Nanogels from metal-chelating crosslinkers as versatile platforms applied to copper-64 PET imaging of tumors and metastases

Exploring the Potential of Nanogels: From Drug Carriers to Radiopharmaceutical Agents

Nanogels open up access to a wide range of applications and offer among others hopeful approaches for use in the field of biomedicine. This review provides a brief overview of current developments of nanogels in general, particularly in the fields of drug delivery, therapeutic applications, tissue engineering, and sensor systems. Specifically, cyclodextrin (CD)-based nanogels are important because they have exceptional complexation properties and are highly biocompatible. Nanogels as a whole and CD-based nanogels in particular can be customized in a wide range of sizes and equipped with a desired surface charge as well as containing additional molecules inside and outside, such as dyes, solubility-mediating groups or even biological vector molecules for pharmaceutical targeting. Currently, biological investigations are mainly carried out in vitro, but more and more in vivo applications are gaining importance. Modern molecular imaging methods are increasingly being used for the latter. Due to an extremely high sensitivity and the possibility of obtaining quantitative data on pharmacokinetic and pharmacodynamic properties, nuclear methods such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) using radiolabeled compounds are particularly suitable here. The use of radiolabeled nanogels for imaging, but also for therapy, is being discussed.

Multi-functional auto-fluorescent nanogels for theranostics

Here in the present article, the state of art for nanotechnology-enabled nanogel theranostics and the upcoming concepts in nanogel-based therapeutics are summarized. The benefits, innovation, and prospects of nanogel technology are also briefly presented.

Green Hydrogel Synthesis: Emphasis on Proteomics and Polymer Particle-Protein Interaction

The field of drug discovery has seen significant progress in recent years. These advances drive the development of new technologies for testing compound's effectiveness, as well as their adverse effects on organs and tissues. As an auxiliary tool for drug discovery, smart biomaterials and biopolymers produced from biodegradable monomers allow the manufacture of multifunctional polymeric devices capable of acting as biosensors, of incorporating bioactives and biomolecules, or even mimicking organs and tissues through self-association and organization between cells and biopolymers. This review discusses in detail the use of natural monomers for the synthesis of hydrogels via green routes. The physical, chemical and morphological characteristics of these polymers are described, in addition to emphasizing polymer-particle-protein interactions and their application in proteomics studies. To highlight the diversity of green synthesis methodologies and the properties of the final hydrogels, applications in the areas of drug delivery, antibody interactions, cancer therapy, imaging and biomarker analysis are also discussed, as well as the use of hydrogels for the discovery of antimicrobial and antiviral peptides with therapeutic potential.

Physically stimulus-responsive nanoparticles for therapy and diagnosis

Nanoparticles offer numerous advantages in various fields of science, particularly in medicine. Over recent years, the use of nanoparticles in disease diagnosis and treatments has increased dramatically by the development of stimuli-responsive nano-systems, which can respond to internal or external stimuli. In the last 10 years, many preclinical studies were performed on physically triggered nano-systems to develop and optimize stable, precise, and selective therapeutic or diagnostic agents. In this regard, the systems must meet the requirements of efficacy, toxicity, pharmacokinetics, and safety before clinical investigation. Several undesired aspects need to be addressed to successfully translate these physical stimuli-responsive nano-systems, as biomaterials, into clinical practice. These have to be commonly taken into account when developing physically triggered systems; thus, also applicable for nano-systems based on nanomaterials. This review focuses on physically triggered nano-systems (PTNSs), with diagnostic or therapeutic and theranostic applications. Several types of physically triggered nano-systems based on polymeric micelles and hydrogels, mesoporous silica, and magnets are reviewed and discussed in various aspects.

