Protein release from biodegradable dextran nanogels

Polymeric micelles amplify tumor oxidative stresses through combining PDT and glutathione depletion for synergistic cancer chemotherapy

Cancer has been one of the major healthcare burdens, which demands innovative therapeutic strategies to improve the treatment outcomes. Combination therapy hold great potential to leverage multiple synergistic pathways to improve cancer treatment. Cancer cells often exhibit an increased generation of reactive oxygen species (ROS) and antioxidant species compared with normal cells, and the levels of these species can be further elevated by common therapeutic modalities such as photodynamic therapy (PDT) or chemotherapy. Taking advantage that cancer cells are vulnerable to further oxidative stress, we aim to design a drug delivery system by simultaneously increasing the cellular ROS level, reducing antioxidative capacity, and inducing anticancer chemotherapy in cancer cells. Here, we designed a star-shape polymer, PEG(-b-PCL-Ce6)-b-PBEMA, based on the Passerini three-component reaction, which can both enhance ROS generation during PDT and decrease the GSH level in cancer cells. The polycaprolactone conjugated with photosensitizer Ce6 served as hydrophobic segments to promote micelle formation, and Ce6 was used for PDT. The H₂O₂-labile group of arylboronic esters pendent on the third segment was designed for H₂O₂-induced quinone methide (QM) release for GSH depletion. We thoroughly investigated the spectral properties of blank micelle during its assembling process, ROS generation, and H₂O₂-induced QM release in vitro. Moreover, this polymeric micelle could successfully load hydrophobic anticancer drug Doxorubicin (DOX) and efficiently deliver DOX into cancer cells. The triple combination of ROS generation, GSH elimination, and chemotherapy dramatically improved antitumor efficiency relative to each of them alone in vitro and in vivo.

Strategies to load therapeutics into polysaccharide-based nanogels with a focus on microfluidics: A review

Nowadays nanoparticles are increasingly investigated for the targeted and controlled delivery of therapeutics, as suggested by the high number of research articles (2400 in 2000 vs 8500 in 2020). Among them, almost 2% investigated nanogels in 2020. Nanogels or nanohydrogels (NGs) are nanoparticles formed by a swollen three-dimensional network of synthetic polymers or natural macromolecules such as polysaccharides. NGs represent a highly versatile nanocarrier, able to deliver a number of therapeutics. Currently, NGs are undergoing clinical trials for the delivery of anti-cancer vaccines. Herein, the strategies to load low molecular weight drugs, (poly)peptides and genetic material into polysaccharide NGs as well as to formulate NGs-based vaccines are summarized, with a focus on the microfluidics approach.

Liposome-Enveloped Molecular Nanogels

Novel hydrogel@liposome particles were prepared by pH-triggered molecular gel formation inside of liposomes loaded with a low-molecular weight gelator derived from l-valine (1). Liposome formation was carried out using l-α-phosphatidylcholine (PC) and cholesterol as components of the lipid bilayer. Molecular hydrogelator 1 and pyranine, a ratiometric fluorescent pH probe, were entrapped in the liposomes at pH 9 and posterior acidification with d-glucono-1,5-lactone to pH 5-6 provoked intraliposomal gel formation. Removal of the lipid bilayer with sodium dodecyl sulfate yielded naked nanogel particles. The systems were characterized by transmission electron microscopy and dynamic light scattering. The hydrogel@liposomes were loaded with doxorubicin, showing a similar release than that observed for liposomes. The hybrid particles described here are the first case of nonpolymeric hydrogel@liposome systems reported. This type of nanocarriers merges the benefits of liposomal vehicles with the inherent stimuli responsiveness and enhanced biocompatibility of hydrogels formed by low-molecular weight molecules, foretelling a potential use in environmentally sensitive drug release.

Review of polysaccharide particle-based functional drug delivery

This review investigates the significant role polysaccharide particles play in functional drug delivery. The importance of these systems is due to the wide variety of polysaccharides and their natural source meaning that they can provide biocompatible and biodegradable systems with a range of both biological and chemical functionality valuable for drug delivery. This functionality includes protection and presentation of working therapeutics through avoidance of the reticuloendothelial system, stabilization of biomacromolecules and increasing the bioavailability of incorporated small molecule drugs. Transport of the therapeutic is also key to the utility of polysaccharide particles, moving drugs from the site of administration through mucosal binding and transport and using chemistry, size and receptor mediated drug targeting to specific tissues. This review also scrutinizes the methods of synthesizing and constructing functional polysaccharide particle drug delivery systems that maintain and extend the functionality of the natural polysaccharides.

