pH-responsive Amphiphilic Block Copolymer Research Articles

Therapeutic effect and metabolic fingerprinting of triple-negative breast cancer cells following exposure to a novel pH-responsive, gambogic acid-loaded micelle

Triple-negative breast cancer (TNBC) is a subtype of breast cancer with a poor prognosis and lacks effective therapeutic targets. The use of gambogic acid (GA), a class of active ingredients in traditional Chinese medicine with anti-tumour potential, is limited in tumour therapy owing to its drawbacks and unclear organ toxicity. In this study, we used the pH-responsive amphiphilic block copolymer, PEOz-PCL, to create nanodrugs for GA delivery to MDA-MB-231 cells. The pH-responsive GA-loaded micelles were prepared through nanoprecipitation with a more homogeneous size. The average particle size was 42.29 ± 1.74 nm, and the zeta potential value was 9.88 ± 0.17 mV. The encapsulation rate was 85.06%, and the drug loading rate was 10.63%. The process was reproducible, and sustained release reached 80% in 96 h at acid pH 5.0. Furthermore, cellular tests using CCK-8, TUNEL, and flow cytometry revealed that pH-responsive GA-loaded micelles killed MDA-MB-231 cells more effectively and had much higher activity and targeting compared with free drugs. Metabolomic analysis of the changes in differential metabolites revealed that pH-responsive GA-loaded micelles may inhibit TNBC cells by causing amino acid anabolism, nucleotide metabolism, and glucose metabolism, as well as by affecting their energy sources. The study outcomes will help understand the mechanism of action and the therapeutic efficacy of pH-responsive GA-loaded micelles in vivo.

Tolterodine tartrate loaded biodegradable and pH-responsive amphiphilic block copolymer (PF127) hydrogels: synthesis, characterization, and acute toxicity evaluation

ABSTRACT pH-responsive hydrogels gained remarkable attention for an effective controlled delivery of therapeutic agent for biomedical applications. The purpose of present study was to develop novel pluronic-co-poly (MAA) hydrogels for pH-sensitive controlled release of Tolterodine tartrate. Free radical polymerization of pluronic F127 and methacrylic acid was accomplished in the presence of ethylene glycol dimethacrylate and benzoyl peroxide for controlled release of Tolterodine tartrate by formulating and evaluating chemically cross-linked pluronic-co-poly (MAA) hydrogels. Different proportions of pluronic F127, methacrylic acid and ethylene glycol dimethacrylate were blended to fabricate pH-responsive hydrogels. Effects of pH and concentration of polymer, monomer and crosslinker were evaluated on degree of grafting. Fabricated hydrogels were characterized for compatibility of drug and excipients by Fourier Transform Infrared spectroscopic analysis, thermal analysis by using Differential Scanning Calorimetry and Thermogravimetric analysis, surface morphology by Scanning Electron Microscopy, X-ray diffraction analysis and sol-gel fraction analysis. Acute toxicity studies on animal model were carried out. Present study concludes that Pluronic-co-poly (MAA) hydrogels are definitely an effective and promising approach for controlled drug delivery of Tolterodine tartrate.

Chemical Architecture of Block Copolymers Differentially Abrogate Cardiotoxicity and Maintain the Anticancer Efficacy of Doxorubicin.

