Cyclodextrin-based supramolecular architectures: syntheses, structures, and applications for drug and gene delivery

A Green Host-Guest Protocol to Improve Water Solubility of Fluorescent Dyes

Improving fluorescence emission efficiency is essential to develop novel luminescent materials. However, the low water solubility of conventional fluorescent dyes is a serious obstacle to broadening the application scope. Herein, a green protocol have been proposed: Two poorly water-soluble naphthalimide derivatives MONI and MANI with high fluorescent quantum yields (larger than 0.95 in toluene solution) were loaded in three different sizes of cyclodextrin (CD; α, β, γ-CD) with high water solubility. To further check the feasibility of the proposal, density functional theory (DFT) and time dependent-DFT (TD-DFT) methods combining the Own N-layer Integrated molecular Orbital molecular Mechanics (ONIOM) model with dispersion correction were employed to investigate the geometric and electronic structures of complexes CD·MXNI (X = N, O) in the excited-state process. TD-DFT calculations predict that the fantastic emission behavior of MXNI can be reserved after binding with CD, even improving fluorescent intensity in aqueous solution. Basis set superposition error (BSSE) correction and symmetry adapted perturbation theory (SAPT) were adopted to estimate the complexation energies and weak noncovalent interactions. The middle-sized β-CD is the perfect candidate to allow fluorescent molecules to settle into its cavity, forming an inclusion complex. Energy decomposition analysis (EDA) indicates that dispersion is superior to electrostatics interaction in embedding-type β-CD·MXNI, while it is contrary in α,γ-CD·MXNI. NMR calculations further prove the existence of a strong intermolecular hydrogen bond interaction between host and guest. Weak interactions that limited molecular vibration and hampered the nonradiative inactivation channel are conducive to the enhanced emission intensity.

Beyond Lipids: Exploring Advances in Polymeric Gene Delivery in the Lipid Nanoparticles Era

The recent success of gene therapy during the COVID-19 pandemic has underscored the importance of effective and safe delivery systems. Complementing lipid-based delivery systems, polymers present a promising alternative for gene delivery. Significant advances have been made in the recent past, with multiple clinical trials progressing beyond phase I and several companies actively working on polymeric delivery systems which provides assurance that polymeric carriers can soon achieve clinical translation. The massive advantage of structural tunability and vast chemical space of polymers is being actively leveraged to mitigate shortcomings of traditional polycationic polymers and improve the translatability of delivery systems. Tailored polymeric approaches for diverse nucleic acids and for specific subcellular targets are now being designed to improve therapeutic efficacy. This review describes the recent advances in polymer design for improved gene delivery by polyplexes and covalent polymer-nucleic acid conjugates. The review also offers a brief note on novel computational techniques for improved polymer design. The review concludes with an overview of the current state of polymeric gene therapies in the clinic as well as future directions on their translation to the clinic.

Synthesis of cyclodextrin-based polyrotaxanes and polycatenanes for supramolecular pharmaceutical sciences

Cyclodextrins (CDs) are essential in the pharmaceutical industry and have long been used as food and pharmaceutical additives. CD-based interlocked molecules, such as rotaxanes, polyrotaxanes, catenanes, and polycatenanes, have been synthesized and have attracted considerable attention in supramolecular chemistry. Among them, CD polyrotaxanes have been employed as slide-ring materials and biomaterials. CD polycatenanes are new materials; therefore, to date, no examples of applied research on CD polycatenanes have been reported. Consequently, we expect that applied research on CD polycatenanes will accelerate in the future. This review article summarizes the syntheses and structural analyses of CD polyrotaxanes and polycatenanes to facilitate their applications in the pharmaceutical industry. We believe that this review will promote further research on CD-based interlocked molecules.

β-Cyclodextrin-based nanoassemblies for the treatment of atherosclerosis

Atherosclerosis, a chronic and progressive condition characterized by the accumulation of inflammatory cells and lipids within artery walls, remains a leading cause of cardiovascular diseases globally. Despite considerable advancements in drug therapeutic strategies aimed at managing atherosclerosis, more effective treatment options for atherosclerosis are still warranted. In this pursuit, the emergence of β-cyclodextrin (β-CD) as a promising therapeutic agent offers a novel therapeutic approach to drug delivery targeting atherosclerosis. The hydrophobic cavity of β-CD facilitates its role as a carrier, enabling the encapsulation and delivery of various therapeutic compounds to affected sites within the vasculature. Notably, β-CD-based nanoassemblies possess the ability to reduce cholesterol levels, mitigate inflammation, solubilize hydrophobic drugs and deliver drugs to affected tissues, making these nanocomponents promising candidates for atherosclerosis management. This review focuses on three major classes of β-CD-based nanoassemblies, including β-CD derivatives-based, β-CD/polymer conjugates-based and polymer β-CD-based nanoassemblies, highlighting a variety of formulations and assembly methods to improve drug delivery and therapeutic efficacy. These β-CD-based nanoassemblies exhibit a variety of therapeutic mechanisms for atherosclerosis and offer systematic strategies for overcoming barriers to drug delivery. Finally, we discuss the present obstacles and potential opportunities in the development and application of β-CD-based nanoassemblies as novel therapeutics for managing atherosclerosis and addressing cardiovascular diseases.

Thermal-responsive β-cyclodextrin-based magnetic hydrogel as a de novo nanomedicine for chemo/hyperthermia treatment of cancerous cells

A novel thermal-responsive β-cyclodextrin-based magnetic hydrogel [β-cyclodextrin-graft-poly(N-isopropylacrylamide)/Fe3O4 (β-CD-g-PNIPAAm/Fe3O4)] was fabricated as a novel nanomedicine for chemo/hyperthermia treatment of cancer cells. Firstly, β-CD was modified by maleic anhydride (MA) followed by copolymerization with NIPAAm monomer and thiol-end capped Fe3O4 nanoparticles (NPs) in the presence of a crosslinker through acrylamide-thiol polymerization system to afford a magnetic hydrogel. The saturation magnetization (δ s) value for developed hydrogel was determined to be 8.2 emu g-1. The hydrogel was physically loaded with an anticancer agent, doxorubicin hydrochloride (Dox). The encapsulation efficiency (EE) of drug into the hydrogel was obtained as 73 %. The system represented acceptable thermal-triggered drug release behavior that best fitted with Higuchi model, demonstrating the release of drug is mostly controlled by diffusion mechanism. The anticancer performance of the β-CD-g-PNIPAAm/Fe3O4-Dox was evaluated using MCF7 cells by MTT-assay. In addition, flow cytometry analyses showed considerable cellular uptake of Dox in the cells treated with β-CD-g-PNIPAAm/Fe3O4-Dox (∼70 %) compared to free Dox (∼28 %). As results, in time period of 48 h by combination of chemo- and hyperthermia-therapies, the developed system displayed greater anticancer efficiency than the free Dox.

