Biomedical applications of nontoxic amorphous calcium carbonate (ACC) have mainly been restricted because of its aqueous instability. Herein, we report the successful synthesis of highly stable ACC–methotrexate (MTX)@SiO2 nanospheres in vitro for use in cancer therapy. Further, vaterite–MTX@SiO2 nanospheres were also prepared for comparison. In our synthesis procedure, ACC–MTX and vaterite–MTX were firstly prepared at different pH values, and then SiO2 layers were subsequently deposited by the well-known Stöber method. The results indicated that the special structure of ACC–MTX@SiO2 presents better controlled-release and results in efficient death of cancer cells, thus showing its great potential as a desirable chemotherapeutic system for cancer therapy.

•MTX is served as both the target drug and effective complex agents to modify and control the morphology.•ACC-MTX presents high drug-loading and excellent anticancer effect.•The biodegradation of MTX-ACC was due to the synergy effect of drug release and the phase transformation.The formation and stabilization of amorphous calcium carbonate (ACC) is an active area of research owing to the presence of stable ACC in various biogenic minerals. In this paper, the synthesis of calcium carbonate (CaCO3) under the participation of methotrexate (MTX) via a facile gas diffusion route was reported. The results indicated that the addition of MTX can result in the phase transformation of CaCO3, and then two kinds of hybrids, i.e., MTX-vaterite and stable MTX-ACC came into being. Interestingly, the functional agent MTX served as both the target anticancer drug loaded and effective complexation agents to modify and control the morphology of final samples. The examination of MTX-ACC biodegradation process revealed that the collapse of MTX-ACC nanoparticles was due to the synergistic effect of drug release and the phase transformation. Finally, our study also proved that MTX-ACC exhibited the most excellent suppressing function on the viability of cancer cells, especially after long-time duration.

In this paper, anticancer drug methotrexate (MTX) is applied as a coupling agent to fabricate Au@SiO2 core–shell structures for the first time. Then, a novel kind of Au yolk/LDH shell nanoparticles is obtained by using Au@SiO2 as the template. Finally, the in vitro cytotoxicity is examined and the result indicates that the yolk/shell nanovehicles loaded with MTX exhibit superior anticancer efficacy, compared to the free drug.

•Orthogonal test design was used to find out optimum synthesis conditions.•Colloid state of pristine LDHs can improve the morphology of the hybrids greatly.•Hybrids from ion-exchange method exhibit hexagonal plates.Based on orthogonal test design, the factors influencing the synthesis of methotrexate intercalated magnesium–aluminum layered double hydroxides (MTX/LDHs for short) by ion-exchange method, such as weight ratio of pristine LDHs to MTX (R for short), exchange temperature, time and pH value were investigated. Of the four controllable independent variables, R had the strongest effect on the crystallinity and the drug-loading capacity and the optimum synthesis conditions considered from the crystallinity and the drug-loading capacity both pointed to the same values, i.e., R=2:1, pH=9.5, temperature of 80 °C and exchange time of 3 day. The XRD diffractions indicated that high MTX content was in favor of the formation of intercalated hybrids, while low content lead to the failure of it. TEM photos indicated that the intercalated hybrids all exhibited aggregated hexagonal plates. In order to improve the morphology, two different states of pristine LDHs, i.e., powder and colloid, were chosen to prepare MTX/LDHs hybrids and the results indicated that colloid state of pristine was advantageous to obtain regular particles. The study also revealed that the properties of hybrids obtained at optimum conditions by ion-exchange were superior to that obtained from standard methods, such as co-precipitation method.The intercalation of MTX anions into LDHs interlayer by ion-exchange method was examined by orthogonal test design and the results indicated the arrangement of MTX belonged to pseudo-monolayer with their carboxylic groups alternatively pointing toward the upper and lower layers.

