ABSTRACT
Objective To establish a finite element model of cell perfusion culture, and study the effect of different perfusion speeds on the movement of suspended cells. Methods The two-dimensional (2D) model of cell and microchannels was established using COMSOL Multiphysics and meshed. Three groups were established according to the perfusion speed, namely, u0=0.196 mm/s, u1=0.117 mm/s, u2=0.04 mm/s. The fluid-structure interaction module was used for calculation. Results The flow field distribution in the microchannel was relatively uniform. During the equal period of time, the ratio of cell suspension perfusion speed was u0∶u1∶u2=5∶3∶1, and the ratio of cell displacement in the microchannel was D0∶D1∶D2=4.1∶ 2.9∶1. When the speed was proportional, the displacement of cells also roughly followed the corresponding proportional change. With the increase of perfusion speed, stress concentration in cells during movement would occur. The stress and fluid shear force (FSS) of cells during movement were within the safe value range, and cell destruction would not occur. Conclusions The suspended cells can enter into the microchannel without injury at a certain perfusion speed. Perfusion techniques can be used in cell implantation of in vitro tissue engineering products.
ABSTRACT
To investigate the influence factors and effects of metal or dissolving microneedles on the formation and healing of skin microchannels, the pencil-shaped or conical stainless steel microneedles with different lengths, tip to tip space and base area, and the pencil-shaped dissolving microneedles with different tip to tip space were used. The microneedles were applied to the skin of epilatory mice and rats, and the effects of various microneedle parameters, application parameters, and animals on the microchannels were explored by the transepidermal water loss (TEWL) and methylene blue staining. Visually observe the skin local irritation caused by the microneedles. The animal experiments were approved by the Animal Experiments Welfare and Ethical Committee of Zhejiang University of Technology. The application time of the microneedle should be maintained at 30 s or more. When the insertion forces were 2, 4, 8 N, and the TEWL initial values of the formed microchannels were 12.9, 33.0, 40.4 g·m-2·h-1, respectively. When the length of metal microneedle were 400, 600, 800 μm, and the TEWL initial values of the formed microchannels were 37.1, 40.4, 49.5 g·m-2·h-1, respectively. When the tip to tip space of metal microneedle were 400, 600, 800 μm, and the TEWL initial values of the formed microchannels were 33.2, 40.4, 55.8 g·m-2·h-1, respectively. When the base area of metal microneedle were 0.16, 0.35, 0.62 cm2, and the TEWL initial values of the formed microchannels were 35.1, 40.4, 67.1 g·m-2·h-1, respectively. The effects of conical and pencil-shaped microneedles are similar. When the tip to tip space of pencil shaped dissolving microneedle were 400, 600, 800 μm, and the TEWL initial values of the formed microchannels were 49.8, 60.5, 70.5 g·m-2·h-1, respectively. The TEWL baseline values of animal skins of different genders and series are different, but the tendency of microchannels formation and closure is similar. Visual inspection revealed that the slight erythema caused by the microneedles subsided within 24 h. Microneedles of different parameters have different effects on microchannels. The microchannels closed within 24 or 48 h, and the skin local irritation caused by microneedle was mild.
ABSTRACT
Objective To evaluate the clinical safety of the collagen nerve scaffold with longitudinally oriented microchannels in bridging peripheral nerve defect.Methods Five patients with 8 peripheral nerve defects of 18 to 30 (mean,23.8) mm in length were involved in the pilot study and treated from July,2017 to March,2018,including 6 digital nerves and 2 medial antebrachial cutaneous nerves.The defects were repaired with the collagen nerve scaffold with longitudinally oriented microchannels independently developed.Routine therapy of prophylactic systemic antibiotics but no immunosuppressive drugs was given to all patients post-operatively.All patients were followed-up by regular review in the outpatient department combined with WeChat and telephone.The clinical safety of the nerve scaffold was preliminarily evaluated through observing the condition of the healing of the local wound and the whole body.The blood routine examineation and biochemical test were detected.The statistical analysis of the measurement data was performed by the analysis of variance of repeated measurement data,and the difference was statistically significant when P＜0.05.Results All patients were followed-up for 7 to 15 months (average,10 months).No adverse events such as infection,allergy,damage of liver and kidney function occurred.The operative incisions healed primarily,with no redness,exudation and rupture in the local area.There was no systemic symptoms such as fever,nausea,vomiting,skin itching,etc.The results of blood routine tests and biochemical tests were normal.The data of tests was compared,and the difference was not statistically significant (P＞0.05).Conclusion The preliminary study shows that it is clinically safe to bridge peripheral nerve defects with the collagen nerve scaffold with longitudinally oriented microchannels.