The molecular architecture of pH-responsive amphiphilic block copolymers, their self-assembly behavior to form nanoparticles (NPs), and doxorubicin (DOX)-loading technique govern the extent of DOX-induced cardiotoxicity. We observed that the choice of pH-sensitive tertiary amines, surface charge, and DOX-loading techniques within the self-assembled NPs strongly influence the release and stimulation of DOX-induced cardiotoxicity in primary cardiomyocytes. However, covalent conjugation of DOX to a pH-sensitive nanocarrier through a "conditionally unstable amide" linkage (PCPY-cDOX; PC = polycarbonate and PY = 2-pyrrolidine-1-yl-ethyl-amine) significantly reduced the cardiotoxicity of DOX in cardiomyocytes as compared to noncovalently encapsulated DOX NPs (PCPY-eDOX). When these formulations were tested for drug release in serum-containing media, the PCPY-cDOX systems showed prolonged control over drug release (for ∼72 h) at acidic pH compared to DOX-encapsulated nanocarriers, as expected. We found that DOX-encapsulated nanoformulations triggered cardiotoxicity in primary cardiomyocytes more acutely, while conjugated systems such as PCPY-cDOX prevented cardiotoxicity by disabling the nuclear entry of the drug. Using 2D and 3D (spheroid) cultures of an ER + breast cancer cell line (MCF-7) and a triple-negative breast cancer cell line (MDA-MB-231), we unravel that, similar to encapsulated systems (PCPY-eDOX-type) as reported earlier, the PCPY-cDOX system suppresses cellular proliferation in both cell lines and enhances trafficking through 3D spheroids of MDA-MB-231 cells. Collectively, our studies indicate that PCPY-cDOX is less cardiotoxic as compared to noncovalently encapsulated variants without compromising the chemotherapeutic properties of the drug. Thus, our studies suggest that the appropriate selection of the nanocarrier for DOX delivery may prove fruitful in shifting the balance between low cardiotoxicity and triggering the chemotherapeutic potency of DOX.

Mesoscale Simulations of pH-Responsive Amphiphilic Polymeric Micelles for Oral Drug Delivery.

It is of great significance to study the structure property and self-assembly of amphiphilic block copolymer in order to effectively and efficiently design and prepare drug delivery systems. In this work, dissipative particle dynamics (DPD) simulation method was used to investigate the structure property and self-assembly ability of pH-responsive amphiphilic block copolymer poly(methyl methacrylate-co-methacrylic acid)-b-poly(aminoethyl methacrylate) (poly(MMA-co-MAA)-b-PAEMA). The effects of different block ratios (hydrophilic PAEMA segment and pH-sensitive PMAA segment) in copolymer on self-assembly and drug loading capacity including drug distribution were extensively investigated. The increase of hydrophilic PAEMA facilitated the formation of a typical core-shell structure as well as a hydrophobic PMAA segment. Furthermore, the optimal drug-carrier ratio was confirmed by an analysis of the drug distribution during the self-assembly process of block copolymer and model drug Ibuprofen (IBU). In addition, the drug distribution and nanostructure of IBU-loaded polymeric micelles (PMs) self-assembled from precise block copolymer (PMMA-b-PMAA-b-PAEMA) and block copolymer (poly(MMA-co-MAA)-b-PAEMA) with random pH-responsive/hydrophobic structure were evaluated, showing that almost all drug molecules were encapsulated into a core for a random copolymer compared to the analogue. The nanostructures of IBU-loaded PMs at different pH values were evaluated. The results displayed that the nanostructure was stable at pH < pKa and anomalous at pH > pKa which indicated drug release, suggesting that the PMs could be used in oral drug delivery. These findings proved that the amphiphilic block copolymer P(MMA30-co-MAA33)-b-PAEMA38 with random structure and pH-sensitivity might be a potential drug carrier. Moreover, DPD simulation shows potential to study the structure property of PMs self-assembled from amphiphilic block copolymer.

Acid-Triggered Nanoexpansion Polymeric Micelles for Enhanced Photodynamic Therapy.

Photodynamic therapy (PDT) as a noninvasive and selective treatment technology has presented great potential in cancer prevention and precision medicine, but its therapeutic efficacy is still greatly inhibited by the limitations of photosensitizers (PSs) in the microenvironment such as the aggregation caused quenching (ACQ) of PSs. Herein, we proposed an "acid-triggered nanoexpansion" method to further reduce the aggregation of photosensitizers by constructing acetal-based polymeric micelles. A pH-responsive amphiphilic block copolymer, POEGMA-b-[PTTMA-co-PTPPC6MA] was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization and self-assembled into spherical micelles. In the normal physiological environment, the micelles were stable and had good biocompatibility. Upon entry into the acidic microenvironment of the tumor, the acid-responsive hydrophobic 2, 4, 6-trimethoxybenzaldehyde in the micelles hydrolyzed and generated a hydrophilic diol moiety. Although the hydrophility of the micellar core was increased, the assembled structure of block copolymers was not dissociated but expanded. The responsive expansion of the micelles could allow the photosensitizers to well-disperse in the core, whereas more tumor-dissolved oxygen entered the micelles. This phenomenon could provide a better nanoenvironment for photosensitizers to reduce the ACQ of the photosensitizers, leading to more singlet oxygen (1O2) produced under the laser irradiation (650 nm). Both in vitro and in vivo studies have demonstrated that the remarkable photodynamic therapeutic efficacy of acid-responsive micelles could be realized. Thus, the acid-triggered nanoexpansion method might provide more possibilities to develop efficient platforms for treating cancers.

