Embedding fluorescent mesoporous silica nanoparticles into biocompatible nanogels for tumor cell imaging and thermo/pH-sensitive in vitro drug release

Multifunctional stimuli-responsive hybrid nanogels for cancer therapy: Current status and challenges

With cancer research shifting focus to achieving multifunctionality in cancer treatment strategies, hybrid nanogels are making a rapid rise to the spotlight as novel, multifunctional, stimuli-responsive, and biocompatible cancer therapeutic strategies. They can possess cancer cell-specific cytotoxic effects themselves, carry drugs or enzymes that can produce cytotoxic effects, improve imaging modalities, and target tumor cells over normal cells. Hybrid nanogels bring together a wide range of desirable properties for cancer treatment such as stimuli-responsiveness, efficient loading and protection of molecules such as drugs or enzymes, and effective crossing of cellular barriers among other properties. Despite their promising abilities, hybrid nanogels are still far from being used in the clinic, and their available data remains relatively limited. However, many studies can be done to facilitate this clinical transition. This review is critically summarizing and analyzing the recent information and progress on the use of hybrid nanogels particularly inorganic nanoparticle-based and organic nanoparticle-based hybrid nanogels in the field of oncology and future directions to aid in transferring those results to the clinic. This work concludes that the future of hybrid nanogels is greatly impacted by therapeutic and non-therapeutic factors. Therapeutic factors include the lack of hemocompatibility studies, acute and chronic toxicological studies, and information on agglomeration capability and extent, tumor heterogeneity, interaction with proteins in physiological fluids, endocytosis-exocytosis, and toxicity of the nanogels' breakdown products. Non-therapeutic factors include the lack of clear regulatory guidelines and standardized assays, limitations of animal models, and difficulties associated with good manufacture practices (GMP).

Polysaccharide/mesoporous silica nanoparticle-based drug delivery systems: A review

Mesoporous silica nanoparticles (MSNs) have been well-researched in the design and fabrication of advanced drug delivery systems (DDSs) due to their advantages such as good biocompatibility, large specific surface area and pore volume for drug loading, easily surface modification, adjusted size and good thermal/chemical stability. For MSN-based DDSs, gate materials are also necessary. And natural polysaccharides, one kind of the most abundant natural resource, have been widely applied as the "gatekeepers" in MSN-based DDSs. Polysaccharides are cheap and rich in sources with good biocompatibility, and some of them have important biological functions. In this review article, polysaccharides including chitosan, hyaluronic acid, sodium alginate and dextran, et al. are briefly introduced. And the preparation processes and properties such as controlled drug release, cancer targeting and disease diagnosis of functional polysaccharide/MSN-based DDSs are discussed.

Multifunctional Polymeric Nanogels for Biomedical Applications

Currently, research in nanoparticles as a drug delivery system has broadened to include their use as a delivery system for bioactive substances and a diagnostic or theranostic system. Nanogels, nanoparticles containing a high amount of water, have gained attention due to their advantages of colloidal stability, core-shell structure, and adjustable structural components. These advantages provide the potential to design and fabricate multifunctional nanosystems for various biomedical applications. Modified or functionalized polymers and some metals are components that markedly enhance the features of the nanogels, such as tunable amphiphilicity, biocompatibility, stimuli-responsiveness, or sensing moieties, leading to specificity, stability, and tracking abilities. Here, we review the diverse designs of core-shell structure nanogels along with studies on the fabrication and demonstration of the responsiveness of nanogels to different stimuli, temperature, pH, reductive environment, or radiation. Furthermore, additional biomedical applications are presented to illustrate the versatility of the nanogels.

