Redox Stimulus Response Before Medicine, Such As The Construction Of Micelle And Characterization

Amphiphilic prodrugs with the propensity to selfassemble into micelles or vesicles exploited as drug delivery systems have become increasingly attractive in systemic cancer drug delivery because of their ability to prolong drug circulation half-life, reduce nonspecific uptake, and better accumulate at the tumors through enhanced permeation and retention (EPR) effect or active targeting. Recently, to address some of the systemic and intracellular delivery barriers, a nanosystem incorporated with stimuli-responsive property attracts intense attention. The advancement in material science has led to design of a variety of materials, which are employed to the development of nanocarrier systems to release drugs rapidly according to many stimuli-responsive factors based on temperature, pH, photo, magnetic resonance, ultrasound, reduction agent, and so forth. Reduction agent such as glutathione (GSH) that regulates cellular redox status in vivo, which is produced intracellularly and maintained at mM concentrations in the cytosol and subcellular compartments, respectively. In plasma, however, rapid enzymatic degradation limits GSH concentrations to μM levels. Adaptation to intrinsic oxidative stress of cancer cells generally results in upregulation of antioxidant capacity in the surrounding tumor tissue offering a selective, internal stimulus to trigger release of antitumor agents at the desired target site.This thesis will focus mainly on the technology and knowledge above and try to introduce some novel conceptions and designs according to the existed work. The main conclusions are as follow:1. Successful synthesis of a novel, amphilic camptothecin (CPT) prodrug engineered with a redox-sensitive drug release mechanism is reported. The unique design comprises covalent conjugation of two hydrophobic CPT to a hydrophilic poly(ethylene) glycol bridge via disulfide linkers (CPT-SS-PEG-SS-CPT). Drug loading capacity for this antineoplastic can reach above20%(w/w). Aqueous solutions of CPT-SS-PEG-SS-CPT>60μg/mL spontaneously form nanosized aggregates with a mean diameter of about225nm by DLS. In the presence of tumor-relevant concentrations of potent reducing agents reductive cleavage of disulfide bonds initiates rearrangement of the nanomicelle architecture leading to stimulus-induced release of the antitumor agent. Pharmacological activity of released CPT was confirmed in vitro using the HepG2human hepatoma cell model. These results imply that redox-sensitive CPT-SS-PEG-SS-CPT nanomicelles have the potential to augment localized cancer treatment due to preferential accumulation at the tumor site and rapid bioconversion to the pharmacologically active drug under tumor-relevant reductive conditions. 2. Successful synthesis of a novel prodrug (MTX-Lys-SS-MTX)-PEG-(MTX-Lys-SS-MTX) is reported based on the work above. The unique design comprises covalent conjugation of two hydrophobic MTX moieties to a lysine via solid phase synthesis. One of them is conjugated with the lysine via a disulfide linker, compared to the only amide of the other one. Drug loading capacity for this antineoplastic can reach about40%(w/w). Aqueous solutions of (MTX-Lys-SS-MTX)-PEG-(MTX-Lys-SS-MTX)>13μg/mL spontaneously form nanosized aggregates with a mean diameter of about150nm by DLS. In the presence of tumor-relevant concentrations of GSH reductive cleavage of disulfide bonds initiates rearrangement of the nanomicelle architecture leading to stimulus-induced release of part of the antitumor agent conjugated with lysine via disulfide, and the other will be slow-released via enzymolysis. Pharmacological activity of released MTX was confirmed in vitro using the MCF-7human breast cancer culture model. These results imply that redox-sensitive (MTX-Lys-SS-MTX)-PEG-(MTX-Lys-SS-MTX) nanomicelles have the potential to augment localized cancer treatment due to preferential accumulation at the tumor site and bioconversion to the pharmacologically active drug under tumor-relevant reductive conditions. Meanwhile, part of the MTX will be low-releaseed and bioconverted to the active drug.3. Successful synthesis of a novel prodrug engineered with a redox-sensitive drug release mechanism, is reported based on the work above. The unique design comprises covalent conjugation of two hydrophobic MTX moieties and one hydrophobic AKBA to a lysine via solid phase synthesis. And the two lysines are conjugated with a linear, hydrophilic poly(ethylene) glycol (MW=2,000) bridge via disulfide linkers ((MTX)2-Lys-AKBA)-SS-PEG-SS-((MTX)2-Lys-AKBA). Drug loading capacity for this antineoplastic can reach about45%(w/w). Aqueous solutions of ((MTX)2-Lys-AKBA)-SS-PEG-SS-((MTX)2-Lys-AKBA)>47μg/mL spontaneously form nanosized aggregates with a mean diameter of about160nm by DLS. In the presence of tumor-relevant concentrations of GSH reductive cleavage of disulfide bonds initiates rearrangement of the nanomicelle architecture leading to stimulus-induced release of (MTX)2-Lys-AKBA. Pharmacological activity of released antineoplastic was confirmed in vitro using the MCF-7human breast cancer cell culture model. These results imply that redox-sensitive ((MTX)2-Lys-AKBA)-SS-PEG-SS-((MTX)2-Lys-AKBA) nanomicelles have the potential to augment localized cancer treatment due to preferential accumulation at the tumor site and rapid bioconversion to the pharmacologically active drug under tumor-relevant reductive conditions. Precise ratiometric control over drug loading for combination therapy according to the clinical damand will be achieved.