pH/Reduction Dual-Responsive Oxidized Alginate-Doxorubicin (mPEG-OAL-DOX/Cys) Prodrug Nanohydrogels: Effect of Complexation with Cyclodextrins

Multi-stimuli-responsive Hydrogels for Therapeutic Systems: An Overview on Emerging Materials, Devices, and Drugs

The rising interest in hydrogels nowadays is due to their usefulness in physiological conditions as multi-stimuli-responsive hydrogels. To reply to the prearranged stimuli, including chemical triggers, light, magnetic field, electric field, ionic strength, temperature, pH, and glucose levels, dual/multi-stimuli-sensitive gels/hydrogels display controllable variations in mechanical characteristics and swelling. Recent attention has focused on injectable hydrogel-based drug delivery systems (DDS) because of its promise to offer regulated, controlled, and targeted medication release to the tumor site. These technologies have great potential to improve treatment outcomes and lessen side effects from prolonged chemotherapy exposure.

L-asparaginase immobilization in supramolecular nanogels of PEG-grafted poly HPMA and bis(α-cyclodextrin) to enhance pharmacokinetics and lower enzyme antigenicity

L-asparaginase (ASNase) enzyme has limited therapeutic use due to its poor pharmacokinetics and immunogenicity. To overcome these obstacles, we immobilized ASNase in biocompatible poly hydroxypropyl methacrylamide (P(HPMA))-based nanogels simply formed through the host-guest inclusion complex of ASNase-conjugated random copolymer of HPMA and polyethylene glycol (PEG) acrylate (P(HPMA-MPEGA)) and α-cyclodextrin dimer (bisCD) using cystamine as a linker. The effects of bisCD and polymer concentrations on particle size, gelation time, and recovery of enzyme activity were investigated. The ASNase-conjugated bisCD nanogels were discrete, homogeneous, and spherical with a mean projected diameter of 148 ± 41 nm. ASNase immobilized in the bisCD nanogels caused cytotoxicity on HL-60 cell line with IC₅₀ of 3 IU/ml. In-vivo rat study revealed that the immobilized ASNase reduced the enzyme antigenicity and resulted in 8.1 folds longer circulation half-life than the native enzyme. Conclusively, immobilization of ASNase in P(HPMA-MPEGA) and bisCD supramolecular nanogels could enhance the therapeutic value of ASNase in cancer chemotherapy.

Targeted Delivery of Zinc Ion Derived by Pseudopolyrotaxane Gel Polymer Electrolyte for Long-Life Zn Anode

Aqueous zinc ion battery is a potential alternative for a stationary energy storage system owing to the inherent properties of the Zn anode. However, the Zn anode suffers from serious Zn dendrite due to the uneven Zn plating. Thus, inspired by the nano-drug delivery to the target site of the tumor cell, it would be a promising strategy to introduce targeted delivery of zinc ion in the electrolyte for even Zn plating. Passive targeted transport plays an important role in nano-drug delivery, which presents the nano-drug would be released by the nano-drug carrier based on polymer to the particular target site. As a proof-of-concept, a pseudopolyrotaxane conducting the nano-drug carrier applied in targeted cancer therapy is employed as the gel polymer electrolyte (GPE) for long-life Zn anodes. The pseudopolyrotaxane is formed by the self-assembling of α-cyclodextrin (CD) and poly(ethylene oxide), where the zinc ion can be absorbed and delivered to the target site of the Zn anode benefiting from the hydrogen-bond. Impressively, even Zn plating can be induced by the hydroxyl groups of CD to inhibit Zn dendrite. Moreover, the hydrogen evolution reaction is suppressed by the GPE. Less produced H₂ is detected in the GPE, which is demonstrated by the online mass spectrometry. Thus, the Zn||Zn symmetrical cell based on the GPE exhibits a cycling life of 1370 h. Compared to the one based on aqueous electrolyte, Zn||MnO₂ battery based on the GPE shows a higher capacity retention. This work is expected to avail the development of the aqueous zinc ion battery.

