pH-Responsive Micelles Assembled by Three-Armed Degradable Block Copolymers with a Cholic Acid Core for Drug Controlled-Release

Tumor Microenvironment-Responsive Drug Delivery Based on Polymeric Micelles for Precision Cancer Therapy: Strategies and Prospects

In clinical practice, drug therapy for cancer is still limited by its inefficiency and high toxicity. For precision therapy, various drug delivery systems, including polymeric micelles self-assembled from amphiphilic polymeric materials, have been developed to achieve tumor-targeting drug delivery. Considering the characteristics of the pathophysiological environment at the drug target site, the design, synthesis, or modification of environmentally responsive polymeric materials has become a crucial strategy for drug-targeted delivery. In comparison to the normal physiological environment, tumors possess a unique microenvironment, characterized by a low pH, high reactive oxygen species concentration, hypoxia, and distinct enzyme systems, providing various stimuli for the environmentally responsive design of polymeric micelles. Polymeric micelles with tumor microenvironment (TME)-responsive characteristics have shown significant improvement in precision therapy for cancer treatment. This review mainly outlines the most promising strategies available for exploiting the tumor microenvironment to construct internal stimulus-responsive drug delivery micelles that target tumors and achieve enhanced antitumor efficacy. In addition, the prospects of TME-responsive polymeric micelles for gene therapy and immunotherapy, the most popular current cancer treatments, are also discussed. TME-responsive drug delivery via polymeric micelles will be an efficient and robust approach for developing clinical cancer therapies in the future.

Borneol-modified docetaxel plus tetrandrine micelles for treatment of drug-resistant brain glioma

OBJECTIVE

Glioma is the most common and deadly primary malignant tumor in adults. Treatment outcomes are ungratified due to the presence of blood-brain barrier (BBB), glioma stem cells (GSCs) and multidrug resistance (MDR). Docetaxel (DTX) is considered as a potential drug for the treatment of brain tumor, but its effectiveness is limited by its low bioavailability and drug resistance. Tetrandrine (TET) reverses the resistance of tumor cells to chemotherapy drugs. Borneol (BO) modified in micelles has been shown to promote DTX plus TET to cross the BBB, allowing the drug to better act on tumors. Therefore, we constructed BO-modified DTX plus TET micelles to inhibit chemotherapeutic drug resistance.

SIGNIFICANCE

Provide a new treatment method for drug-resistant brain gliomas.

METHODS

In this study, BO-modified DTX plus TET micelles were prepared by thin film dispersion method, their physicochemical properties were characterized. Its targeting ability was investigated. The therapeutic effect on GSCs was investigated by in vivo and in vitro experiments.

RESULTS

The BO-modified DTX plus TET micelles were successfully constructed by thin film dispersion method, and the micelles showed good stability. The results showed that targeting micelles increased bEnd.3 uptake and helped drugs cross the BBB in vitro. And we also found that targeting micelles could inhibit cell proliferation, promote cell apoptosis and inhibit the expression of drug-resistant protein, thus provide a new treatment method for GSCs in vitro and in vivo.

CONCLUSIONS

BO-modified DTX plus TET micelles may provide a new treatment method for drug-resistant brain gliomas.

Delivery of Chemotherapy Agents and Nucleic Acids with pH-Dependent Nanoparticles

With less than one percent of systemically injected nanoparticles accumulating in tumors, several novel approaches have been spurred to direct and release the therapy in or near tumors. One such approach depends on the acidic pH of the extracellular matrix and endosomes of the tumor. With an average pH of 6.8, the extracellular tumor matrix provides a gradient for pH-responsive particles to accumulate, enabling greater specificity. Upon uptake by tumor cells, nanoparticles are further exposed to lower pHs, reaching a pH of 5 in late endosomes. Based on these two acidic environments in the tumor, various pH-dependent targeting strategies have been employed to release chemotherapy or the combination of chemotherapy and nucleic acids from macromolecules such as the keratin protein or polymeric nanoparticles. We will review these release strategies, including pH-sensitive linkages between the carrier and hydrophobic chemotherapy agent, the protonation and disruption of polymeric nanoparticles, an amalgam of these first two approaches, and the release of polymers shielding drug-loaded nanoparticles. While several pH-sensitive strategies have demonstrated marked antitumor efficacy in preclinical trials, many studies are early in their development with several obstacles that may limit their clinical use.

