Advancements in tissue and organ 3D bioprinting: Current techniques, applications, and future perspectives

3D bioprinting techniques have emerged as a flexible tool in tissue engineering and regenerative medicine to fabricate or pattern functional 3D bio-structures with precise geometric designs, bridging the divergence between engineered and natural tissue constructs. A significantly increasing development has been achieved in understanding the relationship between the 3D-printing process and the structures, properties, and applications of the objects created. The ongoing advancement of novel biomaterial inks has enabled manufacturing of models and in vitro implants capable of achieving some level of success in preclinical trials. Remarkable progress in cell biology and biology-inspired computational design has assisted in achieving the latest milestone with planned tissue- or organ-like constructs having specific levels of functionality. However, biofabricated constructs still have a long way to go before reaching clinics. This review presents a picture of 3D bioprinting in the context of tissue engineering and regenerative medicine, with focus on biomaterials-related and design-centred aspects. Biomedical applications are described in detail in relation to major tissues or organs considered in the human body. Current technical limitations, challenges, future prospects and improvements are critically outlined and discussed

PVA-Based Nanofibers Containing Chitosan Modified with Graphene Oxide and Carbon Quantum Dot-Doped TiO2 Enhance Wound Healing in a Rat Model

Electrospun nanofibrous constructs based on nanoparticles and biopolymers have recently been used in tissue engineering because of their similarity to the extracellular matrix in nature. In this study, electrospun chitosan-carbon quantum dot-titanium dioxide-graphene oxide (CS-CQD-TiO2-GO) nanofibrous mats were synthesized for use as wound dressings by the electrospinning method. To increase the biodegradation rate and water resistance, the fabricated nanofibrous mats were cross-linked. SEM images showed a uniform and coherent structure of CS-CQD-TiO2-GO nanocomposites and CS-CQD-TiO2-GO electrospun nanofibers mats. FTIR analysis, XRD pattern, SEM mapping, and EDS spectrum demonstrate the accuracy of the synthesis as well as the elemental and chemical structure of the nanofibrous mat. The water contact angle indicated that the nanofibrous mat had a hydrophilic property, which is essential for controlling wound exudates. The tensile strength and elongation tests showed that the nanofibrous mat has suitable mechanical properties for wound dressing, including significant flexibility and strength. Interestingly, antimicrobial testing illustrated that the fabricated nanofibrous mat had antibacterial activity against Gram-negative and Gram-positive bacteria. Appropriate cell viability and cytocompatibility of treated mouse fibroblast NIH3T3 cells with the nanofibrous mat were determined using an MTT assay. The animal study results confirmed the proper potential of the nanofibrous mat in wound dressing applications

Poly(3-hydroxybutyrate) Production from Natural Gas by a Methanotroph Native Bacterium in a Bubble Column Bioreactor

Reducing the total cost of poly(3-hydroxybutyrate) (PHB) production as an attractive substitute for conventional petrochemical plastics still remains an unsolved problem. The aim of this research was the screening of PHB-producing microorganisms and selection of the best suitable medium for microbial growth and PHB production from methane. A new isolated methanotroph for PHB production from natural gas was studied in different media. After selection of the suitable medium, the effect of five process variables (content of nitrogen source, disodium hydrogen phosphate, methane to air ratio, seed age, and pH) on PHB production was investigated in a bubble column bioreactor. Also, hydrodynamic and mass transfer factors (flow regime, mixing time, gas hold up, and kLa) were considered. At optimum operating conditions and engineering parameters in a bubble column, PHB content in the dried biomass reached 25 % w/w. The results showed that pH is the most important variable in the selected conditions

Fabrication and precipitation hardening characterization of nanostructure A17075 alloy

30-34<span style="font-size: 9.0pt;mso-bidi-font-size:10.0pt" lang="EN-US">In this paper the fabrication and precipitation hardening behavior of bulk nanostructure A17075 alloy is investigated. In order to produce this alloy, the elemental powder based on the nominal composition of conventional A17075 alloy is milled up to 15 h and then hot pressed. The milled and hot pressed samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The results show that after 15 h of milling, the alloying elements are dissolved in Al matrix and a supersaturated solid solution with average crystallite size of about 30±5 nm is obtained. Hot pressing the powder samples at 500°C under 400 MPa led to the fully dense bulk nanostructure A17075 alloy. The consolidated sample has a hardness value of 165 HV which increases to 240 HV after appropriation hardening. </span

Pregermination treatment and germination characteristics of oriental beech (Fagus orientalis Lipsky) in the Caspian region

Oriental beech is one of the most important tree species in the Caspian region that regeneratesnaturally.Seed pretreatment plays an important role in beech reforestation .For this reason the seeds ofthree different provenances; Gilan (Asalem), Nowshahr (Makarood), Gorgan (Cheshmeh gholgholy),across the Caspian region, were collected and after viability test (TTC) placed under cold stratification(for 8-19 weeks) to overcome dormancy. The results have shown that pregermination treatments haddesirable effects on seed germination. There were significant variations between three origins anddifferent treatment duration and germination characterstics. The Nowshahr and Gilan origins showedmore similarity

Efficacy of polyextremophilic Aeribacillus pallidus on bioprocessing of beet vinasse derived from ethanol industries

This work aimed to evaluate the applicability of Aeribacillus pallidus for the aerobic treatment of the concentrated beet vinasse with high chemical oxygen demand (COD 685 g.L−1) that is defined as an environmental pollutant. This bacterium is a polyextremophilic strain and grow aerobically up to 7.5% vinasse at high temperature (50 °C). In the bioreactor and under controlled conditions, A. pallidus reduced the soluble COD content of 5% vinasse up to 27% during 48 h and utilized glucose and glycerol, completely. Furthermore, a reduction of manganese, copper, aluminum, and nickel concentrations was observed in the treated vinasse with A. pallidus. The obtained results make this strain as an appropriate alternative to be used for the aerobic bioprocessing of the vinasse. © 2020 The Author(s