Recent Advances in Degradable Hybrids of Biomolecules and NGs for Targeted Delivery

Recently, the fast development of hybrid nanogels dedicated to various applications has been seen. In this context, nanogels incorporating biomolecules into their nanonetworks are promising innovative carriers that gain great potential in biomedical applications. Hybrid nanogels containing various types of biomolecules are exclusively designed for: improved and controlled release of drugs, targeted delivery, improvement of biocompatibility, and overcoming of immunological response and cell self-defense. This review provides recent advances in this rapidly developing field and concentrates on: (1) the key physical consequences of using hybrid nanogels and introduction of biomolecules; (2) the construction and functionalization of degradable hybrid nanogels; (3) the advantages of hybrid nanogels in controlled and targeted delivery; and (4) the analysis of the specificity of drug release mechanisms in hybrid nanogels. The limitations and future directions of hybrid nanogels in targeted specific- and real-time delivery are also discussed.

Functional Microgels: Recent Advances in Their Biomedical Applications

Here, a spotlight is shown on aqueous microgel particles which exhibit a great potential for various biomedical applications such as drug delivery, cell imaging, and tissue engineering. Herein, different synthetic methods to develop microgels with desirable functionality and properties along with degradable strategies to ensure their renal clearance are briefly presented. A special focus is given on the ability of microgels to respond to various stimuli such as temperature, pH, redox potential, magnetic field, light, etc., which helps not only to adjust their physical and chemical properties, and degradability on demand, but also the release of encapsulated bioactive molecules and thus making them suitable for drug delivery. Furthermore, recent developments in using the functional microgels for cell imaging and tissue regeneration are reviewed. The results reviewed here encourage the development of a new class of microgels which are able to intelligently perform in a complex biological environment. Finally, various challenges and possibilities are discussed in order to achieve their successful clinical use in future.

TPGS-functionalized and ortho ester-crosslinked dextran nanogels for enhanced cytotoxicity on multidrug resistant tumor cells

Herein pH-sensitive nanogels (NG1) and P-glycoprotein-repressive nanogels (NG2) were prepared by copolymerization between an ortho ester crosslinker (OEAM) and tocopheryl polyethylene glycol succinate (TPGS)-free or conjugated dextran. Nanogels with or without TPGS possessed a uniform diameter (∼180 nm) and excellent stability in various physiological environments. Doxorubicin (DOX) was successfully loaded into NG1 and NG2 to give NG1/DOX and NG2/DOX, both of them showed appropriate drug release profiles under mildly acidic conditions (pH 5.0). NG2/DOX possessed higher drug enrichment and lethality than NG1/DOX did on MCF-7/ADR cells. Analysis of corresponding index of efflux activity showed that NG2 could induce depolarization of mitochondrial membrane and interfere with ATP metabolism. NG2/DOX also displayed increased penetration and growth inhibition on MCF-7/ADR multicellular spheroids. These results demonstrated that pH-sensitive TPGS-functionalized nanogels (NG2) as drug carriers had great potential to suppress drug efflux in MCF-7/ADR cells and even overcome MDR on cancer cells.

Bioengineered liposome-scaffold composites as therapeutic delivery systems

The therapeutic potential of liposomes can be amplified when combined with biomaterial scaffolds. Such configurations overcome the convergent demands of therapies by enabling enhanced delivery, environmental responsiveness and potency. Liposomes benefit from the increased physical and mechanical strength, favorable rheological properties and natural environment conducive to improved tissue formation that scaffolds provide, while enabling biocompatible delivery of hydrophilic and lipophilic compounds that can be further functionalized to achieve targeted delivery. Topical, ocular, oral, nasal and vaginal applications have been explored using various polymer- or nanofiber-based scaffolds. Mechanistic and rheological findings on complexation between biomaterials, liposomes and cargo have led to multimodal systems with tremendous clinical potential. A review of the key developments in bioengineered liposome-scaffold composites is presented in this manuscript.