Bioengineered nanogels for cancer immunotherapy

Recent years have witnessed increasingly rapid advances in nanocarrier-based biomedicine aimed at improving treatment paradigms for cancer. Nanogels serve as multipurpose and constructed vectors formed via intramolecular cross-linking to generate drug delivery systems, which is attributed predominantly to their satisfactory biocompatibility, bio-responsiveness, high stability, and low toxicity. Recently, immunotherapy has experienced unprecedented growth and has become the preferred strategy for cancer treatment, and mainly involves the mobilisation of the immune system and an enhanced anti-tumour immunity of the tumour microenvironment. Despite the inspiring success, immunotherapeutic strategies are limited due to the low response rates and immune-related adverse events. Like other nanomedicines, nanogels are comparably limited by lower focal enrichment rates upon introduction into the organism via injection. Because nanogels are three-dimensional cross-linked aqueous materials that exhibit similar properties to natural tissues and are structurally stable, they can comfortably cope with shear forces and serum proteins in the bloodstream, and the longer circulation life increases the chance of nanogel accumulation in the tumour, conferring deep tumour penetration. The large specific surface area can reduce or eliminate off-target effects by introducing stimuli-responsive functional groups, allowing multiple physical and chemical modifications for specific purposes to improve targeting to specific immune cell subpopulations or immune organs, increasing the bioavailability of the drug, and conferring a low immune-related adverse events on nanogel therapies. The slow release upon reaching the tumour site facilitates long-term awakening of the host's immune system, ultimately achieving enhanced therapeutic effects. As an effective candidate for cancer immunotherapy, nanogel-based immunotherapy has been widely used. In this review, we mainly summarize the recent advances of nanogel-based immunotherapy to deliver immunomodulatory small molecule drugs, antibodies, genes and cytokines, to target antigen presenting cells, form cancer vaccines, and enable chimeric antigen receptor (CAR)-T cell therapy. Future challenges as well as expected and feasible prospects for clinical treatment are also highlighted.

Radiolabeled Nanocarriers as Theranostics-Advancement from Peptides to Nanocarriers

Endogenous targeted radiotherapy is emerging as an integral modality to treat a variety of cancer entities. Nevertheless, despite the positive clinical outcome of the treatment using radiolabeled peptides, small molecules, antibodies, and nanobodies, a high degree of hepatotoxicity and nephrotoxicity still persist. This limits the amount of dose that can be injected. In an attempt to mitigate these side effects, the use of nanocarriers such as nanoparticles (NPs), dendrimers, micelles, liposomes, and nanogels (NGs) is currently being explored. Nanocarriers can prolong circulation time and tumor retention, maximize radiation dosage, and offer multifunctionality for different targeting strategies. In this review, the authors first provide a summary of radiation therapy and imaging and discuss the new radiotracers that are used preclinically and clinically. They then highlight and identify the advantages of radio-nanomedicine and its potential in overcoming the limitations of endogenous radiotherapy. Finally, the review points to the ongoing efforts to maximize the use of radio-nanomedicine for efficient clinical translation.

Multiplexed Analysis of the Cellular Uptake of Polymeric Nanocarriers

Polymeric nanocarriers (PNCs) are versatile drug delivery vehicles capable of delivering a variety of therapeutics. Quantitatively monitoring their uptake in biological systems is essential for realizing their potential as next-generation delivery systems; however, existing quantification strategies are limited due to the challenges of detecting polymeric materials in complex biological samples. Here, we describe a metal-coded mass tagging approach that enables the multiplexed quantification of the PNC uptake in cells using mass spectrometry (MS). In this approach, PNCs are conjugated with ligands that bind strongly to lanthanide ions, allowing the PNCs to be sensitively quantitated by inductively coupled plasma-MS. The metal-coded tags have little effect on the properties or toxicity of the PNCs, making them biocompatible. We demonstrate that the conjugation of different metals to the PNCs enables the multiplexed analysis of cellular uptake of multiple distinct PNCs at the same time. This multiplexing capability should improve the design and optimization of PNCs by minimizing biological variability and reducing analysis time, effort, and cost.

Tetraphenylethylene-conjugated polycation covered iron oxide nanoparticles for magnetic resonance/optical dual-mode imaging

Magnetic resonance (MR)/optical dual-mode imaging with high sensitivity and high tissue resolution have attracted many attentions in biomedical applications. To avert aggregation-caused quenching of conventional fluorescence chromophores, an aggregation-induced emission molecule tetraphenylethylene (TPE)-conjugated amphiphilic polyethylenimine (PEI) covered superparamagnetic iron oxide (Alkyl-PEI-LAC-TPE/SPIO nanocomposites) was prepared as an MR/optical dual-mode probe. Alkyl-PEI-LAC-TPE/SPIO nanocomposites exhibited good fluorescence property and presented higher T ₂ relaxivity (352 Fe mM^-1s^-1) than a commercial contrast agent Feridex (120 Fe mM^-1s^-1) at 1.5 T. The alkylation degree of Alkyl-PEI-LAC-TPE effects the restriction of intramolecular rotation process of TPE. Reducing alkane chain grafting ratio aggravated the stack of TPE, increasing the fluorescence lifetime of Alkyl-PEI-LAC-TPE/SPIO nanocomposites. Alkyl-PEI-LAC-TPE/SPIO nanocomposites can effectively labelled HeLa cells and resulted in high fluorescence intensity and excellent MR imaging sensitivity. As an MR/optical imaging probe, Alkyl-PEI-LAC-TPE/SPIO nanocomposites may be used in biomedical imaging for certain applications.

