pH-responsive Drug Carriers Research Articles

WITHDRAWN: Folic acid Grafted, cell-penetrating peptide conjugated pH-sensitive hydrophobically modified Glycol chitosan nanoparticles for drug delivery in breast cancer

Nanocarriers are an outcome of the fast development of nanotechnology; however, delivering drugs to tumor sites effectively is still a major difficulty. A pH-responsive drug carrier with good cell penetration and targeting ability was developed to release the drug exactly to the cancer site and overcome these limitations.The drug carrier FA-TAT-HGCNPs/PTX, which is pH-responsive, uses folic acid (FA) and TAT peptide to deliver paclitaxel (PTX) for target folate-receptor-overexpressing breast cancer cells. 2-(diisopropylamino) ethyl methacrylate was connected to glycol chitosan (GC) to form HGCNPs. Then TAT and HGCNPs were conjugated and FA was grafted onto the HGCNPs’ hydroxyl group. Physicochemical characterizations of FA-TAT-HGCNPs was also evaluated. The maximum DLE and EE values of the FA-TAT-HGCNPs at pH 8.0 were 74.0 ± 2.22 % and 93.7 ± 2.8 %, respectively. FA-TAT-HGCNPs, for instance, showed stability during long-term storage and lyophilization while exhibiting pH-responsive dissociation properties. The synthesized drug carrier was characterized by FTIR, XRD, SEM, HRTEM, DLS, and Zeta analysis. MTT assay exhibited the high anticancer activity of the FA-TAT-HGCNPs/PTX against the MCF-7 cells, whereas drug-free ones are highly biocompatible. The pharmacokinetic results showed twice the bioavailability of FA-TAT-HGCNPs/PTX compared to HGCNPs/PTX. Unlike FA-HGCNPs/PTX, CLSM analysis showed that FA-TAT-HGCNPs/PTX had a significantly more efficient intracellular uptake in MCF-7 cells. These data have shown the transmembrane ability of TATpeptide,the targeting effects of folate decoration, and the synergistic interaction between them.According to these findings, PTX-loaded FA-TAT-HGCNPs offer a potentially effective nanoscale drug delivery system for the treatment of breast cancer.

A novel pH-sensitive drug carrier system based on 18-crown ether-6/sodium alginate for curcumin/nido-carborane encapsulation: Studies of release properties, cell imaging and bioactivity evaluation

Curcumin's remarkable anti-tumor action has drawn a lot of interest, however its low bioavailability, poor targeting, and poor water solubility restrict its therapeutic potential. Two fluorescent polymers based on curcumin/nido-carborane-crown ether were produced using a two-phase technique in this study: Cur/Carborane-C/SA (encapsulated with sodium alginate) and Cur/Carborane-C (without sodium alginate). Cur/Carborane-C/SA was thought to be the most promising polymer with anti-tumor properties. The drug delivery method based on the polymer created by tris (3-aminoethyl) amine (TAEA) and 18-crown ether-6 in combination with sodium alginate offers a novel approach to curcumin encapsulation technology. Nido-carborane improves the targeting of curcumin and its tumor-cell-inhibiting properties. Good fluorescence qualities were shown by Cur/Carborane-C/SA's fluorescence quantum yield of 0.119 %. According to in vitro drug release data, the polymer performed well for pH response release at 5.0. The TEM and particle size data demonstrated that curcumin produced uniformLy sized, difficult to agglomerate nanoparticles with a particle size of less than 300 nm. The polymer exhibited a substantial affinity and inhibition of HCT-116 and HeLa cells, with an inhibition rate that may reach 78.3 %, according to the findings of the cytotoxicity assay and cell imaging. As a result, it is anticipated that the produced Cur/Carborane-C/SA would provide a new pH-responsive drug carrier system for curcumin intended for use in cancer treatment.