Synthesis of pH-responsive block copolymer micelles via RAFT polymerization induced self-assembly and its application in emulsifier-free emulsion polymerization

The pH-responsive amphiphilic block copolymer micelles based on poly (2-(dimethylamino) ethyl methacrylate) (PDMAEMA) as a flexible corona and poly(hexafluorobutyl acrylate) (PHFBA) as a core have been synthesized by reversible addition-fragmentation chain transfer polymerization induced self-assembly (RAFT-PISA). This core-shell type amphiphilic copolymer micelles possessed the characteristics of pH-response from pendent tertiary amine groups in PDMAEMA chain. The morphology and size of amphiphilic block copolymer micelles were measured by dynamic light scattering (DLS) and transmission electron microscopy (TEM) analyses. The results indicated that the diameter of micelles narrowed down from 160 nm to 20 nm along with the increased pH value from 1.32 to 2.90. However, the diameter of the amphiphilic block copolymer micelles ranged broadly from 20 nm to more than 100 nm at pH ≥ 5.89. The amphiphilic block copolymer micelles were later used as reactors to synthesize cationic fluorinated polyacrylate emulsifier-free emulsion at pH 2.90, using fluorinated monomers and acrylate monomers as mixed monomers. The latex particles were presented as core-shell morphology with diameter of about 220 nm and narrow distribution, as characterized by TEM and DLS. The obtained emulsion with high zeta potential (+57.8 mV) had excellent stability.

Single-Domain Antibody-Functionalized pH-Responsive Amphiphilic Block Copolymer Nanoparticles for Epidermal Growth Factor Receptor Targeted Cancer Therapy.

Biocompatible antibody-nanoparticle conjugates have attracted interest as anticancer agents due to their potential to selectively target therapeutic agents at disease sites. However, new formulation and conjugation approaches are urgently needed to improve their uniformity for clinical applications. Here, a pH-responsive benzaldehyde-functionalized poly[oligo(ethylene glycol) methacrylate-st-para-formyl phenyl methacrylate]-b-poly[2-(diisopropyl)aminoethyl methacrylate] [P(OEGMA-st-pFPMA)-b-PDPA] block copolymer, prepared by reversible addition-fragmentation chain transfer polymerization, produced PEGylated nanoparticles (pH ∼ 7.4) by a single emulsion-solvent evaporation formulation approach. Efficient site-specific attachment of an aminooxy-functionalized anti-EGFR single-domain antibody (sdAb) on these benzaldehyde-decorated nanoparticles is achieved by oxime bond formation. These nanoconjugates can specifically bind EGFR (modified ELISA) and have enhanced uptake over nonfunctionalized controls in EGFR-positive HeLa cells. Encapsulation of rhodamine 6G dye and its dispersion upon cellular uptake, consistent with nanoparticle stability loss at pH < 5.7, prove their ability to facilitate triggered release in endosomal compartments and highlight their potential for use as next-generation antibody-drug nanoconjugates for therapeutic drug delivery.

Rapid Polymer Conjugation Strategies for the Generation of pH-Responsive, Cancer Targeting, Polymeric Nanoparticles.

