Enzymatic Synthesis of Poly(butylene-<i>co</i>-sebacate-<i>co</i>-glycolate) Copolyesters and Evaluation of the Copolymer Nanoparticles as Biodegradable Carriers for Doxorubicin Delivery

Aliphatic copolyesters consisting of diester, diol, and glycolate repeat units were enzymatically synthesized for the first time via lipase-catalyzed polycondensation reactions. Copolymerization of ethyl glycolate (EGA) with diethyl sebacate (DES) and 1,4-butanediol (BD) in the presence of Candida antarctica lipase B (CALB) resulted in the formation of poly­(butylene-<i>co</i>-sebacate-<i>co</i>-glycolate) (PBSG) copolyesters with molecular weight (<i>M</i>_w) up to 28000 and typical polydispersity between 1.2 and 1.8. The synthesized copolymers contained 10–40 mol % glycolate (GA) units depending on the monomer feed ratio employed. DSC analyses show that the copolyesters with 12–38% GA content are semicrystalline materials that melt between 43 and 59 °C. Free standing nanoparticles with an average size ranging from 250 to 400 nm were successfully fabricated from these PBSG copolymers using a single emulsification-solvent evaporation process. PBSG copolyesters were found to be hydrolytically degradable and doxorubicin- (DOX-) encapsulated PBSG nanoparticles exhibited slow and sustained release of the drug in PBS solution at 37 °C over an extended period of time (60 days). Cellular uptake studies indicate that the drug-loaded PBSG particles are absorbed by a large percentage (up to 95%) of Hela cancer cells within 4 h incubation time. <i>In vitro</i> cytotoxicity investigations reveal that at a same DOX concentration (0.125–2.0 μM), DOX-encapsulated PBSG nanoparticles possess either higher or comparable cytotoxicity toward Hela cells than the free drug DOX·HCl. These results suggest that the PBSG nanoparticles are promising carriers for controlled release delivery of DOX to treat cancers

Multifunctional Poly(amine-<i>co</i>-ester-<i>co</i>-orthoester) for Efficient and Safe Gene Delivery

Cationic polymers are used for nonviral gene delivery, but current materials lack the functionality to address the multiple barriers involved in gene delivery. Here we describe the rational design and synthesis of a new family of quaterpolymers with unprecedented multifunctionality: acid sensitivity, low cationic charge, high hydrophobicity, and biodegradability, all of which are essential for efficient and safe gene delivery. The polymers were synthesized via lipase-catalyzed polymerization of orthoester diester, lactone, dialkyl diester, and amino diol monomers. Polymers containing orthoester groups exhibited acid-sensitive degradation at endosomal pH (4–5), facilitated efficient endosomal escape and unpackaging of the genes, and were efficient in delivering genetic materials to HEK293 cells, human glioma cells, primary mouse melanoma cells, and human umbilical vein endothelial cells (HUVECs). We also developed a highly efficient lyophilized formulation of the nanoparticles, which could be stored for a month without loss of efficiency

Enzymatic PEGylated Poly(lactone-<i>co</i>-β-amino ester) Nanoparticles as Biodegradable, Biocompatible and Stable Vectors for Gene Delivery

We have developed new, efficient gene delivery systems based on PEGylated poly­(lactone-<i>co</i>-β-amino ester) block copolymers that are biodegradable, stable and low in toxicity. The PEG–poly­[PDL-<i>co</i>-3-(4-(methylene)­piperidin-1-yl)­propanoate] (PEG–PPM) diblock and PPM–PEG–PPM triblock copolymers with various compositions were synthesized in one step via lipase-catalyzed copolymerization of ω-pentadecalactone (PDL) and ethyl 3-(4-(hydroxymethyl)­piperidin-1-yl)­propanoate (EHMPP) with an appropriate PEG (MeO–PEG–OH or HO–PEG–OH). The amphiphilic block copolymers are capable of condensing DNA in aqueous medium via a self-assembly process to form polyplex micelle nanoparticles with desirable particle sizes (70–140 nm). These micelles possess low CMC values and are stable in the medium containing serum protein molecules (FBS). Among the PEG–PPM and PPM–PEG–PPM micelles, the PEG–PPM–15% PDL micelle particles exhibited high DNA-binding ability, the fastest cellular uptake rate and highest gene transfection efficacy. Flow cytometry analysis shows that LucDNA/PEG–PPM–15% PDL polyplex micelles can effectively escape from endosomal degradation after cellular uptake likely due to the presence of the tertiary amine groups in the copolymer chains that act as proton sponges. <i>In vitro</i> cytotoxicity and hemolysis assay experiments indicate that all copolymer samples are nonhemolytic and have minimal toxicity toward COS-7 cells within the polymer concentration range (≤200 μg/mL) used for the gene transfection. These results demonstrate that the PEGylated poly­(lactone-<i>co</i>-β-amino ester) block copolymers are promising new vectors for gene delivery applications

Enzymatic PEG-Poly(amine-<i>co</i>-disulfide ester) Nanoparticles as pH- and Redox-Responsive Drug Nanocarriers for Efficient Antitumor Treatment

We have designed and constructed novel multifunctional nanoparticle drug-delivery systems that are stable under physiological conditions and responsive to tumor-relevant pH and intracellular reduction potential. The nanoparticles were fabricated from enzymatically synthesized poly­(ethylene glycol) (PEG)-poly­(ω-pentadecalactone-<i>co</i>-<i>N</i>-methyldiethyleneamine-<i>co</i>-3,3′-dithiodipropionate) (PEG-PPMD) and PEG-poly­(ε-caprolactone-<i>co</i>-<i>N</i>-methyldiethyleneamine-<i>co</i>-3,3′-dithiodipropionate) (PEG-PCMD) block copolymers via self-assembly processes in aqueous solution. At acidic pH and in the presence of a reductant (e.g., d,l-dithiothreitol or glutathione), the nanosized micelle particles rapidly swell and disintegrate due to the protonation of amino groups and reductive cleavage of disulfide bonds in the micelle cores. Consistently, docetaxel (DTX)-loaded PEG-PPMD and PEG-PCMD micelles can be triggered synergistically by acidic endosomal pH and a high intracellular reduction potential to rapidly release the drug for efficient killing of cancer cells. The drug formulations based on PEG-PPMD and PEG-PCMD copolymers exhibited a substantially higher potency than free DTX in inhibiting tumor growth in mice, whereas their therapeutic effects on important organ tissues were minimal. These results demonstrate that PEG-PPMD and PEG-PCMD nanoparticles have a great potential to serve as site-specific, controlled drug-delivery vehicles for safe and efficient antitumor treatment