Preparation and characterization of nanoparticulate poly(N -isopropylacryl- amide) hydrogel for the controlled release of anti-tumour drugs

Coarse-Grained Simulations of Release of Drugs Housed in Flexible Nanogels: New Insights into Kinetic Parameters

The diffusion-controlled release of drugs housed in flexible nanogels has been simulated with the help of a coarse-grained model that explicitly considers polymer chains. In these in silico experiments, the effect of its flexibility is assessed by comparing it with data obtained for a rigid nanogel with the same volume fraction and topology. Our results show that the initial distribution of the drug can exert a great influence on the release kinetics. This work also reveals that certain surface phenomena driven by steric interactions can lead to apparently counterintuitive behaviors. Such phenomena are not usually included in many theoretical treatments used for the analysis of experimental release kinetics. Therefore, one should be very careful in drawing conclusions from these formalisms. In fact, our results suggest that the interpretation of drug release curves in terms of kinetic exponents (obtained from the Ritger-Peppas Equation) is a tricky question. However, such curves can provide a first estimate of the drug diffusion coefficient.

Exploring Endolysin-Loaded Alginate-Chitosan Nanoparticles as Future Remedy for Staphylococcal Infections

Endolysins are a novel class of antibacterials with proven efficacy in combating various bacterial infections, in vitro and in vivo. LysMR-5, an endolysin derived from phage MR-5, demonstrated high lytic activity in our laboratory against multidrug-resistant S. aureus (MRSA) and S. epidermidis strains. However, endolysin and proteins in general are associated with instability and short in vivo half-life, consequently limiting their usage as pharmaceutical preparation to treat bacterial infections. Nanoencapsulation of endolysins could help to achieve better therapeutic outcome, by protecting the proteins from degradation, providing sustained release, thus could increase their stability, shelf life, and therapeutic efficacy. Hence, in this study, the feasibility of alginate-chitosan nanoparticles (Alg-Chi NPs) to serve as drug delivery platform for LysMR-5 was evaluated. LysMR-5-loaded nanoparticles were prepared by calcium ion-induced pre-gelation of alginate core and its complexation with chitosan. The formation of nanoparticles was confirmed on the basis of DLS, zeta potential, and electron microscopy imaging. The LysMR-5-loaded nanoparticles presented a hydrodynamic diameter of 276.5 ± 42, a PDI of 0.342 ± 0.02, a zeta potential - 25 mV, and an entrapment efficiency of 62 ± 3.1%. The potential ionic interaction between alginate, chitosan, and LysMR-5 was investigated by FT-IR and SEM-EDX analysis. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), nano-sized particles with characteristic morphology were seen. Different antibacterial assays and SDS-PAGE analysis showed no change in endolysin's structural integrity and bioactivity after entrapment. A direct antibacterial effect of blank Alg-Chi Nps, showing enhanced bactericidal activity upon LysMR-5 loading, was observed against S. aureus. At physiological pH (7.2), the release profile of LysMR-5 from Alg-Chi NPs showed a biphasic release and followed a non-Fickian release mechanism. The biocompatible nature as revealed by cytocompatibility and hemocompatibility studies endorsed their use as drug delivery system for in vivo studies. Collectively, these results demonstrate the potential of Alg-Chi NPs as nano-delivery vehicle for endolysin LysMR-5 and other therapeutic proteins for their use in various biomedical applications.

Coarse-grained Monte Carlo simulations of nanogel-polyelectrolyte complexes: electrostatic effects

Coarse-grained Monte-Carlo simulations of nanogel-polyelectrolyte complexes have been carried out. The results presented here capture two phenomena reported in experiments with real complexes: (i) the reduction in size after absorbing just a few chains and (ii) the charge inversion detected through electrophoretic mobility data. Our simulations reveal that charge inversion occurs if the polyelectrolyte charge is large enough. In addition, the distribution of chains inside the nanogel strongly depends on whether charge inversion takes place. It should also be stressed that the chain topology has little influence on most of the properties studied here.

