Effect of the hydrophobic segment of an amphiphilic block copolymer on micelle formation, zinc phthalocyanine loading, and photodynamic activity

Construction of Tough Hydrogel Cross-Linked via Ionic Interaction by Protection Effect of Hydrophobic Domains

Most hydrogels have poor mechanical properties, severely limiting their potential applications, and numerous approaches have been introduced to fabricate more robust and durable examples. However, these systems consist of nonbiodegradable polymers which limit their application in tissue engineering. Herein, we focus on the fabrication and investigate the influence of hydrophobic segments on ionic cross-linking properties for the construction of a tough, biodegradable hydrogel. A biodegradable, poly(γ-glutamic acid) polymer conjugated with a hydrophobic amino acid, l-phenylalanine ethyl ester (Phe), together with an ionic cross-linking group, alendronic acid (Aln) resulting in γ-PGA-Aln-Phe, was initially synthesized. Rheological assessments through time sweep oscillation testing revealed that the presence of hydrophobic domains accelerated gelation. Comparing gels with and without hydrophobic domains, the compressive strength of γ-PGA-Aln-Phe was found to be six times higher and exhibited longer stability properties in ethylenediaminetetraacetic acid solution, lasting for up to a month. Significantly, the contribution of the hydrophobic domains to the mechanical strength and stability of ionic cross-linking properties of the gel was found to be the dominant factor for the fabrication of a tough hydrogel. As a result, this study provides a new strategy for mechanical enhancement and preserves ionic cross-linked sites by the addition of hydrophobic domains. The development of tough, biodegradable hydrogels reported herein will open up new possibilities for applications in the field of biomaterials.

Investigation of morphology and structure of drug-loaded PLA-b-PEO-b-PLA polymeric micelle: A dissipative particle dynamics simulations study

The dissipative particle dynamics (DPD) simulation was used to study the morphologies and structures of the paclitaxel-loaded PLA-b-PEO-b-PLA polymeric micelle. We focused on the influences of PLA block length, PLA-b-PEO-b-PLA copolymer concentration, paclitaxel drug content on morphologies and structures of the micelle. Our simulations show that: (i) with the PLA block length increase, the self-assemble structure of PLA-b-PEO-b-PLA copolymers with paclitaxel vary between onion-like structure (core-middle layer-shell) to spherical core-shell structure. The PEO shell thins and the size of the PLA core increases. The onionlike structures are comprised of the PEO hydrophilic core, the PLA hydrophobic middle layer, and the PEO hydrophilic shell, the distribution of the paclitaxel drug predominantly occurs within the hydrophobic intermediate layer; (ii) The system forms a spherical core-shell structure when a small amount of the drug is added, and within a certain range, the size of the spherical structure increases as the drug amount increases. When the drug contents (volume fraction) cdrug = 10%, it can be observed that the PLA4-b-PEO19-b-PLA4 spherical structures connect to form rod-shaped structures. With the length of PLA block NPLA = 8, as the paclitaxel drug concentrations cdrug = 4%, PEO has been insufficient to completely encapsulate the PLA and paclitaxel drug beads. To enhance drug loading capacity while maintaining stability of the system in aqueous solution, the optimal composition for loading paclitaxel is PLA4-b-PEO19-b-PLA4; the drug content is not higher than 4%; (iii) The paclitaxel-loaded PLA4-b-PEO19-b-PLA4 micelle undergo the transition from onionlike (core-middle layer-shell) to spherical (core-shell) to rod-shaped and lamellar structure as the PLA4-b-PEO19-b-PLA4 copolymer concentration increases from ccp = 10% to 40%.

Nanobody-mediated targeting of zinc phthalocyanine with polymer micelles as nanocarriers

Photodynamic therapy (PDT) is a suitable alternative to currently employed cancer treatments. However, the hydrophobicity of most photosensitizers (e.g., zinc phthalocyanine (ZnPC)) leads to their aggregation in blood. Moreover, non-specific accumulation in skin and low clearance rate of ZnPC leads to long-lasting skin photosensitization, forcing patients with a short life expectancy to remain indoors. Consequently, the clinical implementation of these photosensitizers is limited. Here, benzyl-poly(ε-caprolactone)-b-poly(ethylene glycol) micelles encapsulating ZnPC (ZnPC-M) were investigated to increase the solubility of ZnPC and its specificity towards cancers cells. Asymmetric flow field-flow fractionation was used to characterize micelles with different ZnPC-to-polymer ratios and their stability in human plasma. The ZnPC-M with the lowest payload (0.2 and 0.4% ZnPC w/w) were the most stable in plasma, exhibiting minimal ZnPC transfer to lipoproteins, and induced the highest phototoxicity in three cancer cell lines. Nanobodies (Nbs) with binding specificity towards hepatocyte growth factor receptor (MET) or epidermal growth factor receptor (EGFR) were conjugated to ZnPC-M to facilitate cell targeting and internalization. MET- and EGFR-targeting micelles enhanced the association and the phototoxicity in cells expressing the target receptor. Altogether, these results indicate that ZnPC-M decorated with Nbs targeting overexpressed proteins on cancer cells may provide a better alternative to currently approved formulations.