Codelivery of Doxorubicin and p53 Gene by β-Cyclodextrin-Based Supramolecular Nanoparticles Formed via Host-Guest Complexation and Electrostatic Interaction

We developed a supramolecular system for codelivery of doxorubicin (Dox) and p53 gene based on a β-CD-containing star-shaped cationic polymer. First, a star-shaped cationic polymer consisting of a β-CD core and 3 arms of oligoethylenimine (OEI), named CD-OEI, was used to form a supramolecular inclusion complex with hydrophobic Dox. The CD-OEI/Dox complex was subsequently used to condense plasmid DNA via electrostatic interactions to form CD-OEI/Dox/DNA polyplex nanoparticles with positive surface charges that enhanced the cellular uptake of both Dox and DNA. This supramolecular drug and gene codelivery system showed high gene transfection efficiency and effective protein expression in cancer cells. The codelivery of Dox and DNA encoding the p53 gene resulted in reduced cell viability and enhanced antitumor effects at low Dox concentrations. With its enhanced cellular uptake and anticancer efficacy, the system holds promise as a delivery carrier for potential combination cancer therapies.

Overcoming barriers with non-covalent interactions: supramolecular recognition of adamantyl cucurbit[n]uril assemblies for medical applications

Adamantane, a staple in medicinal chemistry, recently became a cornerstone of a supramolecular host-guest drug delivery system, ADA/CB[n]. Owing to a good fit between the adamantane cage and the host cavity of the cucurbit[n]uril macrocycle, formed strong inclusion complexes find applications in drug delivery and controlled drug release. Note that the cucurbit[n]uril host is not solely a delivery vehicle of the ADA/CB[n] system but rather influences the bioactivity and bioavailability of drug molecules and can tune drug properties. Namely, as host-guest interactions are capable of changing the intrinsic properties of the guest molecule, inclusion complexes can become more soluble, bioavailable and more resistant to metabolic conditions compared to individual non-complexed molecules. Such synergistic effects have implications for practical bioapplicability of this complex system and provide a new viewpoint to therapy, beyond the traditional single drug molecule approach. By achieving a balance between guest encapsulation and release, the ADA/CB[n] system has also found use beyond just drug delivery, in fields like bioanalytics, sensing assays, bioimaging, etc. Thus, chemosensing in physiological conditions, indicator displacement assays, in vivo diagnostics and hybrid nanostructures are just some recent examples of the ADA/CB[n] applicability, be it for displacements purposes or as cargo vehicles.

Supramolecular nanoarchitectonics of propionylated polyrotaxanes with bulky nitrobenzyl stoppers for light-triggered drug release

Cyclodextrin (CD)-based polyrotaxanes (PRXs) are supramolecular polymers comprising multiple CDs mechanically interlocked onto a linear polymer chain by capping the polymer ends with bulky stoppers. Among various PRX derivatives, propionylated PRXs (Pr-PRXs) composed of propionylated α-CD and high molecular-weight poly(ethylene glycol) (PEG) form self-assembled nanoparticles in aqueous solution through hydrophobic interactions. Although Pr-PRX nanoparticles can encapsulate hydrophobic drugs in their hydrophobic domains, their release rate is limited. To improve the efficiency of drug release from Pr-PRX nanoparticles, ultraviolet (UV) light-dissociable Pr-PRXs were designed using 4,5-dimethoxy 2-nitrobenzyl groups as UV-cleavable bulky stopper molecules to facilitate UV-induced drug release. Photodegradable Pr-PRX (Pr-PD-PRX) was synthesized, and its UV-induced dissociation was examined. Pr-PD-PRX was completely dissociated via UV irradiation (365 nm) for 30 min. Additionally, Pr-PD-PRX nanoparticles encapsulating hydrophobic drugs collapsed upon UV irradiation, which promoted the release of the encapsulated drugs compared to non-degradable Pr-PRX nanoparticles. UV irradiation of drug-loaded Pr-PD-PRX nanoparticles resulted in higher cytotoxicity than non-irradiated Pr-PD-PRX and non-degradable Pr-PRX. Consequently, designing photodegradable PRX-based nanoparticles provides new insights into developing photoresponsive drug carriers and smart biomedical materials.

Engineered cyclodextrin-based supramolecular hydrogels for biomedical applications

Cyclodextrin (CD)-based supramolecular hydrogels are polymer network systems with the ability to rapidly form reversible three-dimensional porous structures through multiple cross-linking methods, offering potential applications in drug delivery. Although CD-based supramolecular hydrogels have been increasingly used in a wide range of applications in recent years, a comprehensive description of their structure, mechanical property modulation, drug loading, delivery, and applications in biomedical fields from a cross-linking perspective is lacking. To provide a comprehensive overview of CD-based supramolecular hydrogels, this review systematically describes their design, regulation of mechanical properties, modes of drug loading and release, and their roles in various biomedical fields, particularly oncology, wound dressing, bone repair, and myocardial tissue engineering. Additionally, this review provides a rational discussion on the current challenges and prospects of CD-based supramolecular hydrogels, which can provide ideas for the rapid development of CD-based hydrogels and foster their translation from the laboratory to clinical medicine.

Study of Drug Delivery Using Purely Organic Macrocyclic Containers-Cucurbit[7]uril and Pillararene

An impaired immune system is the root of various human ailments provoking the urge to find vehicle-mediated quick delivery of small drug molecules and other vital metabolites to specific tissues and organs. Thus, drug delivery strategies are in need of improvement in therapeutic efficacy. It can be achieved only by increasing the drug-loading capacity, increasing the sustained release of a drug to its target site, easy relocation of drug molecules associated with facile complexation-induced properties of molecular vehicles, and high stimuli-responsive drug administration. Supramolecular drug delivery systems (SDDS) provide a much needed robust yet facile platform for fabricating innovative drug nanocarriers assembled by thermodynamically noncovalent interaction with the tunable framework and above-mentioned properties. Measures of cytotoxicity and biocompatibility are the two main criteria that lie at the root of any promising medicinal applications. This Review features significant advancements in (i) supramolecular host-guest complexation using cucurbit[7]uril (CB[7]), (ii) encapsulation of the drug and its delivery application tailored for CB[7], (iii) self-assembly of supramolecular amphiphiles, (iv) supramolecular guest relay using host-protein nanocavities, (v) pillararene (a unique macrocyclic host)-mediated SDDS for the delivery of smart nanodrugs for siRNA, fluorescent molecules, and insulin for juvenile diabetes. Furthermore, fundamental questions and future hurdles related to smart SDDS based on CB[7] and pillararenes and their future promising breakthrough implementations are also distinctly outlined in this Review.

