Synthesis of three-arm block copolymer poly(lactic-co-glycolic acid)-poly(ethylene glycol) with oxalyl chloride and its application in hydrophobic drug delivery

Doxorubicin-loaded Polymeric Biotin-PEG-SeSe-PBLA Micelles with surface Binding of Biotin-Mediated Cancer Cell Targeting and Redox-Responsive Drug release for enhanced anticancer efficacy

Biotin receptors are overexpressed in various cancer cell types, essential in tumor development, metabolism, and metastasis. Chemotherapeutic agents may be more effective and have fewer adverse effects if they specifically target the biotin receptors on cancer cells. Polymeric micelles (PMs) with nanoscale size via the EPR effect to accumulate near tumor tissue. We utilized the solvent exchange technique to crate polymeric Biotin-PEG-SeSe-PBLA micelles. This underwent self-assembly to create uniformly dispersed PMs with a hydrodynamic diameter of 81.54 ± 0.23 nm. The resulting PMs characterized by 1HNMR, 13CNMR, FTIR, and Raman spectroscopy. PMs exhibited a high efficacy of Doxorubicin encapsulation (EE) and loading content (DLC), with values of 5.93 wt% and 74.32 %, respectively. DOX@Biotin-PEG-SeSe-PBLA micelles showed optimal DOX release, around 89 % and 74 % in 10 mM glutathione and 0.1 % H2O2, respectively, within 72 hours, in the simulated cancer redox pool. Fascinatingly, the blank Biotin-PEG-SeSe-PBLA micelles did not affect the HaCaT or HeLa cell lines; approximately 85 % of the cells were metabolically active. Contrarily, at a 5 μg/ml concentration, DOX@Biotin-PEG-SeSe-PBLA specifically inhibited the proliferation of roughly 76 % of HeLa cells and 11 % of HaCaT cells. The fluorescence microscopy results demonstrated that biotin-decorated micelles were more successfully internalized by HeLa cells, which overexpress the biotin receptor, than by non-targeted micelles in vitro. In summary, the diselenide-linked Biotin-PEGSeSe-PBLA formed smart PMs that could offer DOX specific to cancer cells with precision and are physiologically durable.

Highly sensitive H2O2-scavenging nano-bionic system for precise treatment of atherosclerosis

In atherosclerosis, chronic inflammatory processes in local diseased areas may lead to the accumulation of reactive oxygen species (ROS). In this study, we devised a highly sensitive H₂O₂-scavenging nano-bionic system loaded with probucol (RPP-PU), to treat atherosclerosis more effectively. The RPP material had high sensitivity to H₂O₂, and the response sensitivity could be reduced from 40 to 10 μmol/L which was close to the lowest concentration of H₂O₂ levels of the pathological environment. RPP-PU delayed the release and prolonged the duration of PU in vivo. In Apolipoprotein E deficient (ApoE^‒/‒) mice, RPP-PU effectively eliminated pathological ROS, reduced the level of lipids and related metabolic enzymes, and significantly decreased the area of vascular plaques and fibers. Our study demonstrated that the H₂O₂-scavenging nano-bionic system could scavenge the abundant ROS in the atherosclerosis lesion, thereby reducing the oxidative stress for treating atherosclerosis and thus achieve the therapeutic goals with atherosclerosis more desirably.

ROS-responsive nanoparticle-mediated delivery of CYP2J2 gene for therapeutic angiogenesis in severe hindlimb ischemia

With critical limb ischemia (CLI) being a multi-factorial disease, it is becoming evident that gene therapy with a multiple bio-functional growth factor could achieve better therapeutic outcomes. Cytochrome P450 epoxygenase-2J2 (CYP2J2) and its catalytic products epoxyeicosatrienoic acids (EETs) exhibit pleiotropic biological activities, including pro-angiogenic, anti-inflammatory and cardiovascular protective effects, which are considerably beneficial for reversing ischemia and restoring local blood flow in CLI. Here, we designed a nanoparticle-based pcDNA3.1-CYP2J2 plasmid DNA (pDNA) delivery system (nanoparticle/pDNA complex) composed of a novel three-arm star block copolymer (3S-PLGA-po-PEG), which was achieved by conjugating three-armed PLGA to PEG via the peroxalate ester bond. Considering the multiple bio-functions of CYP2J2-EETs and the sensitivity of the peroxalate ester bond to H₂O₂, this nanoparticle-based gene delivery system is expected to exhibit excellent pro-angiogenic effects while improving the high oxidative stress and inflammatory micro-environment in ischemic hindlimb. Our study reports the first application of CYP2J2 in the field of therapeutic angiogenesis for CLI treatment and our findings demonstrated good biocompatibility, stability and sustained release properties of the CYP2J2 nano-delivery system. In addition, this nanoparticle-based gene delivery system showed high transfection efficiency and efficient VEGF expression in vitro and in vivo. Intramuscular injection of nanoparticle/pDNA complexes into mice with hindlimb ischemia resulted in significant rapid blood flow recovery and improved muscle repair compared to mice treated with naked pDNA. In summary, 3S-PLGA-po-PEG/CYP2J2-pDNA complexes have tremendous potential and provide a practical strategy for the treatment of limb ischemia. Moreover, 3S-PLGA-po-PEG nanoparticles might be useful as a potential non-viral carrier for other gene delivery applications.

