Tunable environmental sensitivity and degradability of nanogels based on derivatives of cystine and poly(ethylene glycols) of various length for biocompatible drug carrier

Polymeric Nanosystems: A Breakthrough Approach to Treating Inflammation and Inflammation Related Diseases

Inflammation processes can cause mild to severe damage in the human body and can lead to a large number of inflammation-related diseases (IRD) such as cancer, neural, vascular, and pulmonary diseases. Limitations of anti-inflammatory drugs (AID) application are reflected in high therapeutic doses, toxicity, low bioavailability and solubility, side effects, etc. Polymeric nanosystems (PS) have been recognized as a safe and effective technology that is able to overcome these limitations by AID encapsulation and is able to answer to the specific demands of the IRD treatment. PS are attracting great attention due to their versatility, biocompatibility, low toxicity, fine-tuned properties, functionality, and ability for precise delivery of anti-inflammatory drugs to the targeted sites in the human body. This article offers an overview of three classes of polymeric nanosystems: a) dendrimers, b) polymeric micelles and polymeric nanoparticles, and c) polymeric filomicelles, as well as their properties, preparation, and application in IRD treatment. In the future, the number of PS formulations in clinical practice will certainly increase.

Enzymatically Triggered Drug Release from Microgels Controlled by Glucose Concentration

This study aims to design microgels for controlled drug release via enzymatically generated pH changes in the presence of glucose. Modern medicine is focused on developing smart delivery systems with controlled release capabilities. In response to this demand, we present the synthesis, characterization, and enzymatically triggered drug release behavior of microgels based on poly(acrylic acid) modified with glucose oxidase (GOx) (p(AA-BIS)-GOx). TEM images revealed that the sizes of air-dried p(AA-BIS)-GOx microgels were approximately 130 nm. DLS measurements showed glucose-triggered microgel size changes upon glucose addition, which depended on buffer concentration. Enzymatically triggered drug release experiments using doxorubicin-loaded microgels with immobilized GOx demonstrated that drug release is strongly dependent on glucose and buffer concentration. The highest differences in release triggered by 5 and 25 mM glucose were observed in HEPES buffer at concentrations of 3 and 9 mM. Under these conditions, 80 and 52% of DOX were released with 25 mM glucose, while 47 and 28% of DOX were released with 5 mM glucose. The interstitial glucose concentration in a tumor ranges from ∼15 to 50 mM. Normal fasting blood glucose levels are about 5.5 mM, and postprandial (2 h after a meal) glucose levels should be less than 7.8 mM. The obtained results highlight the microgel's potential for drug delivery using the enhanced permeability and retention (EPR) effect, where drug release is controlled by enzymatically generated pH changes in response to elevated glucose concentrations.

Single-, Dual-, and Multi-Stimuli-Responsive Nanogels for Biomedical Applications

In recent years, stimuli-responsive nanogels that can undergo suitable transitions under endogenous (e.g., pH, enzymes and reduction) or exogenous stimuli (e.g., temperature, light, and magnetic fields) for on-demand drug delivery, have received significant interest in biomedical fields, including drug delivery, tissue engineering, wound healing, and gene therapy due to their unique environment-sensitive properties. Furthermore, these nanogels have become very popular due to some of their special properties such as good hydrophilicity, high drug loading efficiency, flexibility, and excellent biocompatibility and biodegradability. In this article, the authors discuss current developments in the synthesis, properties, and biomedical applications of stimulus-responsive nanogels. In addition, the opportunities and challenges of nanogels for biomedical applications are also briefly predicted.

Esterase-Responsive Polyglycerol-Based Nanogels for Intracellular Drug Delivery in Rare Gastrointestinal Stromal Tumors

Rare gastrointestinal stromal tumors (GISTs) are caused by mutations in the KIT and PDGFRA genes. Avapritinib (BLU-285) is a targeted selective inhibitor for mutated KIT and PDGFRA receptors that can be used to treat these tumors. However, there are subtypes of GISTs that exhibit resistance against BLU-285 and thus require other treatment strategies. This can be addressed by employing a drug delivery system that transports a combination of drugs with distinct cell targets. In this work, we present the synthesis of esterase-responsive polyglycerol-based nanogels (NGs) to overcome drug resistance in rare GISTs. Using inverse nanoprecipitation mediated with inverse electron-demand Diels-Alder cyclizations (iEDDA) between dPG-methyl tetrazine and dPG-norbornene, multi-drug-loaded NGs were formed based on a surfactant-free encapsulation protocol. The obtained NGs displayed great stability in the presence of fetal bovine serum (FBS) and did not trigger hemolysis in red blood cells over a period of 24 h. Exposing the NGs to Candida Antarctica Lipase B (CALB) led to the degradation of the NG network, indicating the capability of targeted drug release. The bioactivity of the loaded NGs was tested in vitro on various cell lines of the GIST-T1 family, which exhibit different drug resistances. Cell internalization with comparable uptake kinetics of the NGs could be confirmed by confocal laser scanning microscopy (CLSM) and flow cytometry for all cell lines. Cell viability and live cell imaging studies revealed that the loaded NGs are capable of intracellular drug release by showing similar IC50 values to those of the free drugs. Furthermore, multi-drug-loaded NGs were capable of overcoming BLU-285 resistance in T1-α-D842V + G680R cells, demonstrating the utility of this carrier system.

