pH-responsive niosome-based nanocarriers of antineoplastic agents.

Differences in pH between the tumour interstitium and healthy tissues can be used to induce conformational changes in the nanocarrier structure, thereby triggering drug release at the desired site. In the present study, novel pH-responsive nanocarriers were developed by modifying conventional niosomes with hexadecyl-poly(acrylic acid)n copolymers (HD-PAAn). Niosomal vesicles were prepared by the thin film hydration method using Span 60, Span 60/Tween 60 and cholesterol as main constituents, and HD-PAA modifiers of different concentrations (0.5, 1, 2.5, 5 mol%). Next, two model substances, a water-soluble fluorescent dye (calcein) and a hydrophobic agent with pronounced antineoplastic activity (curcumin), were loaded in the aqueous core and hydrophobic membrane of the elaborated niosomes, respectively. Physicochemical properties of blank and loaded nanocarriers such as hydrodynamic diameter (Dh), size distribution, zeta potential, morphology and pH-responsiveness were investigated in detail. The cytotoxicity of niosomal curcumin was evaluated against human malignant cell lines of different origins (MJ, T-24, HUT-78), and the mechanistic aspects of proapoptotic effects were elucidated. The formulation composed of Span 60/Tween 60/cholesterol/2.5% HD-PAA17 exhibited optimal physicochemical characteristics (Dh 302 nm; ζ potential -22.1 mV; high curcumin entrapment 83%), pH-dependent drug release and improved cytotoxic and apoptogenic activity compared to free curcumin.

Functional Hydrogels for Delivery of the Proteolytic Enzyme Serratiopeptidase.

Hydrogels are superior wound dressings because they can provide protection and hydration of the wound, as well as the controlled release of therapeutic substances to aid tissue regeneration and the healing process. Hydrogels obtained from natural precursors are preferred because of their low cost, biocompatibility, and biodegradability. We describe the synthesis of novel functional hydrogels based on two natural products-citric acid (CA) and pentane-1,2,5-triol (PT, a product from lignocellulose processing) and poly(ethylene glycol) (PEG-600)-via an environment friendly approach. The hydrogels were prepared via monomer crosslinking through a polycondensation reaction at an elevated temperature in the absence of any solvent. The reagents were blended at three different compositions with molar ratios of hydroxyl (from PT and PEG) to carboxyl (from CA) groups of 1:1, 1:1.4, and 1.4:1, respectively. The effect of the composition on the physicomechanical properties of materials was investigated. All hydrogels exhibited pH-sensitive behavior, while the swelling degree and elastic modulus were dependent on the composition of the polymer network. The proteolytic enzyme serratiopeptidase (SER) was loaded into a hydrogel via physical absorption as a model drug. The release profile of SER and the effects of the enzyme on healthy skin cells were assessed. The results showed that the hydrogel carrier could provide the complete release of the loaded enzyme.

In Situ Gelling Hydroxypropyl Cellulose Formulation Comprising Cannabidiol-Loaded Block Copolymer Micelles for Sustained Drug Delivery.

Cannabidiol (CBD) is a natural terpenophenolic compound with known pharmacological activities, but the poor solubility of CBD in water limits its widespread use in medicine and pharmacy. Polymeric (nano)carriers demonstrated high potential for enhancing the solubility and therapeutic activity of lipophilic drugs such as CBD. Here, we report the elaboration of a novel hydroxypropyl cellulose (HPC)-based in situ gelling formulation for controlled delivery of CBD. In the first stage, nanosized polymeric micelles from poly(ethylene oxide)-block-poly(α-cinnamyl-ε-caprolactone-co-ε-caprolactone) (PEO-b-P(CyCL-co-CL) diblock copolymers) were used to increase the solubility of CBD in water. Different copolymers were assessed, and the carrier with the highest encapsulation efficiency (EE) and drug loading capacity (DLC) was selected for further elaboration of nanocomposite in situ gel formulations. Next, the sol-to-gel transition behavior of HPC as a function of K2SO4 concentration in the aqueous solution was investigated by microcalorimetry and dynamic oscillatory rheology, and the optimal formulation capable of forming a physical gel under physiological conditions was determined. Finally, injectable nanocomposite hydrogels comprising cannabidiol were fabricated, and their drug release profile and cytotoxicity against human tumor cell lines were evaluated. The in situ gels exhibited prolonged drug release over 12 h, controlled by gel erosion, and the cytotoxicity of formulated cannabidiol was comparable with that of a free drug.