Smart Stimuli-responsive Alginate Nanogels for Drug Delivery Systems and Cancer Therapy: A Review

Nanogels are three-dimensional networks at the nanoscale level that can be fabricated through physical or chemical processes using polymers. These nanoparticles' biocompatibility, notable stability, efficacious drug-loading capacity, and ligand-binding proficiency make them highly suitable for employment as drug-delivery vehicles. In addition, they exhibit the ability to react to both endogenous and exogenous stimuli, which may include factors such as temperature, illumination, pH levels, and a diverse range of other factors. This facilitates the consistent administration of the drug to the intended site. Alginate biopolymers have been utilized to encapsulate anticancer drugs due to their biocompatible nature, hydrophilic properties, and cost-effectiveness. The efficacy of alginate nano gel-based systems in cancer treatment has been demonstrated through multiple studies that endorse their progress toward clinical implementation. This paper comprehensively reviews alginate and its associated systems in drug delivery systems.

K. ZHENG ET AL.Gold-nanoparticle-based multistage drug delivery system for antitumor therapy

Nanoparticles can promote the accumulation of drugs in tumors. However, they find limited clinical applications because they cannot easily penetrate the stroma of cancer tissues, and it is difficult to control drug release. We developed a multiresponse multistage drug-delivery nanogel with improved tumor permeability and responsiveness to the tumor microenvironment for the controlled delivery of anticancer agents. For this purpose, ∼100 nm multistage drug delivery nanogels with pH, redox, near-infrared stimulation, and enzyme responsiveness were grown in situ using 20 nm gold nanoparticles (AuNPs) via an emulsion-aiding crosslinking technique with cysteine crosslinker. An alginate cysteine AuNP (ACA) nanocarrier can efficiently load the cationic drug doxorubicin (DOX) to produce a multistage drug delivery nanocarrier (DOX@ACA). DOX@ACA can maintain the slow release of DOX and reduce its toxicity. In cancer tissues, the high pH and reductase microenvironment combined with the in vitro delivery of alginate and near-infrared light drove drug release. The developed nanoparticles effectively inhibited cancer cells, and in vivo evaluations showed that they effectively enhanced antitumor activity while having negligible in vivo toxicity to major organs.

Nanohydrogels: Advanced Polymeric Nanomaterials in the Era of Nanotechnology for Robust Functionalization and Cumulative Applications

In the era of nanotechnology, the synthesis of nanomaterials for advanced applications has grown enormously. Effective therapeutics and functionalization of effective drugs using nano-vehicles are considered highly productive and selectively necessary. Polymeric nanomaterials have shown their impact and influential role in this process. Polymeric nanomaterials in molecular science are well facilitated due to their low cytotoxic behavior, robust functionalization, and practical approach towards in vitro and in vivo therapeutics. This review highlights a brief discussion on recent techniques used in nanohydrogel designs, biomedical applications, and the applied role of nanohydrogels in the construction of advanced therapeutics. We reviewed recent studies on nanohydrogels for their wide applications in building strategies for advantageously controlled biological applications. The classification of polymers is based on their sources of origin. Nanohydrogel studies are based on their polymeric types and their endorsed utilization for reported applications. Nanotechnology has developed significantly in the past decades. The novel and active role of nano biomaterials with amplified aspects are consistently being studied to minimize the deleterious practices and side effects. Here, we put forth challenges and discuss the outlook regarding the role of nanohydrogels, with future perspectives on delivering constructive strategies and overcoming the critical objectives in nanotherapeutic systems.

Self-assembled biocompatible heparin-based supramolecular hydrogel for doxorubicin delivery

An array of self-assembled biocompatible doxorubicin (DOX) loaded heparin--cyclodextrin supramolecular hydrogels (DOX@HGs) with highly encapsulated efficiency was constructed using heparin-β-cyclodextrin derivatives (Hep-β-CD), α-cyclodextrin (α-CD), pluronic F-127 and DOX via the synergy of host-guest and multiple hydrogen bonding interactions. These hydrogels were characterized by GPC measurements (GPC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Size and zeta potential determinations, X-ray diffraction (XRD), and rheological characteristics; the data confirmed successful formation of the hydrogels. Furthermore, these hydrogels demonstrated distinctive thixotropy, indicating rapid self-repairing after continuously oscillatory shear stress. Variable release of DOX from DOX @HGs was obtained at various pH after 84 h depending on the strength of the hydrogels. At pH 7.4, cumulative DOX release was approximately 49.07% for DOX@HG 1, 32.15% for DOX@HG 2, and 27.12% for DOX@HG 3. While at pH 5.5, release of DOX was increased to 59.08% for DOX@HG 1 and to 43.2% for DOX@HG 3 after 84 h (P < 0.05). This information demonstrated that a higher DOX release rate was observed under a lower pH due to strong charge expansion of CDs and weakening of electrostatic interactions between heparin and DOX. Additionally, cytotoxicity of free DOX and DOX@HGs in ovarian cancer SKOV-3 cells was studied at various exposure durations. The results revealed that cytotoxicity of DOX@HG 1-3 toward ovarian cancer SKOV-3 cells was lower than that of free DOX (P < 0.05), suggesting prolonged DOX release from the hydrogels in SKOV-3 cells.