Gold-stabilized carboxymethyl dextran nanoparticles for image-guided photodynamic therapy of cancer

Photodynamic therapy (PDT) has been extensively investigated to treat cancer since it induces cell death through the activation of photosensitizers by light.

Nanogels: An overview of properties, biomedical applications and obstacles to clinical translation

Nanogels have emerged as a versatile hydrophilic platform for encapsulation of guest molecules with a capability to respond to external stimuli that can be used for a multitude of applications. These are soft materials capable of holding small molecular therapeutics, biomacromolecules, and inorganic nanoparticles within their crosslinked networks, which allows them to find applications for therapy as well as imaging of a variety of disease conditions. Their stimuli-responsive behavior can be easily controlled by selection of constituent polymer and crosslinker components to achieve a desired response at the site of action, which imparts nanogels the ability to participate actively in the intended function of the carrier system rather than being passive carriers of their cargo. These properties not only enhance the functionality of the carrier system but also help in overcoming many of the challenges associated with the delivery of cargo molecules, and this review aims to highlight the distinct and unique capabilities of nanogels as carrier systems for the delivery of an array of cargo molecules over other nanomaterials. Despite their obvious usefulness, nanogels are still not a commonplace occurrence in clinical practice. We have also made an attempt to highlight some of the major challenges that need to be overcome to advance nanogels further in the field of biomedical applications.

Enhanced photocatalytic degradation of norfloxacin in aqueous Bi2WO6 dispersions containing nonionic surfactant under visible light irradiation

Photocatalytic degradation is an alternative method to remove pharmaceutical compounds in water, however it is hard to achieve efficient rate because of the poor solubility of pharmaceutical compounds in water. This study investigated the photodegradation of norfloxacin in a nonionic surfactant Triton-X100 (TX100)/Bi2WO6 dispersion under visible light irradiation (400-750nm). It was found that the degradation of poorly soluble NOF can be strongly enhanced with the addition of TX100. TX100 was adsorbed strongly on Bi2WO6 surface and accelerated NOF photodegradation at the critical micelle concentration (CMC=0.25mM). Higher TX100 concentration (>0.25mM) lowered the degradation rate. In the presence of TX100, the degradation rate reached the maximum value when the pH value was 8.06. FTIR analyses demonstrated that the adsorbed NOF on the catalyst was completely degraded after 2h irradiation. According to the intermediates identified by HPLC/MS/MS, three possible degradation pathways were proposed to include addition of hydroxyl radical to quinolone ring, elimination of piperazynilic ring in fluoroquinolone molecules, and replacement of F atoms on the aromatic ring by hydroxyl radicals.

Liposome-Templated Hydrogel Nanoparticles as Vehicles for Enzyme-Based Therapies

Several diseases are related to the lack or to the defective activity of a particular enzyme; therefore, these proteins potentially represent a very interesting class of therapeutics. However, their application is hampered by their rapid degradation and immunogenic side effects. Most attempts to increase the bioavailability of therapeutic enzymes are based on formulations in which the protein is entrapped within a scaffold structure but needs to be released to exert its activity. In this work, an alternative method will be described, designed to keep the enzyme in its active form inside a nanoparticle (NP) without the need to release it, thus maintaining the protective action of the nanoscaffold during the entire period of administration. In this approach, liposomes were used as nanotemplates for the synthesis of polyacrylamide hydrogel NPs under nondenaturing conditions, optimizing the polymer properties to obtain a mesh size small enough to limit the enzyme release while allowing the free diffusion of its substrates and products. The enzyme Cu, Zn-superoxide dismutase was chosen as a test case for this study, but our results indicate that the approach is generalizable to other enzymes. Biocompatible, size-tunable nanoparticles have been obtained, with a good encapsulation efficiency (37%), in which the enzyme maintains its activity. This system represents a promising tool for enzyme-based therapy, which would protect the protein from antibodies and degradation while allowing it to exert its catalytic activity.