Highly Porous pH-Responsive Carboxymethyl Chitosan-Grafted-Poly (Acrylic Acid) Based Smart Hydrogels for 5-Fluorouracil Controlled Delivery and Colon Targeting

In the present investigation, new formulations of CMCS/AA hydrogels with varying composition of Carboxymethyl chitosan, acrylic acid, and ethylene glycol dimethacrylate (EGDMA) were prepared by free radical polymerization technique using benzoyl peroxide as catalyst. The bioavailability of 5-FU through the oral route is very limited owing to its rapid metabolism and clearance from the general circulation. Current work was aimed at increasing the bioavailability of 5-FU via smart hydrogels and at investigating their potential in delivering 5-FU to target colon cancer. Swelling studies were carried out on dried hydrogel discs in different USP phosphate buffer solutions of various pH values. Porosity and gel fraction of all the samples were measured. 5-FU was used as a model drug and loaded in selected hydrogel samples. The amount of drug loaded and released was determined. Experimental data was fitted to various model equations, and corresponding parameters were calculated to study the release mechanism. Many structural parameters were calculated. The prepared hydrogels were also characterized by FTIR and SEM to study the structure, crystallinity, compatibility, and morphology of the smart hydrogels. The biocompatibility and cytotoxic potential blank and drug-loaded hydrogels were assessed through MTT assay. The prepared hydrogels were found to be an excellent carrier for 5-FU in targeting colon cancer.

An overview on the mathematical modeling of hydrogels' behavior for drug delivery systems

Hydrogels-based systems (HBSs) for drug delivery are nowadays extensively used and the interest in modeling their behavior is dramatically increasing. In this review a critical overview on the modeling approaches is given, quantitatively and qualitatively analyzing the publications on the subject, the trend of the publications per year and the type of modeling approaches. It was found that, despite the drug release fitting models (i.e. Higuchi's equation) are the most abundant, their use for HBSs is decreasing in the last years and luckily, considering the limiting assumption on which they were built, they will be confined to simple mathematical fitting equations. Within the mechanistic models the "multi-component" with the swelling approximation (mass transport only) and with the mechanics (fully coupled) are experiencing the highest growth rate, with much more interest toward the last one that, in the next years could be able to provide a first principles model. Statistical models, especially based on the response surface methodology, are rapidly spreading in the scientific community mainly thanks to their ability to be predictive, regardless of the phenomenology, in the analyzed design space with very low efforts. Neural Networks models for HBSs, in countertrend with their use in the pharmaceutical industry, have never take off preferring less data demanding statistical models.

Soft Nanohydrogels Based on Laponite Nanodiscs: A Versatile Drug Delivery Platform for Theranostics and Drug Cocktails

A new nanohydrogel drug delivery platform based on Laponite nanodiscs, polyacrylate, and sodium phosphate salts is described. The hybrid nanohydrogel is tailored to obtain soft and flexible nanohydrogels with G' around 3 kPa, which has been proposed as the ideal stiffness for drug delivery applications. In vitro studies demonstrate that the new nanohydrogels are biocompatible, biodegradable, nonswellable, pH-responsive, and noncytotoxic and are able to deliver antineoplastic drugs into cancer cells. The IC₅₀ of nanohydrogels containing cisplatin, 4-fluorouracil, and cyclophosphamide is significantly lower than the IC₅₀ of the free drugs. In vivo experiments suggest that the new nanomaterials are biocompatible and do not accumulate in crucial organs. The simple formulation procedure enables encapsulation of virtually any water-soluble molecule, without the need for chemical modification of the guests. These nanohydrogels are a versatile platform that enables the simultaneous encapsulation of several cancer drugs, yielding an efficient drug cocktail delivery system, which for instance presents a positive synergistic effect against MCF-7 cells.

