Chitosan/halloysite nanotubes microcomposites: A double header approach for sustained release of ciprofloxacin and its hemostatic effects

Effects of pure and intercalated halloysites on thermal properties of phthalonitrile resin nanocomposites

The enhancement of mechanical and thermal properties of rigid polyurethane foam (RPUF) achieved through a cost‐effective and sustainable approach remains an ongoing interest in both industry and academia. In this study, water‐blown rigid polyurethane (PU) foams based on crude glycerol (CG) polyol are developed and halloysite nanotubes (HN) and microcrystalline cellulose (MC) with different loadings of 1.0, 3.0, and 5.0% are incorporated to improve the performance of the foams, respectively. Effects of different loadings of HN or MC on the viscosity of CG polyols and the foaming process are investigated. CG‐based polyurethane (CGPU) foams and their foam composites (CG‐HN PU foams and CG‐MC PU foams) are characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results reveal that HN is easier to disperse uniformly in the CG polyol than MC and CGPU foams with 1.0% of HN and MC shows significantly improved performance. Their compressive strength increases by 3.8 and 12.5%, respectively, as the HN and MC loadings increases from 0 to 1.0%. The thermal conductivities of CG PU foams reinforced with 1.0% of HN and MC are 37.79 and 37.94 mWm−1K−1, which are lower than that (38.24 mWm−1K−1) of CGPU foams without the addition of fillers. Moreover, compared to CGPU foams, both CG‐HN PU foams and CG‐MC PU foams show improved thermal stabilities, and the latter is higher than the former.Practical Applications: Different fillers (HN and MC) are used to reinforce the CG‐based polyurethane, and water‐blown rigid PU biofoam composites with improved properties are prepared. The use of fillers (HN and MC) has the potential for the production of advanced CG‐based rigid PU foams.Water‐blown rigid crude glycerol‐based polyurethane foams (PU) reinforced with halloysite nanotubes (HN) and microcrystalline cellulose (MC). The results reveal that HN is easier to disperse uniformly in the CG polyol than MC and CGPU foams with 1.0% of HN and MC show significantly improved performance. The thermal conductivities of CG PU foams reinforced with 1.0% of HN and MC are 37.79 and 37.94 mWm−1K−1, which are lower than that of CGPU foams without the addition of fillers. Moreover, compared to CGPU foams, both CG‐HN PU foams and CG‐MC PU foams show improved thermal stabilities.

Improvement of mechanical and thermal properties of poly(3-hydroxybutyrate) (PHB) blends with surface-modified halloysite nanotubes (HNT)

There is a need for titanium (Ti), an antimicrobial implant coating that provides sustained protection against bacterial infection. Chitosan (CS) coatings, combined with halloysite nanotubes (HNTs), are an attractive solution due to the inherent biocompatibility of halloysite, its ability to provide sustained drug release, and the antimicrobial properties of CS. In this study, the electrodeposition (EPD) method was used to coat titanium foil with CS blended with zinc-coated HNTs (ZnHNTs) and pre-loaded with the antibiotic gentamicin. The CS-ZnHNTs-gentamycin sulfate (GS) coatings were characterized using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), and UV-visible spectroscopy. The coatings were further examined for their ability to sustain GS release, resist bacterial colonization and growth, and prevent biofilm formation. The CS-ZnHNTs-GS coatings were cytocompatible, exhibited significant antimicrobial properties, and supported pre-osteoblast cell proliferation. Hydroxyapatite also formed on the coatings after immersion in simulated body fluid. While the focus in this study was on zinc-coated HNTs doped into CS, our design offers tunability, as different metals can be coated onto the HNT surface and different drugs or growth factors loaded into the HNT lumen. Our results, and the potential for customization, suggest that these coatings have potential in the construction of an array of infection-resistant implant coatings.

