Rationally Designed Eco-Friendly Solvent System for High-Performance, Large-Area Perovskite Solar Cells and Modules.

The important but remained issue to be addressed to achieve the mass production of perovskite solar modules include a large-area fabrication of high-quality perovskite film with eco-friendly, viable production methods. Although several efforts are made to achieve large-area fabrication of perovskite, the development of eco-friendly solvent system, which is precisely designed to be fit to scale-up methods are still challenging. Herein, this work develops the eco-friendly solvent/co-solvent system to produce a high-quality perovskite layer with a bathing in eco-friendly antisolvent. The new co-solvent/additive, methylsulfonylmethane (MSM), efficiently improves the overall solubility and has a suitable binding strength to the perovskite precursor, resulting in a high-quality perovskite film with antisolvent bathing method in large area. The resultant perovskite solar cells showed high power conversion efficiency of over 24% (in reverse scan), with a good long-term stability under continuous light illumination or damp-heat condition. MSM is also beneficial to produce a perovskite layer at low-temperature or high-humidity. MSM-based solvent system is finally applied to large-area, resulting in highly efficiency perovskite solar modules with PCE of 19.9% (by aperture) or 21.2% (by active area) in reverse scan. These findings contribute to step forward to a mass production of perovskite solar modules with eco-friendly way.

Tissue Regeneration of Human Mesenchymal Stem Cells on Porous Gelatin Micro-Carriers by Long-Term Dynamic In Vitro Culture.

Background: Tissue engineering is a multidisciplinary field which attracted much attention in recent years. One of the most important issue in tissue engineering is how to obtain high cell numbers and tissue regeneration while maintaining appropriate cellular characteristics in vitro for restoring damaged or dysfunctional body tissues and organs. These demands can be achieved by the use of three dimensional (3D) dynamic cultures of cells combined with cell-adhesive micro-carriers. Method: In this study, human mesenchymal stem cells (hMSCs) were cultured in a wave-bioreactor system for up to 100 days, after seeding on Cultisphere-S porous gelatin micro-carriers. Cell counting was performed at the time points of 7, 12, 17, 31 days and compared to those of hMSCs cultured under static condition. Higher growth and proliferation rates was achieved in wave-type dynamic culture, when cell culture continued to day 31. A scanning electron microscope (SEM) photographs, both live and dead and MTT assays were taken to confirm the survival and distribution of cells on porous gelatin micro-carrier surfaces. The results of histological stains such as hematoxylin and eosin, Masson's trichrome, Alcian blue and Alizarin red S also showed improved proliferation and tissue regeneration of hMSCs on porous gelatin micro-carriers. Conclusion: The experimental results demonstrated the effect and importance of both micro-carriers and bioreactor in hMSC expansion on cell proliferation and migration as well as extracellular matrix formation on the superficial and pore surfaces of the porous gelatin micro-carriers, and then their inter-connections, leading to tissue regeneration.

Synthesis and Biocompatibility Characterizations of in Situ Chondroitin Sulfate-Gelatin Hydrogel for Tissue Engineering.

Novel hydrogel composed of both chondroitin sulfate (CS) and gelatin was developed for better cellular interaction through two step double crosslinking of N-(3-diethylpropyl)-N-ethylcarbodiimide hydrochloride (EDC) chemistries and then click chemistry. EDC chemistry was proceeded during grafting of amino acid dihydrazide (ADH) to carboxylic groups in CS and gelatin network in separate reactions, thus obtaining CS-ADH and gelatin-ADH, respectively. CS-acrylate and gelatin-TCEP was obtained through a second EDC chemistry of the unreacted free amines of CS-ADH and gelatin-ADH with acrylic acid and tri(carboxyethyl)phosphine (TCEP), respectively. In situ CS-gelatin hydrogel was obtained via click chemistry by simple mixing of aqueous solutions of both CS-acrylate and gelatin-TCEP. ATR-FTIR spectroscopy showed formation of the new chemical bonds between CS and gelatin in CS-gelatin hydrogel network. SEM demonstrated microporous structure of the hydrogel. Within serial precursor concentrations of the CS-gelatin hydrogels studied, they showed trends of the reaction rates of gelation, where the higher concentration, the quicker the gelation occurred. In vitro studies, including assessment of cell viability (live and dead assay), cytotoxicity, biocompatibility via direct contacts of the hydrogels with cells, as well as measurement of inflammatory responses, showed their excellent biocompatibility. Eventually, the test results verified a promising potency for further application of CS-gelatin hydrogel in many biomedical fields, including drug delivery and tissue engineering by mimicking extracellular matrix components of tissues such as collagen and CS in cartilage.