Biopolymeric Prodrug Systems as Potential Antineoplastic Therapy

Nowadays, cancer represents a major public health issue, a substantial economic issue, and a burden for society. Limited by numerous disadvantages, conventional chemotherapy is being replaced by new strategies targeting tumor cells. In this context, therapies based on biopolymer prodrug systems represent a promising alternative for improving the pharmacokinetic and pharmacologic properties of drugs and reducing their toxicity. The polymer-directed enzyme prodrug therapy is based on tumor cell targeting and release of the drug using polymer–drug and polymer–enzyme conjugates. In addition, current trends are oriented towards natural sources. They are biocompatible, biodegradable, and represent a valuable and renewable source. Therefore, numerous antitumor molecules have been conjugated with natural polymers. The present manuscript highlights the latest research focused on polymer–drug conjugates containing natural polymers such as chitosan, hyaluronic acid, dextran, pullulan, silk fibroin, heparin, and polysaccharides from Auricularia auricula.

Recent Advancement of Polymersomes as Drug Delivery Carrier

BACKGROUND

Biomedical applications of polymersomes have been explored, including drug and gene delivery, insulin delivery, hemoglobin delivery, the delivery of anticancer agents, and various diagnostic purposes.

OBJECTIVES

Polymersomes, which are self-assembled amphiphilic block copolymers, have received a lot of attention in drug delivery approaches. This review represents the methods of preparation of polymersomes including thin-film rehydration, electroformation, double emulsion, gel-assisted rehydration, PAPYRUS method, and solvent injection methods including various therapeutic applications of polymersomes.

METHODS

Data we searched from PubMed, Google Scholar, and Science Direct through searching of keywords: Polymersomes, methods of preparation, amphiphilic block copolymers, anticancer drug delivery Results: Polymersomes provide both hydrophilic and hydrophobic drug delivery to a targeted site with an increase in the stability of the formulation and reduce the cytotoxic side effects of drugs.

CONCLUSION

A wide range of biological applications, including drug and gene delivery, insulin delivery, hemoglobin delivery, delivery of anticancer agents as well as in various diagnostic purposes. Recently, polymersomes have been used more frequently because of their stability, reducing the encapsulated drug's leakage, site-specific drug delivery, and increasing the bioavailability of the drugs and different diagnostic purposes. The liposomes encapsulate only hydrophilic drugs, but polymersomes encapsulate both hydrophilic and hydrophobic drugs in their cores.

Smart Nanocarrier Based on Poly(oligo(ethylene glycol) methyl ether acrylate) Terminated pH-Responsive Polymer Brushes Grafted Mesoporous Silica Nanoparticles

A platform technology based on inorganic/organic nanoparticles for carrying drugs could be of enormous potential benefit in treating cancer. Surface modification of the nanoparticles with pH-responsive and biocompatible polymers can improve the selectivity and targeting toward the tumor cells. Polyethylene glycol (PEG) and its derivatives being present on the surface could enhance the ability to tailor nanomaterial hydrophilicity and to resist the adhesion of proteins and/or cells. Herein, we report a new nanoplatform based on mesoporous silica nanoparticles (MSNs) conjugated with poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA) brushes as a candidate for stimuli-responsive intracellular drug delivery system. Alkyl bromide functional initiators (end-functionalized PDEAEMA brushes) were derivatized to amine, followed by the reaction with ethylene sulfide and poly(oligo(ethylene glycol) methyl ether acrylate (POEGMEA). Using X-ray photoelectron spectroscopy (XPS) to examine the attachment of POEGMEA, it was found that the POEGMEA molecules in the outer surface of PDEAEMA brushes have been successfully reacted with thiol groups, as indicated by the increase in the peak intensity of the C–O group at 286.5 eV. Brush-modified silica hybrids have an average diameter of ca. 250 nm, as estimated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Rhodamine B dye was loaded into the brush-modified silica hybrids nanoparticles with loading capacity of ca. 74%. The accumulated dye released from brush-modified particles in acidic media was approximately 60%, whereas the dye amount release in basic media was less than 15% after 10 h exposure time. Alamar Blue assay was used to assess the cytotoxicity of MSNs–PDEAEMA, MSNs–PDEAEMA–SH, and MSNs–PDEAEMA–POEGMEA. The results show that all three nanosystems were non-toxic to hMSC with an increase in cell proliferation for MSNs–PDEAEMA–POEGMEA at 50 µg/mL after both 24 and 48 h of incubation.