Chitosan-Based Biocompatible Copolymers for Thermoresponsive Drug Delivery Systems: On the Development of a Standardization System

Chitosan is a natural polysaccharide that is considered to be biocompatible, biodegradable and non-toxic. The polymer has been used in drug delivery applications for its positive charge, which allows for adhesion with and recognition of biological tissues via non-covalent interactions. In recent times, chitosan has been used for the preparation of graft copolymers with thermoresponsive polymers such as poly-N-vinylcaprolactam (PNVCL) and poly-N-isopropylamide (PNIPAM), allowing the combination of the biodegradability of the natural polymer with the ability to respond to changes in temperature. Due to the growing interest in the utilization of thermoresponsive polymers in the biological context, it is necessary to increase the knowledge of the key principles of thermoresponsivity in order to obtain comparable results between different studies or applications. In the present review, we provide an overview of the basic principles of thermoresponsivity, as well as a description of the main polysaccharides and thermoresponsive materials, with a special focus on chitosan and poly-N-Vinyl caprolactam (PNVCL) and their biomedical applications.

Spontaneously Self-Assembled Microgel Film as Co-Delivery System for Skincare Applications

Nowadays, the design of innovative delivery systems is driving new product developments in the field of skincare. In this regard, serving as potential candidates for on-demand drug delivery and fulfilling advanced mechanical and optical properties together with surface protection, spontaneously self-assembled microgel films can be proposed as ideal smart skincare systems. Currently, the high encapsulation of more than one drug simultaneously in a film is a very challenging task. Herein, different ratios (1:1, 3:1, 9:1) of different mixtures of hydrophilic/hydrophobic UVA/UVB-absorbers working together in synergy and used for skin protection were encapsulated efficiently into spontaneously self-assembled microgel films. In addition, in vitro release profiles show a controlled release of the different active molecules regulated by the pH and temperature of the medium. The analysis of the release mechanisms by the Peppas-Sahlin model indicated a superposition of diffusion-controlled and swelling-controlled releases. Finally, the distribution of active molecule mixtures into the film was studied by confocal Raman microscopy imaging corroborating the release profiles obtained.

Stimuli-responsive mesoporous silica nanoparticles: A custom-tailored next generation approach in cargo delivery

The pre-mature release of therapeutic cargos in the bloodstream or off-target sites is a major hurdle in drug delivery. However, stimuli-specific drug release responses are capable of providing greater control over the cargo release. Herein, various types of nanocarriers have been employed for such applications. Among various types of nanoparticles, mesoporous silica nanoparticles (MSNPs) have several attractive characteristics, such as high loading capacity, biocompatibility, small size, porous structure, high surface area, tunable pore size and ease of functionalization of the external and internal surfaces, which facilitates the entrapment and development of stimuli-dependent release of drugs. MSNPs could be modified with such stimuli-responsive entities like nucleic acid, peptides, polymers, organic molecules, etc., to prevent pre-mature cargo release, improving the therapeutic outcome. This controlled drug release system could be modulated to function upon extracellular or intracellular specific stimuli, including pH, enzyme, glucose, glutathione, light, temperature, etc., and thus provide minimal side effects at non-target sites. This system has great potential applications for the targeted delivery of therapeutics to treat clinically challenging diseases like cancer. This review summarizes the synthesis and design of stimuli-responsive release strategies of MSNP-based drug delivery systems along with investigations in biomedical applications.

Fabrication of PNIPAM-chitosan/decatungstoeuropate/silica nanocomposite for thermo/pH dual-stimuli-responsive and luminescent drug delivery system

A luminescent and dual-stimuli-responsive nanocomposite based on mesoporous silica, poly (N-isopropylacrylamide)-chitosan and decatungstoeuropate was prepared. To fabricate the nanocomposite, the mesoporous silica nanoparticles were coated with thermo/pH dual-responsive poly (N-isopropylacrylamide)-chitosan and the luminescent decatungstoeuropate particles were grafted onto copolymers. The designed nanocarrier could show exhibit good red luminescence as well as obvious thermo/pH stimuli-responsive properties, which could be employed as a drug storage reservoir for the loading and release of anticancer drug doxorubicin (DOX). The research indicated that the releases of DOX were thermo/pH dependent and high temperatures/acidic conditions were favorable for the fast release of drug. In vitro cytotoxicity tests revealed that the drug delivery carrier displayed excellent biocompatible and the composites loaded with DOX showed significant suppression effect on HeLa cells. Luminescence spectra showed that the composite containing decatungstoeuropate displayed fine red luminescence at various temperatures and pH values, which could be utilized as a potential labeling material in field of medicine.