Evaluation of MC3T3 Cells Proliferation and Drug Release Study from Sodium Hyaluronate-1,4-butanediol Diglycidyl Ether Patterned Gel.

A pattern gel has been fabricated using sodium hyaluronate (HA) and 1,4-butanediol diglycidyl ether (BDDGE) through the micro-molding technique. The cellular behavior of osteoblast cells (MC3T3) in the presence and absence of dimethyloxalylglycine (DMOG) and sodium borate (NaB) in the pattern gel (HA-BDDGE) has been evaluated for its potential application in bone regeneration. The Fourier transform infrared spectroscopy (FTIR), 13C-nuclear magnetic resonance spectroscopy (13C NMR), and thermogravimetric analysis (TGA) results implied the crosslinking reaction between HA and BDDGE. The scanning electron microscopy (SEM) analysis confirmed the formation of pattern on the surface of HA-BDDGE. The gel property of the crosslinked HA-BDDGE has been investigated by swelling study in distilled water at 37 °C. The HA-BDDGE gel releases DMOG in a controlled way for up to seven days in water at 37 °C. The synthesized gel is biocompatible and the bolus drug delivery results indicated that the DMOG containing patterned gel demonstrates a better cell migration ability on the surface than NaB. For local delivery, the pattern gel with 300 µM NaB or 300 µM DMOG induced cell clusters formation, and the gel with 150 µM NaB/DMOG showed high cell proliferation capability only. The vital role of NaB for bone regeneration has been endorsed from the formation of cell clusters in presence of NaB in the media. The in vitro results indicated that the pattern gel showed angiogenic and osteogenic responses with good ALP activity and enhanced HIF-1α, and Runx2 levels in the presence of DMOG and NaB in MC3T3 cells. Hence, the HA-BDDGE gel could be used in bone regeneration application.

Bioactive Molecules Release and Cellular Responses of Alginate-Tricalcium Phosphate Particles Hybrid Gel.

In this article, a hybrid gel has been developed using sodium alginate (Alg) and α-tricalcium phosphate (α-TCP) particles through ionic crosslinking process for the application in bone tissue engineering. The effects of pH and composition of the gel on osteoblast cells (MC3T3) response and bioactive molecules release have been evaluated. At first, a slurry of Alg and α-TCP has been prepared using an ultrasonicator for the homogeneous distribution of α-TCP particles in the Alg network and to achieve adequate interfacial interaction between them. After that, CaCl2 solution has been added to the slurry so that ionic crosslinked gel (Alg-α-TCP) is formed. The developed hybrid gel has been physico-chemically characterized using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and a swelling study. The SEM analysis depicted the presence of α-TCP micro-particles on the surface of the hybrid gel, while cross-section images signified that the α-TCP particles are fully embedded in the porous gel network. Different % swelling ratio at pH 4, 7 and 7.4 confirmed the pH responsiveness of the Alg-α-TCP gel. The hybrid gel having lower % α-TCP particles showed higher % swelling at pH 7.4. The hybrid gel demonstrated a faster release rate of bovine serum albumin (BSA), tetracycline (TCN) and dimethyloxalylglycine (DMOG) at pH 7.4 and for the grade having lower % α-TCP particles. The MC3T3 cells are viable inside the hybrid gel, while the rate of cell proliferation is higher at pH 7.4 compared to pH 7. The in vitro cytotoxicity analysis using thiazolyl blue tetrazolium bromide (MTT), bromodeoxyuridine (BrdU) and neutral red assays ascertained that the hybrid gel is non-toxic for MC3T3 cells. The experimental results implied that the non-toxic and biocompatible Alg-α-TCP hybrid gel could be used as scaffold in bone tissue engineering.

Preventing postoperative tissue adhesion using injectable carboxymethyl cellulose-pullulan hydrogels.

An injectable adhesive hydrogel composed of carboxymethyl cellulose (CMC) and pullulan is developed and evaluated as a postoperative anti-adhesion barrier. CMC was modified with tyramine to introduce crosslinking site via an EDC-NHS reaction. The in situ hydrogel was prepared by an enzyme-mediated reaction of tyramine-immobilized CMC with horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). Pullulan was added to the hydrogel solution to improve adhesiveness to the wound area and accelerate biodegradation. The modified CMC was confirmed by ATR-FTIR spectroscopy. The gelation time, storage modulus (G'), and weight loss of the hydrogels were measured as functions of the amounts of HRP and H2O2. The hydrogel group showed negligible cell proliferation and cytotoxicity, compared to that shown by the control group. The in vivo animal test demonstrated that significant decrease of postoperative tissue adhesion by applying the hydrogels. The CMC-pullulan hydrogel could be a useful treatment as an injectable in situ anti-adhesive agent.

