Molecular imprinting as a simple way for the long-term maintenance of the stemness and proliferation potential of adipose-derived stem cells: an in vitro study.

Cells are smart creatures that respond to every signal after isolation and in vitro culture. Adipose-derived stem cells (ADSCs) gradually lose their characteristic spindle shape, multi-lineage differentiation potential, and self-renewal ability, and enter replicative senescence after in vitro expansion. This loss of cellular function is a serious impediment to clinical applications that require huge numbers of cells. It has been proven that substrates with cell imprints can be applied for stem cells' differentiation into desired cells or to re-culture any cell type while maintaining its ordinary activity. This study demonstrated the application of cell-imprinted substrates as a novel method in the long-term expansion of ADSCs while maintaining their stemness. Here we used molecular imprinting of stem cells as a physical signal to maintain stem cells' stemness. First, ADSCs were isolated and cultured on the tissue culture plate. Then, cells were fixed, and stem cell-imprinted substrates were fabricated using PDMS. Afterward, ADSCs were cultured on these substrates and subjected to osteogenic and adipogenic differentiation signals. The results were compared with ADSCs cultured on a polystyrene tissue culture plate and non-patterned PDMS. Morphology analysis with optical and fluorescence microscopy and SEM images illustrated that ADSCs seeded on imprinted substrates kept ADSC morphology. Alizarin Red S and Oil Red O staining, flow cytometry, and qPCR results showed that ADSC-imprinted substrates could reduce the differentiation of stem cells in vitro even if the differentiating stimulations were applied. Also, cell cycle analysis revealed that ADSCs could maintain their proliferation potential. So this method can maintain stem cells' stemness for a long time and reduce the unwanted stem cell differentiation that occurs in conventional cell culture on tissue culture plates.

Computational and experimental studies of a cell-imprinted-based integrated microfluidic device for biomedical applications.

It has been proved that cell-imprinted substrates molded from template cells can be used for the re-culture of that cell while preserving its normal behavior or to differentiate the cultured stem cells into the template cell. In this study, a microfluidic device was presented to modify the previous irregular cell-imprinted substrate and increase imprinting efficiency by regular and objective cell culture. First, a cell-imprinted substrate from template cells was prepared using a microfluidic chip in a regular pattern. Another microfluidic chip with the same pattern was then aligned on the cell-imprinted substrate to create a chondrocyte-imprinted-based integrated microfluidic device. Computational fluid dynamics (CFD) simulations were used to obtain suitable conditions for injecting cells into the microfluidic chip before performing experimental evaluations. In this simulation, the effect of input flow rate, number per unit volume, and size of injected cells in two different chip sizes were examined on exerted shear stress and cell trajectories. This numerical simulation was first validated with experiments with cell lines. Finally, chondrocyte was used as template cell to evaluate the chondrogenic differentiation of adipose-derived mesenchymal stem cells (ADSCs) in the chondrocyte-imprinted-based integrated microfluidic device. ADSCs were positioned precisely on the chondrocyte patterns, and without using any chemical growth factor, their fibroblast-like morphology was modified to the spherical morphology of chondrocytes after 14 days of culture. Both immunostaining and gene expression analysis showed improvement in chondrogenic differentiation compared to traditional imprinting methods. This study demonstrated the effectiveness of cell-imprinted-based integrated microfluidic devices for biomedical applications.

An integrated microfluidic device for stem cell differentiation based on cell-imprinted substrate designed for cartilage regeneration in a rabbit model.

Separating cells from the body and cultivating them in vitro will alter the function of cells. Therefore, for optimal cell culture in the laboratory, conditions similar to those of their natural growth should be provided. In previous studies, it has been shown that the use of cellular shape at the culture surface can regulate cellular function. In this work, the efficiency of the imprinting method increased by using microfluidic chip design and fabrication. In this method, first, a cell-imprinted substrate of chondrocytes was made using a microfluidic chip. Afterwards, stem cells were cultured on a cell-imprinted substrate using a second microfluidic chip aligned with the substrate. Therefore, stem cells were precisely placed on the chondrocyte patterns on the substrate and their fibroblast-like morphology was changed to chondrocyte's spherical morphology after 14-days culture in the chip without using any chemical growth factor. After chondrogenic differentiation and in vitro assessments (real-time PCR and immunocytotoxicity), differentiated stem cells were transferred on a collagen-hyaluronic acid scaffold and transplanted in articular cartilage defect of the rabbit. After 6 months, the post-transplantation analysis showed that the articular cartilage defect had been successfully regenerated in differentiated stem cell groups in comparison with the controls. In conclusion, this study showed the potency of the imprinting method for inducing chondrogenicity in stem cells, which can be used in clinical trials due to the safety of the procedure.

Microfluidics for core-shell drug carrier particles - a review.

Core-shell drug-carrier particles are known for their unique features. Due to the combination of superior properties not exhibited by the individual components, core-shell particles have gained a lot of interest. The structures could integrate core and shell characteristics and properties. These particles were designed for controlled drug release in the desired location. Therefore, the side effects would be minimized. So, these particles' advantages have led to the introduction of new methods and ideas for their fabrication. In the past few years, the generation of drug carrier core-shell particles in microfluidic chips has attracted much attention. This method makes it possible to produce particles at nanometer and micrometer levels of the same shape and size; it usually costs less than other methods. The other advantages of using microfluidic techniques compared to conventional bulk methods are integration capability, reproducibility, and higher efficiency. These advantages have created a positive outlook on this approach. This review gives an overview of the various fluidic concepts that are used to generate microparticles or nanoparticles. Also, an overview of traditional and more recent microfluidic devices and their design and structure for the generation of core-shell particles is given. The unique benefits of the microfluidic technique for core-shell drug carrier particle generation are demonstrated.