Porosity and dielectric properties as tools to predict drug release trends from hydrogels

Conventional studies on hydrogel properties such as viscosity, pH and swelling provide information without treating the components of hydrogel, viz., water and polymer individually. Water and hydrophilic polymers need to be studied individually to understand their relationship with each other to relate their influence on drug release. In this context, we have assigned the combination of porosity and dielectric properties as tools to explore the hydrogels. Porosity and dielectric properties have been analyzed using thermoporometry and alternative current impedance measurements, respectively. A well-known hydrogel genipin cross linked gelatin-chitosan (GC) composite, with catechin as model drug has been studied. The increasing concentration of chitosan in the hydrogel composites led to increase in bound water content and incorporation of charge entrapping moieties. Controlled and medium drug release are observed for GC1 whereas the native hydrogels and composites with lower ratio of chitosan yield immediate release and composites with higher ratio effects in slow release for limited duration (9 hours) of drug delivery process. This trend of drug release is in accordance with the results obtained from porosity and dielectric properties where reduction in pore radii to lower range and increase in relaxation time of polymeric components were observed at higher concentration of chitosan. Thus, these properties can be judiciously used for predicting drug release and designing biomaterials according to it.

Multi-responsive protein nanocarriers from an anionic dynamic covalent copolymer

PIC micelles were formed through electrostatic interactions between the anionic dynamer and lysozyme, and the micelles possessed pH-, salt-, and enzyme-responsive features.

Thiol-ene clickable hyaluronans: from macro-to nanogels

The fabrication of hyaluronic acid (HA) nanogels using a thiol-ene reaction has been demonstrated. HA was modified with pentenoate groups and then cross-linked with poly(ethylene glycol)-bis(thiol) by exposure to UV light. The cross-linking density and thereby the rigidity of the obtained gels were precisely controlled by the degree of substitution of pentenoate-modified HA. Their swelling properties also depended on cross-linking density. To produce hydrogels at the nanoscale, hyaluronic acid precursors were solely confined inside liposomes before cross-linking and purified after cross-linking. The size of the resulting nanogels followed their swelling properties and was also affected by their cross-linking density. Such bionanogels with tunable mechanical and swelling properties have potential in drug delivery.

Merging the best of both worlds: hybrid lipid-enveloped matrix nanocomposites in drug delivery

The advent of nanotechnology has revolutionized drug delivery in terms of improving drug efficacy and safety. Both polymer-based and lipid-based drug-loaded nanocarriers have demonstrated clinical benefit to date. However, to address the multifaceted drug delivery challenges ahead and further expand the spectrum of therapeutic applications, hybrid lipid-polymer nanocomposites have been designed to merge the beneficial features of both polymeric drug delivery systems and liposomes in a single nanocarrier. This review focuses on different classes of nanohybrids characterized by a drug-loaded polymeric matrix core enclosed in a lipid shell. Various nanoengineering approaches to obtain lipid-polymer nanocomposites with a core-shell nanoarchitecture will be discussed as well as their predominant applications in drug delivery.

Active drug encapsulation and release kinetics from hydrogel-in-liposome nanoparticles

Herein, we demonstrate for the first time the use of hydrogel-in-liposome nanoparticles (lipogels) as a promising drug delivery vehicle for the active encapsulation of the anticancer drug 17-DMAPG, a geldanamycin (GA) derivative. This model drug was chosen due to its improved aqueous solubility (4.6 mg/ml) compared to the parent GA (<0.01 mg/ml), and presence of a tertiary amine which readily protonates at low pH. For the design of lipogels, a PAA hydrogel core was formed inside liposomes through UV-initiated DEAP activation and polymerization of AA and BA. We have demonstrated here that electrostatic interactions between drug and gel are critical for active encapsulation and sustained release of 17-DMAPG. We found that optimal loading conditions could be obtained (88% loading efficiency) through control of pH, temperature and incubation time. Dramatic sustained drug release from lipogels was achieved independent of the external solution pH (ca. 54 h to 50% drug release) and confirmed that the lipid bilayer was intact in the presence of the gel core. In vitro cell culture studies revealed that at the highest concentration tested, which corresponded to approximately 0.4 mg/ml of material, lipogels did not exert cytotoxicity to cells.