Redox-sensitive self-assembled micelles based on low molecular weight chitosan-lipoic acid conjugates for the delivery of doxorubicin: Effect of substitution degree of lipoic acid

Amphiphilic low molecular weight chitosan-lipoic acid (LC-LA) conjugates with different degrees of substitution (DS) of LA were synthesized by N, N'‑carbonyldiimidazole (CDI) catalysis to self-assemble into redox-sensitive micelles. Critical micelle concentration (CMC), size, zeta potential, biocompatibility and redox-sensitive behavior of blank micelles were investigated. The results indicated that blank micelles with low CMC, nanoscale size and positive zeta potential showed excellent biocompatibility and redox-sensitive behavior. Doxorubicin (Dox) loaded micelles were prepared by encapsulating Dox into blank micelles. The loading ability, trigger-release behavior, antitumor activity and cellular uptake of Dox loaded micelles were studied. The results demonstrated that Dox loaded micelles with superior loading ability exhibited redox-trigger behavior, strong antitumor activity and increased cellular uptake efficiency against A549 cell. Besides, the effect of DS of LA on above properties was estimated. An increase in DS of LA reduced the CMC and cumulative release amount of Dox, but improved the loading efficiency, antitumor activity, and cellular uptake of Dox loaded micelles, which resulted from stronger interaction of hydrophobic groups in micelles with the DS of LA increased. Overall, self-assembled LC-LA micelles with good biosecurity and redox-sensitive behavior hold promising application prospects in Dox delivery and improving cancer therapeutic effect of Dox.

RAFT Synthesis and Characterization of Poly(Butyl-co-2-(N,N-Dimethylamino)Ethyl Acrylates)-block-Poly(Polyethylene Glycol Monomethyl Ether Acrylate) as a Photosensitizer Carrier for Photodynamic Therapy

Polymer micelles are promising drug delivery systems for highly hydrophobic photosensitizers in photodynamic therapy (PDT) applications. We previously developed pH-responsive polymer micelles consisting of poly(styrene-co-2-(N,N-dimethylamino)ethyl acrylate)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA) for zinc phthalocyanine (ZnPc) delivery. In this study, poly(butyl-co-2-(N,N-dimethylamino)ethyl acrylates)-block-poly(polyethylene glycol monomethyl ether acrylate) (P(BA-co-DMAEA)-b-PPEGA) was synthesized via reversible addition and fragmentation chain transfer (RAFT) polymerization to explore the role of neutral hydrophobic units in photosensitizer delivery. The composition of DMAEA units in P(BA-co-DMAEA) was adjusted to 0.46, which is comparable to that of P(St-co-DMAEA)-b-PPEGA. The size distribution of the P(BA-co-DMAEA)-b-PPEGA micelles changed when the pH decreased from 7.4 to 5.0, indicating their pH-responsive ability. The photosensitizers, 5,10,15,20-tetrakis(pentafluorophenyl)chlorin (TFPC), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TFPP), protoporphyrin IX (PPIX), and ZnPc were examined as payloads for the P(BA-co-DMAEA)-b-PPEGA micelles. The encapsulation efficiency depended on the nature of the photosensitizer. TFPC-loaded P(BA-co-DMAEA)-b-PPEGA micelles exhibited higher photocytotoxicity than free TFPC in the MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line (RGK-1), indicating their superiority for photosensitizer delivery. ZnPc-loaded P(BA-co-DMAEA)-b-PPEGA micelles also exhibited superior photocytotoxicity compared to free ZnPc. However, their photocytotoxicity was lower than that of P(St-co-DMAEA)-b-PPEGA. Therefore, neutral hydrophobic units, as well as pH-responsive units, must be designed for the encapsulation of photosensitizers.

Polymeric Nanosystems Applied for Metal-Based Drugs and Photosensitizers Delivery: The State of the Art and Recent Advancements

Nanotechnology-based approaches for targeting the delivery and controlled release of metal-based therapeutic agents have revealed significant potential as tools for enhancing the therapeutic effect of metal-based agents and minimizing their systemic toxicities. In this context, a series of polymer-based nanosized systems designed to physically load or covalently conjugate metal-based therapeutic agents have been remarkably improving their bioavailability and anticancer efficacy. Initially, the polymeric nanocarriers were applied for platinum-based chemotherapeutic agents resulting in some nanoformulations currently in clinical tests and even in medical applications. At present, these nanoassemblies have been slowly expanding for nonplatinum-containing metal-based chemotherapeutic agents. Interestingly, for metal-based photosensitizers (PS) applied in photodynamic therapy (PDT), especially for cancer treatment, strategies employing polymeric nanocarriers have been investigated for almost 30 years. In this review, we address the polymeric nanocarrier-assisted metal-based therapeutics agent delivery systems with a specific focus on non-platinum systems; we explore some biological and physicochemical aspects of the polymer–metallodrug assembly. Finally, we summarize some recent advances in polymeric nanosystems coupled with metal-based compounds that present potential for successful clinical applications as chemotherapeutic or photosensitizing agents. We hope this review can provide a fertile ground for the innovative design of polymeric nanosystems for targeting the delivery and controlled release of metal-containing therapeutic agents.