Electrophoretic deposition of chitosan–bioglass ^® –hydroxyapatite–halloysite nanotube composite coating

High modulus and thermal stability of polyimide (PI)/reactive halloysite nanotubes (HNTs) nanocomposites were prepared by in situ polymerization. The pristine HNTs were firstly handled with the tetraethoxysilane (TEOS) and secondly grafted with the silane agent. The fourier transform infrared spectroscopy (FTIR) approved that TEOS was beneficial for the silane agent to modify the HNTs. Scanning electron microscopy (SEM) showed the differences of the morphology between the reactive HNTs and pristine HNTs. PI/reactive HNTs nanocomposites exhibited lower moisture absorption than pure polyimide. The reactive HNTs reduced the transmittance of the nanocomposites. Significant improvements in the thermal stability and glass transition temperature (Tg) of PI/reactive HNTs nanocomposites were achieved by addition of only a small amount of reactive HNTs. It was noteworthy that both the tensile strength and Young' modulus of PI/reactive HNTs nanocomposites were significantly enhanced. A 62.8 % increase in tensile strength and a 63.7 % increase in Young' modulus of the nanocomposites with 3 wt.% of the reactive HNTs were achieved. Finally, the preparation mechanism to obtain PI/reactive HNTs nanocomposites was proposed.

The problem of traumatic hemorrhage is difficult to be quickly and effectively controlled and bacterial infection is one of the major limitations in the field of biomedical dressings worldwide. This issue prolongs the time of wound healing and presents a considerable threat to safety and life of patient. In this study, medical dressings blended with silk fibroin (SF), chitosan (CS) and halloysite nanotubes (HNTs) were successfully prepared by electrospinning. The broad-spectrum antibacterial drug, chlorhexidine digluconate (CHD), was initially loaded into HNTs. Drug-loaded HNTs were dispersed into a mixture of SF and CS to prepare a micro-nanofiber dressing and its performance was examined. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the addition of HNTs had a significant effect on the micro morphology of the nanofibers. Data of thermogravimetric analysis and mechanical testing disclosed that HNTs improved the thermal stability and tensile properties of electrospun materials. Moreover, the incorporation of HNTs led to rapid coagulation of blood, as observed from the in vitro whole blood coagulation time (WBCT) experiment. In the drug release experiment, the release time of the drug was prolonged by about 8 days when drug-loaded HNTs were incorporated into electrospinning materials. Additionally, the release rate of CHD in an acidic environment was higher than that in a neutral system. In summary, the micro-nanofiber medical dressing prepared in this study presents stable mechanical strength, rapid hemostasis and antibacterial activity and has a potential for biomedical application.

Halloysite nanotubes (HNTs) are natural clay minerals with a tubular structure. They have attracted considerable attention as a potential nanocontainer due to their abundance, biocompatibility and nontoxicity. In this study, HNTs were handled with H₂SO₄ at 70 °C. The morphology and structure of these acid-treated and original HNTs were investigated by scanning electron microscopy (SEM), energy dispersion spectrum (EDS), transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), and their specific surface area was determined by automatic gas adsorption analyzer. The loading efficiency and release behavior of acid-treated HNTs for 2-Mercaptobenzothiazole (MBT) were investigated by UV-vis spectrophotometer. Results show that acid-treated HNTs retained their tubular structure, but their internal diameter expanded by 35-37 nm after 32 h of acid treatment. After 72 h of acid treatment, HNTs can be transferred into amorphous silica nanotubes. Moreover, the specific surface area of these HNTs samples initially increased with the increase in acid treatment time but then started to decrease after 32 h. The specific surface area of acid-treated HNTs at 32 h can reach 251.6 m₂/g, which was much higher than that for untreated HNTs (55.3 m₂/g). In addition, the loading capacity of acid-treated HNTs can reach 32.1% for HNTs-32, which is about three times higher than that of original HNTs. The acid treatment has slight effect on the release behavior.

