Highly photostable nanogels for fluorescence-based theranostics.
ABSTRACT: A novel photo-crosslinkable nanogel is prepared from a biodegradable polymer template with intrinsic photoluminescence and high photostability. The fluorescent nanogels display excellent biodegradability and cytocompatibility owed to the facile synthesis scheme involving a solvent-and surfactant-free one-pot reaction, derived entirely from biocompatible monomers citric acid, maleic acid, L-cysteine, and poly(ethylene glycol). The resultant nanogels are less than 200 nm in diameter with a narrow size distribution and monodispersity, and demonstrate long-term structural stability in biological buffer for two weeks. To gauge potential in theranostic applications, the fluorescent nanogels were surface functionalized with biologically active RGD peptides and encapsulated with active anti-cancer drug Doxorubicin, resulting in a pH-responsive controlled drug release in acidic pH resembling tumor environments. The strong fluorescence of the nanogels enabled tracking of targeted drug delivery, showing that drug-loaded nanogels homed into the cytoplasmic regions of prostate cancer cells to significantly induce cell death. These photo-crosslinkable and biodegradable nanogels pose as a strong candidate for theranostic medicine, demonstrating versatile functionalization, high stability in biological buffers, and capacity for real-time fluorescence-based monitoring of targeted drug delivery.
Project description:A method of introducing intrinsically photo luminescent properties to biodegradable polymer is introduced, exemplified by the synthesis of intrinsically photoluminescent polylactones that enable non-invasive monitoring and tracking of material degradation in vivo in realtime, as well as the formation of theranostic nanoparticles for cancer imaging and drug delivery.
Project description:Nanogels have been widely used in biomedical applications, such as carriers for hyperthermia cancer treatment, drug delivery, and imaging. Owing to the enhanced permeability and retention effect, nanogels have shown a great potential in cancer therapy. In this study, sodium copper chlorophyllin (SCC), a low cytotoxicity and biodegradable photothermal agent, was copolymerized with a nanogel of N-[3-(dimethylamino)propyl]methacrylamide. The nanogels could produce heat under exposure to a green laser with a 532 nm wavelength. The positively charged nature of the nanogels enhanced the endocytosis of the nanogels. The cell mortality was greatly enhanced with the treatment of the SCC-containing nanogels and green light illumination. Our results suggest the potential of SCC-containing nanogels in photothermal cancer therapy.
Project description:Nanogels, nanometer-sized hydrogel particles, have great potential as drug delivery carriers. To achieve effective drug delivery to the active sites in a cell, control of intracellular traffic is important. In this study, we prepared nanogels composed of dextran with oligolactide (OLA) chains attached via disulfide bonds (Dex-g-SS-OLA) that collapse under the reductive conditions of the cytosol to achieve efficient drug delivery. In addition, we introduced galactose (Gal) residues on the nanogels, to enhance cellular uptake by receptor-mediated endocytosis, and secondary oligo-amine (tetraethylenepentamine) groups, to aid in escape from endosomes via proton sponge effects. The obtained Dex-g-SS-OLA with attached Gal residues and tetraethylenepentamine (EI?) groups, EI?/Gal-Dex-g-SS-OLA, formed a nanogel with a hydrodynamic diameter of ca. 203 nm in phosphate-buffered solution. The collapse of the EI?/Gal-Dex-g-SS-OLA nanogels under reductive conditions was confirmed by a decrease in the hydrodynamic diameter in the presence of reductive agents. The specific uptake of the hydrogels into HepG2 cells and their intercellular behavior were investigated by flow cytometry and confocal laser scanning microscopy using fluorescence dye-labeled nanogels. Escape from the endosome and subsequent collapse in the cytosol of the EI?/Gal-Dex-g-SS-OLA were observed. These biodegradable nanogels that collapse under reductive conditions in the cytosol should have great potential as efficient drug carriers in, for example, cancer chemotherapy.