Injectable pullulan hydrogel for the prevention of postoperative tissue adhesion.

Methods for reducing and preventing postoperative abdominal adhesions have been researched for decades; however, despite these efforts, the formation of postoperative peritoneal adhesions is continuously reported. Adhesions cause serious complications such as postoperative pain, intestinal obstruction, and infertility. Tissue adhesion barriers have been developed as films, membranes, knits, sprays, and hydrogels. Hydrogels have several advantages when used as adhesion barriers, including flexibility, low tissue adhesiveness, biodegradability, and non-toxic degraded products. Furthermore, compared with preformed hydrogels, injectable hydrogels can fill and cover spaces of any shape and do not require a surgical procedure for implantation. In this study, pullulan was modified through reaction with 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) to introduce carboxyl and phenyl groups as crosslinking sites. The grafting of tyramine on pullulan allows crosslinking branches on pullulan backbone. We successfully fabricated pullulan hydrogel with an enzymatic reaction using horseradish peroxidase (HRP) and hydrogen peroxide (H2O2). The chemical structure of modified pullulan was analyzed with ATR-FTIR and (1)H NMR spectroscopies. Rheological properties were tested by measuring storage modulus with varying H2O2, HRP, polymer solution concentrations and tyramine substitution rates. Cell viability and animal tests were performed. The modified pullulan hydrogel is an invaluable advance in anti-adhesion agents.

Research trends in biomimetic medical materials for tissue engineering: 3D bioprinting, surface modification, nano/micro-technology and clinical aspects in tissue engineering of cartilage and bone.

This review discusses about biomimetic medical materials for tissue engineering of bone and cartilage, after previous scientific commentary of the invitation-based, Korea-China joint symposium on biomimetic medical materials, which was held in Seoul, Korea, from October 22 to 26, 2015. The contents of this review were evolved from the presentations of that symposium. Four topics of biomimetic medical materials were discussed from different research groups here: 1) 3D bioprinting medical materials, 2) nano/micro-technology, 3) surface modification of biomaterials for their interactions with cells and 4) clinical aspects of biomaterials for cartilage focusing on cells, scaffolds and cytokines.

Synthesis and in vitro characterizations of porous carboxymethyl cellulose-poly(ethylene oxide) hydrogel film.

BACKGROUND: Cellulose and its derivatives such as carboxymethyl cellulose (CMC) have been employed as a biomaterial for their diverse applications such as tissue engineering, drug delivery and other medical materials. Porosity of the scaffolds has advantages in their applications to tissue engineering such as more cell adhesion and migration leading to better tissue regeneration. After synthesis of CMC-poly(ethylene oxide) (PEO) hydrogel by mixing the solutions of both CMC-acrylate and PEO-hexa-thiols, fabrication and evaluation of a CMC-PEO gel and its film in porous form have been made for its possible applications to tissue regeneration. Physicochemical and biological properties of both CMC-PEO hydrogel and porous films have been evaluated by using physicochemical assays by SEM, FTIR and swelling behaviors as well as in vitro assays of MTT, Neutral red, BrdU, gel covering and tissue ingrowth into the pores of the CMC-PEO gel films. Degradation of CMC-PEO hydrogel was also evaluated by treating with esterase over time. RESULTS: Chemical grafting of acrylate to CMC was verified by analyses of both FTIR and NMR. CMC-PEO hydrogel was obtained by mixing two precursor polymer solutions of CMC-acrylate and PEO-hexa-thiols and by transforming into a porous CMC-PEO gel film by gas forming of ammonium bicarbonate particles. The fabricated hydrogel has swollen in buffer to more than 6 times and degraded by esterase. The results of in vitro assays of live and dead, MTT, BrdU, Neutral red and gel covering on the cells showed excellent cell compatibility of CMC-PEO hydrogel and porous gel films. Furthermore the porous films showed excellent in vitro adhesion and migration of cells into their pore channels as observed by H&E and MT stains. CONCLUSIONS: Both CMC-PEO hydrogel and porous gel films showed excellent biocompatibility and were expected to be a good candidate scaffold for tissue engineering.