Nanoengineering Branched Star Polymer-Based Formulations: Scope, Strategies, and Advances

Soft nanoparticles continue to offer a promising platform for the encapsulation and controlled delivery of poorly water-soluble drugs and help enhance their bioavailability at targeted sites. Linear amphiphilic block copolymers are the most extensively investigated in formulating delivery vehicles. However, more recently, there has been increasing interest in utilizing branched macromolecules for nanomedicine, as these have been shown to lower critical micelle concentrations, form particles of smaller dimensions, facilitate the inclusion of varied compositions and function-based entities, as well as provide prolonged and sustained release of cargo. In this review, it is aimed to discuss some of the key variables that are studied in tailoring branched architecture-based assemblies, and their influence on drug loading and delivery. By understanding structure-property relationships in these formulations, one can better design branched star polymers with suitable characteristics for efficient therapeutic interventions. The role played by polymer composition, chain architecture, crosslinking, stereocomplexation, compatibility between polymers and drugs, drug/polymer concentrations, and self-assembly methods in their performance as nanocarriers is highlighted.

pH and Reduction Dual-Responsive Bi-Drugs Conjugated Dextran Assemblies for Combination Chemotherapy and In Vitro Evaluation

Polymeric prodrugs, synthesized by conjugating chemotherapeutic agents to functional polymers, have been extensively investigated and employed for safer and more efficacious cancer therapy. By rational design, a pH and reduction dual-sensitive dextran-di-drugs conjugate (oDex-g-Pt+DOX) was synthesized by the covalent conjugation of Pt (IV) prodrug and doxorubicin (DOX) to an oxidized dextran (oDex). Pt (IV) prodrug and DOX were linked by the versatile efficient esterification reactions and Schiff base reaction, respectively. oDex-g-Pt+DOX could self-assemble into nanoparticles with an average diameter at around 180 nm. The acidic and reductive (GSH) environment induced degradation and drug release behavior of the resulting nanoparticles (oDex-g-Pt+DOX NPs) were systematically investigated by optical experiment, DLS analysis, TEM measurement, and in vitro drugs release experiment. Effective cellular uptake of the oDex-g-Pt+DOX NPs was identified by the human cervical carcinoma HeLa cells via confocal laser scanning microscopy. Furthermore, oDex-g-Pt+DOX NPs displayed a comparable antiproliferative activity than the simple combination of free cisplatin and DOX (Cis+DOX) as the extension of time. More importantly, oDex-g-Pt+DOX NPs exhibited remarkable reversal ability of tumor resistance compared to the cisplatin in cisplatin-resistant lung carcinoma A549 cells. Take advantage of the acidic and reductive microenvironment of tumors, this smart polymer-dual-drugs conjugate could serve as a promising and effective nanomedicine for combination chemotherapy.

Poly(oligo(ethylene glycol) methyl ether methacrylate) Capped pH-Responsive Poly(2-(diethylamino)ethyl methacrylate) Brushes Grafted on Mesoporous Silica Nanoparticles as Nanocarrier

In this paper, a new pH-responsive nanosystem based on mesoporous silica nanoparticles (MSNs) was developed for cancer therapy. Poly(2-(diethylamino) ethyl methacrylate) (PDEAEMA) was grafted on their outer surface and acts as a gatekeeper, followed by subsequent modification of the polymer by cysteine (MSN-PDEAEMA-Cys) and poly(oligo(ethylene glycol) methyl ether methacrylate) (MSN-PDEAEMA-Cys-POEGMEMA). The physicochemical properties of these nanocarriers were characterized using scanning and transmission electron microscopies (SEM and TEM), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and dynamic light scattering (DLS). The synthesized nanoparticles were well-dispersed with a diameter of ca. 200 nm. The obtained XPS results confirm the successful modification of MSN-PDEAEMA with Cys and POEGMEMA by increasing the peak intensity of C-O and C=O groups at 286.5 and 288.5 eV, respectively. An anti-cancer drug, doxorubicin (DOX), was encapsulated into the fabricated nanoplatform. The DOX release amount at physiological pH of 7.4 was limited (10%), while an accumulation drug release of ca. 35% was accomplished after 30 h in acidic media. The MTT cell line was used to assess the cytotoxicity of the unloaded and DOX-loaded fabricated nanoplatforms. Upon loading of DOX on these nanomaterials, they showed significant toxicity to human liver cancer cells. These results suggest that the prepared nano-structured materials showed good biocompatibility as well, and they can serve as nanocarriers for the delivery of anti-cancer drugs.