Targeted and stimuli-responsive mesoporous silica nanoparticles for drug delivery and theranostic use

For cancer therapy, the usefulness of mesoporous silica nanoparticles (MPSNPs) has been widely discussed, likely due to its inorganic nature and excellent structural features. The MPSNPs-based chemotherapeutics have been promisingly delivered to their target sites that help to minimize side effects and improve therapeutic effectiveness. A wide array of studies have been conducted to functionalize drug-loaded MPSNPs using targeting ligands and stimuli-sensitive substances. In addition, anticancer drugs have been precisely delivered to their target sites using MPSNPs, which respond to multi-stimuli. Furthermore, MPSNPs have been extensively tested for their safety and compatibility. The toxicity level of MPSNPs is substantially lower as compared to that of colloidal silica; however, in oxidative stress, they exhibit cytotoxic features. The biocompatibility of MPSNPs can be improved by modifying their surfaces. This article describes the production procedures, functionalization, and applications of biocompatible MPSNPs in drug delivery.

Versatile oligo(ethylene glycol)-based biocompatible microgels for loading/release of active bio(macro)molecules

The present study aims in the understanding of the effect of oligo(ethylene glycol)-based biocompatible microgels inner structure on the encapsulation/release mechanisms of different types of cosmetic active molecules. For that, multi-responsive microgels were synthesized using three types of cross-linkers: ethylene glycol dimethacrylate (EGDMA), oligo(ethylene glycol) diacrylate (OEGDA) and N,N-methylenebisacrylamide (MBA). The inner morphology of the microgels synthesized was studied by ¹H-nuclear magnetic resonance (¹H NMR) and small-angle neutron scattering (SANS) techniques and no effect of cross-linker type on microgel microstructure was observed in the case of analysing purified microgel dispersions. Moreover, all the microgels synthesized presented conventional swelling/de-swelling behavior as a function of temperature and pH. Two hydrophobic, one hydrophilic, and one macromolecule as cosmetic active molecules were effectively loaded into different microgel particles via hydrophobic interactions and hydrogen-bonding interactions between -OH groups of active molecules and ether oxygens of different microgel particles. Their release profiles as a function of cross-linker type used and encapsulated amounts were studied by Peppas-Sahlin model. No effect of the cross-linker type was observed due to the similar inner structure of all the microgels synthesized.

Investigation of magnetic silica with thermoresponsive chitosan coating for drug controlled release and magnetic hyperthermia application

In this study, a drug delivery system for chemo-hyperthermia applications is proposed and fabricated. The delivery system consists of magnetic-silica (MagSi) particles being encapsulated within a pH/thermo-responsive chitosan‑g‑N‑isopropylacrylamide (Chi-g-NIPAAm) polymer matrix. The as-prepared MagSi@Chi-g-NIPAAm particles exhibit superparamagnetic behavior with a saturation magnetization (Ms) of 20.14 emu/g. In addition, the MagSi@Chi-g-NIPAAm particles can act as a heat source when subject to an alternating magnetic field (AMF) and have a specific absorptions rate (SAR) of 8.36 Wg^-1. The release of the drug DOX from the synthesized particles is sensitive to both the pH and temperature of its environment. We have compared the drug release when the solution is externally heated up and when it is heated up by the AMF (internal heating). For external heating (when the pH/temperature is 4.0/45 °C), 83.30 ± 2.92% of the DOX were released within the first 5 h. The release of the DOX by the particles in pH 7.4 (temperature of 37 °C) was much slower (around 25.87 ± 1.30% after 25 h). The release of the DOX was much higher (under an acidic condition pH = 4.0) around 57.13 ± 2.36% within 1 h in the presence of AMF heating. The in vitro cytotoxicity tests of the of DOX-loaded MagSi@Chi-g-NIPAAm particles towards HeLa cancer cells. In general, the toxicities of the drug DOX as part of a MagSi@Chi-g-NIPAAm particles were less than those of the standalone DOX until the concentration of DOX-loaded particles reached 250 μg/mL, after which the toxicity of DOX in both forms were the same.