Synthesis and Formulation of Thermosensitive Drug Carrier for Temperature Triggered Delivery of Naproxen Sodium

Nanospheres and microspheres are known as a multipurpose compounds and are used in various branches of science. Recent controlled delivery systems for drugs are also based on poly-micro and nanospheres. In our study we describe an investigation of the influence of thermosensitive polymer N-isopropylacrylamide (NIPA) on the release of the drug naproxen sodium (NS) with a hydrogel hydroxypropyl methylcellulose (HPMC) base. The hydrodynamic diameter (D_H) of the obtained polymer was measured by using dynamic light scattering (DLS) at a wavelength of 678 nm. Hydrogel formulations of NS were prepared in a specific way ex tempore. NS was sprinkled on the surface of a distilled water, then polymer soluted in water was added. Afterward, HPMC was affixed to the solution. Prepared samples were stored at room temperature for 24 h. Release tests showed that modification of thevcross-linker type influenced the properties of synthesized polymeric particles. The NIPA derivatives obtained via surfactant free precipitation polymerization (SFPP) may be formulated as hydrogel preparations using HPMC. The obtained formulations presented varied half-release times, depending on the type of applied NIPA derivatives in hydrogel formulations. At 18 °C, the release rates were lower comparing to the reference HPMC hydrogel, whereas at 42 °C, the release rates were significantly higher. The synthesized thermosensitive polymers enabled temperature-triggered release of NS.

Controlled synthesis and characterization of nanohydrogels formed from copolymer (2-acrylamido-2-methylpropane sulfonic acid/acrylamide)

Nanohydrogels were prepared from copolymer 2-acrylamido-2-methylpropane sulfonic acid (AMPS)/acrylamide (AAm) in the presence of sodium lauryl sulfate (SLS) followed by γ-ray exposure. Different molar ratios of AMPS to AAm, 100:0 to 0:100, were investigated. The particle sizes of nanohydrogels were examined by high-resolution transmission electron microscopy (HR-TEM). The effects of different comonomer composition and pH on swelling (%) and gelation (%) were studied. The characterization of nanohydrogels was performed by Fourier transform infrared (FTIR) spectroscopy, energy dispersion X-ray (EDX), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The results indicate that particle sizes ranged from ~9.5 to ~39 nm.

Characterization and in-vitro bioactivity evaluation of paclitaxel-loaded polyester nanoparticles

Paclitaxel, an antimicrotubular agent used in the treatment of ovarian and breast cancer, was encapsulated in nanoparticles of poly(DL-lactide-co-glycolide) and poly(ε-caprolactone) polymers using the double emulsion-solvent evaporation technique. The morphology, size distribution, drug encapsulation efficiency, thermal degradation and in-vitro drug release profile were characterized. High-performance liquid chromatography was used to determine the drug encapsulation efficiency and in-vitro drug release profile. MCF-7 breast cancer cells were used to evaluate the cytotoxicity (MTT assay), the cellular uptake and the cell cycle. The particle size was in the range of 200-400 nm. Poly(lactide-co-glycolide) nanoparticles showed more effective cellular uptake compared with those of poly(ε-caprolactone). Unloaded nanoparticles were found to be cytocompatible on MCF-7 cells and paclitaxel formulations showed efficacy in killing MCF-7 cells. Paclitaxel-loaded nanoparticles induced the release of the drug-blocking cells in the G2/M phase. Paclitaxel-loaded nanoparticles may be considered a promising drug delivery system in the evaluation of an in-vivo model.

Paclitaxel-loaded polyester nanoparticles prepared by spray-drying technology: in vitro bioactivity evaluation

Paclitaxel (PTX), an antimicrotubular agent used in the treatment of ovarian and breast cancer, was encapsulated in nanoparticles (NPs) of poly(lactide-co-glycolide) (PLGA) and poly(ε-caprolactone) (PCL) polymers using the spray-drying technique. Morphology, size distribution, drug encapsulation efficiency, thermal degradation and drug release were characterized. MCF7 cells were employed to evaluate the efficacy of the systems on cell cycle and cytotoxicity. The particle size was in the range 0.8-1 µm. The incorporation efficiency of PTX was more than 80% in all NPs obtained. In vitro drug release took place during 35 days, and drug release rates were in the order PCL > PLGA 50:50 > PLGA 75:25. Unloaded NPs showed to be cytocompatible at MCF7 cells. PTX-loaded NPs demonstrated the release of the drug block cells in the G2/M phase. All PTX-loaded formulations showed their efficacy in killing MCF7 cells, mainly PTX-loaded PLGA 50:50 and PLGA 75:25 that cause a decrease in cell viability lower than 20%.