Sustained release of therapeutic gene by injectable hydrogel for hepatocellular carcinoma

Gene therapy has shown remarkable effectiveness in the management of disease like cancer and inflammation as a revolutionary therapeutic. Nonetheless, therapeutic drug target discovery, efficient gene delivery, and gene delivery vehicles continue to be significant obstacles. Due to their effective gene transport capabilities and low immunogenicity, supramolecular polymers have garnered significant interest. Herein, ABHD5 is identified as a potential therapeutic target since it is dysregulated in hepatocellular carcinoma (HCC). Interestingly, the downregulation of ABHD5 could induce programmed death-ligand 1 (PD-L1) expression in liver cancer, which may contribute to the immunosuppression. To overcome the immunosuppression caused by PD-L1, an injectable hydrogel is designed to achieve efficient abhydrolase domain containing 5 (ABHD5) gene delivery via the host-guest interaction with branched polyethyleneimine-g-poly (ethylene glycol), poly (ethylene oxide) and poly (propylene oxide) block copolymers and α-CD (PPA/CD), demonstrating the capability for sustained gene release. The co-assembly hydrogel demonstrates good biocompatibility and enhanced gene transfection efficiency, efficiently triggering tumor cell apoptosis. Overall, the results of this study suggest that ABHD5 is a potential therapeutic target, and that a host-guest-based supramolecular hydrogel could serve as a promising platform for the inhibition of HCC.

Controlled delivery of sildenafil by β-Cyclodextrin-decorated sulfur-doped carbon nanodots: a synergistic activation of ROS signaling in tumors overexpressing PDE-5

Fluorescent sulfur- and nitrogen-doped carbon nanodots (CDs) are zero-dimensional nanoparticles that mediate ROS production in cancer cells, displaying inherent anticancer properties. Thus, they have been proposed as nanotheranostic tools useful in image-guided cancer therapy. Here, we try to show that cancerous cells (high PDE-5 expression) receiving sildenafil delivered by CDs-based nanostructures promote positive reinforcement of PDE-5-mediated cell death via the overexpression of genes involved in the production of ROS. We explored the regioselective Huisgen cycloaddition between azide-β-cyclodextrin and CDs-alkyne to synthetize homogeneous nanostructures, named CDs-PEG4-β-Cdx, consisting of CDs functionalized at the surface with β-cyclodextrins capable of including high amount drugs such as sildenafil (>20 % w/w), and releasing them in a controlled manner. We investigated how CDs-PEG4-β-Cdx bearing sildenafil enter cells, enhancing ROS production and cell death specifically in cancer cells overexpressing PDE-5. These nanoplatforms go beyond the bounds of EPR-based nanomedicines in which carriers are conceived as inert vehicles of toxic drugs. Our findings enable the development of clever anticancer nanoplatforms that synergistically combine nanomedicines that perturb the mitochondrial electron transport chain (ROS production) with PDE-5 inhibitors which trigger oxidative stress specifically in cancer cells regardless of their location.

Lignin-Cobalt Nano-Enabled Poly(pseudo)rotaxane Supramolecular Hydrogel for Treating Chronic Wounds

Chronic wounds (CWs) are a growing issue for the health care system. Their treatment requires a synergic approach to reduce both inflammation and the bacterial burden. In this work, a promising system for treating CWs was developed, comprising cobalt-lignin nanoparticles (NPs) embedded in a supramolecular (SM) hydrogel. First, NPs were obtained through cobalt reduction with phenolated lignin, and their antibacterial properties were tested against both Gram-negative and Gram-positive strains. The anti-inflammatory capacity of the NPs was proven through their ability to inhibit myeloperoxidase (MPO) and matrix metalloproteases (MMPs), which are enzymes involved in the inflammatory process and wound chronicity. Then, the NPs were loaded in an SM hydrogel based on a blend of α-cyclodextrin and custom-made poly(ether urethane)s. The nano-enabled hydrogel showed injectability, self-healing properties, and linear release of the loaded cargo. Moreover, the SM hydrogel's characteristics were optimized to absorb proteins when in contact with liquid, suggesting its capacity to uptake harmful enzymes from the wound exudate. These results render the developed multifunctional SM material an interesting candidate for the management of CWs.

Exploring Receptor Binding Affinities and Hepatic Cell Association of N-Acetyl-d-Galactosamine-Modified β-Cyclodextrin-Based Polyrotaxanes for Liver-Targeted Therapies

Acid-degradable polyrotaxanes (PRXs) containing threading β-cyclodextrins (β-CDs) are promising candidates for therapeutic applications of β-CDs in metabolic diseases with cholesterol overload or imbalance. To improve cellular uptake specificity and efficiency of PRXs in hepatocytes, N-acetyl-d-galactosamine (GalNAc)-modified PRXs were developed to facilitate asialoglycoprotein receptor (ASGR)-mediated endocytosis. Binding affinity studies revealed that the dissociation constant (K_D) values between recombinant ASGR and GalNAc-PRXs decreased with an increase in the number of modified GalNAc units. Additionally, the K_D values for GalNAc-PRXs were smaller than those for GalNAc-modified β-CD and amylose, suggesting that the PRX backbone structure improves the binding affinity with ASGR. However, the intracellular uptake levels of GalNAc-PRXs in HepG2 cells increased with a decrease in the number of modified GalNAc units, which was opposite to the trend observed in the binding affinity study. We found that GalNAc-PRXs had a large number of GalNAc units localized in recycling endosomes, resulting in the low intracellular uptake. The cholesterol-reducing abilities of GalNAc-PRXs were assessed using cholesterol-overloaded HepG2 cells. GalNAc-PRXs with a small number of GalNAc units were demonstrated to show superior cholesterol-reducing effects compared to previously designed acid-degradable PRX and clinically tested β-CD derivatives. Thus, we conclude that GalNAc modification is a promising molecular design for the therapeutic application of β-CD-threaded PRXs in various metabolic diseases with cholesterol overload or imbalance in the liver.