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Cytochrome P450 epoxygenase-2J2 (CYP2J2) was first applied in the field of therapeutic angiogenesis for critical limb ischemia treatment.

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The ROS-responsive three-arm star block copolymer (3S-PLGA-po-PEG) was synthesized with peroxalate ester as H₂O₂-responsive linkages through the esterification reaction of oxalyl chloride and hydroxyl group.

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The CYP2J2 nano-delivery system achieved high transfection efficiency and significant therapeutic angiogenesis effect.

Assessment of the Effect of PLGA Co-polymers and PEG on the Formation and Characteristics of PLGA-PEG-PLGA Co-block Polymer Using Statistical Approach

Purpose: To assess the effect of the lactic acid (LA)-to-glycolic acid (GA) molar ratio and polyethylene glycol (PEG) concentration on the formation of poly-lactide co-glycolide acid (PLGA)-PEG-PLGA co-block polymers simultaneously using statistical approach. Methods: A 22 full factorial design with the addition of a point in the center of the design, namely curvature, was applied. Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), and nuclear magnetic resonance (NMR) were performed to confirm the formation of the co-block polymer. Simvastatin (SMV), a drug model was incorporated into the nano-polymeric micellar (NpM) of PLGA-PEG-PLGA followed by solubility phase, particle size, zeta potential, and entrapment efficiency characterizations. Results: FTIR, DSC, and NMR successfully confirmed the formation of co-block polymers. Solubility of SMV increased from 2 to 44-folds depending on co-block concentration with entrapment efficiency of 59%-80%. The NpM had size in the range of 206 to 402 nm with negative zeta potential. LA to GA ratio had greater effect on particle size reduction and increasing of co-polymer length. In addition, it had higher contributions on increasing of solubility and entrapment efficiency of SMV than PEG. Conclusion: According to these findings, the LA to GA ratio and PEG concentration gained a great consideration in order to prepare the PLGA-PEG-PLGA co-block which fulfilled the quality target product profile of NpM delivery system.

Tumor microenvironment-labile polymer-doxorubicin conjugate thermogel combined with docetaxel for in situ synergistic chemotherapy of hepatoma

Topical chemotherapy with complementary drugs is one of the most promising strategies to achieve an effective antitumor activity. Herein, a synergistic strategy for hepatoma therapy by the combination of tumor microenvironment-sensitive polymer-doxorubicin (DOX) conjugate thermogel, containing a DNA intercalator DOX, and docetaxel (DTX), a microtubule-interfering agent, was proposed. First, cis-aconitic anhydride-functionalized DOX (CAD) and succinic anhydride-modified DOX (SAD) were conjugated onto the terminal hydroxyl groups of poly(lactide-co-glycolide)-block-poly(ethylene glycol)-block-poly(lactide-co-glycolide) (PLGA-PEG-PLGA), yielding the acid-sensitive CAD-PLGA-PEG-PLGA-CAD and the insensitive SAD-PLGA-PEG-PLGA-SAD conjugates, respectively. The prodrug aqueous solution exhibited a thermoreversible sol-gel transition between room and physiological temperature. Meantime, appropriate mechanical property, biodegradability, as well as a sustained release profile were revealed in such prodrug thermogels. More importantly, the addition of DTX to the DOX-conjugated thermogels (i.e., Gel-CAD and Gel-SAD) was verified with enhanced curative effect against tumor, where the antitumor efficacy of Gel-CAD+DTX was obviously higher than the other groups. A reliable security in vivo was also showed in the Gel-CAD+DTX group. Taken together, such combination of tumor microenvironment-labile prodrug thermogel and a complementary drug exhibited fascinating prospect for local synergistic antineoplastic therapy.