Construction and evaluation of biomass-modified mesoporous silica nanoparticles as enzyme-responsive and pH-Responsive drug carriers for the controlled release of quercetin

This study constructed a biomass-modified mesoporous silica nanoparticle with enzyme-responsive and pH-responsive properties. The nanoparticles were used to evaluate the loading and release capacities of quercetin (QU). The multifunctional nanoparticles (MSN@CMCS-HA) were constructed by using hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as shells and mesoporous silica nanoparticles (MSN) as cores. The carrier's structure and properties were evaluated utilizing zeta, FTIR, TGA, XPS, XRD, BET, SEM, and TEM. The drug adsorption test revealed that the maximum equilibrium adsorption capacity of MSN@CMCS-HA for QU was 314.4 mg/g. In vitro drug release demonstrated that, under the influence of hyaluronidase (100 μg/mL) and pH of 5, the high drug release rate (63.73 %) was achieved. In addition, hemolysis and CCK8 tests confirmed the high biocompatibility of MSN@CMCS-HA. Consequently, MSN@CMCS-HA exhibited promising potential as an enzyme-responsive and pH-responsive drug carrier.

PH‐responsive polyurethane‐acrylate from palm olein and sunflower oil: Sustainable synthesis, enhanced lovastatin solubility, and potential drug carrier for targeted delivery

AbstractA pH responsive non‐isocyanate polyurethane‐acrylate (NIPUA) is synthesized through utilizing palm olein and sunflower oil as feedstock. The unsaturated acyl chains of both vegetable oils are converted into epoxy rings through epoxidation and subjected to carbonation with binary catalytic system under a solventless and mild condition to produce the cyclic carbonates. The cyclic carbonates were reacted with 1,4‐butanediamine and itaconic acid to produce the NIPUA. The intermediates and product were characterized by FTIR spectroscopy, NMR spectroscopy and gel permeation chromatography. The NIPUA was incorporated with poly(vinyl pyrrolidone) (PVP) to form a polymer carrier system loaded with a hydrophobic model drug, lovastatin (LOV). All NIPUA/PVP preformulations demonstrated pH responsiveness, with 1 to 2‐folds enhanced solubility at pH 7.4 compared to pH 2.0. NIPUA/PVP exhibited solubility enhancer effect by significantly enhanced solubility (2–4 times) compared to pure LOV, LOV‐loaded PVP, and Medostatin tablets at both pH levels. LOV‐loaded NIPUA/PVP exhibited lower enthalpy energy in DSC thermogram than LOV‐loaded PVP, indicating disruption of LOV's crystalline structure. In MTT assay, IC50 values were 30.76 μg mL−1 for pure LOV and 273.53 μg mL−1 for NIPUA/PVP, demonstrating the potential of NIPUA as an environmentally friendly, pH responsive drug carrier for controlled release of poorly water‐soluble drugs.

Amidoxime functionalized mesoporous silica nanoparticles for pH-responsive delivery of anticancer drug

Abstract In recent decades, nanomedicine has attracted much attention at the forefront of nanotechnology, gaining great expectations in the biomedical sectors. Among various nanomaterials, silica nanoparticles-based drug delivery is considered effective owing to their physicochemical stability and biological compatibility. Surface grafting and chemical conversion techniques were used to create an amphoteric functional ligand known as amidoxime ligand (AL) modified mesoporous silica material (MS-AL NPs). With this technique, amidoxime ligand groups can be introduced in greater concentration to the silica surface without compromising its structure. The active surface allows for surface functionalization and integration of medicinal substances. They are widely employed in the bio-medical industry for diagnostics, target administration of drugs, bio-sensing, cellular absorption, and so on. The function of the produced MS-AL NPs as a regulated drug delivery system was studied utilizing doxorubicin (Dox) as a model anticancer drug. Using the MCF-7 cell line, the biocompatibility and cellular uptake characteristics were investigated. Considering all factors, the MS-AL NPs may be used as pH-responsive drug carriers in cancer treatment applications.

Unravelling pH/pKa influence on pH-responsive drug carriers: Insights from ibuprofen-silica interactions and comparative analysis with carbon nanotubes, sulfasalazine, and alendronate