Polyglutamic acid-based crosslinked doxorubicin nanogels as an anti-metastatic treatment for triple negative breast cancer

Treatment of triple negative breast cancer (TNBC)-associated metastasis represents an unmet clinical need, and we lack effective therapeutics for a disease that exhibits high relapse rates and associates with poor patient outcomes. Advanced nanosized drug delivery systems may enhance the efficacy of first-line chemotherapeutics by altering drug pharmacokinetics and enhancing tumor/metastasis targeting to significantly improve efficacy and safety. Herein, we propose the application of injectable poly-amino acid-based nanogels (NGs) as a versatile hydrophilic drug delivery platform for the treatment of TNBC lung metastasis. We prepared biocompatible and biodegradable cross-linked NGs from polyglutamic acid (PGA) loaded with the chemotherapeutic agent doxorubicin (DOX). Our optimized synthetic procedures generated NGs of ~100 nm in size and 25 wt% drug loading content that became rapidly internalized in TNBC cell lines and displayed IC50 values comparable to the free form of DOX. Importantly, PGA-DOX NGs significantly inhibited lung metastases and almost completely suppressed lymph node metastases in a spontaneously metastatic orthotopic mouse TNBC model. Overall, our newly developed PGA-DOX NGs represent a potentially effective therapeutic strategy for the treatment of TNBC metastases.

Recent advances in theranostic polymeric nanoparticles for cancer treatment: A review

Nanotheranostics is fast-growing pharmaceutical technology for simultaneously monitoring drug release and its distribution, and to evaluate the real time therapeutic efficacy through a single nanoscale for treatment and diagnosis of deadly disease such as cancers. In recent two decades, biodegradable polymers have been discovered as important carriers to accommodate therapeutic and medical imaging agents to facilitate construction of multi-modal formulations. In this review, we summarize various multifunctional polymeric nano-sized formulations such as polymer-based super paramagnetic nanoparticles, ultrasound-triggered polymeric nanoparticles, polymeric nanoparticles bearing radionuclides, and fluorescent polymeric nano-sized formulations for purpose of theranostics. The use of such multi-modal nano-sized formulations for near future clinical trials can assist clinicians to predict therapeutic properties (for instance, depending upon the quantity of drug accumulated at the cancerous site) and observed the progress of tumor growth in patients, thus improving tailored medicines.

Hydrogel-Based Controlled Drug Delivery for Cancer Treatment: A Review

As an emerging drug carrier, hydrogels have been widely used for tumor drug delivery. A hydrogel drug carrier can cause less severe side effects than systemic chemotherapy and can achieve sustained delivery of a drug at tumor sites. In addition, hydrogels have excellent biocompatibility and biodegradability and lower toxicity than nanoparticle carriers. Smart hydrogels can respond to stimuli in the environment (e.g., heat, pH, light, and ultrasound), enabling in situ gelation and controlled drug release, which greatly enhance the convenience and efficiency of drug delivery. Here, we summarize the different sizes of hydrogels used for cancer treatment and their related delivery routes, discuss the design strategies for stimuli-responsive hydrogels, and review the research concerning smart hydrogels reported in the past few years.

Synthesis of a novel 3,5-diacrylamidobenzoic acid based hyper-cross-linked resin for the efficient adsorption of Congo Red and Rhodamine B

A novel hyper cross-linked, 3,5-diacrylamidobenzoic acid based resin (APEADA) has been synthesized for the highly efficient removal of Congo red (CR) and Rhodamine B (RhB) from aqueous solution. The synthesized resin was extensively characterized by FT-IR, FESEM, PXRD, EDX, BET analysis, TGA and solid state ¹³C (CP-MAS) NMR. APEADA exhibits thermal stability (≈ 200 °C) and a considerable surface area (64.78 m² g^-1), as suggested by Thermogravimetric Analysis (TGA) and Brunauer-Emmett-Teller (BET) analysis, respectively. The experimental data of dyes adsorption onto resin was examined by a variety of isotherm models wherein Langmuir and Temkin models were found to be the best fit for explaining the adsorption of both RhB (R² = 0.9899) and CR (R² = 0.9919). The resin can efficiently remove CR (92.03%) at pH 8.14 and moderately adsorb RhB (45.3%) at pH 5.01 and exhibits maximum adsorption capacity (Q_max) for CR (280.0 mg g^-1) and RhB (23.28 mg g^-1) at 318.6 K. The thermodynamic analysis of the data revealed that the adsorption processes were exothermic and spontaneous. Moreover, APEADA showed efficient removal efficiency (80.13%) for dyes in simulated effluents which warrants its utility and effectiveness in industrial waste water treatment.

