A 3D printed hydrogel to promote human keratinocytes' spheroid-based growth

Tissue engineering uses cells and biomaterials to develop bioartificial tissue substitutes for different purposes. For example, although several skin models have been developed for pharmaceutical and cosmetic research and skin wound healing, there are few studies on 3D cultures of keratinocytes in 3D printed scaffolds. So, this work aimed to develop a 3D-printed hydrogel scaffold to promote human keratinocyte growth. Mesh 3D scaffolds were printed using an extrusion-based method with a 20% gelatin/5% alginate hydrogel, where HaCaT cells were cultured for 7 days. Scaffolds kept their structure for over 1 week, and their stiffness only decreased after 7 days, showing good mechanical and structural characteristics and biodegradability (27% weight lost). Viable keratinocytes (MTT assay) are aggregated into spheroids, a 3D model capable of mimicking in vivo cell properties and phenotypes. Spheroids were formed on 47% of scaffolds pores and grew over time, showing promising cell proliferation. F-actin staining showed cells' irregular and interconnected shapes and organization over time. This method offers an easy and inexpensive solution for keratinocyte spheroid formation, which may be helpful in tissue engineering as a cell delivery system, for pharmacological or basic research, or wound healing medical applications.

The impact of GAL6, GAL80, and MIG1 on glucose control of the GAL system in Saccharomyces cerevisiae

The role of the proteins encoded by the GAL80 gene, the MIG1 gene and the GAL6 gene in glucose control of galactose consumption by Saccharomyces cerevisiae was studied by physiological characterisation of various GAL mutant strains. Dynamic experiments with the CEN.PK 113-7D wild-type strain and a deltagal80deltamig1 double-mutant strain in aerobic nitrogen-limited continuous cultivations at a dilution rate of 0.1 h(-1), showed simultaneous glucose and galactose consumption by the deltagal80deltamig1 strain. The wild-type strain did not consume galactose in the presence of glucose. Aerobic batch cultivations on glucose-galactose mixtures with the wild-type strain and with recombinant strains with a de-regulated GAL system (the deltagal80deltamig1 strain, a deltagal6 deleted strain, a deltagal6deltagal80deltamig1 triple mutant, and a deltagal6deltagal80deltamig1 triple mutant harbouring a GAL4 high-copy vector) were carried out. Generally, a reduction of glucose control lowered the maximum specific growth rate on glucose and increased the ethanol yield obtained on galactose with more than 100%. In contrast to the wild-type strain, the deltagal6deltagal80deltamig1 triple mutant strain consumed glucose and galactose simultaneously, and this strain also showed the highest ethanol production with an overall ethanol yield of 0.35 g g-1 sugar, which is 17% higher than the yield on glucose obtained with the wild-type strain. GAL80 and MIG1 were demonstrated to be responsible for the majority of the glucose control on the GAL system, whereas GAL6 has a minor role in glucose control. Deletion of GAL6 was shown to have a major impact on biomass and ethanol formation when cells were grown on galactose, and from the data obtained we speculate that Gal6 may be involved in mRNA degradation of the GAL gene transcripts.