This study employs density functional theory to explore the interaction between ibuprofen (IBU) and silica, emphasizing the influence of the trimethylsilyl (TMS) functional group for designing pH-responsive drug carriers. The surface (S) and drug (D) molecules' neutral (0) or deprotonated (−1) states were taken into consideration during the investigation. The likelihood of these states was determined based on the pKa values and the desired pH conditions. To calculate the pH-dependent interaction energy (EintpH), four different situations have been identified: S0D0, S0D−1, S−1D0, and S−1D−1.The electrostatic component of interaction energy aligns favorably with its theoretical value in both the Debye-Hückel and Grahame models. The investigation has gathered first-hand experimental data on the drug loading and release of pH-responsive mesoporous silica nanoparticles. Effective drug loading was observed in the acidic environment of the stomach (pH 2–5), followed by a release in the slightly basic to neutral pH of the small intestine (pH 7.4), These findings align with existing literature. The results revealed horizontal drug adherence on silica surfaces, improving binding capabilities. Comparisons were made with combinations involving carboxylated carbon nanotubes and ibuprofen, silica, and sulfasalazine, and silica and alendronate, exploring drug loading/release dynamics associated with positive/negative interaction energies. The investigation, supported by experimental data, contributes valuable insights into pH-responsive mesoporous silica nanoparticles, offering new design possibilities for drug carriers.

PH-Responsive Theranostic Colloidosome Drug Carriers Enable Real-Time Imaging of Targeted Thrombolytic Process with Near-Infrared-II for Deep Venous Thrombosis.

Thrombosis can cause life-threatening disorders. Unfortunately, current therapeutic methods for thrombosis using injecting thrombolytic medicines systemically resulted in unexpected bleeding complications. Moreover, the absence of practical imaging tools for thrombi raised dangers of undertreatment and overtreatment. This study develops a theranostic drug carrier, Pkr(IR-Ca/Pda-uPA)-cRGD, that enables real-time monitoring of the targeted thrombolytic process of deep vein thrombosis (DVT). Pkr(IR-Ca/Pda-uPA)-cRGD, which is prepared from a Pickering-emulsion-like system, encapsulates both near-infrared-II (NIR-II) contrast agent (IR-1048 dye, loading capacity: 28%) and urokinase plasminogen activators (uPAs, encapsulation efficiency: 89%), pioneering the loading of multiple drugs with contrasting hydrophilicity into one single-drug carrier. Upon intravenous injection, Pkr(IR-Ca/Pda-uPA)-cRGD considerably targets to thrombi selectively (targeting rate: 91%) and disintegrates in response to acidic thrombi to release IR-1048 dye and uPA for imaging and thrombolysis, respectively. Investigations indicate that Pkr(IR-Ca/Pda-uPA)-cRGD enabled real-time visualization of targeted thrombolysis using NIR-II imaging in DVT models, in which thrombi were eliminated (120 min after drug injection) without bleeding complications. This may be the first study using convenient NIR-II imaging for real-time visualization of targeted thrombolysis. It represents the precision medicine that enables rapid response to acquire instantaneous medical images and make necessary real-time adjustments to diagnostic and therapeutic protocols during treatment.

Dual stimuli-responsive delivery system for self-regulated colon-targeted delivery of poorly water-soluble drugs

Inflammatory bowel disease (IBD) are chronic inflammatory conditions which cause significant patient morbidity. Local drug delivery to the colon can improve treatment efficacy and reduce side effects associated with IBD treatment. Smart drug delivery systems are designed to regulate the release of therapeutic agents at the desired site of action. pH-responsive drug carriers have been previously utilised for improved oral drug delivery beyond stomach harsh conditions. Additionally, the colon possesses a diverse microbiome secreting bioactive molecules e.g., enzymes, that can be exploited for targeted drug delivery. We herein synthesised and characterised a 2-hydroxyethyl methacrylate and methacrylic acid copolymer, crosslinked with an azobenzyl crosslinker, that displayed pH- and enzyme-responsive properties. The swelling and drug release from hydrogel were analysed in pH 1.2, 6.5 and 7.4 buffers, and in the presence of rat caecal matter using metronidazole and mesalamine as model BCS Class I and IV drugs, respectively. Swelling studies displayed pH-responsive swelling behaviour, where swelling was maximum at pH 7.4 and minimum at pH 1.2 (69 % versus 32 %). Consequently, drug release was limited in gastric and small intestinal conditions but increased significantly when exposed to colonic conditions containing caecal matter. This system displays promising capacity for achieving colon-targeted drug delivery with enhanced dissolution of poorly water-soluble drugs for local treatment of IBD and other colon-targeted therapies.

Recombinant Collagen-Templated Biomineralized Synthesis of Biocompatible pH-Responsive Porous Calcium Carbonate Nanospheres.

