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The CNT sponge-based 3D frame hydrogel showed remarkable responses to electrical and thermal stimuli, exhibited excellent controllable/switchable drug delivery, and has great potential in biomedical engineering and medicine applications.

Various drug delivery techniques have contributed significantly to medical practice. In particular, molecular imprinting is a suitable method to increase the drug-loading efficiency in limited 3D spaces, such as hydrogels. This method has recently been studied for the transdermal delivery of various therapeutic agents, but its full potential is yet to be achieved in molecular systems. In this study, thermoresponsive and molecularly imprinted hydrogels were prepared by radical polymerization with molecular imprinting using three types of drug molecules as templates. The drug templates—acyclovir (ACV), diclofenac (DFN), and doxorubicin (DXR)—were used to establish molecular correlations between molecularly imprinted hydrogels and drug molecules by using non-covalent Lewis acid–base interactions, hydrophilicity and molecular size. The DXR-imprinted hydrogel exhibited a much greater imprinting efficiency than ACV- and DFN-imprinted hydrogels because of the hydrophilic characteristics and large molecular size of DXR compared with the other drugs. The morphology, surface area, and swelling behavior, dependent on the temperature, were also investigated. The in vitro drug release studies performed at various temperatures revealed unique drug release profiles unlike previous thermoresponsive studies. This study demonstrated a facile strategy to construct molecularly imprinted hydrogels that exhibit thermoresponsive delivery and offer new guidelines to identify optimal combination between drugs and hydrogels.

A novel Pd-nanoparticle-catalyst supported on chitosan-pyridine-modified carbon nanotube (CNT) was prepared. The obtained Pd-catalytic platform (Pd@CS-Py@CNT) was fully characterized and employed to the Suzuki–Miyaura coupling reaction as a heterogeneous catalyst, showing an excellent catalytic activity in aqueous media in the absence of phase transfer agents. Moreover, the easy recoverability and reusability of the catalytic system after a simple manipulation is a great benefit.

In glucose sensors, the direct electron transfer (DET) method delivers electrons from glucose oxidase (GOx) to an electrode without the intervention of a mediator. Many researchers have developed the DET method using carbon nanotube (CNT)-based composites for the permeation into the enzyme co-factor. We synthesized chitosan (Chit) core-shelled CNTs that were hydrophilic, biocompatible, and easily prepared. Electrodes with three different Chit-CNT weight ratios were prepared, and their morphological and physicochemical properties were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), scanning electron microscopy (SEM), and transition electron microscopy (TEM). The Chit-CNT85 composite (85 wt% Chit) performed optimally by cyclic voltammetry (CV), and was covalently modified with GOx via a routine coupling protocol to form the GOx-Chit-CNT85/ITO electrode. This electrode was electrochemically characterized by impedance spectroscopy (EIS). The GOx loading and pH were optimized against the CV redox potential. The electrode exhibited a fast electron-transfer constant (ks) of 8.2 s−1. The cathodic peak of GOx decreased in response to increasing glucose concentrations, but no changes were observed in the presence of physiological interfering substances such as ascorbic acid and uric acid. Therefore, our GOx-Chit-CNT85/ITO electrode has the potential for use in glucose sensing directly without a mediator.

A novel palladium-nanohybrid (Pd–Chitosan–CNT) catalytic composite has been developed using CNT–chitosan nanocomposite and palladium nitrate. The prepared catalytic platform displays excellent catalytic reactivity for the ipso-hydroxylation of various arylboronic acids with a mild oxidant aqueous H2O2 at room temperature, affording the corresponding phenols in excellent yields. Significantly, the easy recovery and reusability by simple manipulation demonstrate the green credentials of this catalytic platform.

A convenient heterogeneous catalytic system consisting of recyclable and reusable carbon nanotube-chitosan nanohybrid film and copper salt was developed for the aerobic ipso-hydroxylation of arylboronic acids. A variety of arylboronic acids bearing electron-withdrawing or electron-donating groups were smoothly transformed at room temperature in water to afford the corresponding phenols in high yields.