This work aims at exploring a novel environment-friendly nanomaterial based on natural clay minerals for arsenic removal in aqueous samples. Halloysite nanotubes (HNTs) were selected as the substrate with Mn oxides loaded on the surface to enhance its arsenic adsorption ability and then grafted onto the SiO2-coated Fe3O4 microsphere to get a just enough magnetic performance facilitating the material's post-treatment. The prepared composite (Fe3O4@SiO2@Mn-HNTs) was extensively characterized by various instruments including Fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TG), vibrating sample magnetometer (VSM), X-ray photoelectron spectroscope (XPS), and X-ray diffraction (XRD). Batch experiments were carried out to get the optimum test conditions for arsenic adsorption by the composite, including pH, loading amount of Mn oxides, adsorbent dosage, and the co-existing ions. The adsorption of AsIII and AsV on Fe3O4@SiO2@Mn-HNTs were both well fitted with the pseudo-second-order kinetic model as well as the Langmuir adsorption isotherm model revealing the chemisorption between arsenic and Fe3O4@SiO2@Mn-HNTs. The adsorption process of AsIII and AsV were both endothermic and spontaneous displayed by the thermodynamic study. The capacities of the prepared composite are 3.28mgg-1 for AsIII and 3.52mgg-1 for AsV, respectively, which are comparable or better than those of many reported materials in the references. Toxicity characteristic leaching procedure (TCLP) and synthetic precipitation leaching procedure (SPLP) tests were carried out to access the secondary environmental risk of the composite and showed that it was quite environmentally stable and can be safely disposed. The composite was successfully applied in environmental water samples indicating its great potential applicability in future.

The development of stimuli-responsive drug nanocarriers is an increasingly important area in nanomedicine because efficient delivery of toxic drugs to targeted tissues minimizes side effects. The specific objective of this study was to synthesize and characterize a novel pH-responsive drug carrier based on halloysite nanotubes for the controlled release of the anticancer drug doxorubicin. Poly(N,N-dimethylaminoethyl methacrylate) brushes were grafted from the surface of halloysite nanotubes using the combination of mussel-inspired polydopamine surface modification and activators regenerated by electron transfer in atom transfer radical polymerization. The chemical structure and morphology of the modified halloysite nanotubes were investigated by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermal gravimetric analysis as well as scanning and transmission electron microscopies. Dynamic light scattering and zeta potential analysis were carried out to evaluate the pH-responsivity of the functionalized halloysite nanotubes. The results of the drug loading and release study of pristine and functionalized halloysite nanotubes showed that grafting of poly(N,N-dimethylaminoethyl methacrylate) brushes on the polydopamine-modified halloysite nanotubes surface leads to a drastic increase in doxorubicin loading capacity and a highly pH-sensitive release behaviour. Less than 10 % of the loaded doxorubicin was released from poly (N,N-dimethylaminoethyl methacrylate)-grafted halloysite nanotubes at pH 7.4 after 24 h; in contrast, at pH 5.5 there was a continuous release of doxorubicin totalling 13 % in the first 30 min, i.e. lower than for the pristine halloysite nanotubes (32 %), but reaching 48 % after 24 h. Poly (N,N-dimethylaminoethyl methacrylate)-grafted halloysite nanotubes can hence be considered as a potential candidate for delivering highly toxic drug molecules to the acidic target sites.

This study investigated the potential of halloysite nanotubes (HNTs) to improve the sustained release properties of chitosan (CS) microparticles cross-linked ionically with tripolyphosphate (TPP). Composite CS-HNTs microparticles were obtained by a simple and eco-friendly procedure based on a coaxial extrusion technique. Prior to encapsulation, a water-soluble model drug, verapamil hydrochloride (VH), was adsorbed successfully on HNTs. The microparticles were characterized by optical microscopy, Fourier transform infrared (FTIR) spectroscopy, differential thermal analysis/ thermogravimetric analysis (DTA/TG) and evaluated for encapsulation efficiency and drug-release properties. The composite particles had a slightly deformed spherical shape and micrometric size with average perimeters ranging from 485.4 ± 13.3 to 492.4 ± 11.9 μm. The results of FTIR spectroscopy confirmed non-covalent interactions between CS and HNTs within composite particle structures. The DTA and TG studies revealed increased thermal stability of the composite particles in comparison to the CS-TPP particles. Drug adsorption on HNTs prior to encapsulation led to an increase in encapsulation efficiency from 19.6 ± 2.9 to 84.3 ± 1.9%. In contrast to the rapid release of encapsulated model drug from CS-TPP microparticles, the composite CS-HNTs microparticles released drug in a sustained manner, showing the best fit to the Bhaskar model. The results presented here imply that HNTs could be used to improve morphology, encapsulation efficiency and sustained drug-release properties of CS microparticles cross-linked ionically with TPP.