MnO2 Nanospheres Assisted by Cysteine Combined with MnO2 Nanosheets as a Fluorescence Resonance Energy Transfer System for "Switch-on" Detection of Glutathione

Manganese dioxide nanosheets combined with cysteine-assisted emitting manganese dioxide nanospheres (Cys-MnO₂ nanospheres) is fabricated for the first time as an "off-on" fluorescence detection platform for glutathione (GSH). In this sensing system, Cys-MnO₂ nanospheres served as energy donors, while MnO₂ nanosheets were used as both energy acceptors and recognition units. MnO₂ nanosheets can effectively quench the fluorescence of Cys-MnO₂ nanospheres through the fluorescence resonance energy transfer (FRET). The addition of GSH could reduce MnO₂ nanosheets into Mn²⁺, disrupting the FRET process and restoring the fluorescence of Cys-MnO₂ nanospheres. Under the optimum conditions, the "switch-on" platform we established has a wide response to GSH with a range of 5-50 μM and 150-800 μM, as well as a superior specificity. Importantly, all components of the sensor are nontoxic, biocompatible, easily prepared, and have a high utilization of raw materials. Moreover, the sensing system achieved satisfactory results in human serum, showing a tremendous potential in the field of biomedicine.

A comprehensive review on alginate-based delivery systems for the delivery of chemotherapeutic agent: Doxorubicin

Doxorubicin (DOX), an anthracycline drug, is widely used for the treatment of several cancers like osteosarcoma, cervical carcinoma, breast cancer, etc. DOX lacks target specificity; thereby it also affects normal cells thus resulting in several side-effects. A drug delivery system (DDS) can be used to deliver the drug in a controlled and sustained manner at a targeted site within the body. Various DDS like nanoemulsions, polymeric nanoparticles, and liposomes are used for loading DOX. Alginate, a polysaccharide is widely used for fabricating DDS due to its biodegradable and bio-compatible properties. Alginates, in combination with other biomaterials, have been extensively used as a novel drug delivery carrier for DOX. Alginate provides a platform for drug delivery in different forms like hydrogels, nanogels, nanoparticles, microparticles, graphene oxide systems, magnetic systems, etc. Herein, we briefly describe alginate in combination with other materials as a nanocarrier for targeted delivery of DOX for anti-cancer treatment.

Smart stimuli-responsive drug delivery systems based on cyclodextrin: A review

Stimulated by researches in materials chemistry and medicine fields, drug delivery has entered a new stage of development. Drug delivery systems have been extensively studied according to the differences in the drug therapeutic environment such as pH, light, temperature, magnet, redox, enzymes, etc. Cyclodextrin is a smart tool that has been proven to be used in the preparation of drug delivery, and has become a new area of concern in recent years. In this review, we discuss recent research advances in smart stimuli-responsive cyclodextrin-based drug delivery. First, different stimuli-responsive drug delivery systems based on cyclodextrin are introduced and classified. Then, the characteristics of different types of stimuli-responsive drug delivery systems are described, and their applications are emphasized. Finally, current challenges and future development opportunities of smart stimuli-responsive drug delivery systems based on cyclodextrin are discussed.

