the electric field can be used in therapeutic approaches in several ways. The electric field can act on drug carriers, cells and tissues. Understanding the multiple effects of this powerful tool will help harnessing its full therapeutic potential in an efficient and safe way.

On the electrical conductivity of alginate hydrogels

Hydrogels have been extensively used in the field of biomedical applications, offering customizable natural, synthetic or hybrid materials, particularly relevant in the field of tissue engineering. In the bioelectronics discipline, hydrogels are promising mainly as sensing platforms with or without encapsulated cells, showing great potential in healthcare and medicine. However, to date there is little data in the literature which characterizes the electrical properties of tissue engineering materials which are relevant to bioelectronics. In this work, we present electrical characterization of alginate hydrogels, a natural polysaccharide, using a four-probe method similar to electrical impedance spectroscopy. The acquired conductance data show distinct frequency-dependent features that change as a function of alginate and crosslinker concentration reflecting ion kinetics inside the measured sample. Furthermore, the presence of NIH 3T3 fibroblasts encapsulated in the hydrogels matrix was found to alter the artificial tissue's electrical properties. The method used provides valuable insight to the frequency-dependent electrical response of the resulting systems. It is hoped that the outcome of this research will be of use in the development of cell/electronic interfaces, possibly toward diagnostic biosensors and therapeutic bioelectronics.

Conducting Polymers for Tissue Engineering

Electrically conducting polymers such as polyaniline, polypyrrole, polythiophene, and their derivatives (mainly aniline oligomer and poly(3,4-ethylenedioxythiophene)) with good biocompatibility find wide applications in biomedical fields including bioactuators, biosensors, neural implants, drug delivery systems, and tissue engineering scaffolds. This review focuses on these conductive polymers for tissue engineering applications. Conductive polymers exhibit promising conductivity as bioactive scaffolds for tissue regeneration, and their conductive nature allows cells or tissue cultured on them to be stimulated by electrical signals. However, their mechanical brittleness and poor processability restrict their application. Therefore, conductive polymeric composites based on conductive polymers and biocompatible biodegradable polymers (natural or synthetic) were developed. The major objective of this review is to summarize the conductive biomaterials used in tissue engineering including conductive composite films, conductive nanofibers, conductive hydrogels, and conductive composite scaffolds fabricated by various methods such as electrospinning, coating, or deposition by in situ polymerization. Furthermore, recent progress in tissue engineering applications using these conductive biomaterials including bone tissue engineering, muscle tissue engineering, nerve tissue engineering, cardiac tissue engineering, and wound healing application are discussed in detail.

Differentiation of neural crest stem cells from nasal mucosa into motor neuron-like cells

Cell transplantation is a potential therapeutic approach for repairing neuropathological and neurodegenerative disorders of central nervous system by replacing the degenerated cells with new ones. Among a variety of stem cell candidates to provide these new cells, olfactory ectomesenchymal stem cells (OE-MSCs) have attracted a great attention due to their neural crest origin, easy harvest, high proliferation, and autologous transplantation. Since there is no report on differentiation potential of these cells into motor neuron-like cells, we evaluated this potential using Real-time PCR, flowcytometry and immunocytochemistry after the treatment with differentiation cocktail containing retinoic acid and Sonic Hedgehog. Immunocytochemistry staining of the isolated OE-MSCs demonstrated their capability to express nestin and vimentin, as the two markers of primitive neuroectoderm. The motor neuron differentiation of OE-MSCs resulted in changing their morphology into bipolar cells with high expression of motor neuron markers of ChAT, Hb-9 and Islet-1 at the level of mRNA and protein. Consequently, we believe that the OE-MSCs have great potential to differentiate into motor neuron-like cells and can be an ideal stem cell source for the treatment of motor neuron-related disorders of central nervous system.