Natural inorganic/organic nanohybrids are a fascinating model in biomaterials design due to their ultra-microstructure and extraordinary properties. Here, we report unique-structured nanohybrids through self-assembly of biomedical inorganic/organic nanounits, composed of bioactive inorganic nanoparticle core (hydroxyapatite, bioactive glass, or mesoporous silica) and chitosan shell - namely Chit@IOC. The inorganic core thin-shelled with chitosan could constitute as high as 90%, strikingly contrasted with the conventional composites. The Chit@IOC nanohybrids were highly resilient under cyclic load and resisted external stress almost an order of magnitude effectively than the conventional composites. The nanohybrids, with the nano-roughened surface topography, could accelerate the cellular responses through stimulated integrin-mediated focal adhesions. The nanohybrids were also able to load multiple therapeutic molecules in the core and shell compartment and then release sequentially, demonstrating controlled delivery systems. The nanohybrids compartmentally-loaded with therapeutic molecules (dexamethasone, fibroblast growth factor 2, and phenamil) were shown to stimulate the anti-inflammatory, pro-angiogenic and osteogenic events of relevant cells. When implanted in the in vivo calvarium defect model with 3D-printed scaffold forms, the therapeutic nanohybrids were proven to accelerate new bone formation. Overall, the nanohybrids self-assembled from Chit@IOC nanounits, with their unique properties (ultrahigh inorganic content, nano-topography, high resilience, multiple-therapeutics delivery, and cellular activation), can be considered as promising 3D tissue regenerative platforms.

In recent years, there has been a significant increase in strategies for the development of small intestine (and colon)-specific oral drug-delivery systems to maximize the efficiency of therapeutic agents and reduce side effects. However, only a few strategies are capable of working in the complicated environment of the human intestinal tract. In this study, the preparation of a basic pH/temperature-responsive co-polymer (p-NIVIm) and its in-vitro-drug delivery function in the pH range of 1-8 and temperature range of 25-42 °C are reported. The basic copolymer was prepared by radical copolymerization of N-isopropyl acryl amide (NIPAAm) and N-vinylimidazole (VIm). The lower critical solution temperature (LCST) of p-NIVIm was higher in stomach pH (~1.0) conditions (36.5-42 °C) and lower in small intestine and/or colon pH (~8.0) conditions (35.8-38.2 °C). The ability to uptake a model protein (BSA) at body temperature and to release it in conditions of 37 °C and pH 1-8 was determined. The drug loading capacity (0.231 mg per 1.0 mg copolymer) and efficiency (92.4%) were high at 37 °C/pH 7. The drug carrier showed a slow release pattern at pH 1 (~0.084 mg; ~35%) and then a sudden release pattern (~0.177 mg; ~73%) at pH 8. The cytotoxicity of p-NIVIm to MCF-7 cells in vitro was minimal at concentrations168.9 μg/mL after 72 h. The prepared copolymer with its pH-/temperature-responsive protein-entrapping and -releasing behavior at body temperature may potentially be applied as a novel small intestine (and colon)-specific oral drug delivery system.

Smart carbon nanotube (CNT)-framed (SCNF) membranes were prepared by self-assembly of highly thermo conductive CNT molecules hybridized with chitosan (Chit) in a core–shell structure and then by chemical integration of a temperature-responsive copolymer, poly(NIPAAm-co-BVIm) (or pNIBIm), as an additional outer shell. CNT, Chit, and pNIBIm components used in the SCNF membranes function as a thermally conductive CNT-framework, a biocompatible glue to stick the CNT building blocks together, and a temperature-responsive copolymer, respectively. The SCNF membranes with different Chit/CNT ratios and an almost constant pNIBIm concentration (Chit-CNT25-pNIBIm, Chit-CNT50-pNIBIm and Chit-CNT75-pNIBIm) had a three-dimensional interwoven porous nanostructure. Scanning electron microscopy clearly showed the temperature-responsive swelling and deswelling characteristics of the triple core–shell structured CNT-frames. Temperature-dependent bovine serum albumin (BSA)-loading and -release profiles were obtained at 4 °C, 25 °C, 36.5 °C, and 40 °C. The SCNF membranes, especially the Chit-CNT50-pNIBIm hybrid membrane, showed a markedly high loading capacity of 9.7 mg per mg of membrane at 4 °C. The membrane also showed a temperature-dependent BSA-release characteristic (0.92 mg per mg of membrane at 36.5 °C and 3.41 mg per mg of membrane at 40 °C). The SCNF membranes showing highly effective drug-loading/-releasing characteristics could be potentially used as a skin heat signal-responsive patch type transdermal drug delivery (PTDD) system in the medicinal field.