Controlled Release of Salidroside Microspheres Prepared Using a Chitosan and Methylcellulose Interpenetrating Polymer Network

In this work, salidroside, a functional food agent, was incorporated into novel interpenetrating polymer network microspheres (IPN-Ms) prepared by chitosan (CS) and methylcellulose (MC) for controlled release and stabilization. IPN-Ms were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry and X-ray diffraction. The result indicated that salidroside-loaded IPN-Ms (S-IPN-Ms) are hollow and highly spherical, with a coarse pleated surface and a particle size ranging from 5 to 30 µm. Schiff base formation and the hemiacetal reaction are the primary mechanisms underlying the interpenetrating network cross-linking of IPN-Ms. In S-IPN-Ms, the CS and MC were homogeneously blended, and the salidroside was molecularly and amorphously dispersed. The encapsulation efficiency of the salidroside within the S-IPN-Ms was up to 75.64 %. In the S-IPN-M complex, the release of salidroside by S-IPN-Ms was governed by burst and sustained release, and Fickian diffusion was the primary release mechanism for the entire release process. Thus, controlled release and stabilization of salidroside were achieved through incorporation of salidroside into IPN-Ms prepared by chitosan (CS) and methylcellulose.

Glycerol-regulated facile synthesis and targeted cell imaging of highly luminescent Ag2Te quantum dots with tunable near-infrared emission

In this work, highly luminescent and emission tunable Ag2Te quantum dots (QDs) were facilely prepared by using water-dispersed glycerol as viscous solvent and CH3COOAg/Na2TeO3 as Ag/Te precursors. Viscous glycerol was utilized to slow the nucleation and growth of QDs at 200°C, and enabled the isolation of QDs with different emission wavelengths. Experimental results revealed that the as-prepared Ag2Te QDs exhibited tunable near-infrared emission from 930 to 1084nm, high photoluminescence (PL) quantum yields (QYs, more than 20%), good photostability and low cytotoxicity. After surface coating of a thin silica shell (∼1.4nm), the resulting NH2 terminated Ag2Te@SiO2-NH2 displayed enhanced PL QYs, higher photostability and biocompatibility when compared with the original Ag2Te QDs. Through a facile carboxy-amine coupling, folic acid (FA) was grafted with Ag2Te@SiO2-NH2 to form Ag2Te@SiO2-FA nanocomposites, which were used for targeted PL imaging of folate receptor over-expressed tumor cells.

Retracted Article: CuS nanocrystal@microgel nanocomposites for light-regulated release of dual-drugs and chemo-photothermal synergistic therapy in vitro

This article reported the facile synthesis of CuS nanocrystal@microgel nanocomposites that were further developed towards the light-regulated release of dual-drugs and chemo-photothermal synergistic therapy in vitro.

Multifunctional hybrid nanogels for theranostic applications

This paper reviews a wide set of theranostic applications based on the special properties associated with composite nanogels. The nanogels presented here are mostly hybridized with quantum dots, magnetic nanoparticles, and plasmonic metal noble nanoparticles. These inorganic components confer nanogels multifunctional properties that extend their applications from drug delivery systems to diagnosis and therapy. Nanogels can also be surface functionalized with specific ligands to achieve targeted therapy and reduce toxicity. This versatility makes hybrid nanogels very promising agents for imaging, diagnosis and treatment of cancer and other diseases.