Copolymeric Micelles of Poly(ε-caprolactone) and Poly(methacrylic acid) as Carriers for the Oral Delivery of Resveratrol.

In this study, we report the development of a micellar system based on a poly(methacrylic acid)-b-poly(ε-caprolactone)-b-poly(methacrylic acid) triblock copolymer (PMAA16-b-PCL35-b-PMAA16) for the oral delivery of resveratrol. The micellar nanocarriers were designed to comprise a PCL core for solubilizing the poorly water-soluble drug and a hydrated PMAA corona with bioadhesive properties for providing better contact with the gastrointestinal mucosa. The micelles were first formed in an aqueous media via the solvent evaporation method and then loaded with resveratrol (72% encapsulation efficiency). Studies by transmission electron microscopy (TEM) and dynamic and electrophoretic light scattering (DLS and PALS) revealed a spherical shape, nanoscopic size (100 nm) and a negative surface charge (-30 mV) of the nanocarriers. Loading of the drug slightly decreased the hydrodynamic diameter (Dh) and increased the ƺ-potential of micelles. In vitro dissolution tests showed that 80% and 100% of resveratrol were released in 24 h in buffers with pH 1.2 and 6.8, respectively, whereas for the same time, not more than 10% of pure resveratrol was dissolved. A heat-induced albumin denaturation assay demonstrated the advantage of the aqueous micellar formulation of resveratrol, which possessed anti-inflammatory potential as high as that of the pure drug. Further, the micellar resveratrol (5 µM) exerted a strong protective effect and maintained viability of mucosa epithelial HT-29 cells in a co-cultural model, representing the production of inflammatory cytokines. For comparison, the pure resveratrol at the same concentration did not protect the damaged HT-29 cells at all. Thus, the present study revealed that the PMAA-b-PCL-b-PMAA copolymeric micelles might be considered appropriate nanocarriers for the oral delivery of resveratrol.

Incorporation of Resveratrol in Polymeric Nanogel for Improvement of Its Protective Effects on Cellular and Microsomal Oxidative Stress Models.

Nanogels are attractive drug delivery systems that provide high loading capacity for drug molecules, improve their stability, and increase cellular uptake. Natural antioxidants, especially polyphenols such as resveratrol, are distinguished by low aqueous solubility, which hinders therapeutic activity. Thus, in the present study, resveratrol was incorporated into nanogel particles, aiming to improve its protective effects in vitro. The nanogel was prepared from natural substances via esterification of citric acid and pentane-1,2,5-triol. High encapsulation efficiency (94.5%) was achieved by applying the solvent evaporation method. Dynamic light scattering, atomic force microscopy, and transmission electron microscopy revealed that the resveratrol-loaded nanogel particles were spherical in shape with nanoscopic dimensions (220 nm). In vitro release tests showed that a complete release of resveratrol was achieved for 24 h, whereas at the same time the non-encapsulated drug was poorly dissolved. The protective effect of the encapsulated resveratrol against oxidative stress in fibroblast and neuroblastoma cells was significantly stronger compared to the non-encapsulated drug. Similarly, the protection in a model of iron/ascorbic acid-induced lipid peroxidation on rat liver and brain microsomes was higher with the encapsulated resveratrol. In conclusion, embedding resveratrol in this newly developed nanogel improved its biopharmaceutical properties and protective effects in oxidative stress models.

Functional Nanogel from Natural Substances for Delivery of Doxorubicin.

