Hyaluronic acid nanogels prepared via ortho ester linkages show pH-triggered behavior, enhanced penetration and antitumor efficacy in 3-D tumor spheroids

Stimuli-Responsive and Multifunctional Nanogels in Drug Delivery

Nanogels represent promising drug delivery systems in the biomedical field, designed to overcome challenges associated with standard treatment approaches. Stimuli-responsive nanogels, often referred to as intelligent materials, have garnered significant attention for their potential to enhance control over properties such as drug release and targeting. Furthermore, researchers have recently explored the application of nanogels in diverse sectors beyond biomedicine including sensing materials, catalysts, or adsorbents for environmental applications. However, to fully harness their potential as practical delivery systems, further research is required to better understand their pharmacokinetic behaviour, interactions between nanogels and bio distributions, as well as toxicities. One promising future application of stimuli-responsive multifunctional nanogels is their use as delivery agents in cancer treatment, offering an alternative to overcome the challenges with conventional approaches. This review discusses various synthetic methods employed in developing nanogels as efficient carriers for drug delivery in cancer treatment. The investigations explore, the key aspects of nanogels, including their multifunctionality and stimuli-responsive properties, as well as associated toxicity concerns. The discussions presented herein aim to provide the readers a comprehensive understanding of the potential of nanogels as smart drug delivery systems in the context of cancer therapy.

Hyaluronic Acid Methacrylate Hydrogel-Modified Electrochemical Device for Adsorptive Removal of Lead(II)

This paper presents the development of a compact, three-electrode electrochemical device functionalized by a biocompatible layer of hyaluronic acid methacrylate (HAMA) hydrogel for the adsorptive removal of detrimental lead (Pb(II)) ions in aqueous solutions. An adsorption mechanism pertaining to the observed analytical performance of the device is proposed and further experimentally corroborated. It is demonstrated that both the molecular interactions originating from the HAMA hydrogel and electrochemical accumulation originating from the electrode beneath contribute to the adsorption capability of the device. Infrared spectral analysis reveals that the molecular interaction is mainly induced by the amide functional group of the HAMA hydrogel, which is capable of forming the Pb(II)–amide complex. In addition, inductively coupled plasma mass spectrometric (ICP-MS) analysis indicates that the electrochemical accumulation is particularly valuable in facilitating the adsorption rate of the device by maintaining a high ion-concentration gradient between the solution and the hydrogel layer. ICP-MS measurements show that 94.08% of Pb(II) ions present in the test solution can be adsorbed by the device within 30 min. The HAMA hydrogel-modified electrochemical devices exhibit reproducible performance in the aspect of Pb(II) removal from tap water, with a relative standard deviation (RSD) of 1.28% (for n = 8). The experimental results suggest that the HAMA hydrogel-modified electrochemical device can potentially be used for the rapid, on-field remediation of Pb(II) contamination.

Recent Progress in Bio-Responsive Drug Delivery Systems for Tumor Therapy

Spatially- and/or temporally-controlled drug release has always been the pursuit of drug delivery systems (DDSs) to achieve the ideal therapeutic effect. The abnormal pathophysiological characteristics of the tumor microenvironment, including acidosis, overexpression of special enzymes, hypoxia, and high levels of ROS, GSH, and ATP, offer the possibility for the design of stimulus-responsive DDSs for controlled drug release to realize more efficient drug delivery and anti-tumor activity. With the help of these stimulus signals, responsive DDSs can realize controlled drug release more precisely within the local tumor site and decrease the injected dose and systemic toxicity. This review first describes the major pathophysiological characteristics of the tumor microenvironment, and highlights the recent cutting-edge advances in DDSs responding to the tumor pathophysiological environment for cancer therapy. Finally, the challenges and future directions of bio-responsive DDSs are discussed.

Nanoscale Drug Delivery Systems in Glioblastoma

Glioblastoma is the most aggressive cerebral tumor in adults. However, the current pharmaceuticals in GBM treatment are mainly restricted to few chemotherapeutic drugs and have limited efficacy. Therefore, various nanoscale biomaterials that possess distinct structure and unique property were constructed as vehicles to precisely deliver molecules with potential therapeutic effect. In this review, nanoparticle drug delivery systems including CNTs, GBNs, C-dots, MOFs, Liposomes, MSNs, GNPs, PMs, Dendrimers and Nanogel were exemplified. The advantages and disadvantages of these nanoparticles in GBM treatment were illustrated.