Near-infrared light remote-controlled intracellular anti-cancer drug delivery using thermo/pH sensitive nanovehicle

Stimuli-responsive drug delivery systems have been developed to enhance the tumor-targeting drug transportation and minimize the severe side effects along with the chemotherapy. In this study, a near-infrared (NIR) light triggered drug delivery system was developed based on the amphiphilic chitosan derivative-coated single-wall carbon nanotubes (CNT) encapsulated in the thermo/pH sensitive nanogel (CS/PNIPAAm@CNT). The PEG diacrylate (Mw = 250 Da) was applied in the present work to tune the nanoparticles with the phase transition temperature at ∼ 38 °C, which was an attempt to match the prerequisite for the in vivo applications. Owing to the π-π stacking, hydrophobic interaction and the opportunity of Schiff-base formation between chitosan and doxorubicin (DOX), the nanoparticles possessed a relative high drug loading capacity (∼ 43%). The DOX loaded CS/PNIPAAm@CNT released DOX faster at 40 °C than at 25 °C, meanwhile faster at pH 5.0 in comparison with that at pH 7.4. Moreover, the rapid and repetitive release of DOX was observed when the DOX-loaded CS/PNIPAAm@CNT was irradiated under NIR light. Furthermore, DOX-loaded CS/PNIPAAm@CNT upon NIR irradiation showed significantly greater cytotoxicity in HeLa cells owing to NIR-triggered increase in temperature and enhanced DOX release. Confocal laser scanning microscopy (CLSM) was utilized to demonstrate the enhanced cell uptake of the as prepared nanoparticles and the faster drug release under the NIR irradiation and lower pH. All the results suggest that multifunctional DOX-loaded CS/PNIPAAm@CNT nanocomposite is a promising therapeutic nanocarrier for intracellular drug delivery with great potential for targeted cancer therapy.

Facile synthesis of gold nanorods/hydrogels core/shell nanospheres for pH and near-infrared-light induced release of 5-fluorouracil and chemo-photothermal therapy

We described a facile synthesis of pH and near-infrared (NIR) light dual-sensitive core/shell hybrid nanospheres, consisting of gold nanorods (GNR) as the core and poly(N-isopropylacrylamide-co-methacrylic acid) as the shell, p(NIPAM-MAA). The resultant GNR/p(NIPAM-MAA) nanospheres showed a core/shell structure, with an average diameter of ∼110nm and a strong longitudinal surface plasmon band at NIR region. Due to the photothermal effect of GNR and pH/thermal-sensitive volume transition of p(NIPAM-MAA) hydrogels, the nanospheres with loading of 5-fluorouracil (5-FU) by electrostatic interactions were developed as a smart carrier for pH- and photothermal-induced release of 5-FU. Experimental results testified that the cumulative release of 5-FU from nanospheres was markedly increased in a mild acidic medium. Moreover, a NIR light (808nm) irradiation triggered a greater and faster release of 5-FU, which was further testified by relevant results from in vitro cytotoxicity assay, in vivo tumor growth inhibition and histological images of ex vivo tumor sections. These results revealed significant applications of GNR/p(NIPAM-MAA) nanospheres in controlled release of anticancer agents and photothermal ablation therapy of tumor tissues, accompanied by synergistic effect of chem-photothermal therapy.

Photophysical properties, aggregation-induced fluorescence in nanoaggregates and cell imaging of 2,5-bisaryl 1,3,4-oxadiazoles

Conjugated fluorescence dyes of 2,5-bisaryl 1,3,4-oxadiazoles with carbazole-triphenylamine moieties encapsulated into different nanoparticles are successfully applied to cell imaging.

Retracted Article: Facile fabrication of water-dispersible AgInS2 quantum dots and mesoporous AgInS2 nanospheres with visible photoluminescence

This article reported the facile preparation of water-dispersible near-infrared-emitting AgInS₂ quantum dots and mesoporous AgInS₂ nanospheres with visible photoluminescence.

A biodegradable thermosensitive hydrogel with tuneable properties for mimicking three-dimensional microenvironments of stem cells

Chitosan-g-poly(N-isopropylacrylamide) was synthesized as a stem cell mimicking microenvironment. Solubility and gel mechanical strength were optimised through manipulating the grafting parameters.