Effect of tertiary amino groups in the hydrophobic segment of an amphiphilic block copolymer on zinc phthalocyanine encapsulation and photodynamic activity

Polymer micelles are promising nanocarriers for hydrophobic photosensitizers of photodynamic therapy (PDT). Poly(styrene-co-(2-(N,N-dimethylamino)ethyl acrylate))-block-poly(polyethylene glycol monomethyl ether acrylate) (P(St-co-DMAEA)-b-PPEGA; 1) was prepared via reversible addition and fragmentation chain transfer (RAFT) polymerization as a carrier for a zinc phthalocyanine (ZnPc) photosensitizer to be used in PDT. The DMAEA-unit composition in the P(St-co-DMAEA) segment was adjusted to 0.40 molar ratio, which caused a sharp increase in water-solubility when the pH decreased from 7.4 to 5.0. The polymer 1 micelle size distribution also shifted to lower when the pH decreased, whereas this change was not observed in PSt-co-PPEGA (2), which was previously reported. The UV-vis spectrum of the ZnPc-loaded micelles of polymer 1 exhibited relatively sharp Q bands, comparable to those measured in DMSO, indicating good compatibility of the condensed core with ZnPc. ZnPc-loaded micelles of polymer 1 exerted excellent photocytotoxicity in the MNNG-induced mutant of the rat murine RGM-1 gastric epithelial cell line (RGK-1). In contrast, the ZnPc-loaded micelles of polymer 2 were completely inactive under the same conditions. Fluorescence from the RGK-1 cells treated with ZnPc-loaded micelles of polymer 1 was observed after 4 h of co-incubation, while no fluorescence was observed in cells treated with ZnPc-loaded micelles of polymer 2. These results indicate that the pH-responsive nature and good compatibility with ZnPc exhibited by the polymer 1 micelles are essential characteristics of ZnPc carriers for efficient photodynamic therapy.

Tertiary amino groups in the hydrophobic core of polymer micelles affect the encapsulation and photodynamic activity of zinc phthalocyanine.

Photophysical Properties of Linked Zinc Phthalocyanine to Acryloyl Chloride:N-vinylpyrrolidone Copolymer

This paper focuses on the linking of zinc phthalocyanine (ZnPc) to N-vinylpyrrolidone (N-VP): acryloyl chloride (ClAC) copolymer. The synthesis of binary N-VP:ClAC copolymer was performed by the radical polymerization method and then grafted to ZnPc by the Friedel Crafts acylation reaction. We have developed a water-soluble ZnPc:ClAC:N-VP photosensitizer with a narrow absorption band at 970 nm, fluorescence at λ_em = 825 nm and the decay fluorescence profile with 3-decay relatively longer times of 1.2 µs, 4.6 µs, and 37 µs. The concentration-dependent dark cytotoxicity investigated in normal fibroblasts (NHDF), malignant melanoma (MeWo), adenocarcinoma (HeLa), and hepatocellular carcinoma (HepG2) cell lines incubated to increased concentrations of ZnPc:ClAC:N-VP (up to 40 μM) for 24 h in the dark show low cytotoxicity. Maximum cell viability in HeLa and HepG2 tumor cell lines was observed.

Recent Progress in Phthalocyanine-Polymeric Nanoparticle Delivery Systems for Cancer Photodynamic Therapy

This perspective article summarizes the last decade’s developments in the field of phthalocyanine (Pc)-polymeric nanoparticle (NP) delivery systems for cancer photodynamic therapy (PDT), including studies with at least in vitro data. Moreover, special attention will be paid to the various strategies for enhancing the behavior of Pc-polymeric NPs in PDT, underlining the great potential of this class of nanomaterials as advanced Pcs’ nanocarriers for cancer PDT. This review shows that there is still a lot of research to be done, opening the door to new and interesting nanodelivery systems.

Poly ethylene glycol (PEG)-Related controllable and sustainable antidiabetic drug delivery systems

Diabetes mellitus is one of the most challenging threats to global public health. To improve the therapy efficacy of antidiabetic drugs, numerous drug delivery systems have been developed. Polyethylene glycol (PEG) is a polymeric family sharing the same skeleton but with different molecular weights which is considered as a promising material for drug delivery. In the delivery of antidiabetic drugs, PEG captures much attention in the designing and preparation of sustainable and controllable release systems due to its unique features including hydrophilicity, biocompatibility and biodegradability. Due to the unique architecture, PEG molecules are also able to shelter delivery systems to decrease their immunogenicity and avoid undesirable enzymolysis. PEG has been applied in plenty of delivery systems such as micelles, vesicles, nanoparticles and hydrogels. In this review, we summarized several commonly used PEG-contained antidiabetic drug delivery systems and emphasized the advantages of stimuli-responsive function in these sustainable and controllable formations.