The Effective Combination between 3D Cancer Models and Stimuli-Responsive Nanoscale Drug Delivery Systems

Stimuli-responsive drug-delivery systems (DDSs) have emerged as a potential tool for applications in healthcare, mainly in the treatment of cancer where versatile nanocarriers are co-triggered by endogenous and exogenous stimuli. Two-dimensional (2D) cell cultures are the most important in vitro model used to evaluate the anticancer activity of these stimuli-responsive DDSs due to their easy manipulation and versatility. However, some limitations suggest that these in vitro models poorly predict the outcome of in vivo studies. One of the main drawbacks of 2D cell cultures is their inadequate representation of the 3D environment's physiological complexity, which sees cells interact with each other and the extracellular matrix (ECM) according to their specific cellular organization. In this regard, 3D cancer models are a promising approach that can overcome the main shortcomings of 2D cancer cell cultures, as these in vitro models possess many peculiarities by which they mimic in vivo tumors, including physiologically relevant cell-cell and cell-ECM interactions. This is, in our opinion, even more relevant when a stimuli-responsive DDS is being investigated. In this review, we therefore report and discuss endogenous and exogenous stimuli-responsive DDSs whose effectiveness has been tested using 3D cancer cell cultures.

Chitosan-based nanodelivery systems for cancer therapy: Recent advances

Nowadays, cancer is one of the most prominent issues related to human health since it causes more than one-tenth of death cases throughout the world. On the other hand, routine therapeutic approaches in cancer suppression such as radiation therapy, chemotherapy, surgery, etc. due to their undesirable therapeutic outputs, including low efficiency in cancer inhibition, non-targeted drug delivery, nonselective distribution, and enormous side effects, have been indicated inefficient potency in cancer therapy or at least its growth inhibition. As a result, the development of novel and practical therapeutic methods such as nanoparticle-based drug delivery systems can be outstandingly beneficial in cancer suppression. Among various nanoparticles used in the delivery of bioactive to the tumor site, chitosan (CS) nanoparticles have received high attention. CS, poly [β-(1-4)-linked-2-amino-2-deoxy-d-glucose], is a natural linear amino polysaccharide derived from chitin which is made of irregularly distributed d-glucosamine and N-acetyl-d-glucosamine units. CS nanoparticles owing to their appropriate aspects, including nanometric size, great drug loading efficacy, ease of manipulation, non-toxicity, excellent availability and biocompatibility, good serum stability, long-term circulation time, suitable pharmacokinetic and pharmacodynamics, non-immunogenicity, and enhanced drug solubility in the human body, have been designated as an efficient candidate for drug delivery systems. They can be involved in both passive (based on the enhanced permeability and retention effect cancer targeting) and active (receptor-mediated or stimuli-responsive cancer targeting) drug delivery systems for potential cancer therapy. This review presents the properties, preparation, modification, and numerous pharmaceutical applications of CS-based drug nanodelivery systems in the diagnosis and therapy of cancer.

Acid-sensitive and L61-crosslinked hyaluronic acid nanogels for overcoming tumor drug-resistance

Low intracellular drugs concentration is one of the main representations of multidrug resistance (MDR), which often results in a weak or failed chemotherapy on cancer treatment. Herein, an acid-sensitive and pluronic L61-linked hyaluronic acid nanogels (HA-L61OE/NGs) were developed for solving this problem. The nanogels could well hold more drugs under neutral condition, while triggering efficiently drugs release (61.42% within 24 h) in acidic environment. In vitro cells experiments demonstrated that the nanogels greatly increased intracellular drugs concentration by CD44-mediated endocytosis and L61-mediated anti-MDR effect, resulting in the enhanced cell-killing in MDR cells. In vivo studies verified HA-L61OE/NGs could avoid drugs leakage in blood and reduce systemic toxicity. Subsequently, the specific accumulation and penetration of nanogels at tumor regions lead to the highest tumor growth inhibition (TGI, 77.42%). Overall, HA-L61OE/NGs were effective on MDR tumor therapy and expected to be further used in clinical trials.