The combination of controlled living polymerization in association with rapid and highly efficient macromolecule conjugation strategies provides a powerful tool for the synthesis of novel polymeric materials. Here functional block copolymers were rapidly and quantitatively conjugated using an efficient reaction between polymers containing a phenolic group and the 4-phenyl-3 H-1,2,4-triazole-3,5(4 H)-dione (PTAD) moiety and used to generate nanoparticles that encapsulated drugs. pH responsive amphiphilic block copolymers, which self-assemble into nanoparticles, were fabricated using our novel polymer conjugation strategy with the resulting system designed to promote drug release within the acidic milieu of the cancer microenvironment. The conjugation strategy also enabled the direct tagging of the nanoparticles with a range of fluorophores, targeting assets, or both with cargo release demonstrated in cancer cells.

Design and development of pH-sensitive liposomes by evaluating the thermotropic behavior of their chimeric bilayers

This study is focused on mixed/chimeric advanced drug delivery nanosystems and specifically on pH-sensitive liposomes, combining lipids and pH-responsive amphiphilic block copolymers. Chimeric liposomes are composed of hydrogenated soy phosphatidylcholine (HSPC) and two different poly(n-butylacrylate)-b-poly(acrylic acid) (PnBA-b-PAA) block copolymers with 85 and 70% content of PAA, at six different molar ratios. PAA block exhibits pH responsiveness, because of the regulative group of –COOH. Chimeric bilayers are composed of HSPC and PnBA-b-PAA. Experiments are carried out by using differential scanning calorimetry (DSC) in order to investigate their thermotropic properties. DSC indicated disappearance of the pretransition effect in all chimeric lipid bilayers, at both buffers [phosphate buffer saline (PBS) and citrate buffer], and slight changes of the main transition temperature (T m). Contrariwise, the cooperativity (T 1/2) presented alterations between the two different buffers. Chimeric liposomes have been prepared and their physicochemical characteristics have been explored in PBS and citrate buffer by measuring the size, size distribution and ζ-potential. Liposomes are found to retain the mean value of their size during the stability studies. The physicochemical characteristics and the stability assessment of chimeric liposomes are correlated with DSC measurements of mixed bilayers. The incorporation of the appropriate amount of these novel pH-responsive block copolymers affects the cooperativity and the liposomal stabilization and imparts pH responsiveness (functionality), which was confirmed by performing experiments in acidic environment (citrate buffer). In conclusion, the results from DSC measurements provide useful information regarding the quality by design process for rationally preparing mixed/chimeric liposomal platforms to incorporate bioactive molecules.

Calorimetric study on pH-responsive block copolymer grafted lipid bilayers: rational design and development of liposomes

This study is focused on chimeric advanced drug delivery nanosystems and specifically on pH-sensitive liposomes, combining lipids and pH-responsive amphiphilic block copolymers. Chimeric liposomes composed of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and two different forms of block copolymers, i.e. poly(n-butylacrylate)-b-poly(acrylic acid) (PnBA-b-PAA) at 70 and 85% content of PAA at six different molar ratios, each form respectively. PAA block exhibits pH-responsiveness, because of the regulative group of –COOH. –COOH is protonated under acidic pH (pKa ca. 4.2), while remains ionized under basic or neutral pH, leading to liposomes repulse and eventually stability. Lipid bilayers were prepared composed of DPPC and PnBA-b-PAA. Experiments were carried out using differential scanning calorimetry (DSC) in order to investigate their thermotropic properties. DSC indicated disappearance of pre-transition at all chimeric lipid bilayers and slight thermotropic changes of the main transition temperature. Chimeric liposomes have been prepared and their physicochemical characteristics have been explored by measuring the size, size distribution and ζ-potential, owned to the presence of pH-responsive polymer. At percentages containing medium to high amounts of the polymer, chimeric liposomes were found to retain their size during the stability studies. These results were well correlated with those indicated in the DSC measurements of lipid bilayers incorporating polymers in order to explain their physicochemical behavior. The incorporation of the appropriate amount of these novel pH-responsive block copolymers affects thus the cooperativity, the liposomal stabilization and imparts pH-responsiveness.