•Exfoliation-reassembly process is a good method to synthesize hybrids.•MTX/LDHs from low concentration of MTX solution presented better release property.•MTX/LDHs from low concentration of MTX solution presented good anticancer effects.In this paper, the intercalation of methotrexatum (MTX) into layered double hydroxides (LDHs) via an exfoliation-reassembly process was reported and the resulting hybrids were then characterized by X-ray diffraction (XRD) patterns, Fourier transform infrared (FTIR) spectroscopy and atomic force microscopy (AFM) patterns etc. In the synthesis procedure, LDHs particles were firstly delaminated into well-dispersed 2D nanosheets in formamide by ultrasonic treatment at room temperature, and then the resulting LDH nanosheets were reassembled in MTX solution to form MTX intercalated LDH (MTX/LDHs) hybrids. AFM images showed that during the exfoliation process a large part of LDHs particles were delaminated into single and double brucite layers. XRD patterns and FTIR investigations manifested the successful intercalation of MTX anions into LDHs interlayers for the final samples. It was also found out that the drug-loading capacity of the hybrids increased with the concentrations of MTX solutions, while the morphology became even aggregated. At last, the cell cytotoxicity of the hybrids was estimated by MTT assays on the human lung cancer cells (A549), and the results stated that MTX/LDHs hybrids had effective suppress role on the proliferation of cancer cells.The intercalation of methotrexatum (MTX) into layered double hydroxides (LDHs) via an exfoliation-reassembly process was studied and the resulting MTX/LDHs hybrids were evaluated by anticancer effects on A549 cells together with pristine LDHs and MTX itself, the results indicated that the hybrids obtained from low concentration of MTX solution presented much better anticancer effect.

•Surfactants could be used to modify the dispersing state of MTX/LDHs hybrids.•Surfactants have great effect on the morphology of MTX/LDHs hybrids.•MTX/LDHs with good monodisperse degree are more efficient in the suppression of the tumor cells.Methotrexatum intercalated layered double hydroxides (MTX/LDHs) hybrids were synthesized by the co-precipitation method and three kinds of nonionic surfactants with different hydrocarbon chain lengths were used. The resulting hybrids were then characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). XRD and FTIR investigations manifest the successful intercalation of MTX anions into the interlayer of LDHs. TEM graphs indicate that the morphology of the hybrids changes with the variation of the chain length of the surfactants, i.e., the particles synthesized using polyethylene glycol (PEG-7) present regular disc morphology with good monodispersity, while samples with the mediation of alkyl polyglycoside (APG-14) are heavily aggregated and samples with the addition of polyvinylpyrrolidone (PVP-10) exhibit irregular branches. Furthermore, the release and bioassay experiments show that monodisperse MTX/LDHs present good controlled-release and are more efficient in the suppression of the tumor cells.

•Increasing NaOH solution gives rise to high drug-loading capacity.•Increasing the alkali solution leads to high layer charge and regular morphology.•The monodispersity has critical effect on the tumor suppression efficiency.A series of methotrexatum intercalated layered double hydroxide (MTX/LDH for short) hybrids have been synthesized by a mechanochemical–hydrothermal method, the statistical experiments are planned and conducted to find out the critical factor influencing the physicochemical properties. Four variables, i.e., addition of NaOH solution, grinding duration, hydrothermal temperature and time, are chosen to play as the examined factors in the orthogonal design. Furthermore, three respective levels, i.e., high, medium and low levels, are conducted in the design. The resulting hybrids are then characterized by X-ray diffraction (XRD) patterns, transmission electron microscope (TEM) graphs and Zeta potentials. XRD diffractions indicate that MTX anions have been successfully intercalated into LDH interlayers and the amount of NaOH solution can change the gallery height greatly. The information from TEM graphs and Zeta potentials state that the increase of alkali solution gives rise to regular morphology and the increase of Zeta potentials. As a result of the statistical analysis, addition of alkali solution is the major factor affecting the morphology and drug-loading capacity. At last, the mechanism of particle growth is explored emphatically, and the anticancer efficacy of some MTX/LDH hybrids is estimated by MTT assay on A549 cells as well.Schematic illustration of synthesis and properties of MTX intercalated LDH hybrids.Figure optionsDownload full-size imageDownload as PowerPoint slide