Nanogels as a Versatile Drug Delivery System for Brain Cancer

Chemotherapy and radiation remain as mainstays in the treatment of a variety of cancers globally, yet some therapies exhibit limited specificity and result in harsh side effects in patients. Brain tissue differs from other tissue due to restrictions from the blood-brain barrier, thus systemic treatment options are limited. The focus of this review is on nanogels as local and systemic drug delivery systems in the treatment of brain cancer. Nanogels are a unique local or systemic drug delivery system that is tailorable and consists of a three-dimensional polymeric network formed via physical or chemical assembly. For example, thermosensitive nanogels show promise in their ability to incorporate therapeutic agents in nano-structured matrices, be applied in the forms of sprays or sols to the area from which a tumor has been removed, form adhesive gels to fill the cavity and deliver treatment locally. Their usage does come with complications, such as handling, storage, chemical stability, and degradation. Despite these limitations, the current ongoing development of nanogels allows patient-centered treatment that can be considered as a promising tool for the management of brain cancer.

Nanogels Capable of Triggered Release

This chapter provides an overview of soft and environmentally sensitive polymeric nanosystems, which are widely known as nanogels. These particles keep great promise to the area of drug delivery due to their high biocompatibility with body fluids and tissues, as well as due to their ability to encapsulate and release the loaded drugs in a controlled manner. For a long period of time, the controlled drug delivery systems were designed to provide long-termed or sustained release. However, some medical treatments such as cancer chemotherapy, protein and gene delivery do not require the prolonged release of the drug in the site of action. In contrast, the rapid increase of the drug concentration is needed for gaining the desired biological effect. Being very sensitive to surrounding media and different stimuli, nanogels can undergo physico-chemical transitions or chemical changes in their structure. Such changes can result in more rapid release of the drugs, which is usually referred to as triggered drug release. Herein we give the basic information on nanogel unique features, methods of sensitive nanogels preparation, as well as on main mechanisms of triggered release. Additionally, the triggered release of low-molecular drugs and biomacromolecules are discussed.

Lactoferrin/phenylboronic acid-functionalized hyaluronic acid nanogels loading doxorubicin hydrochloride for targeting glioma

Herein, lactoferrin (Lf)/phenylboronic acid (PBA)-functionalized hyaluronic acid nanogels crosslinked with disulfide-bond crosslinker was developed as a reduction-sensitive dual-targeting glioma therapeutic platform for doxorubicin hydrochloride (DOX) delivery (Lf-DOX/PBNG). Spherical Lf-DOX/PBNG with optimized physicochemical properties was obtained, and it could rapidly release the encapsulated DOX under high glutathione concentration. Moreover, enhanced cytotoxicity, superior cellular uptake efficiency, and significantly improved brain permeability of Lf-DOX/PBNG were observed in cytological studies compared with those of DOX solution, DOX-loaded PBA functionalized nanogels (DOX/PBNG), and Lf modified DOX-loaded nanogels (Lf-DOX/NG). The pharmacokinetic study exhibited that the area under the curve of DOX/PBNG, Lf-DOX/NG, and Lf-DOX/PBNG increased by 8.12, 4.20 and 4.32 times compared with that of DOX solution, respectively. The brain accumulation of Lf-DOX/PBNG was verified in biodistribution study to be 12.37 and 4.67 times of DOX solution and DOX/PBNG, respectively. These findings suggest that Lf-DOX/PBNG is an excellent candidate for achieving effective glioma targeting.

pH-Sensitive nanogels for drug delivery in cancer therapy

Compared to normal tissue, solid tumors exhibit a lower pH value. Such pH gradient can be used to design pH-sensitive nanogels for selective drug delivery. The acid-sensitive elements in the nanogel cause it to swell/degrade rapidly, followed by rapid drug release.