Project description:Although nanoparticle-based drug delivery formulations can improve the effectiveness and safety of certain anticancer drugs, many drugs, due to their chemical composition, are unsuitable for nanoparticle loading. Here, we describe a targeted nanogel drug delivery platform that can (i) encapsulate a wide range of drug chemotypes, including biological, small molecule, and cytotoxic agents; (ii) display targeting ligands and polymeric coatings on the surface; (iii) enhance drug retention within the nanogel core after photo-cross-linking; and (iv) retain therapeutic activity after lyophilization allowing for long-term storage. For therapeutic studies, we used integrin ?v?3-targeted lipid-coated nanogels with cross-linked human serum albumin in the core for carrying therapeutic cargoes. These particles exhibited potent activity in tumor cell viability assays with drugs of distinct chemotype, including paclitaxel, docetaxel, bortezomib, 17-AAG, sorafenib, sunitinib, bosutinib, and dasatinib. Treatment of orthotopic breast and pancreas tumors in mice with taxane-loaded nanogels produced a 15-fold improvement in antitumor activity relative to Abraxane by blocking both primary tumor growth and spontaneous metastasis. With a modifiable surface and core, the lipid-coated nanogel represents a platform technology that can be easily adapted for specific drug delivery applications to treat a wide range of malignant diseases.
Project description:The use of functional nanogels based on poly(N-isopropylacrylamide) for effectively scavenging compounds (here, the model drug bupivacaine) is demonstrated using an in vitro cell-based assay. Nanogels containing higher loadings of acidic functional groups or more core-localized functional group distributions bound more bupivacaine, while nanogel size had no significant effect on drug binding. Increasing the dose of nanogel applied also facilitated more bupivacaine binding for all nanogel compositions tested. Binding was driven predominantly by acid-base interactions between the nanogels (anionic) and bupivacaine (cationic) at physiological pH, although both non-specific absorption and hydrophobic partitioning also contributed to drug scavenging. Nanogels exhibited minimal cytotoxicity to multiple cell types and were well tolerated in vivo via peritoneal injections, although larger nanogels caused limited splenic toxicity at higher concentrations. The cell-based assay described herein is found to facilitate more robust drug uptake measurements for nanogels than conventional centrifugation-based assays, in which nanogels can be compressed (and thus drug released) during the measurement.
Project description:Therapeutics, proteins or drugs, can be encapsulated into multilayer systems prepared from chitosan (CS)/tripolyphosphat (TPP) nanogels and polyanions. Such multilayers can be built-up by Layer-by-Layer (LbL) deposition. For use as drug-releasing implant coating, these multilayers must meet high requirements in terms of stability. Therefore, photochemically crosslinkable chitosan arylazide (CS-Az) was synthesized and nanoparticles were generated by ionotropic gelation with TPP. The particles were characterized with regard to particle size and stability and were used to form the top-layer in multilayer films consisting of CS-TPP and three different polysaccharides as polyanions, namely alginate, chondroitin sulfate or hyaluronic acid, respectively. Subsequently, photo-crosslinking was performed by irradiation with UV light. The stability of these films was investigated under physiological conditions and the influence of the blocking layer on layer thickness was investigated by ellipsometry. Furthermore, the polyanion and the degree of acetylation (DA) of chitosan were identified as additional parameters that influence the film structure and stability. Multilayer systems blocked with the photo-crosslinked chitosan arylazide showed enhanced stability against degradation.
Project description:We describe the synthesis and characterization of degradable nanogels that display bulk erosion under physiologic conditions (pH = 7.4, 37 degrees C). Erodible poly(N-isopropylmethacrylamide) nanogels were synthesized by copolymerization with N,O-(dimethacryloyl) hydroxylamine, a cross-linker previously used in the preparation of nontoxic and biodegradable bulk hydrogels. To monitor particle degradation, we employed multiangle light scattering and differential refractometry detection following asymmetrical flow field-flow fractionation. This approach allowed the detection of changes in nanogel molar mass and topology as a function of both temperature and pH. Particle erosion was evident from both an increase in nanogel swelling and a decrease in scattering intensity as a function of time. Following these analyses, the samples were recovered for subsequent characterization by direct particle tracking, which yields hydrodynamic size measurements and enables number density determination. Additionally, we confirmed the conservation of nanogel stimuli-responsivity through turbidity measurements. Thus, we have demonstrated the synthesis of degradable nanogels that erode under conditions and on time scales that are relevant for many drug delivery applications. The combined separation and light scattering detection method is demonstrated to be a versatile means to monitor erosion and should also find applicability in the characterization of other degradable particle constructs.
