Covalently crosslinked chitosan-poly(ethylene glycol) hybrid hydrogels to deliver insulin for adipose-derived stem cells encapsulation

Fabrication and Characterization of 3D Printed, 3D Microelectrode Arrays for Interfacing with a Peripheral Nerve-on-a-Chip

We present a nontraditional fabrication technique for the realization of three-dimensional (3D) microelectrode arrays (MEAs) capable of interfacing with 3D cellular networks in vitro. The technology uses cost-effective makerspace microfabrication techniques to fabricate the 3D MEAs with 3D printed base structures with the metallization of the microtowers and conductive traces being performed by stencil mask evaporation techniques. A biocompatible lamination layer insulates the traces for realization of 3D microtower MEAs (250 μm base diameter, 400 μm height). The process has additionally been extended to realize smaller electrodes (30 μm × 30 μm) at a height of 400 μm atop the 3D microtower using laser micromachining of an additional silicon dioxide (SiO₂) insulation layer. A 3D microengineered, nerve-on-a-chip in vitro model for recording and stimulating electrical activity of dorsal root ganglion (DRG) cells has further been integrated with the 3D MEA. We have characterized the 3D electrodes for electrical, chemical, electrochemical, biological, and chip hydration stability performance metrics. A decrease in impedance from 1.8 kΩ to 670 Ω for the microtower electrodes and 55 to 39 kΩ for the 30 μm × 30 μm microelectrodes can be observed for an electrophysiologically relevant frequency of 1 kHz upon platinum electroless plating. Biocompatibility assays on the components of the system resulted in a large range (∼3%-70% live cells), depending on the components. Fourier-transform infrared (FTIR) spectra of the resin material start to reveal possible compositional clues for the resin, and the hydration stability is demonstrated in in-vitro-like conditions for 30 days. The fabricated 3D MEAs are rapidly produced with minimal usage of a cleanroom and are fully functional for electrical interrogation of the 3D organ-on-a-chip models for high-throughput of pharmaceutical screening and toxicity testing of compounds in vitro.

Advances in biomaterials for adipose tissue reconstruction in plastic surgery

Adipose tissue reconstruction is an important technique for soft tissue defects caused by facial plastic surgery and trauma. Adipose tissue reconstruction can be repaired by fat transplantation and biomaterial filling, but there are some problems in fat transplantation, such as second operation and limited resources. The application of advanced artificial biomaterials is a promising strategy. In this paper, injectable biomaterials and three-dimensional (3D) tissue-engineered scaffold materials for adipose tissue reconstruction in plastic surgery are reviewed. Injectable biomaterials include natural biomaterials and artificial biomaterials, which generally have problems such as high absorptivity of fillers, repeated injection, and rejection. In recent years, the technology of new 3D tissue-engineering scaffold materials with adipose-derived stem cells (ADSCs) and porous scaffold as the core has made good progress in fat reconstruction, which is expected to solve the current problem of clinical adipose tissue reconstruction, and various biomaterials preparation technology and transformation research also provide the basis for clinical transformation of fat tissue reconstruction.

Temperature-responsive collagen–PNIPAAm conjugate: preparation and fibrillogenesis

A collagen–PNIPAAm conjugate is prepared using the “grafting from” method under mild conditions, and fibrillogenesis was realized by the induction of natural collagen.

Review of polysaccharide particle-based functional drug delivery

This review investigates the significant role polysaccharide particles play in functional drug delivery. The importance of these systems is due to the wide variety of polysaccharides and their natural source meaning that they can provide biocompatible and biodegradable systems with a range of both biological and chemical functionality valuable for drug delivery. This functionality includes protection and presentation of working therapeutics through avoidance of the reticuloendothelial system, stabilization of biomacromolecules and increasing the bioavailability of incorporated small molecule drugs. Transport of the therapeutic is also key to the utility of polysaccharide particles, moving drugs from the site of administration through mucosal binding and transport and using chemistry, size and receptor mediated drug targeting to specific tissues. This review also scrutinizes the methods of synthesizing and constructing functional polysaccharide particle drug delivery systems that maintain and extend the functionality of the natural polysaccharides.