Cyclodextrin-Based Polymeric Drug Delivery Systems for Cancer Therapy

Cyclodextrins (CDs) are one of the most extensively studied cyclic-oligosaccharides due to their low toxicity, good biodegradability and biocompatibility, facile chemical modification, and unique inclusion capacity. However, problems such as poor pharmacokinetics, plasma membrane disruption, hemolytic effects and a lack of target specificity still exist for their applications as drug carriers. Recently, polymers have been introduced into CDs to combine the advantages of both biomaterials for the superior delivery of anticancer agents in cancer treatment. In this review, we summarize four types of CD-based polymeric carriers for the delivery of chemotherapeutics or gene agents for cancer therapy. These CD-based polymers were classified based on their structural properties. Most of the CD-based polymers were amphiphilic with the introduction of hydrophobic/hydrophilic segments and were able to form nanoassemblies. Anticancer drugs could be included in the cavity of CDs, encapsulated in the nanoparticles or conjugated on the CD-based polymers. In addition, the unique structures of CDs enable the functionalization of targeting agents and stimuli-responsive materials to realize the targeting and precise release of anticancer agents. In summary, CD-based polymers are attractive carriers for anticancer agents.

Switchable metallacycles and metallacages

Two-dimensional metallacycles and three-dimensional metallacages constructed by coordination-driven self-assembly have attracted much attention because they exhibit unique structures and properties and are highly efficient to synthesize. Introduction of switching into supramolecular chemistry systems is a popular strategy, as switching can endow systems with reversible features that are triggered by different stimuli. Through this strategy, novel switchable metallacycles and metallacages were generated, which can be reversibly switched into different stable states with distinct characteristics by external stimuli. Switchable metallacycles and metallacages exhibit versatile structures and reversible properties and are inherently dynamic and respond to artificial signals; thus, these structures have many promising applications in a wide range of fields, such as drug delivery, data processing, pollutant removal, switchable catalysis, smart functional materials, etc. This review focuses on the design of switchable metallacycles and metallacages, their switching behaviours and mechanisms triggered by external stimuli, and the corresponding structural changes and resultant properties and functions.

Functionalization of the Surface of Porous Nickel-Titanium Alloy with Macrocyclic Compounds

For the first time, we performed functionalization of the surface of porous titanium nickelide alloys with bambusuril[6]-based macrocyclic compounds by different methods in order to provide the basis for saturation with therapeutic agents to impart antibacterial activity and accelerate its osteogenesis. It has been shown for the first time that the vacuum modification method is preferable for bambusuril deposition, since it provides a uniform deposition of organic matter on both the outer and inner surfaces of the pores. The effect of bambusuril deposition methods on the continuity, structure, and cytocompatibility of the porous titanium nickelide surface was evaluated. In vitro tests proved high biocompatibility and low toxicity of porous TiNi treated with BU[6] under vacuum. The SEM study of the structure of the surface layer of TiNi modified with BU[6] under the vacuum method showed that BU[6] agglomerates are uniformly deposited on the inner and outer surfaces of TiNi pores, which will provide an even saturation of BU[6] cavities with various pharmaceuticals, including antibiotics and inhibitors.

Antigen stabilizing hydrogels based on cyclodextrins and polyethylene glycol act as type-2 adjuvants with suppressed local irritation

Recent viral pandemics have increased global demand for vaccines. However, the supply of effective and safe vaccine not only to developed countries but also developing countries with inadequate storage equipment is still challenging due to the lack of robust systems which improve the efficacy and the stability of vaccines with few side effects. In our previous study, polypseudorotaxane (PPRX) hydrogels based on cyclodextrin (CyD) and polyethylene glycol (PEG) significantly improved the stability of antibody preparations and showed no serious adverse effects after subcutaneous injection, suggesting the possibility as safe vaccine formulations to stabilize an antigen protein. Moreover, recent studies have reported that one of the CyD derivatives, hydroxypropyl-β-CyD (HP-β-CyD), acts as an adjuvant to enhance protective type-2 immune responses. However, it is still unknown that CyD PPRX hydrogels enhance not only the stability of an antigen protein but also its immunogenicity with tolerable side effects. Here, we demonstrate that α- and γ-CyD PPRX hydrogels containing an antigen protein significantly induce antigen-specific type-2 immune responses. Moreover, α- and γ-CyD PPRX hydrogels showed negligible local irritation at the injection site, although subcutaneous injection of α-CyD alone induced skin lesion. Finally, shaking stability of the antigen protein at room temperature was significantly improved by being included in α- and γ-CyD PPRX hydrogels. These results propose the possibility of α- and γ-CyD PPRX hydrogels as novel vaccine formulations which improve both the immunogenicity and stability of an antigen protein with suppressed local irritation.

Supramolecular Surface Coatings with Acetylated Polyrotaxane-Based Triblock Copolymers for Thermal Regulation of Cell Adhesion and Fabrication of Cell Sheets

Polyrotaxanes (PRXs) containing acetylated α-cyclodextrins exhibit a temperature-dependent phase transition in aqueous solutions across their lower critical solution temperature (LCST) of approximately 26.6 °C. To gain insights into the interactions of acetylated PRXs (Ac-PRXs) with biological components, thermoresponsive supramolecular surfaces were prepared by coating tissue culture polystyrene (TCPS) surfaces with Ac-PRX triblock copolymers, and their surface properties across the LCST were evaluated. The wettability and protein adsorption of Ac-PRX-coated surfaces changed significantly between 10 and 37 °C, whereas the uncoated TCPS and unmodified PRX-coated surfaces did not alter the wettability and protein adsorption at 10 and 37 °C. The adhesion, proliferation, morphology, and adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces were found to be similar to those of the uncoated and unmodified PRX-coated surfaces. However, the adhesion strength of NIH/3T3 cells on Ac-PRX-coated surfaces decreased drastically at 10 °C. Consequently, the cells spontaneously detached from the Ac-PRX-coated surfaces without enzymatic treatment. Additionally, when incubating confluent cells at 10 °C, the cells detached from Ac-PRX-coated surfaces as cell sheets while retaining extracellular matrix proteins. The findings of this study provide new directions for the design of thermoresponsive supramolecular biointerfaces for applications in bioseparation and cell manipulation.

PLGA–TiO2 as a Carrier System for Drug Release

This paper reports the results of the PLGA–TiO2 nanocomposite regarding the green synthesis of titanium dioxide nanoparticles using a natural extract, its characterization, and encapsulation with poly(lactic-co-glycolic acid) (PLGA). UV–visible spectrometry was used for the identification of terpenes present in the extracts. The morphology of the nanoparticles was determined by scanning electron microscopy. Infrared spectroscopy was used for the determination of functional groups, while X-ray diffraction was used to determine the crystal structure. The analysis of the extended release of the encapsulated extract in the matrix of the nanomaterial resulted in a maximum visible UV absorbance at approximately 260 nm and confirmed the synthesis of titanium dioxide nanoparticles. Moreover, terpenes enhance synthesis and stabilize titanium dioxide nanoparticles. The synthesized structures are spherical and amorphous, 44 nm in size, and encapsulated at 65 nm.