The synthesis of calcium carbonate with controlled morphology is crucial for its biomedical applications. In this study, we synthesized well-ordered porous calcium carbonate nanospheres using recombinant collagen as a biomineralization template. Porous collagen-calcium carbonate was created by incubating calcium chloride and sodium carbonate with collagen biotemplates at room temperature. Our results show that the recombinant collagen-calcium carbonate nanomaterials underwent a morphological transition from solid nanospheres to more porous nanospheres and a phase transformation from vaterite to a mixture of calcite and vaterite. This study highlights the crucial role of recombinant collagen in modulating the morphology and crystallinity of calcium carbonate nanoparticles. Importantly, the highly porous recombinant collagen-calcium carbonate hybrid nanospheres demonstrated superior loading efficacy for the model drug cefoperazone. Furthermore, the drug loading and releasing results suggest that hybrid nanospheres have the potential to be robust and biocompatible pH-responsive drug carriers. Our findings suggest that recombinant collagen's unique amino acid content and rodlike structure make it a superior template for biomineralized synthesis. This study provides a promising avenue for the production of novel organic-inorganic nanostructures, with potential applications in biomedical fields such as drug delivery.

Compartmentalized Polyampholyte Microgels by Depletion Flocculation and Coacervation of Nanogels in Emulsion Droplets.

In pH-responsive drug carriers, the distribution of charges has been proven to affect delivery efficiency but is difficult to control and verify. Herein, we fabricate polyampholyte nanogel-in-microgel colloids (NiM-C) and show that the arrangement of the nanogels (NG) can easily be manipulated by adapting synthesis conditions. Positively and negatively charged pH-responsive NG are synthesized by precipitation polymerization and labelled with different fluorescent dyes. The obtained NG are integrated into microgel (MG) networks by subsequent inverse emulsion polymerization in droplet-based microfluidics. By confocal laser scanning microscopy (CLSM), we verify that depending on NG concentration, pH value and ionic strength, NiM-C with different NG arrangements are obtained, including Janus-like phase-separation of NG, statistical distribution of NG, and core-shell arrangements. Our approach is a major step towards uptake and release of oppositely charged (drug) molecules.

DEVELOPMENT, CHARACTERIZATION AND ANTIBACTERIAL PROPERTIES OF SILVER NANOPARTICLES LOADED SODIUM ALGINATE/XANTHAN GUM MICROBEADS FOR DRUG DELIVERY APPLICATIONS

Objective: The aim of this study is to create pH-responsive drug carriers, which are useful because they have the potential to improve treatment efficacy by controlling the release rate of ofloxacin from the polymer matrix. Methods: In the first step, silver nanoparticles (Ag NPs) were synthesized from silver nitrate using leaf extract of phyllanthus urinaria L as a reducing agent. In the second step, Ag-NPs-loaded polymeric microbeads were synthesized using sodium alginate (SA) and xanthan gum (XG) for controlled release of ofloxacin (OFLX). The developed microbeads were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (X-RD), transition electron microscopy (TEM), Selected Area Electron Diffraction (SAED), and scanning electron microscopy (SEM). Swelling and in vitro release studies were performed at pH 2.0 and 7.4 at 37 °C. The in vitro antibacterial activity of microbeads were tested against S. mutans, K. pneumoniae, and B. subtilis. The release kinetics and mechanism were analyzed by fitting the release data into different kinetic models and the korsmeyer-peppas equation. Results: FTIR confirms the generation of silver nanoparticle and also the generation of polymeric microbeads. SEM studies reveal the developed microbeads are spherical in shape with rough surfaces. TEM studies reveal the size of 20-40 nm. XRD analysis reveals the molecular dispersion of DOX and the presence of silver nanoparticles in the polymeric matrix. Investigations of in vitro release and swelling studies show that the developed microbeads are relatively suitable for intestinal drug delivery because higher release rate was observed at pH 7.4. The developed microbead follows non-Fickian diffusion drug release mechanism. The created samples exhibited antimicrobial activity against S. mutans, K. pneumoniae, and B. subtilis. Conclusion: The results indicate that microbeads containing OFLX and silver nanoparticles are effective drug-delivery vehicles. A further warrant is required for the use of manufactured microbeads in drug delivery applications.