Agarose-based biomaterials for tissue engineering

Agarose is a natural polysaccharide polymer having unique characteristics that give reason to consider it for tissue engineering applications. Special characteristics of agarose such as its excellent biocompatibility, thermo-reversible gelation behavior and physiochemical features support its use as a biomaterial for cell growth and/or controlled/localized drug delivery. The resemblance of this natural carbohydrate polymer to the extracellular matrix results in attractive features that bring about a strong interest in its usage in the field. The scope of this review is to summarize the extensive researches addressing agarose-based biomaterials in order to provide an in-depth understanding of its tissue engineering-related applications.

A facile route to the synthesis of anilinic electroactive colloidal hydrogels for neural tissue engineering applications

An innovative drug-loaded colloidal hydrogel was synthesized for applications in neural interfaces in tissue engineering by reacting carboxyl capped aniline dimer and gelatin molecules. Dexamethasone was loaded into the gelatin-aniline dimer solution as a model drug to form an in situ drug-loaded colloidal hydrogel. The conductivity of the hydrogel samples fluctuated around 10^-5 S/cm which appeared suitable for cellular activities. Cyclic voltammetry was used for electroactivity determination, in which 2 redox states were observed, suggesting that the short chain length and steric hindrance prevented the gel from achieving a fully oxidized state. Rheological data depicted the modulus decreasing with aniline dimer increment due to limited hydrogen bonds accessibility. Though the swelling ratio of pristine gelatin (600%) decreased by the introduction and increasing the concentration of aniline dimer because of its hydrophobic nature, it took the value of 300% at worst, which still seems promising for drug delivery uses. Degradation rate of hydrogel was similarly decreased by adding aniline dimer. Drug release was evaluated in passive and stimulated patterns demonstrating tendency of aniline dimer to form a vesicle that controls the drug release behavior. The optimal cell viability, proper cell attachment and neurite extension was achieved in the case of hydrogel containing 10 wt% aniline dimer. Based on tissue/organ behavior, it was promisingly possible to adjust the characteristics of the hydrogels for an optimal drug release. The outcome of this simple and effective approach can potentially offer additional tunable characteristics for recording and stimulating purposes in neural interfaces.

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

Neuronal disorder is an important health challenge due to inadequate natural regeneration, which has been responded by tissue engineering, particularly with conductive materials. A bifunctional electroactive scaffold having agarose biodegradable and aniline pentamer (AP) conductive parts was designed that exhibits appropriate cell attachment/compatibility, as detected by PC12 cell seeding. The developed carboxyl-capped aniline-pentamer improved agarose cell adhesion potential, also the conductivity of scaffold was in the order 10-5 S/cm reported for cell membrane. Electrochemical impedance spectroscopy was applied to plot the Nyquist graph and subsequent construction of the equivalent circuit model based on the neural model, exhibiting an appropriate cell signaling and an acceptable consistency between the components of the scaffold model with neural cell model. The ionic conductivity was also measured; exhibiting an enhanced ionic conductivity, but lower activation energy upon a temperature rise. Swelling behavior of the sample was measured and compared with pristine agarose; so that aniline oligomer due to its hydrophobic nature decreased water uptake. Dexamethasone release from the developed electroactive scaffold was assessed through voltage-responsive method. Proper voltage-dependent drug release could be rationally expected because of controllable action and elimination of chemically responsive materials. Altogether, these characteristics recommended the agarose/AP biopolymer for neural tissue engineering.

Can regenerative medicine and nanotechnology combine to heal wounds? The search for the ideal wound dressing

Skin is the outermost covering of the human body and at the same time the largest organ comprising 15% of body weight and 2 m2 surface area. Skin plays a key role as a barrier against the outer environment depending on its thickness, color and structure, which differ from one site to another. The four major types of problematic wounds include ulcers (diabetic, venous, pressure) and burn wounds. Developing novel dressings helps us to improve the wound healing process in difficult patients. Recent advances in regenerative medicine and nanotechnology are revolutionizing the field of wound healing. Antimicrobial activity, exogenous cell therapy, growth factor delivery, biodegradable and biocompatible matrix construction, all play a role in hi-tech dressing design. In the present review, we discuss how the principles of regenerative medicine and nanotechnology can be combined in innovative wound dressings.