Redox-Sensitive and Hyaluronic Acid-Functionalized Nanoparticles for Improving Breast Cancer Treatment by Cytoplasmic 17α-Methyltestosterone Delivery

Novel reduction-responsive hyaluronic acid–chitosan–lipoic acid nanoparticles (HACSLA-NPs) were designed and synthesized for effective treatment of breast cancer by targeting Cluster of Differentiation 44 (CD44)-overexpressing cells and reduction-triggered 17α-Methyltestosterone (MT) release for systemic delivery. The effectiveness of these nanoparticles was investigated by different assays, including release rate, 3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT), lactate dehydrogenase (LDH), caspase-3 activity, Rhodamine 123 (RH-123), and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). In vitro experiments revealed that Methyltestosterone/Hyaluronic acid–chitosan–lipoic acid nanoparticles (MT/HACSLA-NPs) illustrated a sustained drug release in the absence of glutathione (GSH), while the presence of GSH led to fast MT release. HACSLA-NPs also showed high cellular internalization via CD44 receptors, quick drug release inside the cells, and amended cytotoxicity against positive CD44 BT-20 breast cancer cell line as opposed to negative CD44, Michigan Cancer Foundation-7 (MCF-7) cell line. These findings supported that these novel reduction-responsive NPs can be promising candidates for efficient targeted delivery of therapeutics in cancer therapy.

pH-sensitive and pluronic-modified pullulan nanogels for greatly improved antitumor in vivo

It remains a crucial challenge to achieve efficient cellular uptake in tumor cells for nanoscale drug delivery systems. This work described that two multi-functional pullulan nanogels were prepared by co-polymerization between methacrylated pullulan (Pullulan-M) and different crosslink agents, an acid-labile ortho ester-modified pluronic (L61-MOE) or non-acid-sensitive methacrylated pluronic (L61-M). The prepared nanogels showed a regular spherical structure with the size about 200 nm measured by dynamic light scattering and transmission electron microscopy (TEM). Doxorubicin as a model drug was successfully encapsulated into nanogels. As expected, Pul-L61-MOE showed pH-dependent DOX release, and 25% of DOX was released at pH 7.4 while 84.48% of DOX was released at pH 5.0. In vitro cellular uptake and MTT results indicated that pH-sensitive nanogels (Pul-L61-MOE) displayed higher cellular internalization and cytotoxicity than acid-insensitive nanogels (Pul-L61-M) and free DOX. Flow cytometry assay suggested these nanogels remarkably increased intracellular reactive oxygen species (ROS) level and induced more cell apoptosis by the function of pluronic. Finally, in vivo antitumor results indicated that the multi-functional nanogels exhibit supreme antitumor efficiency, and the tumor growth inhibition (TGI) was 83.37%. Therefore, the pH-sensitive pullulan nanogels can be potential nano-carriers for drug delivery in tumor treatment.

Stimulus-responsive polymeric nanogels as smart drug delivery systems

Nanogels are three-dimensional nanoscale networks formed by physically or chemically cross-linking polymers. Nanogels have been explored as drug delivery systems due to their advantageous properties, such as biocompatibility, high stability, tunable particle size, drug loading capacity, and possible modification of the surface for active targeting by attaching ligands that recognize cognate receptors on the target cells or tissues. Nanogels can be designed to be stimulus responsive, and react to internal or external stimuli such as pH, temperature, light and redox, thus resulting in the controlled release of loaded drugs. This "smart" targeting ability prevents drug accumulation in non-target tissues and minimizes the side effects of the drug. This review aims to provide an introduction to nanogels, their preparation methods, and to discuss the design of various stimulus-responsive nanogels that are able to provide controlled drug release in response to particular stimuli. STATEMENT OF SIGNIFICANCE: Smart and stimulus-responsive drug delivery is a rapidly growing area of biomaterial research. The explosive rise in nanotechnology and nanomedicine, has provided a host of nanoparticles and nanovehicles which may bewilder the uninitiated reader. This review will lay out the evidence that polymeric nanogels have an important role to play in the design of innovative drug delivery vehicles that respond to internal and external stimuli such as temperature, pH, redox, and light.