Current status of stem cell therapy, scaffolds for the treatment of diabetes mellitus

Diabetes mellitus (DM) remains the 7th leading cause of death in the world. Daily insulin injection is one component of a treatment plan for people with Diabetes mellitus type 1 (T1DM) that restores normal or near-normal blood sugar levels. However, Insulin treatment depends upon a variety of individual factors and leads to poor and drastic glycemic control. The need for an effective cell replacement strategy will be the aim of future clinical trials. Therefore, the aim of this systematic review is to outline the latest advances in scaffolding and stem cell therapy as a non-pharmacologic treatment for T1DM. It also emphasizes on some pancreas differentiation protocols and the clinical trials associated with stem cell therapy regarding T1DM in vitro and in vivo.

Soft tissue fillers for adipose tissue regeneration: From hydrogel development toward clinical applications

There is a clear and urgent clinical need to develop soft tissue fillers that outperform the materials currently used for adipose tissue reconstruction. Recently, extensive research has been performed within this field of adipose tissue engineering as the commercially available products and the currently existing techniques are concomitant with several disadvantages. Commercial products are highly expensive and associated with an imposing need for repeated injections. Lipofilling or free fat transfer has an unpredictable outcome with respect to cell survival and potential resorption of the fat grafts. Therefore, researchers are predominantly investigating two challenging adipose tissue engineering strategies: in situ injectable materials and porous 3D printed scaffolds. The present work provides an overview of current research encompassing synthetic, biopolymer-based and extracellular matrix-derived materials with a clear focus on emerging fabrication technologies and developments realized throughout the last decade. Moreover, clinical relevance of the most promising materials will be discussed, together with potential concerns associated with their application in the clinic.

Smart Polymeric Hydrogels for Cartilage Tissue Engineering: A Review on the Chemistry and Biological Functions

Stimuli responsive hydrogels (SRHs) are attractive bioscaffolds for tissue engineering. The structural similarity of SRHs to the extracellular matrix (ECM) of many tissues offers great advantages for a minimally invasive tissue repair. Among various potential applications of SRHs, cartilage regeneration has attracted significant attention. The repair of cartilage damage is challenging in orthopedics owing to its low repair capacity. Recent advances include development of injectable hydrogels to minimize invasive surgery with nanostructured features and rapid stimuli-responsive characteristics. Nanostructured SRHs with more structural similarity to natural ECM up-regulate cell-material interactions for faster tissue repair and more controlled stimuli-response to environmental changes. This review highlights most recent advances in the development of nanostructured or smart hydrogels for cartilage tissue engineering. Different types of stimuli-responsive hydrogels are introduced and their fabrication processes through physicochemical procedures are reported. The applications and characteristics of natural and synthetic polymers used in SRHs are also reviewed with an outline on clinical considerations and challenges.

Functionalised type-I collagen as a hydrogel building block for bio-orthogonal tissue engineering applications

Modulating the hydrogel properties from injectable to implantable scaffolds using the bio-orthogonal thiol-Michael addition click reaction.

Intelligent semi-IPN chitosan–PEG–PAAm hydrogel for closed-loop insulin delivery and kinetic modeling

Design of an intelligent semi-IPN chitosan–PEG–PAAm hydrogel using glucose oxidase (GOx) and catalase (CAT) to improve closed-loop insulin delivery systems.

N-succinyl chitosan preparation, characterization, properties and biomedical applications: a state of the art review

N-succinyl chitosan (NSC) remains a promising chitosan derivative to develop targeted drug delivery, wound dressings, and tissue engineering systems. All these systems are important in life sciences. NSC is an amphiprotic derivative obtained from the N-acylation of chitosan. NSC exhibits extraordinary biocompatibility, significantly increased aqueous solubility in acidic and basic media without affecting the biological properties, appreciable transfection efficiency, and the ability to stimulate osteogenesis. NSC shows enhanced bioavailability, which highlights its potential applications in the biomedical field. This review briefly introduces chitosan, including its limitations as a biomaterial, and modifications of chitosan with a particular focus on acylation, along with a comprehensive overview of the synthesis, characterization, properties, biodistribution, and toxicological/biopharmaceutical profile of NSC. Furthermore, it extensively surveys current state-of-the-art NSC-based formulations for drug delivery with special emphasis on protein delivery, anti-cancer activity in the colon, as well as nasal and ophthalmic targeted gene/drug delivery. Moreover, it discusses NSC-based biomaterial applications in articular, adipose, and bone tissue engineering. In addition, it describes recent contributions of NSC-based hydrogels in wound dressings along with a brief account of drug delivery in combination with tissue engineering. Finally, it presents potential current challenges and future perspectives of NSC-based formulations in the biomedical field.