Facile Construction of a Two-in-One Injectable Micelleplex-Loaded Thermogel System for the Prolonged Delivery of Plasmid DNA

Nanoparticle-hydrogel systems have recently emerged as a class of interesting hybrid materials with immense potential for several biomedical applications. Remarkably, the incorporation of nanoparticles into a hydrogel may yield synergistic benefits lacking in a singular system. However, most synthetic strategies require laborious steps to achieve the system, severely restricting the process of translational research. Herein, a facile strategy to access a two-in-one system comprising two distinct polyurethane (PU)-based micellar systems is demonstrated and applied as a novel sustained gene delivery platform, where the two PUs are synthesized similarly but with slightly different compositions. One PU forms cationic micelles that complex with plasmid DNA (pDNA), which are loaded into a thermogel formed by another PU micellar system for the prolonged release of pDNA micelleplexes. Specifically, a thermogelling multiblock PU copolymer (denoted as EPH) was synthesized via the step-growth polymerization of poly(ethylene glycol), poly(propylene glycol), and poly(3-hydroxybutyrate). By further introducing a cationic extender, 3-(dimethylamino)-1,2-propanediol, into the reaction feed, a series of cationic PUs (denoted as EPHD) with varying compositions were obtained. The EPHDs formed positively charged micelles in aqueous solutions, efficiently condensed pDNA into nano-sized micelleplexes (<200 nm) at optimized w/w ratios, and mediated transient green fluorescence protein expression in HEK293T cells at 48 h post-transfection. On the other hand, aqueous EPH solution (4 wt %) was injectable at 4 °C and rapidly gelled upon heating to 37 °C to form a stable hydrogel depot. EPHD/pDNA micelleplexes were easily loaded into EPH by mixing the solutions at 4 °C, before heating to 37 °C, leading to the resultant hydrogel system. The in vitro release study revealed that while free pDNA loaded in the thermogel was completely released in 2 weeks, the release of EPHD/pDNA micelleplexes was prolonged to at least 28 days, suggesting substantial micelleplex-hydrogel interactions. Intact, bioactive, and noncytotoxic EPHD/pDNA micelleplexes in the release media were proved by gel retardation, in vitro gene transfection, and CCK-8 cytotoxicity assay results, respectively. Collectively, this work presents a simple approach to achieving and optimizing a novel two-in-one nanoparticle-hydrogel system for the prolonged delivery of pDNA and may be promising for long-term gene delivery applications.

Classifying soft self-assembled materials via unsupervised machine learning of defects

Unlike molecular crystals, soft self-assembled fibers, micelles, vesicles, etc., exhibit a certain order in the arrangement of their constitutive monomers but also high structural dynamicity and variability. Defects and disordered local domains that continuously form-and-repair in their structures impart to such materials unique adaptive and dynamical properties, which make them, e.g., capable to communicate with each other. However, objective criteria to compare such complex dynamical features and to classify soft supramolecular materials are non-trivial to attain. Here we show a data-driven workflow allowing us to achieve this goal. Building on unsupervised clustering of Smooth Overlap of Atomic Position (SOAP) data obtained from equilibrium molecular dynamics simulations, we can compare a variety of soft supramolecular assemblies via a robust SOAP metric. This provides us with a data-driven "defectometer" to classify different types of supramolecular materials based on the structural dynamics of the ordered/disordered local molecular environments that statistically emerge within them.

Heat- and shear-reversible networks in food: A review

While nature behaves like an irreversible network with respect to entropy and time, certain systems in nature exist that are, to some extent, reversible. The property of reversibility imparts unique benefits to systems that possess them, making them suitable for designing self-healing, stimuli-responsive, and smart materials that can be used in widely divergent fields. Reversible networks are currently being exploited for applications in tissue engineering, drug delivery, and soft robotics. They are also being utilized as low-calorie fat mimetics with melt-in-your-mouth textures, as well as being explored as potential scaffolds for three-dimensional (3D) printable food, among other applications. This review aims to gather representative examples of heat- and shear-reversible networks in the food science literature from the last 30 or so years, in other words, reversible food gels made either from linear biopolymers or from colloidal, particulate dispersions, including those that have been modified specifically to induce reversibility. An overview of the network mechanisms involved that impart reversibility, including a discussion of the strength and range of forces involved, will be highlighted. A model that explains why certain networks are thermoreversible while others are shear-reversible, and why others are both, will also be proposed. A fundamental understanding of these mechanisms will prove invaluable when designing reversible networks in the future, making possible the precise control of their properties, thus fostering innovative applications within the food industry and beyond.

Cografting of Zwitterionic Sulfobetaines and Cationic Amines on β-Cyclodextrin-Threaded Polyrotaxanes Facilitates Cellular Association and Tissue Accumulation with High Biocompatibility

β-Cyclodextrins (β-CDs) and β-CD-containing polymers have attracted considerable attention as potential candidates for the treatment of cholesterol-related metabolic and intractable diseases. We have advocated the use of β-CD-threaded acid-degradable polyrotaxanes (PRXs) as intracellular delivery carriers for β-CDs. As unmodified PRXs are insoluble in aqueous solutions, chemical modification of PRXs is an essential process to improve their solubility and impart novel functionalities. In this study, we investigated the effect of the modification of zwitterionic sulfobetaines on PRXs due to their excellent solubility, biocompatibility, and bioinert properties. Sulfobetaine-modified PRXs were synthesized by converting the tertiary amino groups of precursor 2-(N,N-dimethylamino)ethyl carbamate-modified PRXs (DMAE-PRXs) using 1,3-propanesultone. The resulting sulfobetaine-modified PRXs showed high solubility in aqueous solutions and no cytotoxicity, while their intracellular uptake levels were low. To further improve this system, we designed PRXs cografted with zwitterionic sulfobetaine and cationic DMAE groups via partial betainization of the DMAE groups. Consequently, the interaction with proteins, intracellular uptake levels, and liver accumulation of partly betainized PRXs were found to be higher than those of completely betainized PRXs. Additionally, partly betainized PRXs showed no toxicity in vitro or in vivo despite the presence of residual cationic DMAE groups. Furthermore, partly betainized PRXs ameliorated the abnormal free cholesterol accumulation in Niemann-Pick type C disease patient-derived cells at lower concentrations than β-CD derivatives and previously designed PRXs. Overall, the cografting of sulfobetaines and amines on PRXs is a promising chemical modification for therapeutic applications due to the high cholesterol-reducing ability and biocompatibility of such modified PRXs. In addition, modification with both zwitterionic and cationic groups can be used for the design of various polymeric materials exhibiting both bioinert and bioactive characteristics.