Acid-Responsive Adamantane-Cored Amphiphilic Block Polymers as Platforms for Drug Delivery

Four-arm star-shaped (denoted as ‘S’) polymer adamantane-[poly(lactic-co-glycolic acid)-b-poly(N,N’-diethylaminoethyl methacrylate) poly(ethylene glycol) monomethyl ether]₄ (S-PLGA-D-P) and its linear (denoted as ‘L’) counterpart (L-PLGA-D-P) were synthesized, then their self-assembled micelles were further developed to be platforms for anticancer drug delivery. Two types of polymeric micelles exhibited strong pH-responsiveness and good drug loading capacity (21.6% for S-PLGA-D-P and 22.9% for L-PLGA-D-P). Using doxorubicin (DOX) as the model drug, their DOX-loaded micelles displayed well controlled drug release behavior (18.5–19.0% of DOX release at pH 7.4 and 77.6–78.8% of DOX release at pH 5.0 within 80 h), good cytocompatibility against NIH-3T3 cells and effective anticancer efficacy against MCF-7 cells. However, the star-shaped polymeric micelles exhibited preferable stability, which was confirmed by the lower critical micelle concentration (CMC 0.0034 mg/mL) and decrease rate of particle sizes after 7 days incubation (3.5%), compared with the linear polymeric micelle L-PLGA-D-P (CMC 0.0070 mg/mL, decrease rate of particle sizes was 9.6%). Overall, these developed polymeric micelles have promising application as drug delivery system in cancer therapy.

Synthesis Characterization of Platinum (IV) Complex Curcumin Backboned Polyprodrugs: In Vitro Drug Release Anticancer Activity

The conventional mono-chemotherapy still suffers from unsatisfied potency for cancer therapy due to tumor heterogeneity and the occurrence of drug resistance. Combination chemotherapy based on the nanosized drug delivery systems (nDDSs) has been developed as a promising platform to circumvent the limitations of mono-chemotherapy. In this work, starting from cisplatin and curcumin (Cur), we prepared a dual drug backboned shattering polymeric nDDS for synergistic chemotherapy. By in situ polymerization of the Cur, platinum (IV) complex-based prodrug monomer (DHP), L-lysine diisocyanate (LDI), and then conjugation with a hydrophilic poly (ethylene glycol) monomethyl ether (mPEG) derivative, a backbone-type platinum (IV) and Cur linkage containing mPEG-poly(platinum-co-Cur)-mPEG (PCPt) copolymer was synthesized. Notably, the platinum (IV) (Pt (IV)) and Cur were incorporated into the hydrophobic segment of PCPt with the fixed drugs loading ratio and high drugs loading content. The batch-to-batch variability could be decreased. The resulting prodrug copolymer then self-assembled into nanoparticles (PCPt NPs) with an average diameter around 100 nm, to formulate a synergetic nDDS. Importantly, PCPt NPs could greatly improve the solubility and stability of Cur. In vitro drug release profiles have demonstrated that PCPt NPs were stable in PBS 7.4, rapid burst release was greatly decreased, and the Pt and Cur release could be largely enhanced under reductive conditions due to the complete dissociation of the hydrophobic main chain of PCPt. In vitro cell viability test indicated that PCPt NPs were efficient synergistic chemotherapy units. Moreover, PCPt NPs were synergistic for cisplatin-resistant cell lines A549/DDP cells, and they exhibited excellent reversal ability of tumor resistance to cisplatin. This work provides a promising strategy for the design and synthesis of nDDS for combination chemotherapy.