ABSTRACTThis article explores the effect of halloysite nanotubes (HNTs) and modified HNTs (M‐HNTs) on the properties of immiscible blend system based on polar polyoxymethylene (POM) and nonpolar polypropylene (PP) polymers. HNTs have been modified by N‐(β‐aminoethyl)‐γ‐aminopropyltrimethoxysilane (APTMS). Modification is confirmed by Fourier transform infrared spectroscopy (FTIR), also FTIR confirms the interaction between polymer blend and HNTs/M‐HNTs. Morphology of the nanocomposites are demonstrated by scanning electron microscope (SEM) and dispersion of HNTs/M‐HNTs are observed by transmission electron microscope (TEM). In nanocomposites, average dispersed domain sizes reduce in the presence of HNTs/M‐HNTs but significant reduction has been observed in the case of M‐HNT‐filled nanocomposites rather than unmodified HNT‐filled nanocomposites. The M‐HNT acts as a reinforcing agent as well as bridging tool in polar–nonpolar hybrid system. Modification of HNTs brings compatibility in between the blend partners and reveals improved dynamic mechanical, thermal, and tensile properties than that of the pure blend system. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39587.

Purpose: This study presents a novel and sustainable approach to cancer therapy by combining halloysite nanotubes (HNTs), green‐synthesized copper oxide (CuO) nanoparticles, and curcumin (CUR). We demonstrate that the green synthesis of CuO nanoparticles, when combined with CUR and incorporated into HNTs, enhances the delivery and anticancer effects of CUR. This innovative complex could address some of the critical limitations of current anticancer therapies such as poor pharmacokinetics and drug resistance by providing a controlled release mechanism and leveraging the benefits of combination therapy. Methods: We synthesized CuO using green synthesis with lemon peel extract and used this synthesized CuO to formulate a complex with HNT and CUR (CHC). Comprehensive characterization was conducted using UV‐visible spectroscopy, scanning electron microscopy‐energy‐dispersive X‐ray spectroscopy (SEM–EDX), X‐ray diffraction (XRD), thermogravimetric analysis (TGA), and Fourier‐transform infrared spectroscopy (FTIR). We also examined the release kinetics of the formulation. In vitro experiments were performed to evaluate the anticancer effects of the complex on HMVII, HepG2, and MCF‐7 cancer cell lines. In addition, an in silico docking assessment and a 10 ns molecular dynamics simulation were conducted to determine the interaction between CUR and HNTs. Results: The characterization of HNTs loaded with CUR showed a drug loading efficiency of 3%–5% and an encapsulation efficiency of 15%–20%. Drug release kinetics were best described by the Hixson–Crowell model for CHC‐50 and CHC‐20, with R 2 = 0.9897 and R 2 = 0.9900 respectively. CHC‐10 fit the Higuchi model ( R 2 = 0.8838), while free CUR fit the Korsmeyer–Peppas model ( R 2 = 0.9212). The formulations demonstrated significant anticancer effects across all tested cell lines, with CHC‐10 showing the lowest IC 50 value of 10.43 μg/mL. The CHC formulations exhibited enhanced delivery and maintained significant anticancer activity compared to CUR across HepG2, MCF‐7, and HMVII cell lines, with lower IC50 values after UV exposure. Molecular docking analysis revealed a CUR–HNT binding score of −3.803, with the complex remaining stable over a 10 ns simulation. Conclusion: This study demonstrates the successful integration of green‐synthesized CuO nanoparticles with CUR‐loaded HNTs as a novel approach to cancer therapy. The enhanced anticancer effects of the CHC‐10 formulation, coupled with the complex’s stability, suggest significant potential for improving cancer treatment outcomes. This innovative, sustainable approach addresses key limitations of current therapies, potentially offering more effective and patient‐friendly treatments with reduced side effects. Our findings pave the way for further development of targeted, environmentally conscious cancer therapies.

The development and application of nanocomposites with pH-sensitive “gates” to control the release of active agents: Extending the shelf-life of fresh wheat noodles

Polylactic acid (PLA)/halloysite nanotube (HNT) composite mats: Influence of HNT content and modification