In this paper, recommended spiral passive micromixer was designed and simulated. spiral design has the potential to create and strengthen the centrifugal force and the secondary flow. A series of simulations were carried out to evaluate the effects of channel width, channel depth, the gap between loops, and flowrate on the micromixer performance. These features impact the contact area of the two fluids and ultimately lead to an increment in the quality of the mixture. In this study, for the flow rate of 25 μl/min and molecular diffusion coefficient of 1×10-10 m2/s, mixing efficiency of more than 90% is achieved after 30 (approximately one-third of the total channel length). Finally, the optimized design fabricated using proposed 3D printing method.

In recent years, much more attentions have been focused on siRNA-based gene therapy. This approach is based on PTGS (Post-transcriptional gene silencing). Due to some defects in viral vectors, non-viral vectors have been used to deliver nucleic acids into target cells. Although, transfection efficiency in non-viral vectors is less than viral ones, but safety of non-viral vectors is much more. Characteristic features of siRNA, such as high compatibility, application in low doses and its versatility make it suitable in the gene therapy field. However, some challenges, such as stimulating immune system and Off-target silencing will be remain. In this review article, we express bottlenecks existing in siRNA delivery into target cells. According to the information, with further development of siRNA delivery in the future, it could be a promising approach in treatment for a variety of genetic diseases.

The field of drug delivery is a very hot research area as it affects the life of millions of patients every year. Although pharmaceutical agents can be administrated in different ways, the effectiveness of certain drug delivery system (DDS) is directly related to the method of their administration. Polyurethanes are one of the most important classes of polymers, that play an essential role in the development of many different biomedical devices due to their exceptional compatibility, mechanical properties and flexibility. Polyurethanes are formed by the reaction reviewed of isocyanates and diols to produce urethane-bonded polymers (-NH-COO-) in their main chain, which is similar to the peptide bonds in the structure of proteins. Because of this similarity, they have also been used as part of the human body, such as dialysis membranes, intra-aortic balloons, heart valves, temporary scaffolds and breast implants. There are many types of polyurethane structural blocks available that allow the chemical and physical properties of polyurethane to be tailored to their intended applications, especially in the medical and pharmaceutical fields. In this paper, the synthesis and properties of polyurethane, structure, thermal stability, hardness, solvent resistance, drug delivery, mechanical properties as well as biodegradability and biocompatibility with special emphasis on the application of the polymer in controlled release of drugs and delivery to the target tissue were.