Hyaluronic Acid-Coated Nanomedicine for Targeted Cancer Therapy

Hyaluronic acid (HA) has been widely investigated in cancer therapy due to its excellent characteristics. HA, which is a linear anionic polymer, has biocompatibility, biodegradability, non-immunogenicity, non-inflammatory, and non-toxicity properties. Various HA nanomedicines (i.e., micelles, nanogels, and nanoparticles) can be prepared easily using assembly and modification of its functional groups such as carboxy, hydroxy and N-acetyl groups. Nanometer-sized HA nanomedicines can selectively deliver drugs or other molecules into tumor sites via their enhanced permeability and retention (EPR) effect. In addition, HA can interact with overexpressed receptors in cancer cells such as cluster determinant 44 (CD44) and receptor for HA-mediated motility (RHAMM) and be degraded by a family of enzymes called hyaluronidase (HAdase) to release drugs or molecules. By interaction with receptors or degradation by enzymes inside cancer cells, HA nanomedicines allow enhanced targeting cancer therapy. In this article, recent studies about HA nanomedicines in drug delivery systems, photothermal therapy, photodynamic therapy, diagnostics (because of the high biocompatibility), colloidal stability, and cancer targeting are reviewed for strategies using micelles, nanogels, and inorganic nanoparticles.

The study of establishment of an in vivo tumor model by three-dimensional cells culture systems methods and evaluation of antitumor effect of biotin-conjugated pullulan acetate nanoparticles

In this study, three-dimensional (3D) hydrogels were used for human hepatocellular carcinoma (HepG2) cells culture systems in vitro and establishment of an in vivo xenografted tumor model. Based on our previous work on the biotin-conjugated pullulan acetate nanoparticles (Bio-PA NPs) as anticancer drug carriers, we further studied the anti-tumor effect of the NPs in two-dimensional (2D) and 3D cell culture system. When embedded in 3D hydrogels, HepG2 cells formed tumor spheroids and the cytoplasmic actin microfilamentrates were rearranged over a period of 7 days. In vitro cytotoxicity results indicated that HepG2 cells in 3D hydrogels were more resistant to Bio-PA NPs treatments compared to the 2D system. The tumor formation rate of in vivo xenografted tumor model using 3D culture systems method was 98.2%, which was significantly higher than that using of 2D cultured cells (76.4%). Then we injected the 3D HepG2 cells systems in the right anterior axillary of female Balb/c nude mice, and evaluate the in vivo anti-tumor efficacy of Bio-PA NPs. In summary, these results suggested that HepG2 cells in 3D hydrogel system has shown the potential to provide an in vitro and in vivo model and for the evaluation of Bio-PA NPs.

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.

Evaluation of hyaluronic acid-combined ternary complexes for serum-resistant and targeted gene delivery system

Branched polyethylenimine (bPEI) was well known as high transfection agent, which has many amine group. However, utilization of bPEI was limited due to high toxicity. To solve these problems, bPEI was introduced to low molecular weight water-soluble chitosan (LMWSC) with coupling agent. In addition, hyaluronic acid (HA), one of natural anion polymer, was introduced to binary complex of pDNA/bPEI-grafted LMWSC (LMPEI) to target the specific cancer cell and impart the serum resistant. Ternary complexes of pDNA/LMPEI/HA were prepared by electrostatic charge interaction and their binding affinity and DNase protection assay were conducted by gel retardation assay. Particle size of ternary complexes showed that had each 482 ± 245.4 (pDNA/LMPEI2%/HA, 1:16:1, w/w/w) and 410 ± 78.5 nm (pDNA/LMPEI4%/HA, 1:16:2, w/w/w). Moreover, to demonstrate serum-resistant effect of ternary complexes, particle size of them was measured according to incubated time (0-10 h) under serum condition. Transfection assay of ternary complexes showed that their transfection efficiency in CD44-receptor overexpressed HCT116 cell was higher than CD44-receptor negative CT26 cell. Additionally, intracellular uptake of ternary complexes with propidium iodide (PI)-labeled pDNA was observed to confirm targeting effect and cellular internalization by fluorescence microscopy. These results suggest that ternary complexes are superb gene carrier with excellent serum-resistant and high gene transfection.