Synthesis Of A Novel Peptide Amphiphile Of Poly(S-((2-carboxyethyl) Thio)-L-cysteine) And Its Application In Drug Delivery System For Loading Cisplatin

Peptide amphiphiles have been extensively studied as potential biomaterials for tissue engineering scaffolds,3D cell culture,and drug delivery because of its good biocompatibility,biodegradability,and versatile biofunctionalization.Here,a novel peptide amphiphile poly(S-((2-carboxyethyl)thio)-L-cysteine)composed of alkyl tail and derivative of cysteine was prepared by ring-opening polymerization and post-polymerization modification route.The self-assembly of the peptide amphiphile leads to the formation of spherical micelles and(or)nanofibrous micelles,which can undergo physical cross-linking to form three dimensional hydrogel at proper conditions.The spherical micelles and the hydrogels were studied as nano-carrier and implantable carrier for cisplatin,respectively.The research findings are briefly described as follows.1.The S-ethylsulfonyl-L-cysteine is firstly received by nitrosation of L-cysteine followed by reaction with sodium ethanesulfinate.The S-ethylsulfonyl-L-cysteine N-carboxyanhydride is then synthesized by the Fuchs-Farthing method using triphosgene as the phosgene source.The S-ethylsulfonyl-L-cysteine N-carboxyanhydrides are polymerized at 0℃by using the alkylamine as initiator to produce poly(S-ethylsulfonyl-L-cysteine).Finally,the poly(S-((2-carboxyethyl)thio)-L-cysteine)is obtained by reacting poly(S-ethylsulfonyl-L-cysteine)with 3-mercaptopropionic acid.~1H-NMR and IR spectra indicate that all the products are successfully synthesized.2.Poly(S-((2-carboxyethyl)thio)-L-cysteine)micelles and cisplatin-loaded micelles are prepared by self-assembly at a peptide concentration of 1.5mg/mL.Transmission electron microscopy show that both the unloaded micelles and the drug-loaded micelles are spherical.The mean particle diameters obtained by the dynamic light scattering method are 145nm and 52nm,respectively,which is suitable for the particle size requirements of the drug delivery system.The zeta potentials of unloaded micelles and drug-loaded micelles are-32.4mV and-11.5mV,respectively,indicating that they are relatively stable.3.The encapsulation efficiency and loading content of the drug-loaded micelles measured by the o-phenylenediamine method are 56.0%±3.7%and 27.2%±1.3%,respectively.The drug-loaded micelles have the highest drug release amount and rate at pH 5.5 and in the presence of glutathione,which indicate that the drug-loaded micelles have dual responsive characteristics of pH and redox.The dual responsive micelles can theoretically reduce the premature drug release and reduce the drug release in normal tissues while accelerating drug release in tumor tissues.4.In vitro HeLa cytotoxicity experiments showed that the cell viability of unloaded micelles was about 100%after 24 hours within a peptide concentration of 0.15μg/mL~15μg/mL.This indicate that the peptide amphiphiles have no obvious cytotoxicity.Cisplatin-loaded micelles have greater cell viability than free cisplatin at the same drug concentration,indicating that the drug-loaded micelles are less cytotoxic due to the sustained release effect of drug-loaded micelles.5.Nanofibrous hydrogels are successfully prepared by self-assembly with the stimulation of pH or ion at a concentration of 50mg/mL.Poly(S-((2-carboxyethyl)thio)-L-cysteine)firstly self-assemble into nanofibrous hydrogel under acidic condition.After adding sodium hydroxide solution,the hydrogel melts to a clear solution while it turned to gelation when the hydrochloric acid is added again,showing a pH responsive characteristic.In addition,after adding calcium chloride,the amphiphilic peptide solution can also self-assemble to form a nanofibrous hydrogel.After addition of the EDTA solution,the hydrogel turns into a peptide solution again,showing ion responsive characteristics.Hydrogels can recover from damage when exposed to external damage and show good self-healing capabilities.6.Peptide amphiphilic can also self-assemble to nanofibrous hydrogels after loading with cisplatin.When the peptide concentration is 50 mg/mL,transmission electron microscope images show that the length of the nanofibers is at least a few microns and the diameter is about a few nanometers.The hydrogel loaded with cisplatin release the drug slowly under the physiological conditions simulated in vitro.The release is the fastest in the first 4 hours(~4%/h),and become steady in the following 50h.The maximum release is reached at 102h while the cumulative release rate is about 77%.The MCF-7 cell experiments of nanofibers show that the cell viability is greater than 100%after 72h,which indicate that the nanofibers may have no obvious cytotoxicity and possess great potential as implantable drug carriers.