STATEMENT OF SIGNIFICANCE

Multidrug chemotherapy with synergistic effect has been proposed recently for hepatoma treatment in the clinic. However, the quick release, fast elimination, and unselectivity of multidrugs in vivo always limit their further application. To solve this problem, a synergistic combination of tumor microenvironment-sensitive polymeric doxorubicin (DOX) prodrug thermogel for DNA intercalation and a microtubule-interfering agent docetaxel (DTX) is developed in the present study for the local chemotherapy of hepatoma. Interestingly, a pH-triggered sustained release behavior, an enhanced antitumor efficacy, and a favorable security in vivo are observed in the combined dual-drug delivery platform. Therefore, effectively combining tumor microenvironment-labile polymeric prodrug thermogel with a complementary drug provides an advanced system and a promising prospect for local synergistic hepatoma chemotherapy.

Improved vaccine-induced immune responses via a ROS-triggered nanoparticle-based antigen delivery system

Subunit vaccines that are designed based on recombinant antigens or peptides have shown promising potential as viable substitutes for traditional vaccines due to their better safety and specificity. However, the induction of adequate in vivo immune responses with appropriate effectiveness remains a major challenge for vaccine development. More recently, the implementation of a nanoparticle-based antigen delivery system has been considered a promising approach to improve the in vivo efficacy for subunit vaccine development. Thus, we have designed and prepared a nanoparticle-based antigen delivery system composed of three-armed PLGA, which is conjugated to PEG via the peroxalate ester bond (3s-PLGA-PO-PEG) and PEI as a cationic adjuvant (PPO NPs). It is known that during a foreign pathogen attack, NADPH, an oxidase, of the host organism is activated and generates an elevated level of reactive oxygen species, hydrogen peroxide (H2O2) primarily, as a defensive mechanism. Considering the sensitivity of the peroxalate ester bond to H2O2 and the cationic property of PEI for the induction of immune responses, this 3s-PLGA-PO-PEG/PEI antigen delivery system is expected to be both ROS responsive and facilitative in antigen uptake without severe toxicity that has been reported with cationic adjuvants. Indeed, our results demonstrated excellent loading capacity and in vitro stability of the PPO NPs encapsulated with the model antigen, ovalbumin (OVA). Co-culturing of bone marrow dendritic cells with the PPO NPs also led to enhanced dendritic cell maturation, antigen uptake, enhanced lysosomal escape, antigen cross-presentation and in vitro CD8+ T cell activation. In vivo experiments using mice further revealed that the administration of the PPO nanovaccine induced robust OVA-specific antibody production, upregulation of splenic CD4+ and CD8+ T cell proportions as well as an increase in memory T cell generation. In summary, we report here a ROS-triggered nanoparticle-based antigen delivery system that could be employed to promote the in vivo efficacy of vaccine-induced immune responses.

Protein delivery nanosystem of six-arm copolymer poly(ε-caprolactone)-poly(ethylene glycol) for long-term sustained release

Background

To address the issue of delivery of proteins, a six-arm copolymer, six-arm poly (ε-caprolactone)–poly(ethylene glycol) (6S-PCL-PEG), was synthesized by a simple two-step reaction. Thereafter, the application of 6S-PCL-PEG as a protein carrier was evaluated.

Materials and methods

A six-arm copolymer, six-arm poly(ε-caprolactone) (6S-PCL), was synthesized by ring-opening polymerization, with stannous octoate as a catalyst and inositol as an initiator. Then, poly(ethylene glycol) (PEG) was linked with 6S-PCL by oxalyl chloride to obtain 6S-PCL-PEG. Hydrogen-1 nuclear magnetic resonance spectrum, Fourier-transform infrared spectroscopy, and gel-permeation chromatography were conducted to identify the structure of 6S-PCL-PEG. The biocompatibility of the 6S-PCL-PEG was evaluated by a cell counting kit-8 assay. Polymeric nanoparticles (NPs) were prepared by a water-in-oil-in-water double emulsion (W₁/O/W₂) solvent evaporation method. The size distribution and zeta potential of NPs were determined by dynamic light scattering. Transmission electron microscopy was used to observe the morphology of NPs. Drug-loading capacity, encapsulation efficiency, and the release behavior of ovalbumin (OVA)-loading NPs were tested by the bicinchoninic acid assay kit. The stability and activity of OVA released from NPs were detected and the uptake of NPs was evaluated by NIH-3T3 cells.

Results

All results indicated the successful synthesis of amphiphilic copolymer 6S-PCL-PEG, which possessed excellent biocompatibility and could formulate NPs easily. High drug-loading capacity and encapsulation efficiency of protein NPs were observed. In vitro, OVA was released slowly and the bioactivity of OVA was maintained for over 28 days.

Conclusion

6S-PCL-PEG NPs prepared in this study show promising potential for use as a protein carrier.