Project description:ErbB2-driven breast cancers constitute 20-25% of the cases diagnosed within the USA. The humanized anti-ErbB2 monoclonal antibody, Trastuzumab (Herceptin™; Genentech), with chemotherapy is the current standard of treatment. Novel agents and strategies continue to be explored, given the challenges posed by Trastuzumab-resistance development in most patients. The HSP90 inhibitor, 17-allylaminodemethoxygeldanamycin (17-AAG), which induces ErbB2 degradation and attenuates downstream oncogenic signaling, is one such agent that showed significant promise in early phase I and II clinical trials. Its low water solubility, potential toxicities and undesirable side effects observed in patients, partly due to the Cremophor-based formulation, have been discouraging factors in the advancement of this promising drug into clinical use. Encapsulation of 17-AAG into polymeric nanoparticle formulations, particularly in synergistic combination with conventional chemotherapeutics, represents an alternative approach to overcome these problems. Herein, we report an efficient co-encapsulation of 17-AAG and doxorubicin, a clinically well-established and effective modality in breast cancer treatment, into biodegradable and biocompatible polypeptide-based nanogels. Dual drug-loaded nanogels displayed potent cytotoxicity in a breast cancer cell panel and exerted selective synergistic anticancer activity against ErbB2-overexpressing breast cancer cell lines. Analysis of ErbB2 degradation confirmed efficient 17-AAG release from nanogels with activity comparable to free 17-AAG. Furthermore, nanogels containing both 17-AAG and doxorubicin exhibited superior antitumor efficacy in vivo in an ErbB2-driven xenograft model compared to the combination of free drugs. These studies demonstrate that polypeptide-based nanogels can serve as novel nanocarriers for encapsulating 17-AAG along with other chemotherapeutics, providing an opportunity to overcome solubility issues and thereby exploit its full potential as an anti-cancer agent.
Project description:Significant efforts have been expended to mitigate plasticizer migration from crosslinked methacrylic and poly(vinyl chloride) polymer networks by synthesizing reactive plasticizers that can blend homogenously within the networks to reduce polymer property change, acute toxicity and downstream environmental effects of plasticizer migration with limited and varying amount of success. We hypothesized that appropriate thiol-functionalized nanogels synthesized using the same monomers as the parent network to generate highly compact, crosslinked structures will form thermally stable, homogenous networks and perform as optimal reactive plasticizers. Nanogels were synthesized via a thiol-Michael addition solution polymerization and incorporated at different mass ratios within a polyethylene glycol 400 urethane dimethacrylic monomer to form photo-crosslinked networks. While maintaining the inherent hydrolytic stability, thermal stability and biocompatibility of the parent matrix at ~99% acrylic group conversion, the PEG400 urethane dimethacrylic -nanogel networks retained optical clarity with >90% visible light transmission at 20wt% nanogel concentration within the matrix. The addition of the nanogels also enhanced the elongation of the parent matrix by up to 320%, while a 37°C reduction in glass transition temperature (?Tg) and ?50% reduction in modulus was observed. A 52% reduction in the shrinkage stress of the material was also noted. The results indicate that the application of thiol-functionalized nanogels as plasticizers to alter the bulk properties of the parent matrix while mitigating plasticizer migration by covalently crosslinking the nanogels within the polymer matrix provides a simple yet efficient technique to generate network-specific plasticizers with the ability to alter targeted properties within polymers.
Project description:Nanogels are comprised of swollen polymer networks and nearly 95% water and can entrap diverse chemical and biological agents for cancer therapy with very high loading capacities. Here we use diblock copolymer poly(ethylene oxide)-b-poly(methacrylic acid) (PEO-b-PMA) to form nanogels with the desired degree of cross-linking. The nanogels are further conjugated to folic acid (FA) and loaded with different types of drugs (cisplatin, doxorubicin). For the first time we demonstrate a tumor-specific delivery and superior anti-tumor effect in vivo of an anti-cancer drug using these polyelectrolyte nanogels decorated with folate-targeting groups. This reinforces the use of nanogels for the therapy of ovarian and other cancers, where folate receptor (FR) is overexpressed.