Selective Homocysteine Assay with Cucurbit[7]uril by pH Regulation

We report the effect of pH on the supramolecular complexation of two biothiols, viz., homocysteine (Hcy) and cysteine (Cys), with cucurbit[7]uril (CB[7]). Under basic pH conditions, Cys did not complex with CB[7], whereas Hcy efficiently complexed with CB[7], as confirmed by ¹H NMR spectroscopy and Ellman's reagent (5,5'-dithio-bis(2-nitrobenzoic acid), DTNB) assay. ¹H NMR and Raman spectroscopic studies revealed that, in the absence of CB[7], Hcy auto-oxidized slowly (~36 h) to homocystine (HSSH) under basic pH conditions. However, the rate of Hcy oxidation increased by up to 150 fold in the presence of CB[7], as suggested by the DTNB assay. Thus, supramolecular complexation under basic pH conditions led to the formation of a HSSH-CB[7] complex, and not Hcy-CB[7]. The results indicate that Hcy is rapidly oxidized to HSSH under the catalysis of CB[7], which acts as a reaction chamber, in basic pH conditions. Our studies suggest that Hcy concentration, a risk factor for cardiovascular disease, can be selectively and more easily quantified by supramolecular complexation with CB [7].

PCL-PEG copolymer based injectable thermosensitive hydrogels

A number of stimuli-responsive-based hydrogels has been widely explored in biomedical applications in the last few decades because of their excellent biodegradability and biocompatibility. The development of synthetic chemistry and materials science leads to the emergence of in situ stimuli-responsive hydrogels. In this regard, several synthetic and natural polymers have been synthesized and utilized to prepare temperature-sensitive in situ forming hydrogels. This could be best used via injections as temperature stimulus could trigger in situ hydrogels gelation and swelling behaviors. There are many smart polymers available for the formulation of the in situ based thermoresponsive injectable hydrogel. Among these, poly (ε-caprolactone) (PCL) polymer has been recognized and approved by the FDA for numerous biomedical applications. More specifically, the PCL is coupled with polyethylene glycol (PEG) to obtain amphiphilic thermosensitive "smart" copolymers (PCL-PEG), to form rapid and reversible physical gelation behavior. However, the chemical structure of the copolymer is a critical aspect in determining water solubility, thermo-gelation behavior, drug release rate, degradation rate, and the possibility to deliver a diverse range of drugs. In this review, we have highlighted the typical PCL-PEG-based thermosensitive injectable hydrogels progress in the last decade for tissue engineering and localized drug delivery applications to treat various diseases. Additionally, the impact of molecular weight of PCL-PEG upon gelling behavior has also been critically highlighted for optimum hydrogels properties for potential pharmaceutical and biomedical applications.

Doxorubicin-loaded graphene oxide nanocomposites in cancer medicine: Stimuli-responsive carriers, co-delivery and suppressing resistance

INTRODUCTION

The application of doxorubicin (DOX) in cancer therapy has been limited due to its drug resistance and poor internalization. Graphene oxide (GO) nanostructures have the capacity for DOX delivery while promoting its cytotoxicity in cancer.

AREAS COVERED

The favorable characteristics of GO nanocomposites, preparation method, and application in cancer therapy are described. Then, DOX resistance in cancer is discussed. The GO-mediated photothermal therapy and DOX delivery for cancer suppression are described. Preparation of stimuli-responsive GO nanocomposites, surface functionalization, hybrid nanoparticles, and theranostic applications are emphasized in DOX chemotherapy.

EXPERT OPINION

Graphene oxide nanoparticle-based photothermal therapy maximizes the anti-cancer activity of DOX against cancer cells. Apart from DOX delivery, GO nanomaterials are capable of loading anti-cancer agents and genetic tools to minimize drug resistance and enhance the cytolytic impact of DOX in cancer eradication. To enhance DOX accumulation in cancer cells, stimuli-responsive (redox-, light-, enzyme- and pH-sensitive) GO nanoparticles have been developed for DOX delivery. Further development of targeted delivery of DOX-loaded GO nanomaterials against cancer cells may be achieved by surface modification of polymers such as polyethylene glycol, hyaluronic acid, and chitosan. Doxorubicin-loaded GO nanoparticles have demonstrated theranostic potential for simultaneous diagnosis and therapy. Hybridization of GO with other nanocarriers such as silica and gold nanoparticles further broadens their potential anti-cancer therapy applications.

Supramolecular Radiosensitizer Based on Hypoxia-Responsive Macrocycle

Radiotherapy (RT) has been viewed as one of the most effective and extensively applied curatives in clinical cancer therapy. However, the radioresistance of tumor severely discounts the radiotherapy outcomes. Here, an innovative supramolecular radiotherapy strategy, based on the complexation of a hypoxia-responsive macrocycle with small-molecule radiosensitizer, is reported. To exemplify this tactic, a carboxylated azocalix[4]arene (CAC4A) is devised as molecular container to quantitatively package tumor sensitizer banoxantrone dihydrochloride (AQ4N) through reversible host-guest interaction. Benefited from the selective reduction of azo functional groups under hypoxic microenvironment, the supramolecular prodrug CAC4A•AQ4N exhibits high tumor accumulation and efficient cellular internalization, thereby significantly amplifying radiation-mediated tumor destruction without appreciable systemic toxicity. More importantly, this supramolecular radiotherapy strategy achieves an ultrahigh sensitizer enhancement ratio (SER) value of 2.349, which is the supreme among currently reported noncovalent-based radiosensitization approach. Further development by applying different radiosensitizing drugs can make this supramolecular strategy become a general platform for boosting therapeutic effect in cancer radiotherapies, tremendously promising for clinical translation.

Design, Synthesis and Evaluation of Novel Antimicrobial Polymers Based on the Inclusion of Polyethylene Glycol/TiO2 Nanocomposites in Cyclodextrin as Drug Carriers for Sulfaguanidine

Polymers and their composites have recently attracted attention in both pharmaceutical and biomedical applications. Polyethylene glycol (PEG) is a versatile polymer extensively used in medicine. Herein, three novel PEG-based polymers that are pseudopolyrotaxane (PEG/α-CD) (1), titania–nanocomposite (PEG/TiO₂NPs) (2), and pseudopolyrotaxane–titania–nanocomposite (PEG/α-CD/TiO₂NPs) (3), were synthesized and characterized. The chemical structure, surface morphology, and optical properties of the newly materials were examined by FT-IR, ¹H-NMR, SEM, and UV–Vis., respectively. The prepared polymers were used as drug carriers of sulfaguanidine as PEG/α-CD/Drug (4), PEG/TiO₂NPs/Drug (5), and PEG/α-CD/TiO₂NPs/Drug (6). The influence of these drug-carrying formulations on the physical and chemical characteristics of sulfaguanidine including pharmacokinetic response, solubility, and tissue penetration was explored. Evaluation of the antibacterial and antibiofilm effect of sulfaguanidine was tested before and after loading onto the prepared polymers against some Gram-negative and positive bacteria (E. coli, Pseudomonas aeruginosa, and Staphylococcus aureus (MRSA)), as well. The results of this work turned out to be very promising as they confirmed that loading sulfaguanidine to the newly designed polymers not only showed superior antibacterial and antibiofilm efficacy compared to the pure drug, but also modified the properties of the sulfaguanidine drug itself.