PH-Sensitive, Polymer Functionalized, Nonporous Silica Nanoparticles for Quercetin Controlled Release

Some pH-sensitive, poly(2-(diethylamino)ethyl methacrylate) (PDEAEMA) grafted silica nanoparticles (SNPs) (SNPs-g-PDEAEMA) were designed and synthesized via surface initiated, metal-free, photoinduced atom transfer radical polymerization (ATRP). The structures of the polymers formed in solution were determined by 1H NMR. The modified nanoparticles were characterized by FT-IR spectroscopy, XPS, GPC, TEM and TGA. The analytical results show that α-bromoisobutyryl bromide (BIBB) (ATRP initiator) had been successfully anchored onto SNPs' surfaces, and was followed by surface-initiated, metal-free ATRP of 2-(diethylamino)ethyl methacrylate (DEAEMA). The resultant SNPs-g-PDEAEMA were uniform spherical nanoparticles with the particles size of about 22-25 nm, and the graft density of PDEAEMA on SNPs' surfaces obtained by TGA was 19.98 μmol/m2. Owing to the covalent grafting of pH-sensitive PDEAEMA, SNPs-g-PDEAEMA can dispersed well in acidic aqueous solution, but poorly in neutral and alkaline aqueous solutions, which is conducive to being employed as drug carriers to construct a pH-sensitive controlled drug delivery system. In vitro cytotoxicity evaluation results showed that the cytotoxicity of SNPs-g-PDEAEMA to the L929 cells had completely disappeared on the 3rd day. The loading of quercetin on SNPs-g-PDEAEMA was performed using adsorption process from ethanol solutions, and the dialysis release rate increased sharply when the pH value of phosphate-buffered saline (PBS) decreased from 7.4 to 5.5. All these results indicated that the pH-responsive microcapsules could serve as potential anti-cancer drug carriers.

Thermo/pH Responsive Star and Linear Copolymers Containing a Cholic Acid-Derived Monomer, N-Isopropylacrylamide and Acrylic Acid: Synthesis and Solution Properties

In this work three CTAs trithiocarbonate-type were synthesized-bifunctional (with PEG), trifunctional (with glycerol), and tetrafunctional (PERT)-and used in the controlled polymerization of 2-(acryloyloxy)ethyl cholate (CAE) via reversible addition-fragmentation chain transfer (RAFT) polymerization. The resulting macroCTAs containing a cholic acid-derived polymer were chain extended with N-isopropylacrylamide with or without acrylic acid. The thermosensitive and/or pH properties of these copolymers were studied in PBS solutions. The copolymers synthesized without poly(acrylic acid) (PAAc) were unstable above the transition temperature. Similar behavior was observed for the copolymer solutions containing PAAc (2% in feed) at lower values of pH showing a faster precipitation above the LCST. On the contrary, copolymer solutions containing PAAc showed great stability at higher pH values for a longer time period at 37 °C. Interestingly, the Dh of the aggregates ranged from 18 to 30 nm in all copolymers (with or without PAAc) below the transition temperature, although the topology and the block sequence in the chain were significantly different.

Analysis of Drug Release Behavior Utilizing the Swelling Characteristics of Cellulosic Nanofibers

It is known that the behavior of a drug released from a supporting carrier is influenced by the surrounding environment and the carrier. In this study, we investigated the drug behavior of a swellable electrospun nanofibrous membrane. Nanofibrous mats with different swelling ratios were prepared by mixing cellulose acetate (CA) and polyurethane (PU). CA has excellent biocompatibility and is capable of high water uptake, while PU has excellent mechanical properties. Paclitaxel (PTX) was the drug of choice for observing drug release behavior, which was characterized by UV-spectroscopy. FE-SEM was used to confirm the morphology of the nanofibrous mats and to measure the average fiber diameters. We observed a noticeable increase in the total volume of the nanofibrous membrane when it was immersed in water. Also, the drug release behavior increased proportionally with increasing swelling rate of the composite nanofibrous mat. Biocompatibility testing of nanofiber materials was confirmed by CCK-8 assay and cell morphology was observed. Based on these results, we propose nanofibrous mats as promising candidates in wound dressing and other drug carrier applications.