Synthesis and Evaluation of Alginate-Based Nanogels as Sustained Drug Carriers for Caffeine

The objective of this study is to design a polymeric network of nanogels for sustained release of caffeine. Therefore, alginate-based nanogels were fabricated by a free-radical polymerization technique for the sustained delivery of caffeine. Polymer alginate was crosslinked with monomer 2-acrylamido-2-methylpropanesulfonic acid by crosslinker N',N'-methylene bisacrylamide. The prepared nanogels were subjected to sol-gel fraction, polymer volume fraction, swelling, drug loading, and drug release studies. A high gel fraction was seen with the increasing feed ratio of polymer, monomer, and crosslinker. Greater swelling and drug release were observed at pH 4.6 and 7.4 as compared to pH 1.2 due to the deprotonation and protonation of functional groups of alginate and 2-acrylamido-2-methylpropanesulfonic acid. An increase was observed in swelling, loading, and release of the drug with the incorporation of a high feed ratio of polymer and monomer, while a reduction was seen with the increase in crosslinker feed ratio. Similarly, an HET-CAM test was used to evaluate the safety of the prepared nanogels, which showed that the prepared nanogels have no toxic effect on the chorioallantoic membrane of fertilized chicken eggs. Similarly, different characterizations techniques such as FTIR, DSC, SEM, and particle size analysis were carried out to determine the development, thermal stability, surface morphology, and particle size of the synthesized nanogels, respectively. Thus, we can conclude that the prepared nanogels can be used as a suitable agent for the sustained release of caffeine.

Biopolymer-Based Nanogel Approach in Drug Delivery: Basic Concept and Current Developments

Due to their increased surface area, extent of swelling and active substance-loading capacity and flexibility, nanogels made from natural and synthetic polymers have gained significant interest in scientific and industrial areas. In particular, the customized design and implementation of nontoxic, biocompatible, and biodegradable micro/nano carriers makes their usage very feasible for a range of biomedical applications, including drug delivery, tissue engineering, and bioimaging. The design and application methodologies of nanogels are outlined in this review. Additionally, the most recent advancements in nanogel biomedical applications are discussed, with particular emphasis on applications for the delivery of drugs and biomolecules.

Redox-responsive degradable microgel modified with superparamagnetic nanoparticles exhibiting controlled, hyperthermia-enhanced drug release

A novel degradable microgel based on poly(N-isopropylacrylamide) (pNIPA) cross-linked with N,N’-bisacryloylcystine (BISS) and containing superparamagnetic iron oxide nanoparticles (SPION@CA) was synthesized by semi-batch precipitation polymerization and examined as a potential hyperthermia-enhanced drug carrier. The pNIPA provided the microgel with temperature sensitivity, the BISS was responsible for degradation in the presence of glutathione (GSH) (an –S–S–bond reductor naturally present in cells), while the SPION@CA permitted remote control of temperature to improve drug release. The microgels exhibited volume phase transition temperature at ca. 34 °C, which is near the human body temperature, and were stable across a wide range of temperatures and ionic strengths, as well as in the blood plasma at 37 °C. It was found that the presence of SPION@CA in the polymer network of the microgels enabled the temperature to be increased up to 42 °C by an alternating magnetic field, and that increasing the temperature from 37 to 42 °C significantly enhanced the releasing of the anticancer drug doxorubicin (DOX). The highest DOX release (82%) was observed at pH 5, 42 °C, and in the presence of GSH, and the lowest (20%) at pH 7.4, 37 °C, and in the absence of GSH. MTT assay indicated that compared to free doxorubicin, the microgel particles loaded with doxorubicin have comparable cytotoxicity against MCF-7 cancer cells while being significantly less toxic to MCF-10A healthy cells.

