Well-defined polymer-drug conjugate engineered with redox and pH-sensitive release mechanism for efficient delivery of paclitaxel.

The synthesis of polymer-drug conjugate (PDC) capable of convenient preparation and controlled release of therapeutic agents is still an urgent requirement in drug delivery field. Herein, we develop a novel anti-cancer PDC engineered with side groups of disulfide and ester bonds for on-demand delivery of paclitaxel (PTX) with redox and pH dual sensitive behaviors. A simple polymer, 3,3'-dithiodipropionic acid functionalized poly(ethylene glycol)-b-poly(l-lysine) (mPEG-b-P(LL-DTPA)), was synthesized and PTX was directly conjugated to the carboxyl groups of mPEG-b-P(LL-DTPA) to obtain the disulfide-containing polymer-PTX conjugate (P(L-SS-PTX)). Another structural similar polymer-PTX conjugate without disulfide bonds (P(L-PTX)) was also prepared to verify the function of disulfide linkages. The P(L-SS-PTX) micelles showed rapid drug release under tumor-relevant reductive conditions as designed. Interestingly, the PTX release from P(L-SS-PTX) micelles could also be promoted by the increased acidity (pH ≈ 5). In vitro cytotoxicity study showed that the P(L-SS-PTX) micelles exhibited significantly enhanced cytotoxicity against a variety of tumor cells compared to the non-sensitive P(L-PTX) micelles. The in vivo studies on B16F1 melanoma bearing C57BL/6 mice demonstrated the superior antitumor activity of P(L-SS-PTX) over both free PTX and P(L-PTX). This dual-sensitive prodrug provides a useful strategy for anti-tumor drug delivery.

Lv S ，Tang Z ，Zhang D ，Song W ，Li M ，Lin J ，Liu H ，Chen X ... -  《-》

Well-Defined Redox-Sensitive Polyethene Glycol-Paclitaxel Prodrug Conjugate for Tumor-Specific Delivery of Paclitaxel Using Octreotide for Tumor Targeting.

Yin T ，Wu Q ，Wang L ，Yin L ，Zhou J ，Huo M ... -  《-》

Novel free-paclitaxel-loaded redox-responsive nanoparticles based on a disulfide-linked poly(ethylene glycol)-drug conjugate for intracellular drug delivery: synthesis, characterization, and antitumor activity in vitro and in vivo.

Chuan X ，Song Q ，Lin J ，Chen X ，Zhang H ，Dai W ，He B ，Wang X ，Zhang Q ... -  《-》

Redox-sensitive mPEG-SS-PTX/TPGS mixed micelles: An efficient drug delivery system for overcoming multidrug resistance.

The main cause of multidrug resistance (MDR) is overexpression of active efflux transporters, such as P-glycoprotein (P-gp). To reverse MDR and improve the chemotherapy effect of paclitaxel (PTX), we propose a new drug delivery system based on mixed micelles constructed with d-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS) and the mPEG-SS-PTX conjugate with consideration that TPGS is a P-gp inhibitor that can block the cancer cell action of pumping drugs outside of cells and can enhance the anticancer effect. mPEG-SS-PTX is synthesized by conjugating hydrophilic mPEG with a hydrophobic drug, PTX, via a redox-sensitive disulfide bond. The mPEG-SS-PTX conjugate is amphiphilic and can self-assemble in water. Mixed micelles formed by the mPEG-SS-PTX conjugate and TPGS have a low critical micelle concentration (CMC, ∼1.05×10-3mg/mL) and high drug loading content (∼19.6%). The disulfide bond in the mPEG-SS-PTX conjugate can be broken in cancer cells (a reductive environment) and release PTX to kill cancer cells. In vitro cytotoxicity and cell uptake suggest that mixed micelles can effectively improve the accumulation of PTX in multidrug-resistant MCF-7 cells. Therefore, the present as-prepared mixed micelles very effectively reverse the MDR and enhance the therapeutic effect.

Zhao D ，Zhang H ，Yang S ，He W ，Luan Y ... -  《-》

Novel self-associating poly(ethylene oxide)-b-poly(epsilon-caprolactone) based drug conjugates and nano-containers for paclitaxel delivery.

Poly(ethylene oxide)-block-poly(epsilon-caprolactone) (PEO-b-PCL) copolymers bearing paclitaxel (PTX) side groups on PCL (PEO-b-P(CL-PTX) were synthesized and assembled to particles of 123 nm average diameter. At 20% (w/w) PTX to polymer conjugation, PEO-b-P(CL-PTX) demonstrated only 5.0 and 6.7% PTX release after 72 h incubation at pH 7.4 and 5.0, respectively, but revealed signs of chain cleavage at pH 5.0. The cytotoxicity of PEO-b-P(CL-PTX) against MDA-MB-435 cancer cells increased as incubation time was raised from 72 to 96 h (IC(50) of 680 and 475 ng/mL, respectively), but it was still significantly lower than the cytotoxicity of free PTX (IC(50) of 3.5 ng/mL at 72 h). In further studies, micelles of PEO-b-PCL and those bearing benzyl or PTX on PCL were used for physical encapsulation of PTX, where maximum level of loading was achieved by PEO-b-P(CL-PTX) (2.22%, w/w). The release of PTX from this carrier was rapid; however. The in vitro cytotoxicity of physically loaded PTX was independent of carrier and similar to that of free PTX. This was attributed to the low concentration of polymers which fell below their critical micellar concentration in the cytotoxicity study. The results point to the potential of chemically tailored PEO-b-PCL for optimum PTX solubilization and delivery.

Shahin M ，Lavasanifar A 《-》