Effect of Functional Group on the Catalytic Activity of Lipase B from Candida antarctica Immobilized in a Silica-Reinforced Pluronic F127/α-Cyclodextrin Hydrogel

Surface modification plays a key role in the fabrication of highly active and stable enzymatic nanoreactors. In this study, we report for the first time the effect of various functional groups (epoxy, amine, trimethyl, and hexadecyl) on the catalytic performance of lipase B from Candida antarctica (CALB) incorporated within a monolithic supramolecular hydrogel with multiscale pore architecture. The supramolecular hydrogel formed by host-guest interactions between α-cyclodextrin (α-CD) and Pluronic F127 was first silicified to provide a hierarchically porous material whose surface was further modified with different organosilanes permitting both covalent anchoring and interfacial activation of CALB. The catalytic activity of nanoreactors was evaluated in the liquid phase cascade oxidation of 2,5-diformylfuran (DFF) to 2,5-furandicarboxylic acid (FDCA) under mild conditions. Results showed that high FDCA yields and high efficiency conversion of DFF could be correlated with the ability of epoxy and amine moieties to keep CALB attached to the carrier, while the trimethyl and hexadecyl groups could provide a suitable hydrophobic-hydrophilic interface for the interfacial activation of lipase. Cationic cross-linked β-CD was also evaluated as an enzyme-stabilizing agent and was found to provide beneficial effects in the operational stability of the biocatalyst. These supramolecular silicified hydrogel monoliths with hierarchical porosity may be used as promising nanoreactors to provide easier enzyme recovery in other biocatalytic continuous flow processes.

Cyclodextrin-Containing Hydrogels: A Review of Preparation Method, Drug Delivery, and Degradation Behavior

Hydrogels possess porous structures, which are widely applied in the field of materials and biomedicine. As a natural oligosaccharide, cyclodextrin (CD) has shown remarkable application prospects in the synthesis and utilization of hydrogels. CD can be incorporated into hydrogels to form chemically or physically cross-linked networks. Furthermore, the unique cavity structure of CD makes it an ideal vehicle for the delivery of active ingredients into target tissues. This review describes useful methods to prepare CD-containing hydrogels. In addition, the potential biomedical applications of CD-containing hydrogels are reviewed. The release and degradation process of CD-containing hydrogels under different conditions are discussed. Finally, the current challenges and future research directions on CD-containing hydrogels are presented.

A Dispersion Corrected DFT Investigation of the Inclusion Complexation of Dexamethasone with β-Cyclodextrin and Molecular Docking Study of Its Potential Activity against COVID-19

The encapsulation mode of dexamethasone (Dex) into the cavity of β-cyclodextrin (β-CD), as well as its potential as an inhibitor of the COVID-19 main protease, were investigated using density functional theory with the recent dispersion corrections D4 and molecular docking calculations. Independent gradient model and natural bond orbital approaches allowed for the characterization of the host–guest interactions in the studied systems. Structural and energetic computation results revealed that hydrogen bonds and van der Waals interactions played significant roles in the stabilization of the formed Dex@β-CD complex. The complexation energy significantly decreased from −179.50 kJ/mol in the gas phase to −74.14 kJ/mol in the aqueous phase. A molecular docking study was performed to investigate the inhibitory activity of dexamethasone against the COVID-19 target protein (PDB ID: 6LU7). The dexamethasone showed potential therapeutic activity as a SARS CoV-2 main protease inhibitor due to its strong binding to the active sites of the protein target, with predicted free energy of binding values of −29.97 and −32.19 kJ/mol as calculated from AutoDock4 and AutoDock Vina, respectively. This study was intended to explore the potential use of the Dex@β-CD complex in drug delivery to enhance dexamethasone dissolution, thus improving its bioavailability and reducing its side effects.

Injectable nanocomposite hydrogels as an emerging platform for biomedical applications: A review

Hydrogels have attracted much attention for biomedical and pharmaceutical applications due to the similarity of their biomimetic structure to the extracellular matrix of natural living tissues, tunable soft porous microarchitecture, superb biomechanical properties, proper biocompatibility, etc. Injectable hydrogels are an exciting type of hydrogels that can be easily injected into the target sites using needles or catheters in a minimally invasive manner. The more comfortable use, less pain, faster recovery period, lower costs, and fewer side effects make injectable hydrogels more attractive to both patients and clinicians in comparison to non-injectable hydrogels. However, it is difficult to achieve an ideal injectable hydrogel using just a single material (i.e., polymer). This challenge can be overcome by incorporating nanofillers into the polymeric matrix to engineer injectable nanocomposite hydrogels with combined or synergistic properties gained from the constituents. This work aims to critically review injectable nanocomposite hydrogels, their preparation methods, properties, functionalities, and versatile biomedical and pharmaceutical applications such as tissue engineering, drug delivery, and cancer labeling and therapy. The most common natural and synthetic polymers as matrices together with the most popular nanomaterials as reinforcements, including nanoceramics, carbon-based nanostructures, metallic nanomaterials, and various nanosized polymeric materials, are highlighted in this review.

Tissue Adhesion-Anisotropic Polyrotaxane Hydrogels Bilayered with Collagen

Hydrogels are promising materials in tissue engineering scaffolds for healing and regenerating damaged biological tissues. Previously, we developed supramolecular hydrogels using polyrotaxane (PRX), consisting of multiple cyclic molecules threaded by an axis polymer for modulating cellular responses. However, since hydrogels generally have a large amount of water, their adhesion to tissues is extremely weak. Herein, we designed a bilayered hydrogel with a PRX layer and a collagen layer (PRX/collagen hydrogel) to achieve rapid and strong adhesion to the target tissue. The PRX/collagen hydrogel was fabricated by polymerizing PRX crosslinkers in water with placement of a collagen sponge. The differences in components between the PRX and collagen layers were analyzed using Fourier transform infrared spectroscopy (FT-IR). After confirming that the fibroblasts adhered to both layers of the PRX/collagen hydrogels, the hydrogels were implanted subcutaneously in mice. The PRX hydrogel without collagen moved out of its placement site 24 h after implantation, whereas the bilayer hydrogel was perfectly adherent at the site. Together, these findings indicate that the bilayer structure generated using PRX and collagen may be a rational design for performing anisotropic adhesion.

