Studies On Gemini Surfactant-like Peptides Self-assembled Nanocages And Their Applications In Drug Encapsulation

Many anticancer drugs such as paclitaxel,adriamycin,etoposide,etc.are constrained by clinical applications due to poor water solubility.Therefore,novel drug encapsulation and solubilization methods are still the focus of current research in the field of drug delivery.Gemini Surfactant-like peptide(GSLP)is a class of surface active peptide compounds,which is composed of two hydrophilic ends and two hydrophobic ends.GSLP has gradually received attention in the construction and application of biofunctional nanostructures.However,the study of self-assembled structures based on GSLP is still in the initial stage,such as the constructed nanocage structures are poorly stable and easily degraded by proteases.Therefore,novel peptide sequences and patterns need to be urgently explored.In recent years,scientists have discovered that the core sequences of protein accumulation diseases can all form β-sheet structures,which have very stable properties and can even resist protease hydrolysis to a certain extent.Inspired by this,this thesis was assisted by molecular simulation to design a bipartite surface active peptide with two proline linked ends,a hydrophilic end with two lysines and a hydrophobic end that can form a β-sheet with the sequence GNNQQNY-PKKP-GNNNQQNY.These specific combinations facilitate the spontaneous assembly of peptides in solution forming polypeptide nanocages with hollow structures.The aim is to improve the solubility of drugs by encapsulating hydrophobic drugs in such GSLP nanocages.In this thesis,the assembly and drug encapsulation effects of GSPL nanocages were investigated mainly using molecular dynamics simulations and experiments as follows:1.The molecular dynamics simulation revealed that: the single molecule GSLP kinetic simulation formed a natural corner in the presence of proline as envisaged,and it was not only established that the two hydrophobic chains of GSLP could form β-sheet in solution,but also that they had a strong tendency to aggregate in aqueous solution.2.The results of the experimental study revealed that the peptide formed nanocage structures stably in solution,proving that those non-specific hydrophobic sequences in the previous GSLP can be replaced by sequences that can form specific β-sheets.It was also demonstrated by transmission electron microscopy and atomic force microscopy studies that GSLP can form a hollow nanocage structure after self-assembly.3.Further experimental results illustrate that the GSLP nanocage structure composed of natural amino acids can encapsulate the hydrophobic drug paclitaxel and that it exhibits concentration-dependent toxic effects in anti-tumor cells.This study found that the use of formable β-sheet sequences instead of conventional hydrophobic sequences can be successfully assembled into nanocage structures,which belongs to a new strategy based on GSLP nanostructure assembly.By wrapping hydrophobic drugs,this thesis verifies that GSLP-wrapped PTX can kill cancer cells more effectively than PTX alone,showing its application in the stable transport of hydrophobic anticancer drugs.