PH-responsive amphiphilic block copolymer prodrug conjugated near infrared fluorescence probe

A novel amphiphilic multi-block copolymer conjugated with both a near infrared fluorescence probe and drug has been designed and prepared by means of ring-opening polymerization (ROP) of N-Carboxy Anhydride (NCA) monomers following a Reversible Addition-Fragmentation Chain Transfer (RAFT) polymerization. At first, an amino group-containing RAFT agent was synthesized and it served as an initiator for the sequential ROP of aspartic acid β-benzyl ester N-carboxy anhydride (Asp-NCA) and e-carbobenzoxy-L-lysine NCA (ZLLys-NCA). Then the multi-block copolymer was prepared by a succeeding RAFT polymerization of poly(ethylene glycol) methyl ether acrylate (OGEA). At the end, both anticancer drug doxorubicin and hydrophobic aminocyanine dye were chemical conjugated to the block copolymer via a hydrazone or amide bond, respectively. The obtained NIRF copolymer and its micelles were characterized by nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), dynamic light scattering (DLS), and UV-vis and fluorescence spectrophotometry. The prodrug has strong fluorescence in the near infrared region and shows pH-responsive drug release behavior, and it has potential application in the theranostics of cancer.

PH-Regulated Controlled Swelling and Sustained Release from the Core Functionalized Amphiphilic Block Copolymer Micelle.

pH-responsive amphiphilic block copolymers based on poly(ethylene glycol)monomethyl ether-b-poly(methyl methacrylate-co-methacrylamidepropanoic acid) (PEO-b-PMMA-co-PMAPA) with different MMA/MAPA ratios were synthesized from respective amine-reactive prepolymers based on poly(ethylene glycol)monomethyl ether-b-poly(methyl methacrylate-co-methacryloxysuccinimide) (PEO-b-PMMA-co-PMASI) in such a way that the pH-responsive carboxylic acid groups were randomly distributed in the hydrophobic (PMMA) block. In aqueous medium, they formed micellar aggregates. Control experiments showed stability and critical aggregation concentration and dye encapsulation properties were better for carboxylic acid functionalized micelles at acidic pH compared to a structurally similar block copolymer micelle that lacked any carboxylic acid group. This was attributed to H-bonding among the carboxylic acid groups. In basic pH upon deprotonation, controlled swelling of the aggregates was observed due to repulsion among the negatively charged carboxylate groups. The extent of swelling/deswelling was well controlled by simply changing the percentage of the pH-responsive units in the hydrophobic block and could be probed quantitatively by pH-dependent dynamic light scattering (DLS) and fluorescence resonance energy transfer (FRET) studies. The aggregates were able to encapsulate a hydrophobic guest such as pyrene at the interior of the micelle, and sustained release of this hydrophobic probe was achieved selectively at basic pH due to swelling of the micelles instead of complete disassembly that generally leads to burst release.

Synthesis and Self‐Assembly of pH‐Responsive Amphiphilic Poly(dimethylaminoethyl methacrylate)‐block‐Poly(pentafluorostyrene) Block Copolymer in Aqueous Solution

We report the synthesis of a novel pH-responsive amphiphilic block copolymer poly(dimethylaminoethyl methacrylate)-block-poly(pentafluorostyrene) (PDMAEMA-b-PPFS) using RAFT-mediated living radical polymerization. Copolymer micelle formation, in aqueous solution, was investigated using fluorescence spectroscopy, static and dynamic light scattering (SLS and DLS), and transmission electron microscopy (TEM). DLS and SLS measurements revealed that the diblock copolymers form spherical micelles with large aggregation numbers, N(agg) ≈ 30 where the dense PPFS core is surrounded by dangling PDMAEMA chains as the micelle corona. The hydrodynamic radii, R(h) of these micelles is large, at pH 2-5 as the protonated PDMAEMA segments swell the micelle corona. Above pH 5, the PDMAEMA segments are gradually deprotonated, resulting in a lower osmotic pressure and enhanced hydrophobicity within the micelle, thus decreasing the R(h) . However, the radius of gyration, R(g) remains independent of pH as the dense PPFS cores predominate.