| Cancer has become the most lethal disease in human society.Chemotherapy is one of the main treatments for cancer,although its clinical application is greatly limited by multi-drug resistance(MDR)and toxic side-effects.The advanced drug carrier technology is believed an effective way to circumvent these hurdles and is widely discussed.Over past decades,nanoparticle-based drug delivery systems have been developed to improve the efficacy of nanocarrier,among which polymer micelles are thought to be one of the most promising platforms with solubilized hydrophobic drugs and the potential to overcome biological barriers effectively.Polyamino acid-based micelles have become one of the hotspots in polymer micelle system because of their good biocompatibility,strong biodegradability and easy modification of side chains.But self-assembled polypeptide-based micelles still face several problems,such as poor colloidal stability and premature drugs leakage at non-specific sites.Therefore,we designed and synthesized two polyamino acid-based drug carriers for targeted release of antitumor drugs to improve the stability of polyamino acid micelles and reduce the early release of drugs.The specific studies are as follows:(1)A new type of amphiphilic polyamino acid,crosslinked poly(ethylene glycol)-g-poly(aspartic acid)-g-tyrosine(CPPT),was synthesized via a simple one-pot polymerization method with the polyaspartic acid as the main body.The crosslinking degree of the crosslinking polyamino acid could be adjusted by changing the ratio of the crosslinking agent L-cysteine(L-Cys).According to the particle size,zeta potential,drug loading capacity(DLC),encapsulation efficiency(EE)and critical micelle concentration(CMC)of polyamino acid micelles,the optimal crosslinking degree of CPPT were selected.The synthesis of CPPT was verified by ~1H NMR and FT-IR.High resolution transmission electron microscopy(HR-TEM)was used to observe the morphology.The results showed that the CPPT micelles showed unifourmly dispersed regular spherical particles with a particle size of about 60 nm.The results of micelles stability evaluation showed that crosslinking significantly improved the stability of polyamino acid micelles.(2)Doxorubicin hydrochloride(DOX)and curcumin(Cur)were loaded on the crosslinked polyamino acid micelles carrier to produce the co-loaded particles named as CPPT-CD.The optimal drug delivery ratio was determined according to the DLC and EE by adjusting the proportion of drug delivery.In vitro drug release experiments under different simulated physiological conditions were conducted to demonstrate the controllable drug release.The experimental results showed that CPPT-CD micelles had obvious p H and reduction sensitivity.The results of drug release kinetics showed that the release of DOX was mainly achieved by free diffusion,while the release of Cur was realized by the synergistic effect of free diffusion and the dissolution of carrier skeleton.Finally,A549 cells were selected to investigate the cytotoxicity of blank polyamino acid micelles and drug-loaded polyamino acid micelles.(3)A layer of calcium phosphate shell was coated on the surface of polyamino acid micelles by co-precipitation method to prepare polyamino acid calcium-phosphate hybrid nanoparticles with core-shell structure(CPPT@Ca P-CD).The successful preparation of CPPT@Ca P-CD nanoparticles was proved by XRD and FT-IR.The HR-TEM presented that the prepared CPPT@Ca P-CD nanoparticles had a distinct core-shell structure showing a regular spherical shape with an average particle size of about 110 nm,and a shell thickness of about 20 nm,and the nanoparticles could be degraded in a weak acidic microenvironment.The results of in vitro drug release experiments verified that the Cur and DOX releases were less than 20%under the condition of p H 7.4,more than 85%under the condition of p H 5.4and 10 m M glutathione,showing excellent p H and reduction sensitivity.The in vitro cytotoxicity test verified that the dual-responsive nanoparticles CPPT@Ca P-CD showed higher cytotoxicity against A549 cells than that of the free combination of Cur+DOX.All in all,both the two p H and reductive dual-sensitive polyamino acid drug release systems in this paper have the properties of keeping stable in physiological environment and rapid release of drugs at the tumor site.This system could effectively improve the efficiency of anti-tumor drugs,maximize the synergistic effect of a variety of drugs,and reduce the side effects of drugs greatly,exhibiting a promising platform for efficient chemotherapy. |
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