Here we present carbon nanotube (CNT) buckypaper with efficient loading and releasing patterns for negatively charged drug. Carbonaceous membrane (Chit–NH2 /CNT) with three-dimensionally interwoven porous nanostructure and positive surface was prepared by self-assembly of CNT fibers hybridized with chitosan (Chit–NH2 ) in core–shell structure. Transmission electron microscopy and scanning electron microscopy images clearly showed that core–shell structured Chit–NH2 /CNT fibers and countless nanosized pores at less than 30 nm in length were formed between positively charged Chit–NH2 /CNT fibers. Based on Brunauer–Emmett–Teller N2 -adsorption method, the surface area, average pore size, and pore volume were approximately 19.7 m2/g, 9.54 nm, and 0.043 cc/g, respectively. Bovine serum albumin (BSA) loading and releasing profiles of these carbonaceous membrane constructed with positively charged CNT fibers were tested. The maximum entrapment of BSA was at a loading capacity of 0.65 mg/mg for 1.0 mg of Chit–NH2 /CNT hybrid membrane. The maximum release of BSA was about 65% of the entrapped amount for 1.0 mg of Chit–NH2 /CNT hybrid membrane. BSA was almost continuously released over the 11-day period at a rate of about 0.23 g/day. Chit–NH2 /CNT hybrid membranes showing impressive drug-loading/-releasing characteristics could be potentially used as transdermal drug delivery system for negatively charged drugs in the medicinal field and tissue regeneration area.

Multi-walled carbon nanotubes (MWCNTs) were fabricated on a gold electrode to develop a resistance-sensing humidity sensor with low resistance. Core-shell-structured nanohybrids were prepared using Chitosan-MWCNT to obtain good hydrophilicity, resulting in a highly responsive humidity sensor. We also measured resistance, which changes due to hydrogen bonding between the amine group of chitosan and H2O. The structure of the fabricated chitosan-MWCNT core–shell-structured nanohybrid was measured. Furthermore, we determined the highest response and linearity of the CS-MWCNT25 nanohybrids based on the number of coats on the electrode and the composition ratio of chitosan and MWCNTs. The fabricated CS-MWCNT25 nanohybrid humidity sensor exhibited good electrical efficiency without voltage or frequency dependence and a low-temperature dependency with a temperature coefficient (RH/°C) of 0.187%. Finally, a fast recovery time of 40 s between 30% and 100% RH, a maximum humidity hysteresis of less than 0.300 ± 0.001%, and long-term stability for 2 months indicated that this is an excellent humidity sensor.