Investigation of hollow mesoporous NiFe2O4 nanospheres fabricated via a template-free solvothermal route as pH-responsive drug delivery system for potential anticancer application

A novel magnetic-targeted pH-responsive intelligent drug carrier based on hollow mesoporous structured NiFe2O4 nanospheres was designed and developed for potential anticancer treatment in the present study. The hollow mesoporous NiFe2O4 nanospheres were fabricated through a template-free solvothermal approach and the possible formation mechanism of this structure was proposed. The products were investigated comprehensively for their morphology, microstructure, composition and magnetic properties using a wide series of characterization methods. The NiFe2O4 nanospheres were demonstrated to possess a well-defined spherical morphology, homogeneous particle size distribution, large hollow cavities and abundant mesopores, unique superparamagnetic behavior, high saturation magnetization as well as good biocompatibility. Due to these desirable physicochemical properties, the hollow mesoporous NiFe2O4 nanospheres were expected to be employed as a potential vehicle for loading and delivering anticancer drug of doxorubicin hydrochloride (DOX). Drug release behavior was evidenced to be controllable and pH-responsive with effective DOX release of 73.1% and 58.8% in acidic conditions (pH 4.0 and 5.5), whereas insufficient drug release of 44.7% at a neutral atmosphere (pH 7.4) within 48 h. More importantly, the DOX-loaded NiFe2O4 nanospheres displayed significant anti-proliferation and apoptosis effects on human breast cancer cells (MCF-7), which further indicated the promising potential application of constructed drug delivery nanocarriers in the field of cancer therapy.

Anisotropic, Hydrogel Microparticles as pH-Responsive Drug Carriers for Oral Administration of 5-FU.

In the last 20 years, the development of stimuli-responsive drug delivery systems (DDS) has received great attention. Hydrogel microparticles represent one of the candidates with the most potential. However, if the role of the cross-linking method, polymer composition, and concentration on their performance as DDS has been well-studied, still, a lot needs to be explained regarding the effect caused by the morphology. To investigate this, herein, we report the fabrication of PEGDA-ALMA-based microgels with spherical and asymmetric shapes for 5-fluorouracil (5-FU) on-demand loading and in vitro pH-triggered release. Due to anisotropic properties, the asymmetric particles showed an increased drug adsorption and higher pH responsiveness, which in turn led to a higher desorption efficacy at the target pH environment, making them an ideal candidate for oral administration of 5-FU in colorectal cancer. The cytotoxicity of empty spherical microgels was higher than the cytotoxicity of empty asymmetric microgels, suggesting that the gel network's mechanical proprieties of anisotropic particles were a better three-dimensional environment for the vital functions of cells. Upon treatment with drug-loaded microgels, the HeLa cells' viability was lower after incubation with asymmetric particles, confirming a minor release of 5-FU from spherical particles.

Supermolecule-Drug Conjugates Based on Acid-Degradable Polyrotaxanes for pH-Dependent Intracellular Release of Doxorubicin.

Doxorubicin (DOX)-conjugated acid-degradable polyrotaxanes (PRXs) were designed as supramolecular drug carriers capable of releasing drugs in acidic cellular environments. Acid-degradable PRXs composed of α-cyclodextrin (α-CD) as a cyclic molecule, poly(ethylene glycol) (PEG) as a polymer axis, and N-triphenylmethyl (N-Trt) groups as an acid-labile stopper molecules were synthesized and DOX was conjugated with the threaded α-CDs in the PRXs. Because the acid-induced cleavage of N-Trt groups in PRXs leads to PRX dissociation, the DOX-modified α-CDs were released under acidic conditions (pH 5.0). The cytotoxicity of DOX-conjugated PRXs in colon-26 cells revealed significant cell death for DOX-conjugated PRXs after 48 h of treatment. Confocal laser scanning microscopy (CLSM) analysis revealed that the fluorescence signals derived from DOX-conjugated PRXs were observed in cellular nuclei after 48 h, suggesting that the DOX-modified α-CDs were released and accumulated in cellular nuclei. These results confirmed that acid-degradable PRXs can be utilized as drug carriers capable of releasing drug-modified α-CDs in acidic lysosomes and eliciting cytotoxicity. Overall, acid-degradable PRXs represent a promising supramolecular framework for the delivery and intracellular release of drug-modified α-CDs, and PRX-drug conjugates are expected to contribute to the development of pH-responsive drug carriers for cancer therapy.