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Enzyme-triggered- and tumor-targeted delivery with tunable, methacrylated poly(ethylene glycols) and hyaluronic acid hybrid nanogels

Enzyme-responsive polymeric-based nanostructures are potential candidates for serving as key materials in targeted drug delivery carriers. However, the major risk in their prolonged application is fast disassembling of the short-lived polymeric-based structures. Another disadvantage is the limited accessibility of the enzyme to the moieties that are located inside the network. Here, we report on a modified environmentally responsive and enzymatically cleavable nanogel carrier that contains a hybrid network. A properly adjusted volume phase transition (VPT) temperature allowed independent shrinking of a) poly(ethylene glycol) methyl ether methacrylate (OEGMA) with di(ethylene glycol) and b) methyl ether methacrylate (MEO2MA) part of the network, and the exposition of hyaluronic acid methacrylate (MeHa) network based carboxylic groups for its targeted action with the cellular based receptors. This effect was substantial after raising temperature in typical hyperthermia-based treatment therapies. Additionally, novel tunable NGs gained an opportunity to store- and to efficient-enzyme-triggered release relatively low but highly therapeutic doses of doxorubicin (DOX) and mitoxantrone (MTX). The controlled enzymatic degradation of NGs could be enhanced by introducing more hyaluronidase enzyme (HAdase), that is usually overexpressed in cancer environments. MTT assay results revealed effective cytotoxic activity of the NGs against the human MCF-7 breast cancer cells, the A278 ovarian cancer cells and also cytocompatibility against the MCF-10A and HOF healthy cells. The obtained tunable, hybrid network NGs might be used as a useful platform for programmed delivery of other pharmaceuticals and diagnostics in therapeutic applications.

Temperature/pH-responsive carmofur-loaded nanogels rapidly prepared via one-pot laser-induced emulsion polymerization

Tumor microenvironment-responsive nanogels loading antitumor drugs can improve the chemotherapy efficiency due to their suitable size, great hydrophilicity, excellent biocompatibility, and sensitivity to specific stimulation. Herein, a simple and effective strategy of one-pot laser-induced emulsion polymerization at 532 nm was developed to prepare carmofur-loaded nanogels based on biocompatible and temperature/pH-sensitive monomers including polyethylene glycol diacrylate (PEGDA), N-vinylcaprolactam (NVCL), and 2-(dimethylamino) ethyl methacrylate (DMAEMA). The nanogels loading carmofur with dual-stimuli responsive drug release properties were rapidly obtained under laser irradiation (beam diameter 2.5 mm, laser power 60 mW) for only 100 s. These nanogels exhibited an average hydrodynamic diameter of 195.9 nm and a low polydispersity index of 0.115. The effect of monomer ratio on the size, morphology, double-bond conversion, and thermo/pH-sensitivity of nanogels was investigated. The cumulative carmofur release from nanogels at pH 5.0 within 48 h was nearly three times that at pH 7.4, while the release amount at 42 °C was twice that at 25 °C, showing the controlled and sustainable release with the change of pH and temperature. The in vitro release kinetics of carmofur was in accord with first-order release model.

Microgels and Nanogels for the Delivery of Poorly Water-Soluble Drugs

While microgels and nanogels are most commonly used for the delivery of hydrophilic therapeutics, the water-swollen structure, size, deformability, colloidal stability, functionality, and physicochemical tunability of microgels can also offer benefits for addressing many of the barriers of conventional vehicles for the delivery of hydrophobic therapeutics. In this review, we describe approaches for designing microgels with the potential to load and subsequently deliver hydrophobic drugs by creating compartmentalized microgels (e.g., core-shell structures), introducing hydrophobic domains in microgels, leveraging host-guest interactions, and/or applying "smart" environmentally responsive materials with switchable hydrophobicity. In particular, the challenge of promoting hydrophobic drug loading without compromising the inherent advantages of microgels as delivery vehicles and ensuring practically relevant release kinetics from such structures is highlighted, with an eye toward the practical translation of such vehicles to the clinic.

Overview of nanoparticulate strategies for solubility enhancement of poorly soluble drugs

Poor aqueous solubility and poor bioavailability are major issues with many pharmaceutical industries. By some estimation, 70-90% drug candidates in development stage while up-to 40% of the marketed products are poorly soluble which leads to low bioavailability, reduced therapeutic effects and dosage escalation. That's why solubility is an important factor to consider during design and manufacturing of the pharmaceutical products. To-date, various strategies have been explored to tackle the issue of poor solubility. This review article focuses the updated overview of commonly used macro and nano drug delivery systems and techniques such as micronization, solid dispersion (SD), supercritical fluid (SCF), hydrotropy, co-solvency, micellar solubilization, cryogenic technique, inclusion complex formation-based techniques, nanosuspension, solid lipid nanoparticles, and nanogels/nanomatrices explored for solubility enhancement of poorly soluble drugs. Among various techniques, nanomatrices were found a promising and impeccable strategy for solubility enhancement of poorly soluble drugs. This article also describes the mechanism of action of each technique used in solubilization enhancement.

