A sulfobetaine zwitterionic polymer-drug conjugate for multivalent paclitaxel and gemcitabine co-delivery

A zwitterionic polymer-drug conjugate (ZPDC) strategy is developed for the co-delivery of paclitaxel (PTX) and gemcitabine (GEM) chemotherapeutics, as well as a near-infrared fluorescence imaging agent cyanine5.5 (Cy5.5). The well-defined ZPDC is synthesized by tandem azide-alkyne and thiol-ene click functionalization of a biodegradable acetylenyl/allyl-functionalized polylactide and zwitterionic character is conferred by sulfobetaine. It has a number-average molecular weight of 53.6 kDa, comprising 6.5% PTX and 17.7% GEM by weight. Cy5.5 moieties are readily introduced to the ZPDC via conjugation. In aqueous solutions, the ZPDC exhibits a hydrodynamic diameter of 46 nm. In vitro MIA PaCa-2 human pancreatic cancer cells show strong ZPDC cellular uptake and cytotoxicity. In mice, the ZPDC exhibits long blood circulation, effective tumor accumulation, biocompatibility, therapeutic effect, and integrated imaging capacity. Overall, this work illustrates that ZPDCs are promising systems for chemotherapy delivery and bioimaging applications.

Poly(trimethylene carbonate)/Poly(malic acid) Amphiphilic Diblock Copolymers as Biocompatible Nanoparticles

Amphiphilic polycarbonate-poly(hydroxyalkanoate) diblock copolymers, namely, poly(trimethylene carbonate) (PTMC)-b-poly(β-malic acid) (PMLA), are reported for the first time. The synthetic strategy relies on commercially available catalysts and initiator. The controlled ring-opening polymerization (ROP) of trimethylene carbonate (TMC) catalyzed by the organic guanidine base 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), associated with iPrOH as an initiator, provided iPrO-PTMC-OH, which served as a macroinitiator in the controlled ROP of benzyl β-malolactonate (MLABe) catalyzed by the neodymium triflate salt (Nd(OTf)3). The resulting hydrophobic iPrO-PTMC-b-PMLABe-OH copolymers were then hydrogenolyzed into the parent iPrO-PTMC-b-PMLA-OH copolymers. A range of well-defined copolymers, featuring different sizes of segments (Mn,NMR up to 9300 g mol(-1) ; ÐM =1.28-1.40), were thus isolated in gram quantities, as evidenced by NMR spectroscopy, size exclusion chromatography, thermogravimetric analysis, differential scanning calorimetry, and contact angle analyses. Subsequently, PTMC-b-PMLA copolymers with different hydrophilic weight fractions (11-75 %) self-assembled in phosphate-buffered saline upon nanoprecipitation into well-defined nano-objects with Dh =61-176 nm, a polydispersity index <0.25, and a negative surface charge, as characterized by dynamic light scattering and zeta-potential analyses. In addition, these nanoparticles demonstrated no significant effect on cell viability at low concentrations, and a very low cytotoxicity at high concentrations only for PTMC-b-PMLA copolymers exhibiting hydrophilic fractions over 47 %, thus illustrating the potential of these copolymers as promising nanoparticles.

Polylactide-graft-doxorubicin nanoparticles with precisely controlled drug loading for pH-triggered drug delivery

Nanoparticles (NPs) with high drug loading and pH-responsivity were prepared by nanoprecipitation of a hydrophobic polymer-drug conjugate (PDC). The PDC, polylactide-graft-doxorubicin (PLA-g-DOX), was synthesized by azide-alkyne click reaction to transform acetylene-functionalized PLA into PLA-graft-aldehyde (PLA-g-ALD), followed by DOX conjugation to form acid-sensitive Schiff base linkage between drug moieties and polymer scaffold. The DOX loading amount in PLA-g-DOX PDC was determined to be 32 wt % by (1)H NMR and UV-vis spectroscopies. PLA-g-DOX PDC was further used to prepare NPs with precisely controlled drug loading by nanoprecipitation in the presence of a PEGylated surfactant. The effects of organic solvent, PLA-g-DOX PDC concentration and PLA-g-DOX/surfactant mass ratio on size and size distribution of NPs were systematically examined based on analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM). NPs prepared under the optimal conditions exhibited well-defined spherical morphology with volume-average hydrodynamic diameter (Dh) around 100 nm. Due to the Schiff base conjugation linkage in PLA-g-DOX PDC, acid-sensitive drug release behavior of the NPs was observed. In vitro studies against MCF-7 breast cancer cells showed that the NPs can be readily taken up and result in enhanced therapeutic efficiency as compared to DOX·HCl, indicating their promising potential applications as anticancer nanomedicines.

Helical Poly(arginine) Mimics with Superior Cell-Penetrating and Molecular Transporting Properties

Poly(arginine) mimics bearing long hydrophobic side chains adopt stable helical conformation and exhibit helix-related cell-penetrating properties. Elongating polypeptide backbone length and increasing side chain hydrophobicity further increase the helicities of poly(arginine) mimics. They show superior cell membrane permeability up to two orders of magnitude higher than that of HIV-TAT peptide and excellent DNA and siRNA delivery efficiencies in various mammalian cells.