Covalently Crosslinked Nanogels: An NMR Study of the Effect of Monomer Reactivity on Composition and Structure

Covalently crosslinked nanogels are widely explored as drug delivery systems and sensors. Radical polymerization provides a simple, inexpensive, and broadly applicable approach for their preparation, although the random nature of the reaction requires careful study of the final chemical composition. We demonstrate how the different reactivities of the monomers influence the total degree of incorporation into the polymer matrix and the role played by the experimental parameters in maximizing polymerization efficiency. Nanogels based on N-isopropylacrylamide, N-n-propylacrylamide, and acrylamide crosslinked with N,N'-methylenebisacrylamide were included in this study, in combination with functional monomers N-acryloyl-l-proline, 2-acrylamido-2-methyl-1-propanesulfonic acid, and 4-vinyl-1H-imidazole. Total monomer concentration and initiator quantities are determining parameters for maximizing monomer conversions and chemical yields. The results show that the introduction of functional monomers, changes in the chemical structure of the polymerizable unit, and the addition of templating molecules can all have an effect on the polymerization kinetics. This can significantly impact the final composition of the matrices and their chemical structure, which in turn influence the morphology and properties of the nanogels.

Exploiting Nanomaterial-mediated Autophagy for Cancer Therapy

Autophagy is a conserved process that is critical for sequestering and degrading proteins, damaged or aged organelles, and for maintaining cellular homeostasis under stress conditions. Despite its dichotomous role in health and diseases, autophagy usually promotes growth and progression of advanced cancers. In this context, clinical trials using chloroquine and hydroxychloroquine as autophagy inhibitors have suggested that autophagy inhibition is a promising approach for treating advanced malignancies and/or overcoming drug resistance of small molecule therapeutics (i.e., chemotherapy and molecularly targeted therapy). Efficient delivery of autophagy inhibitors may further enhance the therapeutic effect, reduce systemic toxicity, and prevent drug resistance. As such, nanocarriers-based drug delivery systems have several distinct advantages over free autophagy inhibitors that include increased circulation of the drugs, reduced off-target systemic toxicity, increased drug delivery efficiency, and increased solubility and stability of the encapsulated drugs. With their versatile drug encapsulation and surface-functionalization capabilities, nanocarriers can be engineered to deliver autophagy inhibitors to tumor sites in a context-specific and/or tissue-specific manner. This review focuses on the role of nanomaterials utilizing autophagy inhibitors for cancer therapy, with a focus on their applications in different cancer types.

Functionalization of Gadolinium Chelates Silica Nanoparticle through Silane Chemistry for Simultaneous MRI/64Cu PET Imaging

Multimodal nanoprobes are highly demanded for biomedical imaging applications to enhance the reliability of the diagnostic results. Among different types of nano-objects, ultrasmall silica gadolinium nanoparticle (SiGdNP) appears as a safe, effective, and versatile platform for this purpose. In this study, a new method to functionalize SiGdNP based on silane chemistry has been reported. Two types of chelating silanes (APTES-DOTAGA and APTES-NODAGA) have been synthesized and grafted on SiGdNP by a simple one-step protocol. This functionalization strategy requires no other reactants or catalyzers and does not compromise the ultrasmall size of the particles. NODAGA-functionalized particle has been labeled with ⁶⁴Cu isotope and injected intravenously to mice bearing TS/A carcinoma tumor for biodistribution study to demonstrate its potential as a bimodal MRI/PET imaging agent. A fully integrated MRI/PET system was used to simultaneously monitor the distribution of the particle. The results showed that the functionalized particle maintained properties of a renal clearable NP which could rapidly escape through kidneys and had low retention in other organs, especially liver, even though its accumulation in the tumor was modest.

Responsive crosslinked polymer nanogels for imaging and therapeutics delivery

Nanogels are water-soluble crosslinked polymer networks with tremendous potential in targeted imaging and controlled drug and gene delivery.

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.

Facilitating the Clinical Integration of Nanomedicines: The Roles of Theoretical and Computational Scientists

Since the launch of multiple research initiatives on nanotechnology applied to medicine in the early 2000s, a plethora of nanomedicines have been developed that exhibit great therapeutic efficacy in preclinical models but yet minimal impact in daily clinical practice. The successful and complete clinical fruition of nanomedicines requires addressing three major technical challenges: improving loading efficacy and on-command release, modulating recognition and sequestration by immune cells, and maximizing accumulation at biological targets. In this Perspective, I describe how theoretical and computational models can help address each of these challenges. This armamentarium represents an ideal tool for maximizing the therapeutic efficacy of nanomedicines, thus facilitating their integration into daily clinical operations.