Characteristic of Cyclodextrins: Their Role and Use in the Pharmaceutical Technology

About 40% of newly-discovered entities are poorly soluble in water, and this may be an obstacle in the creation of new drugs. To address this problem, the present review article examines the structure and properties of cyclodextrins and the formation and potential uses of drug - cyclodextrin inclusion complexes. Cyclodextrins are cyclic oligosaccharides containing six or more D-(+)- glucopyranose units linked by α-1,4-glycosidic bonds, which are characterized by a favourable toxicological profile, low local toxicity and low mucous and eye irritability; they are virtually non-toxic when administered orally. They can be incorporated in the formulation of new drugs in their natural form (α-, β-, γ-cyclodextrin) or as chemically-modified derivatives. They may also be used as an excipient in drugs delivered by oral, ocular, dermal, nasal and rectal routes, as described in the present paper. Cyclodextrins are promising compounds with many beneficial properties, and their use may be increasingly profitable for pharmaceutical scientists.

A Pseudorotaxane System Containing γ-Cyclodextrin Formed via Chiral Recognition with an AuI 6 AgI 3 CuII 3 Molecular Cap

Solvent-mediated crystal-to-crystal transformations of [Au₆ Ag₃ Cu₃ (H₂ O)₃ (d-pen)₆ (tdme)₂ ]³⁺ (d-[1(H₂ O)₃ ]³⁺ ; pen^2- =penicillaminate, tdme=1,1,1-tris(diphenylphosphinomethyl)ethane) to form unique supramolecular species are reported. Soaking crystals of d-[1(H₂ O)₃ ]³⁺ in aqueous Na₂ bdc (bdc^2- =1,4-benzenedicarboxylate) yielded crystals containing d-[1(bdc)(H₂ O)₂ ]⁺ due to the replacement of a terminal aqua ligand in d-[1(H₂ O)₃ ]³⁺ by a monodentate bdc^2- ligand. When γ-cyclodextrin (γ-CD) was added to aqueous Na₂ bdc, d-[1(H₂ O)₃ ]³⁺ was transformed to d-[1(bdc@γ-CD)(H₂ O)₂ ]⁺ , where a γ-CD ring was threaded by a bdc^2- molecule to construct a pseudorotaxane structure. While the use of dicarboxylates with an aliphatic carbon chain instead of bdc^2- afforded analogous pseudorotaxanes, such pseudorotaxane species were not formed when crystals of [Au₆ Ag₃ Cu₃ (H₂ O)₃ (l-pen)₆ (tdme)₂ ]³⁺ (l-[1(H₂ O)₃ ]³⁺ ) enantiomeric to d-[1(H₂ O)₃ ]³⁺ were soaked in aqueous Na₂ bdc and γ-CD, affording only crystals containing l-[1(bdc)(H₂ O)₂ ]⁺ .

β-Cyclodextrin-Polyacrylamide Hydrogel for Removal of Organic Micropollutants from Water

Water pollution by various toxic substances remains a serious environmental problem, especially the occurrence of organic micropollutants including endocrine disruptors, pharmaceutical pollutants and naphthol pollutants. Adsorption process has been an effective method for pollutant removal in wastewater treatment. However, the thermal regeneration process for the most widely used activated carbon is costly and energy-consuming. Therefore, there has been an increasing need to develop alternative low-cost and effective adsorption materials for pollutant removal. Herein, β-cyclodextrin (β-CD), a cheap and versatile material, was modified with methacrylate groups by reacting with methacryloyl chloride, giving an average degree of substitution of 3 per β-CD molecule. β-CD-methacrylate, which could function as a crosslinker, was then copolymerized with acrylamide monomer via free-radical copolymerization to form β-CD-polyacrylamide (β-CD-PAAm) hydrogel. Interestingly, in the structure of the β-CD-PAAm hydrogel, β-CD is not only a functional unit binding pollutant molecules through inclusion complexation, but also a structural unit crosslinking PAAm leading to the formation of the hydrogel 3D networks. Morphological studies showed that β-CD-PAAm gel had larger pore size than the control PAAm gel, which was synthesized using conventional crosslinker instead of β-CD-methacrylate. This was consistent with the higher swelling ratio of β-CD-PAAm gel than that of PAAm gel (29.4 vs. 12.7). In the kinetic adsorption studies, phenolphthalein, a model dye, and bisphenol A, propranolol hydrochloride, and 2-naphthol were used as model pollutants from different classes. The adsorption data for β-CD-PAAm gel fitted well into the pseudo-second-order model. In addition, the thermodynamic studies revealed that β-CD-PAAm gel was able to effectively adsorb the different dye and pollutants at various concentrations, while the control PAAm gel had very low adsorption, confirming that the pollutant removal was due to the inclusion complexation between β-CD units and pollutant molecules. The adsorption isotherms of the different dye and pollutants by the β-CD-PAAm gel fitted well into the Langmuir model. Furthermore, the β-CD-PAAm gel could be easily recycled by soaking in methanol and reused without compromising its performance for five consecutive adsorption/desorption cycles. Therefore, the β-CD-PAAm gel, which combines the advantage of an easy-to-handle hydrogel platform and the effectiveness of adsorption by β-CD units, could be a promising pollutant removal system for wastewater treatment applications.

Polypseudorotaxane and polydopamine linkage-based hyaluronic acid hydrogel network with a single syringe injection for sustained drug delivery

Polypseudorotaxane structure and polydopamine bond-based crosslinked hyaluronic acid (HA) hydrogels including donepezil-loaded microspheres were developed for subcutaneous injection. Both dopamine and polyethylene glycol (PEG) were covalently bonded to the HA polymer for catechol polymerization and inclusion complexation with alpha-cyclodextrin (α-CD), respectively. A PEG chain of HA-dopamine-PEG (HD-PEG) conjugate was threaded with α-CD to make a polypseudorotaxane structure and its pH was adjusted to 8.5 for dopamine polymerization. Poly(lactic-co-glycolic acid) (PLGA)/donepezil microsphere (PDM) was embedded into the HD-PEG network for its sustained release. The HD-PEG/α-CD/PDM 8.5 hydrogel system exhibited an immediate gelation pattern, injectability through single syringe, self-healing ability, and shear-thinning behavior. Donepezil was released from the HD-PEG/α-CD/PDM 8.5 hydrogel in a sustained pattern. Following subcutaneous injection, the weight of excised HD-PEG/α-CD/PDM 8.5 hydrogel was higher than the other groups on day 14. These findings support the clinical feasibility of the HD-PEG/α-CD/PDM 8.5 hydrogel for subcutaneous injection.