Cellular Uptake and Intracellular Cargo Release From Dextran Based Nanogel Drug Carriers

Nanogels (NG) hold great promise as a drug delivery platform. In this work, we examine the potential of lysozyme-dextran nanogels (LDNG) as drug carriers in vitro using two cell lines: a model target tissue, human umbilical cord vein endothelial cells (HUVEC) and a model of the mononuclear phagocyte system (phorbol 12-myristate 13-acetate (PMA)-stimulated THP-1 cells). The LDNG (∼100 nm) were prepared with rhodamine-label dextran (LRDNG) via Maillard reaction followed by heat-gelation reaction and were loaded with a fluorescent probe, 5-hexadecanoylaminofluorescein (HAF), as a mock drug. Epifluorescence microscopy confirmed rapid uptake of LRDNG by HUVEC. Although LysoTracker Green staining indicated a lysosomal fate for LRDNG, the mock drug cargo (HAF) diffused extensively inside the cell within 15 min. Flow cytometry and confocal microscopy indicated slow uptake of LRDNG in PMA-stimulated THP-1 cells, with only 41% of cells containing LRDNG after 24 h exposure. Finally, 24 h exposure to LRDNG did not affect the viability of either cell type at the dose studied (20 μg/ml). At a higher dose (200 μg/ml), LRDNG resulted in a marked loss of viability of HUVEC and THP-1, measuring 30% and 38%, respectively. Collectively, our results demonstrate the great potential of LRDNG as a drug delivery platform, combining simple production, rapid uptake and cargo release in target cells with "stealth" properties and low cytotoxicity.

In situ forming reduction-sensitive degradable nanogels for facile loading and triggered intracellular release of proteins

In situ forming reduction-sensitive degradable nanogels were designed and developed based on poly(ethylene glycol)-b-poly(2-(hydroxyethyl) methacrylate-co-acryloyl carbonate) (PEG-P(HEMA-co-AC)) block copolymers for efficient loading as well as triggered intracellular release of proteins. PEG-P(HEMA-co-AC) copolymers were prepared with controlled Mn of 9.1, 9.5, and 9.9 kg/mol and varying numbers of AC units per molecule of 7, 9 and 11, respectively (denoted as copolymer 1, 2, and 3) by reversible addition-fragmentation chain transfer copolymerization. These copolymers were freely soluble in phosphate buffer but formed disulfide-cross-linked nanogels with defined sizes ranging from 72.5 to 124.1 nm in the presence of cystamine via ring-opening reaction with cyclic carbonate groups. The sizes of nanogels decreased with increasing AC units as a result of increased cross-linking density. Dynamic light scattering studies showed that these nanogels though stable at physiological conditions were rapidly dissociated in response to 10 mM dithiothreitol (DTT). Interestingly, FITC-labeled cytochrome C (FITC-CC) could be readily loaded into nanogels with remarkable loading efficiencies (up to 98.2%) and loading contents (up to 48.2 wt.%). The in vitro release studies showed that release of FITC-CC was minimal under physiological conditions but significantly enhanced under reductive conditions in the presence of 10 mM DTT with about 96.8% of FITC-CC released in 22 h from nanogel 1. In contrast, protein release from 1,4-butanediamine cross-linked nanogels (reduction-insensitive control) remained low under otherwise the same conditions. MTT assays showed that these nanogels were nontoxic to HeLa cells up to a tested concentration of 2 mg/mL. Confocal microscopy results showed that nanogel 1 delivered and released FITC-CC into the perinuclei region of HeLa cells following 8 h incubation. CC-loaded reductively degradable nanogels demonstrated apparently better apoptotic activity than free CC as well as reduction-insensitive controls. These in situ forming, surfactant and oil-free, and reduction-sensitive degradable nanogels are highly promising for targeted protein therapy.

Combination delivery of TGF-β inhibitor and IL-2 by nanoscale liposomal polymeric gels enhances tumour immunotherapy

The tumour microenvironment thwarts conventional immunotherapy through multiple immunologic mechanisms, such as the secretion of the transforming growth factor-β (TGF-β), which stunts local tumour immune responses. Therefore, high doses of interleukin-2 (IL-2), a conventional cytokine for metastatic melanoma, induces only limited responses. To overcome the immunoinhibitory nature of the tumour microenvironment, we developed nanoscale liposomal polymeric gels (nanolipogels; nLGs) of drug-complexed cyclodextrins and cytokine-encapsulating biodegradable polymers that can deliver small hydrophobic molecular inhibitors and water-soluble protein cytokines in a sustained fashion to the tumour microenvironment. nLGs releasing TGF-β inhibitor and IL-2 significantly delayed tumour growth, increased survival of tumour-bearing mice, and increased the activity of natural killer cells and of intratumoral-activated CD8(+) T-cell infiltration. We demonstrate that the efficacy of nLGs in tumour immunotherapy results from a crucial mechanism involving activation of both innate and adaptive immune responses.

