Monday, January 1, 2018

PLGA-PEG-Mal from PolySciTech used in development of immunosuppressant releasing tissue scaffold


One of the major challenges in stem-cell and tissue engineering is rejection of the new cells by the body through the immune system. Since systemic delivery of immunosuppressant medicines has severe side-effects, a better solution is localized delivery of immunosuppressants to prevent the cells in the scaffold from being attacked by immune cells. Recently, researchers from Fudan University, Tianjin Medical University (China), and Ewha Women’s University (Korea) used PLGA-PEG-Mal (PolyVivo AI136) from PolySciTech (www.polyscitech.com) to create tacrolimus loaded PLGA-PEG- RADA16 self-attractive nanoparticles. These were loaded into stem-cell hydrogels and remained within the hydrogel by electrostatic attraction. This resulted in a consistent and controlled release of immunosuppressant from the scaffold to prevent immune response against the loaded stem cells. This research holds promise to improve results for a wide array of tissue engineering applications. Read more: Li, Ruixiang, Jianming Liang, Yuwei He, Jing Qin, Huining He, Seungjin Lee, Zhiqing Pang, and Jianxin Wang. "Sustained Release of Immunosuppressant by Nanoparticle-anchoring Hydrogel Scaffold Improved the Survival of Transplanted Stem Cells and Tissue Regeneration." Theranostics 2018; 8(4): 878-893. doi: 10.7150/thno.22072 http://www.thno.org/v08p0878.pdf

“The outcome of scaffold-based stem cell transplantation remains unsatisfied due to the poor survival of transplanted cells. One of the major hurdles associated with the stem cell survival is the immune rejection, which can be effectively reduced by the use of immunosuppressant. However, ideal localized and sustained release of immunosuppressant is difficult to be realized, because it is arduous to hold the drug delivery system within scaffold for a long period of time. In the present study, the sustained release of immunosuppressant for the purpose of improving the survival of stem cells was successfully realized by a nanoparticle-anchoring hydrogel scaffold we developed. Methods: Poly (lactic-co-glycolic acid) (PLGA) nanoparticles were modified with RADA16 (RNPs), a self-assembling peptide, and then anchored to a RADA16 hydrogel (RNPs + Gel). The immobilization of RNPs in hydrogel was measured in vitro and in vivo, including the Brownian motion and cumulative leakage of RNPs and the in vivo retention of injected RNPs with hydrogel. Tacrolimus, as a typical immunosuppressant, was encapsulated in RNPs (T-RNPs) that were anchored to the hydrogel and its release behavior were studied. Endothelial progenitor cells (EPCs), as model stem cells, were cultured in the T-RNPs-anchoring hydrogel to test the immune-suppressing effect. The cytotoxicity of the scaffold against EPCs was also measured compared with free tacrolimus-loaded hydrogel. The therapeutic efficacy of the scaffold laden with EPCs on the hind limb ischemia was further evaluated in mice. Results: The Brownian motion and cumulative leakage of RNPs were significantly decreased compared with the un-modified nanoparticles (NPs). The in vivo retention of injected RNPs with hydrogel was obviously longer than that of NPs with hydrogel. The release of tacrolimus from T-RNPs + Gel could be sustained for 28 days. Compared with free tacrolimus-loaded hydrogel, the immune responses were significantly reduced and the survival of EPCs was greatly improved both in vitro and in vivo. The results of histological evaluation, including accumulation of immune cells and deposition of anti-graft antibodies, further revealed significantly lessened immune rejection in T-RNPs-anchoring hydrogel group compared with other groups. In pharmacodynamics study, the scaffold laden with EPCs was applied to treat hind limb ischemia in mice and significantly promoted the blood perfusion (~91 % versus ~36 % in control group). Conclusion: The nanoparticle-anchoring hydrogel scaffold is promising for localized immunosuppressant release, thereby can enhance the survival of transplanted cells and finally lead to successful tissue regeneration. Key words: stem cell; immune suppression; tacrolimus; nanoparticles; endothelial progenitor cells; RADA16 hydrogel.”
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