http://www.tissueeng.net/lab/papers/1-s2.0-S014296121500719X-main.pdf

Synthesis, properties, and biomedical applications of gelatin methacryloyl (GelMA) hydrogels

Click hydrogels, microgels and nanogels: Emerging platforms for drug delivery and tissue engineering

Hydrogels are hydrophilic, three-dimensional networks that are able to absorb large quantities of water or biological fluids, and thus have the potential to be used as prime candidates for biosensors, drug delivery vectors, and carriers or matrices for cells in tissue engineering. In this critical review article, advantages of the hydrogels that overcome the limitations from other types of biomaterials will be discussed. Hydrogels, depending on their chemical composition, are responsive to various stimuli including heating, pH, light, and chemicals. Two swelling mechanisms will be discussed to give a detailed understanding of how the structure parameters affect swelling properties, followed by the gelation mechanism and mesh size calculation. Hydrogels prepared from natural materials such as polysaccharides and polypeptides, along with different types of synthetic hydrogels from the recent reported literature, will be discussed in detail. Finally, attention will be given to biomedical applications of different kinds of hydrogels including cell culture, self-healing, and drug delivery.

Hydrogels for Biomedical Applications: Their Characteristics and the Mechanisms behind Them

3D bioprinting shows significant promise for creating complex tissue and organ mimics to solve transplant needs and to provide platforms for drug testing and studying tissue morphogenesis[1][2][3]. However, the lack of 3D printable and cell-compatible bioinks as well as the limited ability to tune bioink material properties are cited as significant inhibitors to the growth of bioprinting[4][5]. Pioneers in the field of tissue engineering and biomaterials have established and validated that changing materials properties such as stiffness[6], bioactive moieties[7][8], and degradation[7][9] significantly impacts cell behavior and tissue formation. Thus, developing novel, versatile and tunable bioink methods that will facilitate advanced material and construct design will have important implications in the field of bioprinting and biofabrication. Versatile bioink synthesis techniques, ones that can be used with many materials, will improve both printability of existing bioinks and most importantly, can add completely new biomaterials to the 3D bioprinting material palette. Furthermore, development of tunable bioink methods will provide additional means to customize mechanical, chemical, physical, and biological properties of printed structures towards creating compositionally and structurally complex structures and functional tissues beyond the rudimentary tissue structures presented thus far.

/pdf/a-multimaterial-bioink-method-for-3d-printing-tunable-cell-nlvqhqq77t.pdf

A multimaterial bioink method for 3D printing tunable, cell-compatible hydrogels.

Functional active wound dressings are expected to provide a moist wound environment, offer protection from secondary infections, remove wound exudate and accelerate tissue regeneration, as well as to improve the efficiency of wound healing. Chitosan-based hydrogels are considered as ideal materials for enhancing wound healing owing to their biodegradable, biocompatible, non-toxic, antimicrobial, biologically adhesive, biological activity and hemostatic effects. Chitosan-based hydrogels have been demonstrated to promote wound healing at different wound healing stages, and also can alleviate the factors against wound healing (such as excessive inflammatory and chronic wound infection). The unique biological properties of a chitosan-based hydrogel enable it to serve as both a wound dressing and as a drug delivery system (DDS) to deliver antibacterial agents, growth factors, stem cells and so on, which could further accelerate wound healing. For various kinds of wounds, chitosan-based hydrogels are able to promote the effectiveness of wound healing by modifying or combining with other polymers, and carrying different types of active substances. In this review, we will take a close look at the application of chitosan-based hydrogels in wound dressings and DDS to enhance wound healing.

/pdf/a-functional-chitosan-based-hydrogel-as-a-wound-dressing-and-51ryslhwg4.pdf

A functional chitosan-based hydrogel as a wound dressing and drug delivery system in the treatment of wound healing

3D cell entrapment in crosslinked thiolated gelatin-poly(ethylene glycol) diacrylate hydrogels.

Thiol-ene Michael-type formation of gelatin/poly(ethylene glycol) biomatrices for three-dimensional mesenchymal stromal/stem cell administration to cutaneous wounds.

Thiol–ene-based biological/synthetic hybrid biomatrix for 3-D living cell culture

Significant variation in performance in motor imagery (MI) tasks impedes their wide adoption for brain-computer interface (BCI) applications. Previous researchers have found that resting-state alpha-band power is positively correlated with MI-BCI performance. In this study, we designed a neurofeedback training (NFT) protocol based on the up-regulation of the alpha band relative power (RP) to investigate its effect on MI-BCI performance. The principal finding of this study is that alpha NFT could successfully help subjects increase alpha-rhythm power and improve their MI-BCI performance. An individual difference was also found in this study in that subjects who increased alpha power more had a better performance improvement. Additionally, the functional connectivity (FC) of the frontal-parietal (FP) network was found to be enhanced after alpha NFT. However, the enhancement failed to reach a significant level after multiple comparisons correction. These findings contribute to a better understanding of the neurophysiological mechanism of cognitive control through alpha regulation.

/pdf/neurofeedback-training-of-alpha-relative-power-improves-the-3g98x5m4.pdf

Neurofeedback Training of Alpha Relative Power Improves the Performance of Motor Imagery Brain-Computer Interface

Wireless neural-recording instruments eliminate the bulky cables in multi-channel signal transmission, while the system size should be reduced to mitigate the impact on freely-moving animals. As the battery usually dominates the system size, the neural-recording chip should be low power to minimize the battery in long-termly monitoring. In general, a neural-recording chip consists of an analog front end (AFE) and an 8 bit <inline-formula><tex-math notation="LaTeX">$-$</tex-math></inline-formula>10 bit analog-to-digital converter (ADC), while it's challenging to design an ADC with an 8<inline-formula><tex-math notation="LaTeX">$-$</tex-math></inline-formula>10 effective number of bits (ENOB) and sub-<inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> W power consumption due to the kickback noise. In this work, we propose a kickback-reduction technique for a successive-approximation-register (SAR) ADC based on neural-recording chip. Fabricated in 65 nm CMOS process, the proposed technique reduce the ADC power to 315 nW, resulting in an 8-channel neural-recording chip with 249 <inline-formula><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>W in total. Measured results show that the chip achieves an ADC ENOB of 9.73 bits, as well as an AFE gain of 43.3 dB and input-referred noise (IRN) of 9.68 <inline-formula><tex-math notation="LaTeX">$\mu V_{rms}$</tex-math></inline-formula> in a bandwidth of 0.9 Hz<inline-formula><tex-math notation="LaTeX">$-$</tex-math></inline-formula>7.2 kHz. Combined with a BLE chip and a PCB antenna, the chip is implemented into a 2.6 g wireless headstage system (w/o battery), and an <italic>in-vivo</italic> demonstration is conducted on a male Sprague-Dawley rat with Parkinson's disease. The headstage system transfers the <italic>in-vivo</italic> neural signals to a commodity smartphone through BLE, and the miniature size induces little impact on freely-moving activities.

Kedi Xu

Papers

3D cell entrapment in crosslinked thiolated gelatin-poly(ethylene glycol) diacrylate hydrogels.

Thiol-ene Michael-type formation of gelatin/poly(ethylene glycol) biomatrices for three-dimensional mesenchymal stromal/stem cell administration to cutaneous wounds.

Thiol–ene-based biological/synthetic hybrid biomatrix for 3-D living cell culture

Neurofeedback Training of Alpha Relative Power Improves the Performance of Motor Imagery Brain-Computer Interface

A Wireless Headstage System Based on Neural-Recording Chip Featuring 315 nW Kickback-Reduction SAR ADC