Biocompatible poly(galacturonic acid) micro/nanogels with controllable degradation via tunable chemical crosslinking

Here, one-pot labor-less preparation of two different polygalacturonic acid (PGA) micro/nanogel formulations, PGA-1 and PGA-2, by respectively crosslinking the PGA chains with divinyl sulfone (DVS) and trimethylolpropane triglycidyl ether (TMPGDE) were reported. Various crosslinker ratios, 2.5, 10, 50, and 100% were used for both crosslinkers to demonstrate the tunability of their degradation properties. The PGA micro/nanogels were found spherical-shaped porous particles in 0.5-5.0 μm size range by SEM. The hydrolytic degradation and stability of PGA micro/nanogels in pH 1.0, 7.4, and 9.0 buffer solutions can be controlled by changing the degree of crosslinking. Accordingly, 32 ± 8% and 36 ± 2% weight losses were attained for PGA-1-10% and PGA-2-10% micro/nanogels at pH 1, respectively, and 46 ± 6%, and 68 ± 6% degradations were determined at pH 7.4 within 4 weeks. However, no degradation was observed for both PGA-based micro/nanogel formulations prepared at 25% and 100% crosslinker ratios at all pH conditions. All PGA-based micro/nanogels were totally degraded within 7-10 days at pH 9.0. In the presence of pectinase and amyloglucosidase enzymes, all formulations of PGA micro/nanogels showed more than 80% degradation within 12 h. Furthermore, both PGA formulations showed no significant cytotoxicity against L929 fibroblast cells with 90% and above cell viability up to 250 mg/mL concentrations.

Tumor Microenvironment-Responsive Polypeptide Nanogels for Controlled Antitumor Drug Delivery

Tumor microenvironment-responsive polypeptide nanogels belong to a biomaterial with excellent biocompatibility, easily adjustable performance, biodegradability, and non-toxic properties. They are developed for selective delivery of antitumor drugs into target organs to promote tumor cell uptake, which has become an effective measure of tumor treatment. Endogenous (such as reduction, reactive oxygen species, pH, and enzyme) and exogenous (such as light and temperature) responsive nanogels can release drugs in response to tumor tissues or cells to improve drug distribution and reduce drug side effects. This article systematically introduces the research progress in tumor microenvironment-responsive polypeptide nanogels to deliver antitumor drugs and provides a reference for the development of antitumor nanoformulations.

Design and Applications of Tumor Microenvironment-Responsive Nanogels as Drug Carriers

In recent years, the exploration of tumor microenvironment has provided a new approach for tumor treatment. More and more researches are devoted to designing tumor microenvironment-responsive nanogels loaded with therapeutic drugs. Compared with other drug carriers, nanogel has shown great potential in improving the effect of chemotherapy, which is attributed to its stable size, superior hydrophilicity, excellent biocompatibility, and responsiveness to specific environment. This review primarily summarizes the common preparation techniques of nanogels (such as free radical polymerization, covalent cross-linking, and physical self-assembly) and loading ways of drug in nanogels (including physical encapsulation and chemical coupling) as well as the controlled drug release behaviors. Furthermore, the difficulties and prospects of nanogels as drug carriers are also briefly described.

Influence of the Core Formulation on Features and Drug Delivery Ability of Carbamate-Based Nanogels

In the last years, nanogels have emerged as one of the most promising classes of novel drug delivery vehicles since they can be employed in multiple fields, such as various therapeutics or diagnostics, and with different classes of compounds and active molecules. Their features, such as a high volume to surface ratio, excellent drug loading and release ability, as well as biocompatibility and tunable behavior, are unique, and, nowadays, great efforts are made to develop new formulations that can be employed in a wider range of applications. Polyethylene glycol (PEG)-polyethylenimine (PEI) nanogels probably represent the baseline of this class of biomaterials and they are still largely employed and studied. In any way, the possibility to exploit new core formulations for nanogels is certainly very interesting in order to understand the influence of different polymer chains on the final properties of the system. In this research, we explore and make a comparison between PEG-PEI nanogels and two other different formulations: pluronic F127-PEI nanogels and PEG-Jeffamine nanogels. We propose nanogels synthesis methods, their chemical and physical characterization, as well as their stability analysis, and we focus on the different drug delivery ability that these structures exhibit working with different typologies of drug mimetics.