Zwitterionic Polymer Micelles with Dual Conjugation of Doxorubicin and Curcumin: Synergistically Enhanced Efficacy against Multidrug-Resistant Tumor Cells

This paper reports a novel redox-sensitive micellar system for the co-delivery of doxorubicin (Dox) and a chemosensitizer (curcumin, Cur) to overcome the multidrug resistance (MDR) in cancer cells. Dox and Cur were co-conjugated onto a zwitterionic polymer, poly(carboxybetaine) (pCB), to form Cur-pCB-Dox that self-assembled into stable micelles (164.2 ± 4.8 nm). Single-drug conjugates (pCB-Dox and pCB-Cur) were prepared for comparisons. Compared to the high half-maximal inhibitory concentration (IC₅₀) of Dox (437.2 μg/mL), the IC₅₀ value of pCB-Dox (14.1 μg/mL) was only 1/33 that of Dox. Confocal laser scanning microscopy and flow cytometry revealed the greatly enhanced cell uptake of the conjugate due to the enhanced permeability and retention effect of tumor cells on the micellar conjugate. Co-delivery of pCB-Dox with pCB-Cur further reduced the IC₅₀ value by 37% (8.9 μg/mL). More importantly, Cur-pCB-Dox exhibited the strongest cytotoxicity against MCF-7/Adr cells (IC₅₀, 5.87 μg/mL) because the co-delivered Dox and Cur on one carrier specifically transported into the same cells, which inhibited the efflux of Dox by Cur, led to a higher intracellular Dox concentration and made the drugs exert synergistic effects at the targeting regions. The results proved the zwitterionic micelles as promising drug co-delivery vehicles for fighting against MDR.

Synthetic routes to nanoconjugates of anthracyclines

Anthracyclines (Anth) are widely used in the treatment of various types of cancer. Unfortunately, they exhibit serious adverse effects, such as hematopoietic depression and cardiotoxicity, leading to heart failure. In this review, we focus on recently developed conjugates of anthracyclines with a range of nanocarriers, such as polymers, peptides, DNA or inorganic systems. Manipulation of the composition, size and shape of chemical entities at the nanometer scale makes possible the design and development of a range of prodrugs. In this review we concentrate on synthetic chemistry in the long process leading to the introduction of novel therapeutic products.

α-Cyclodextrin-Based Polypseudorotaxane Hydrogels

Supramolecular hydrogels that are based on inclusion complexes between α-cyclodextrin and (co)polymers have gained significant attention over the last decade. They are formed via dynamic noncovalent bonds, such as host-guest interactions and hydrogen bonds, between various building blocks. In contrast to typical chemical crosslinking (covalent linkages), supramolecular crosslinking is a type of physical interaction that is characterized by great flexibility and it can be used with ease to create a variety of "smart" hydrogels. Supramolecular hydrogels based on the self-assembly of polypseudorotaxanes formed by a polymer chain "guest" and α-cyclodextrin "host" are promising materials for a wide range of applications. α-cyclodextrin-based polypseudorotaxane hydrogels are an attractive platform for engineering novel functional materials due to their excellent biocompatibility, thixotropic nature, and reversible and stimuli-responsiveness properties. The aim of this review is to provide an overview of the current progress in the chemistry and methods of designing and creating α-cyclodextrin-based supramolecular polypseudorotaxane hydrogels. In the described systems, the guests are (co)polymer chains with various architectures or polymeric nanoparticles. The potential applications of such supramolecular hydrogels are also described.

One-Pot Synthesis of Chicken-Feather-Keratin-Based Prodrug Nanoparticles with High Drug Content for Tumor Intracellular DOX Delivery

pH/reduction dual-triggered chicken-feather-keratin-based prodrug nanoparticles (C-PK/- SS-Hy-D NPs) were designed via a facile one-pot oxidation coupling reaction between the thiol-functional acid-labile prodrug M-Hy-D and the PEGylated keratin (PK) graft copolymer, for tumor intracellular doxorubicin (DOX) delivery. Due to the encapsulation of the pH and the reduction of the dual-responsive small prodrug D-Hy- SS-Hy-D, a high drug content of 45.8% was obtained in the proposed prodrug nanoparticles. They exhibited excellent pH and reduction of dual-triggered drug release, with cumulative drug release of 88.6% within 51 h in the simulated tumor intracellular microenvironment, while the premature drug leakage was only 13.7% in the simulated normal physiological medium. The in vitro experiments revealed the enhanced antitumor efficacy of the C-PK/- SS-Hy-D NPs than the free DOX at a higher dosage of >10 μg/mL.

