Development And Evaluation Of A Novel Nanostructured Lipid Delivery System For The Anticancer Lead β-rubromycin

Purpose of research: Solid lipid nanoparticles(SLN)are composed of a single lipid,and drugs with poor water solubility have better bioavailability,stability,and solubility after being combined with lipids.Nanostructured lipid carriers(NLC)are based on SLNs by adding liquid lipids,so that the complete lipid structure of SLNs is destroyed and the drug loading capacity is improved.At the same time,the addition of oil and liquid lipid increases the physical stability of the drug,reduces the drug discharge,and regulates the drug release,has good biopermeability,and improves the bioavailability of the drug.Nowadays,NLCs are widely used in the field of medicine and cosmetics.The type and percentage of lipids affect properties such as encapsulation efficiency,stability,and drug release of NLCs.And the transport mechanism of NLCs in the human body is through pinocytosis and exocytosis,which also depends on the lipid composition of NLCs.Therefore,the preparation of NLCs requires the selection of appropriate solid lipids and liquid lipids.β-rubromycin is an early discovered natural product derived from microorganisms,which can inhibit the activity of telomerase and thus inhibit the growth of tumor cells.However,the low yield of β-rubromycin,poor cell permeability,and extremely low solubility in common solvents hinder its clinical application.In our previous study,the production of β-rubromycin was increased by about tenfold,solving the problem of insufficient production of β-rubromycin.However,in the study of anti-tumor activity,the activity of β-rubromycin against human normal colon gland epithelial cells NCM460 and human colon cancer cells Caco2 is between 15 – 20 μM,and has no cell selectivity.Therefore,it is of high value to develop a nano-delivery system suitable for β-rubromycin.Methods and results: In this project,β-rubromycin was used as the lead to develop and evaluate novel nanolipid delivery systems prepared from different lipids.We first prepared β-rubromycin-loaded SLN(Rub@SLN)using soybean lecithin as solid lipid.And its particle size,Zeta potential were characterized.The particle size of Rub@SLN is about212 nm,and the encapsulation efficiency is low,only 36%.Zeta potential is positive.Rub@SLN has good placement stability and the effect of delaying drug release.In the biological activity study in vitro,the antitumor activity of Rub@SLN was increased by about 3 times compared with that of free β-rubromycin,and the improvement effect was not significant.We continue to select solid lipid monostearate Glyceryl Monostearate(GM),and two different liquid lipids Oleinic Acid(OA),Glycerol Trioleate(GT)to prepare the load NLCs of β-rubromycin(Rub@GM-NLCs).The optimal drug-to-lipid ratio,solid-to-liquid-to-lipid ratio,surfactant concentration and ultrasonic power were determined by single factor investigation.The encapsulation efficiency of Rub@GM-NLCs can reach about 75%.And it has good storage stability within 7 days,and the delayed drug release is about 1 times higher than that of Rub@SLN.In the biological activity study in vitro,the anti-tumor activity of Rub@GMNLCs was about 5 times higher than that of free β-rubromycin,but the toxicity to normal cells was increased about 10 times.Changes in liquid lipids had no significant effect on the characterization and in vitro bioactivity of Rub@GM-NLCs.So,we replaced the solid lipid GM with Palmitic Acid(PA).PA is widespread in cell membranes.We used PA and two liquid lipids,OA,GT to prepare β-rubromycin-loaded NLCs(Rub@PA-NLCs)for particle size and zeta potential characterization.The in vitro characterization of Rub@PA-NLCs is similar to Rub@GM-NLCs,with good stability and delayed drug release.The in vitro biological activity of Rub@PA-NLCs showed no significant difference in antitumor activity and toxic effect on normal cells,and showed no selectivity.We finally used natural solid lipid Beeswax(BW)and liquid lipid OA,GT to prepare β-rubromycin-loaded NLCs(Rub@BW-NLCs).The particle size of Rub@BW-NLCs is larger,between 700-800 nm.The Zeta potential is negative,the placement stability is good,and the drug release effect is greatly delayed.In the in vitro biological activity of Rub@BW-NLCs,its antitumor activity was about 3 times higher than that of β-rubromycin,while its toxicity to normal cells was weaker,about 2 times higher than that of β-rubromycin.In vivo anticancer experiments proved that NLCs prepared by BW could effectively deliver β-rubromycin,increase the antitumor activity of β-rubromycin,and improve the bioavailability of β-rubromycin.Conclusion: This subject verifies that NLCs are an effective drug carrier that can deliver low-solubility drugs such as β-rubromycin,providing a reliable method for the clinical use of β-rubromycin.At the same time,it also verified the important role of solid lipids in nanostructured lipid carriers,and improved a set of feasible solutions for the selection of solid lipids.Using NLCs prepared from different solid lipids to target different types of cells,a variety of nanolipid delivery systems can be developed.The NLCs prepared from PA provide a good idea for the delivery of nutrients such as dopamine,and the NLCs prepared from PA can be used in cosmetics or antibacterial drugs to improve the permeability of active substances or drugs.The NLCs prepared from BW are anti-tumor The increased cell selectivity of the drug enables the drug to target tumor cells to a certain extent and reduces the toxic and side effects of the drug.