Bimolecular integrin-ligand interactions quantified using peptide-functionalized dextran-coated microparticles

Integrins play a key role in cell-cell and cell-matrix interactions. Artificial surfaces grafted with integrin ligands, mimicking natural interfaces, have been used to study integrin-mediated cell adhesion. Here we report the use of a new chemical engineering technology in combination with single-molecule nanomechanical measurements to quantify peptide binding to integrins. We prepared latex beads with covalently-attached dextran. The beads were then functionalized with the bioactive peptides, cyclic RGDFK (cRGD) and the fibrinogen γC-dodecapeptide (H12), corresponding to the active sites for fibrinogen binding to the platelet integrin αIIbβ3. Using optical tweezers-based force spectroscopy to measure non-specific protein-protein interactions, we found the dextran-coated beads nonreactive towards fibrinogen, thus providing an inert platform for biospecific modifications. Using periodate oxidation followed by reductive amination, we functionalized the bead-attached dextran with either cRGD or H12 and used the peptide-grafted beads to measure single-molecule interactions with the purified αIIbβ3. Bimolecular force spectroscopy revealed that the peptide-functionalized beads were highly and specifically reactive with the immobilized αIIbβ3. Further, the cRGD- and H12-functionalized beads displayed a remarkable interaction profile with a bimodal force distribution up to 90 pN. The cRGD-αIIbβ3 interactions had greater binding strength than that of H12-αIIbβ3, indicating that they are more stable and resistant mechanically, consistent with the platelet reactivity of RGD-containing ligands. Thus, the results reported here describe the mechanistic characteristics of αIIbβ3-ligand interactions, confirming the utility of peptide-functionalized latex beads for the quantitative analysis of molecular recognition.

Chitosan nanogels by template chemical cross-linking in polyion complex micelle nanoreactors

Chitosan covalent nanogels cross-linked with genipin were prepared by template chemical cross-linking of chitosan in polyion complex micelle (PIC) nanoreactors. By using this method, we were able to prepare chitosan nanogels using only biocompatible materials without organic solvents. PIC were prepared by interaction between chitosan (X(n) = 23, 44, and 130) and block copolymer poly(ethylene oxide)-block-poly[sodium 2-(acrylamido)-2-methylpropanesulfonate] (PEO-b-PAMPS) synthesized by single-electron transfer-living radical polymerization (SET-LRP). PIC with small size (diameter about 50 nm) and low polydispersity were obtained up to 5 mg/mL. After cross-linking of chitosan with genipin, the nanoreactors were dissociated by adding NaCl. The dissociation of the nanoreactors and the formation of the nanogels were confirmed by (1)H NMR, DLS, and TEM. The size of the smallest nanogels was about 50 nm in the swollen state and 20 nm in the dry state. The amount of genipin used during reticulation was an important parameter to modulate the size of the nanogels in solution.

Characterizing proton relaxation times for metallic and magnetic layer-by-layer-coated, DNA-templated nanoparticle chains

Metallic and superparamagnetic DNA-templated nanoparticle (NP) chains are examined as potential imaging agents. Proton relaxation times (T(1) and T(2)) are measured for DNA nanostructures using nuclear magnetic resonance (NMR) spectroscopy. The layer-by-layer (LBL) method was used to encapsulate the DNA-templated NP chains and demonstrated a change in proton relaxation times. Results from this study suggest that LBL-coated, DNA-templated nanostructures can serve as effective imaging agents for magnetic resonance imaging (MRI) applications.