Immobilization of iron oxide nanoparticles within alginate nanogels for enhanced MR imaging applications

We report the design of iron oxide (Fe3O4) nanoparticle (NP)-immobilized alginate (AG) nanogels (NGs) as a novel contrast agent for enhanced magnetic resonance (MR) imaging applications. In this study, an aqueous solution of AG activated by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride was double emulsified to form NGs, followed by in situ cross-linking with polyethyleneimine (PEI)-coated Fe3O4 NPs (PEI-Fe3O4 NPs). The resultant Fe3O4 NP-immobilized AG NGs (AG/PEI-Fe3O4 NGs) were characterized via different techniques. Our results reveal that the hybrid NGs with a size of 186.1 ± 33.1 nm are water dispersible, colloidally stable, and cytocompatible in the given concentration range. Importantly, these NGs have a high r2 relaxivity (170.87 mM(-1) s(-1)) due to the high loading of Fe3O4 NPs within the NGs, and can be more significantly uptaken by cancer cells when compared with carboxylated Fe3O4 NPs. The formed AG/PEI-Fe3O4 NGs are able to be used as an effective contrast agent for the MR imaging of cancer cells in vitro and the xenografted tumor model in vivo after intravenous injection. The developed AG/PEI-Fe3O4 NGs may hold great promise for use as a novel contrast agent for the enhanced MR imaging of different biological systems.

Biodegradable Smart Nanogels: A New Platform for Targeting Drug Delivery and Biomedical Diagnostics

Nanogels (or nanohydrogels) have been extensively investigated as one of the most promising nanoparticulate biomedical platforms owing to their advantageous properties that combine the characteristics of hydrogel systems with nanoparticles. Among them, smart nanogels that have the ability to respond to external stimuli, such as pH, redox, temperature, enzymes, light, magnetic field and so forth, are most attractive in the area of drug delivery. Besides, numerous multifunctionalized nanogels with high sensitivity and specificity were designed for diagnostic applications. In this feature article, we have reviewed and discussed the recent progress of biodegradable nanogels as smart nanocarriers of anticancer drugs and biomedical diagnostic agents for cancer.

A pH-Responsive Host-guest Nanosystem Loading Succinobucol Suppresses Lung Metastasis of Breast Cancer

Cancer metastasis is the leading reason for the high mortality of breast cancer. Herein, we report on a pH-responsive host-guest nanosystem of succinobucol (PHN) with pH-stimuli controlled drug release behavior to improve the therapeutic efficacy on lung metastasis of breast cancer. PHN was composed of the host polymer of β-cyclodextrin linked with multiple arms of N,N-diisopropylethylenediamine (βCD-DPA), the guest polymer of adamantyl end-capped methoxy poly(ethylene glycol) (mPEG-Ad), and the active agent of succinobucol. PHN comprises nanometer-sized homogenous spherical particles, and exhibits specific and rapid drug release in response to the intracellular acidic pH-stimuli. Then, the anti-metastatic efficacy of PHN is measured in metastatic 4T1 breast cancer cells, which effectively confirms the superior inhibitory effects on cell migration and invasion activities, VCAM-1 expression and cell-cell binding of RAW 264.7 to 4T1 cells. Moreover, PHN can be specifically delivered to the sites of metastatic nodules in lungs, and result in an obviously improved therapeutic efficacy on lung metastasis of breast cancer. Thereby, the pH-responsive host-guest nanosystem can be a promising drug delivery platform for effective treatment of cancer metastasis.

Nanogels as imaging agents for modalities spanning the electromagnetic spectrum

In the past few decades, advances in imaging equipment and protocols have expanded the role of imaging in in vivo diagnosis and disease management, especially in cancer. Traditional imaging agents have rapid clearance and low specificity for disease detection. To improve accuracy in disease identification, localization and assessment, novel nanomaterials are frequently explored as imaging agents to achieve high detection specificity and sensitivity. A promising material for this purpose are hydrogel nanoparticles, whose high hydrophilicity, biocompatibility, and tunable size in the nanometer range make them ideal for imaging. These nanogels (10 to 200 nm) can circumvent uptake by the reticuloendothelial system, allowing longer circulation times than small molecules. In addition, their size/surface properties can be further tailored to optimize their pharmacokinetics for imaging of a particular disease. Herein, we provide a comprehensive review of nanogels as imaging agents in various modalities with sources of signal spanning the electromagnetic spectrum, including MRI, NIR, UV-vis, and PET. Many materials and formulation methods will be reviewed to highlight the versatility of nanogels as imaging agents.