ZnFe2O4@L-cysteine-N/RGO as efficient nano-sonosensitizers, pH-responsive drug carriers and surface charge switchable drug delivery system for targeted chemo-sonodynamic therapy of cancer

ZnFe2O4@L-cysteine-N/RGO as efficient nano-sonosensitizers, pH-responsive drug carriers and surface charge switchable drug delivery system for targeted chemo-sonodynamic therapy of cancer

Folic acid grafted aminated zeolitic imidazolate framework (ZIF-8) as pH responsive drug carrier for targeted delivery of curcumin

Smart drug delivery systems responding to pH gradient between physiological conditions and acidic conditions in tumor cells are very crucial for treating cancer. This article describes the process of developing, zeolitic imidazolate framework (ZIF-8) based novel pH responsive drug carrier for the targeted delivery of curcumin (CUR). To enable folic acid (FA) conjugation the surface of ZIF-8 was modified through amination. The so developed CUR loaded folic acid grafted aminated ZIF-8 (CUR@FA-g-AZIF-8) were characterized with UV–Visible, FT-IR, PXRD, SEM, TGA, TEM and BET analysis. It shows high drug loading efficiency and good chemical stability. In vitro drug release studies of CUR from folic acid grafted aminated ZIF-8 (FA-g- AZIF-8) shows three times higher efficiency in acidic pH (5) than in normal physiological conditions (pH 7.4). The potential cytotoxicity was evaluated by MTT assay on HeLa cells, CUR@FA-g-AZIF-8 shows 76.8% cytotoxicity. The results show that FA-g-AZIF-8 is a promising drug carrier for targeted drug delivery.

Hierarchical hollow monetite microspheres assembled with mesoporous nanosheets: Synthesis and applications in superior adsorbents for lead ions and pH-responsive release drug carrier

Hierarchical hollow monetite microspheres assembled with mesoporous nanosheets were firstly synthesized templating by both large and small micelles of mono-dodecyl phosphate. The obtained hollow monetite microspheres had a diameter of 10 ∼ 30 μm with a specific surface area of 86.76 m2 g−1 and a total pore volume of 0.466 cm3 g−1. The monetite nanosheets which were assembly units of the hollow microspheres possessed many mesopores with a pore size of about 25 nm. The mesoporous hollow monetite microspheres had adsorption capacity of lead ions and vancomycin as high as 1435.6 mg g−1 and 518 mg g−1, respectively. And the vancomycin loaded monetite microspheres exhibited a pH-responsive drug release behavior. The mesoporous hollow monetite microspheres have great potential in contaminants adsorbents and drug carriers.

PH-responsive drug release and antibacterial activity of chitosan-coated core/shell borate glass-hydroxyapatite microspheres

Multifunctional drug delivery system that can treat bone infection and concurrently accelerate bone tissue regeneration is highly desirable. In this study, we developed a pH-responsive local drug carrier in which a core/shell microsphere consisting of a borate glass core and a mesoporous hydroxyapatite HA shell (BG-HA) was coated with glutaraldehyde-crosslinked chitosan (CS). At neutral pH, a negligible concentration of vancomycin was released from the BG-HA@CS microspheres. However, in an acidic environment, the pores on the HA shell were uncapped due to the swelling of CS, thus accelerating the drug release. The advantage of the BG-HA@CS was evidenced by comparing with HA@CS that was prepared by fully converting borate glass followed by CS coating. The dissolution of the unconverted borate glass core upon immersing in PBS led to an increase in the local pH. This change of pH regulated the swelling/de-swelling behaviours of CS, thereby realizing more sustained drug release. Furthermore, it revealed that the vancomycin-loaded BG-HA@CS provided highly effective antibacterial activity against S. aureus and E. coli, while the vancomycin-loaded HA@CS did not show inhibitory effect on E. coli. The results indicated that the BG-HA@CS would be a promising multifunctional delivery system that can achieve self-regulated drug release, control the acidic environment of bone infection sites and promote bone tissue regeneration.

Mussel-inspired grafting pH-responsive brushes onto halloysite nanotubes for controlled release of doxorubicin

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.

Correction to: Preparation and properties of pH-responsive magnetic mesoporous silica drug carrier

Correction to: Preparation and properties of pH-responsive magnetic mesoporous silica drug carrier