Hydrophobically modified biodegradable poly(ethylene glycol) copolymers that form temperature-responsive Nanogels

Biodegradable copolymers consisting of a hydrophilic poly[l-aspartic acid-alt-poly(ethylene glycol)] (poly(l-Asp-alt-PEG)) backbone and hydrophobic capryl units as side chains were synthesized. The amphiphilic copolymer was found to form nanosized hydrogel particles (nanogels) of approximately 15 nm in size by self-assembly at 20 degrees C in aqueous media, and the nanogel solutions displayed phase-transition in response to temperature. The transition of the nanogel solution was reversible and tunable in the range from 19 to 55 degrees C by variation of the amounts of capryl units introduced and the solution concentration. The nanogels were gradually degraded within days in a phosphate buffer solution (PBS) at 37 degrees C. Temperature-responsive biodegradable nanogel systems consisting of biocompatible PEG may have potential utility for high biocompatibility temperature-responsive nanodevices such as microreactor systems, molecular-chaperones, and drug delivery vehicles.

Degradable nanogels as a nanoreactor for growing silica colloids

Degradable nanogels with cleavable disulfide bonds were designed and used as a catalytic template, providing an alkali microenvironment. Well-defined hybrid silica colloids could be obtained by hydrolyzing tetraethyl orthosilicate (TEOS) in the nanogels. The size of silica colloids was found to be dependent on the size of the nanogels. After the removal of nanogels through reduction with 1,4-dithiothreitol (DTT), mesoporous silica colloids with a rough surface were obtained. The mesoporous structure of the colloids after reduction was characterized by transmission electron microscopy (TEM), surface area analysis, and X-ray diffraction (XRD). This work also provides an effective route for the preparation of mesoporous silica nanostructures, which may find wide applications as catalyst templates and drug carriers.

Biodegradable nanogels prepared by self-assembly of poly(L-lactide)-grafted dextran: entrapment and release of proteins

We showed previously that poly(L-lactide)-grafted dextran could form biodegradable nanogels in water. In this paper, various properties of Dex-g-PLLA nanogels were compared with Dex-Chol (dextran-cholesterol conjugate) nanogels to investigate the effects of hydrophobic units. Dex-g-PLLA nanogels exhibited significantly lower CAC and higher colloidal stability, indicating a strong tendency to form nanogels. We prepared lysozyme-loaded Dex-g-PLLA nanogels, and they exhibited a sustained release of lysozyme for 1 week without denaturation in PBS at 37 degrees C. The Dex-g-PLLA nanogels therefore have great potential as a delivery vehicle for therapeutic protein.

Thermosensitive P(NIPAAm-co-PAAc-co-HEMA) nanogels conjugated with transferrin for tumor cell targeting delivery

Multifunctional and thermosensitive poly(N-isopropylacrylamide-co-propyl acrylic acid-co-hydroxyethyl methacrylate) (P(NIPAAm-co-PAAc-co-HEMA)) nanogels were prepared by miniemulsion polymerization. The mean sizes of the nanogels measured by dynamic light scattering (DLS) varied from 120 to 400 nm with an increase in temperature. Transmission electron microscopy (TEM) showed that the nanogels displayed well-dispersed spherical morphology. The nanogels were conjugated by human transferrin (Tf) and the coupling of transferrin molecules with nanogels was verified by UV-vis spectroscopy. The cytotoxicity study indicated that the nanogels did not exhibit apparent cytotoxicity. Fluorescence spectroscopy analysis as well as confocal laser scanning microscopy (CLSM) was used to confirm that the Tf-conjugated nanogels could specifically bind to A549 tumor cells. In addition, the Tf-conjugated nanogels loaded with Doxorubicin (Dox) could efficiently release the drug inside the cell, suggesting that the Tf-conjugated nanogels are useful drug carriers for tumor cell targeting.

Preparation of chitosan nanoparticles using methacrylic acid

In this work the preparation of chitosan nanoparticle was investigated using methacrylic acid in different conditions and studied by particle size analyzer, zeta-potential, Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) and transmission electron microscopy (TEM). The particle size was dependent on the chitosan concentration used during the preparation method. Nanoparticles with sizes as small as 60 nm were achieved, that can be extremely important for several applications. The nanoparticles solution was also pH-sensitive, due to swelling and aggregation of the nanoparticles. The nanoparticles obtained presented a very homogeneous morphology showing a quite uniform particles size distribution and a rather spherical shape.