| Efficient drug delivery is one of the key issues in cancer treatment.Generally,nanodrugs reach the lesion site through 1)blood circulation;2)tumor accumulation;3)tumor penetration;4)cellular uptake;and 5)drug release after intravenous injection.The complex and variable environment in the body often results in the drug amount reaching the lesion site being less than 0.7% of the initial injection amount.Therefore,improving the efficiency of drug delivery in the body is a critical factor in exerting therapeutic effects.The "in vivo self-assembly" strategy involves the in situ assembly of drugs at the biological level of pathological tissues.This process accumulates and assembles exogenous precursor molecules at the pathological site to form specific nanostructures,which can ultimately play a diagnostic and therapeutic role.The "in vivo self-assembly" strategy can design various endogenous and exogenous signals as regulatory factors to precisely control the assembly behavior and morphology of drugs,thereby achieving efficient drug delivery.In this article,we applied the "in vivo self-assembly" strategy to design a multi-level responsive peptide polymer nano-drug.By combining the regulation methods of ultrasound(US)and tumor micro-acidic environment,we achieved on-demand conversion of the size and charge of the nano-drug during different stages of in vivo delivery,ultimately achieving efficient delivery of the nano-drug and enhancing its anti-tumor activity.Firstly,we designed and synthesized a multi-level responsive peptide polymer(P1).This material consists of three parts: 1)porphyrin unit(C-TCPP)that produces ROS under ultrasound stimulation;2)p H-sensitive treatment unit: KFx AK(sequence: CGGGKFx AKFx AKKFx AKFx AK)modified by cis-aconitic anhydride(CAA)targeting mitochondria therapy peptide;and 3)β-thiolactone polymer skeleton that can be induced to change its hydrophilicity and hydrophobicity by ultrasound ROS.C-TCPP and KFx AK modified by CAA were linked to the β-thiolactone polymer skeleton through Michael addition reaction,obtaining material P1.Secondly,we confirmed the sequential assembly process of P1 during in vivo deliveryto solid tumors as follows: the β-thiolactone polymer skeleton has good biocompatibility and chemical stability in blood circulation.Therefore,the P1 aggregate can stably circulate in the body for a long time and accumulate at the tumor site.Under ultrasound stimulation applied to the tumor site,ROS produced by C-TCPP in the localized P1 will oxidize sulfur ether in the β-thiolactone polymer to sulfoxides(P1O),which enhances the hydrophilicity of P1 O compared to P1,making the original aggregated body gradually disassemble into smaller single-molecule chains that penetrate deeper into the tumor tissue.In the acidic microenvironment of the tumor with p H 6.5,CAA on P1 O is hydrolyzed,and the amide bond is broken,exposing the therapeutic peptide KFx AK.Meanwhile,as CAA departs,the hydrophobicity of the material increases,and the single-molecule chain reassembles into positively charged nanospheres(P1O-A).P1O-A is more conducive to cellular uptake,and the exposed therapeutic peptide targets mitochondria and destroys them,killing tumor cells.Specifically,we mainly investigated the following three research dimensions:1.Whether P1 can dissolve and aggregate under ultrasound and p H6.5,which detected by TEM,DLS,NBD fluorescence method and other methods to explored at the solution level.2.Whether the material can have long circulation,deep penetration,target mitochondria after entering cells,and the ability to kill cells,which were mainly verified by pharmacokinetics,tissue slices,and lysosome co-localization at the cellular level.3.To verify the effect of the material at the in vivo level,we treated mice with P1 for 13 days and observed the inhibition of tumors by the material.In conclusion,we proposed a new concept of in vivo sequential assembly and achieved transformation of the size and charge of multi-peptide polymer nano-drugs by regulating ultrasound and p H,ultimately achieving efficient drug delivery.This provides a new approach for achieving high penetration,high accumulation and easy internalization of drugs in solid tumors in vivo... |
PDF Full Text Request