Design, postpolymerization conjugation and self-assembly of a di-block copolymer-based prodrug for tumor intracellular acid-triggered DOX release

A novel di-block copolymer-based prodrug was designed by atom transfer radical polymerization (ATRP) of glycidyl methacrylate (GMA) with a polyethylene glycol-based initiator (PEG-Br), postpolymerization aldehyde-modification, and doxorubicin (DOX) conjugation via an acid-labile imine bond.

Codelivery of Hydrophobic and Hydrophilic Drugs by Graphene-Decorated Magnetic Dendrimers

In this study, a nanocarrier was prepared for the codelivery of a hydrophilic drug (doxorubicin) and a hydrophobic drug (curcumin) to cancer cells. In this nanocarrier, the edges of graphene oxide sheets were decorated with a magnetic-functionalized polyamidoamine dendrimer with hydrazone groups at the end of the polymer. The edge functionalization of graphene sheets not only improved the solubility and dispersibility of graphene sheets but also imparted the magnetic properties to the nanocarrier. The resulting nanocarrier was loaded with doxorubicin through the covalent linkage and curcumin through π-π stacking. The nanocarrier showed a pH-sensitive release for both drugs, and the drug release behavior was also improved by the coimmobilization of both drugs. The cytotoxicity assay of nanocarrier showed low toxicity toward MCF-7 cell compared to unmodified graphene oxide, which was attributed to the presence of a magnetic dendrimer. Besides, the drug-loaded nanocarrier was highly toxic for cells even more than for free drugs. The cellular uptake images revealed higher drug internalization for coloaded nanocarrier than for the nanocarrier loaded with one drug alone. All of the results showed that the codelivery of curcumin and doxorubicin in the presence of the nanocarrier was more effective in chemotherapy than the nanocarrier loaded with one drug.

pH-Controlled Drug Release by Diffusion through Silica Nanochannel Membranes

We report in this work the fabrication of a flow-through silica nanochannel membrane (SNM) for controlled drug release applications. The ultrathin SNM consists of parallel nanochannels with a uniform diameter of ∼2.3 nm and a density of 4 × 10¹² cm^-2, which provide simultaneously high permeability and size selectivity toward small molecules. The track-etched porous polyethylene terephthalate film premodified with silane on its surface was used to support the ultrathin SNM via irreversible covalent bond formation, thus offering mechanical strength, flexibility, and stability to the ultrathin SNM for continuous and long-term use. Alkylamines were subsequently grafted onto the SNM surface to modulate the "on" and "off" state of nanochannels by medium pH for controlled drug release. Thiamphenicol glycinate hydrochloride (TPG), an intestinal drug, was studied as a model to permeate through an ultrathin SNM in both simulated gastric fluid (pH = 1.2) and simulated intestinal fluid (pH = 7.5). The release in the latter case was 178 times faster than that in the former. Moreover, a nearly zero-order constant release of TPG via single-file diffusion was achieved up to 24 h, demonstrating the feasibility of sustained and continuous release of small-molecule drugs in a pH-controlled manner.

Facile Synthesis of Fluorescent Hyper-Cross-Linked β-Cyclodextrin-Carbon Quantum Dot Hybrid Nanosponges for Tumor Theranostic Application with Enhanced Antitumor Efficacy

Fluorescent hyper-cross-linked β-cyclodextrin-carbon quantum dot (β-CD-CQD) hybrid nanosponges of about 200 nm with excellent biocompatibility and strong bright blue fluorescence excited at 365 nm with a high photoluminescence quantum yield (PLQY) of 38.0% were synthesized for tumor theranostic application by facile condensation polymerization of carbon quantum dots (CQDs) with β-cyclodextrin (β-CD) at a feeding ratio of 1:5. The DOX@β-CD-CQD theranostic nanomedicine, around 300 nm with DOX-loading capacity of 39.5% by loading doxorubicin (DOX) via host-guest complexation, showed a pH responsive controlled release and released DOX in the simulated tumor microenvironment in a sustained release mode, owing to the formation constant in the supramolecular complexation of DOX with the β-CD units in the β-CD-CQD nanosponges. The proposed DOX@β-CD-CQD theranostic nanomedicine could be internalized into HepG2 cells, and the released DOX was accumulated into the cell nuclei, demonstrating an antitumor efficacy more enhanced than that of the free drug.