Cyclosporine A (CsA) is an extremely hydrophobic immunosuppressive drug, whose systemic administration to suppress the activity of T cells and T cell-based immune responses is frequently associated with a number of adverse drug reactions. Local delivery of CsA focused on a specific target organ has been proposed as a possible solution to this problem. In this study, we developed biodegradable sol-gel drug delivery systems, consisting of HA-Ca-Alg hydrogels combining hyaluronic acid calcium complex (HA-Ca) and sodium alginate (Alg-Na) components, for the local sustained delivery of CsA. A HA-Ca complex with very high degree of substitution was prepared by the acid-base reaction of hyaluronic acid and calcium acetate. The gelation was completed within about 2–45 min without external addition of calcium salts such as CaSO4 and CaCl2, indicating the high potential of the present hydrogel systems for drug delivery by injection in vivo. The HA-Ca system was characterized by high-resolution inductively coupled plasma-optical emission spectroscopy, 1H NMR, FT-IR, and thermogravimetric analysis methods. Moreover, the scanning electron microscopy analysis of the HA-Ca-Alg hydrogels showed an irregular porous morphology, with interconnected pores of 50–300 μm width. The sol-gel transition and the maximum viscosity (about 10,000 cP) of the HA-Ca-Alg hydrogels were characterized by examining the time evolution of the viscosity at 37 °C. The hydrolytic degradation of the HA-Ca-Alg hydrogel was also examined at 37 °C. CsA-encapsulated HA-Ca-Alg hydrogels exhibited sustained in vitro release of CsA over 14 days, which was confirmed through in vitro measurements of the activity of murine T cells over 2 weeks. These results show that the present injectable HA-Ca-Alg hydrogels can be used effectively for the sustained delivery of extremely hydrophobic immunosuppressive drugs, including CsA.

Carbon nanotubes (CNTs) have an important role in nanotechnology due to their unique properties, retaining the inherent material flexibility, superior strength, and electrical conductivity, unless the bottleneck of CNTs persists and the aggregated structure is overcome. Here, we report on the highly enhanced mechanical and electrical properties of the CNT-chitosan nanocomposites through homogeneous dispersion of CNTs into chitosan solution using a high-pressure homogenizer. The optimal condition is a 50% (w/w) chitosan-CNT film, providing about 7 nm thickness of homogeneous chitosan layer on CNTs, a good tensile strength of 51 MPa, high electrical conductivity under 16 Ω/sq, and a stable bending and folding performance. This CNT-chitosan nanocomposite with highly enhanced properties is an amenable material to fabricate structures of various shapes such as films, sensors, and circuits and also enables a simple and cost-effective approach to improve the performance of a device that presents the first flexible and soft electric circuits yet reported using only CNT-chitosan as the conductor.

Phosphorylation of sodium alginate salt (NaAlg) was carried out using H3PO4/P2O5/Et3PO4 followed by acid-base reaction with Ca(OAc)2 to give phosphorylated alginic acid calcium complexes (CaPAlg), as a water dispersible alginic acid derivative. The modified alginate derivatives including phosphorylated alginic acid (PAlg) and CaPAlg were characterized by nuclear magnetic resonance spectroscopy for (1)H, and (31)P nuclei, high resolution inductively coupled plasma optical emission spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. CaPAlg hydrogels were prepared simply by mixing CaPAlg solution (2w/v%) with NaAlg solution (2w/v%) in various ratios (2:8, 4:6, 6:4, 8:2) of volume. No additional calcium salts such as CaSO4 or CaCl2 were added externally. The gelation was completed within about 3-40min indicating a high potential of hydrogel delivery by injection in vivo. Their mechanical properties were tested to be ≤6.7kPa for compressive strength at break and about 8.4kPa/mm for elastic modulus. SEM analysis of the CaPAlg hydrogels showed highly porous morphology with interconnected pores of width in the range of 100-800μm. Cell culture results showed that the injectable hydrogels exhibited comparable properties to the pure alginate hydrogel in terms of cytotoxicity and 3D encapsulation of cells for a short time period. The developed injectable hydrogels showed suitable physicochemical and mechanical properties for injection in vivo, and could therefore be beneficial for the field of soft tissue engineering.

We present CNT bucky-sponges prepared using CS-NH 2 /CNT-cement (CNT nanohybrid molecules individually wrapped with chitosan molecules) as a construction material and an imidazolium based room temperature ionic liquid (RTIL) as a liquid porogen. The nano-sized and micro-sized pores with various width (respectively, about 2 /g and 0.022–3.22 Ω cm. The prepared CNT sponges showed important characteristics indicating broad applicability as a conductive polymer framework, drug carrying scaffold, catalyst support, oil adsorbents, and molecular sieve membrane.