Nanogels (NGs) have attracted great attention because of their outstanding biocompatibility, biodegradability, very low toxicity, flexibility, and softness. NGs are characterized with a low and nonspecific interaction with blood proteins, meaning that they do not induce any immunological responses in the body. Due to these properties, NGs are considered promising candidates for pharmaceutical and biomedical application. In this work, we introduce the development of novel functional nanogel obtained from two naturally based products-citric acid (CA) and pentane-1,2,5-triol (PT). The nanogel was synthesized by precipitation esterification reaction of CA and PT in tetrahydrofuran using N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide (EDC) and 4-(dimethylamino)pyridine (DMAP) catalyst system. Dynamic light scattering (DLS), cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM) analyses revealed formation of spherical nanogel particles with a negative surface charge. Next, the nanogel was loaded with doxorubicin hydrochloride (DOX) by electrostatic interactions between carboxylic groups present in the nanogel and amino groups of DOX. The drug-loaded nanogel exhibited high encapsulation efficiency (EE~95%), and a bi-phasic release behavior. Embedding DOX into nanogel also stabilized the drug against photodegradation. The degradability of nanogel under acidic and neutral conditions with time was investigated as well.

Redox-Responsive Crosslinked Mixed Micelles for Controllable Release of Caffeic Acid Phenethyl Ester.

We report the elaboration of redox-responsive functional micellar nanocarriers designed for triggered release of caffeic acid phenethyl ester (CAPE) in cancer therapy. Three-layered micelles, comprising a poly(ε-caprolactone) (PCL) core, a middle poly(acrylic acid)/poly(ethylene oxide) (PAA/PEO) layer and a PEO outer corona, were prepared by co-assembly of PEO113-b-PCL35-b-PEO113 and PAA13-b-PCL35-b-PAA13 amphiphilic triblock copolymers in aqueous media. The preformed micelles were loaded with CAPE via hydrophobic interactions between the drug molecules and PCL core, and subsequently crosslinked by reaction of carboxyl groups from PAA and a disulfide crosslinking agent. The reaction of crosslinking took place in the middle layer of the nanocarriers without changing the encapsulation efficiency (EE~90%) of the system. The crosslinked polymeric micelles (CPMs) exhibited superior structural stability and did not release CAPE in phosphate buffer (pH 7.4). However, in weak acidic media and in the presence of 10 mM reducing agent (dithiothreitol, DTT), the payload was released at a high rate from CPMs due to the breakup of disulfide linkages. The physicochemical properties of the nanocarriers were investigated by dynamic and electrophoretic light scattering (DLS and ELS) and atomic force microscopy (AFM). The rapid release of CAPE under intracellular-like conditions and the lack of premature drug release in media resembling the blood stream (neutral pH) make the developed CPMs a promising candidate for controllable drug release in the microenvironment of tumors.

Cationic triblock copolymer micelles enhance antioxidant activity, intracellular uptake and cytotoxicity of curcumin.

The aim of the present study was to develop curcumin loaded cationic polymeric micelles and to evaluate their loading, preservation of curcumin antioxidant activity and intracellular uptake ability. The micelles were prepared from a triblock copolymer consisting of poly(ϵ-caprolactone) and very short poly(2-(dimethylamino) ethyl methacrylate) segments (PDMAEMA9-PCL70-PDMAEMA9). The micelles showed monomodal size distribution, mean diameter of 145 nm, positive charge (+72 mV), critical micellar concentration around 0.05 g/l and encapsulation efficiency of 87%. The ability of the micellar curcumin to scavenge the ABTS radical and hypochlorite ions was higher than that of the free curcumin. Confocal microscopy revealed that the uptake of curcumin by chronic myeloid leukemia derived K-562 cells and human multiple myeloma cells U-266 was more intensive when curcumin was loaded into the micelles. These results correlated with the higher cytotoxicity of the micellar curcumin compared to free curcumin. Intraperitoneal treatment of Wistar rats indicated that PDMAEMA-PCL-PDMAEMA copolymer, comprising very short cationic chains, did not change the levels of malondialdehyde and glutathione in livers indicating an absence of oxidative stress. Thus, PDMAEMA-PCL-PDMAEMA triblock micelles could be considered efficient and safe platform for curcumin delivery.