•MTX is served as both the target anticancer drug loaded and effective complex agents to modify and control the morphologies of MTX/HAp.•MTX/HAp nanorods present high drug-loading, favorable sustained-release and excellent anticancer effect than pure MTX.•A possible mechanism that MTX mediates the crystal growth of MTX/HAp nanostructures is proposed.In this study, a new structure of methotrexate/hydroxyapatite (MTX/HAp) nanorods via a facile hydrothermal route was reported. The as-synthesized samples were then characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis. In order to explore the formation mechanism, the effects of reaction time, MTX concentrations and addition of ethylene glycol (PEG) were emphatically examined. The results indicated that, with the increase in reaction time, the fibrous nanoparticles turned to needle-like and then to rod-like. Our study also proved that reaction time of 12 h was enough for the full-growth of the nanostructure. Drug-loading capacities (AIn) rose dramatically in the first 12 h and reached a plateau afterwards. Importantly, MTX played a critical role in the longitudinal growth of MTX/HAp nanostructure and polyethylene glyco (PEG) was a good dispersing agent to improve the monodispersity. As expected, the functional agent of MTX was served as both the target anticancer drug loaded in HAp and effective complex agents to modify and control the morphologies of MTX/HAp. Lastly, in vitro bioassay tests gave us evidence that obvious tumor inhibition can be achieved when MTX was hybridized with HAp.Scheme illustration of synthesis and characterizations of MTX/HAp nanostructure.

•The particle size can be precisely controlled between 90 and 140 nm.•Different dropping ways can affect the morphology greatly.•Larger particles are more efficient in the suppression of the tumor cells.•Longer time treatment will weaken the bond between the MTX and LDH layers.To study the influence of particle size on drug efficacy and other properties, a series of methotrexate intercalated layered double hydroxides (MTX/LDHs) were synthesized through the traditional coprecipitation method, using a mixture of water and polyethylene glycol (PEG-400) as the solvent. To adjust the particle size of MTX/LDHs, the dropping way, the volume ratio of water to PEG-400 and different hydrothermal treatment time changed accordingly, and the results indicate that the particle size can be controlled between 90 and 140 nm. Elemental C/H/N and inductive coupled plasma (ICP) analysis indicated that different synthesis conditions almost have no effect on the compositions of the nanohybrids. X-ray diffraction (XRD) patterns manifested the successful intercalation of MTX anions into the LDH interlayers, and it's also found out that different volume ratios of water to PEG-400 and variable dropping way can affect the crystallinity of the final samples, i.e., the volume ratio of 3:1 and pH decreasing are proved to be optimum conditions. Furthermore, both antiparallel monolayer and bilayers adopting different orientations are suggested for four samples from XRD results. Fourier transform infrared spectroscopy (FTIR) investigations proved the coexistence of CO32− and MTX anions in the interlayer of the nanohybrids. MTX/LDH particles exhibited hexagonal platelet morphology with round corner and different dropping  ways can affect the morphology greatly. Moreover, a DSC study indicated that longer time treatment can weaken the bond between the MTX anions and LDH layers. The kinetic release profiles told us that larger MTX/LDH particles have enhanced the ability of LDH layers to protect interlayer molecules. At last, the bioassay study indicated that the nanohybrids with larger diameters have higher tumor suppression efficiency.A series of methotrexate intercalated layered double hydroxides were synthesized by changing the dropping way, volume ratio of PEG-400 to water and hydrothermal treatment time and the release mechanism and the bioassay tests had been systematically investigated. Our study indicated that nanohybrids with larger diameters have higher tumor suppression efficiency.

•The particle size can be precisely controlled by hydrothermal treatment.•Hydrothermal treatment has no effect on compositions of MTX/LDHs.•Inversion of (0 0 3) and (0 0 6) intensity is due to π–π stacking of benzene ring.•The particle size can greatly influence the properties of MTX/LDHs.•Larger particles are more efficient in the suppression of the tumor cells.To study the influence of particle size on release properties, drug efficacy and other properties, a series of methotrexate intercalated layered double hydroxides (MTX/LDHs) nanohybrids with different particle sizes were synthesized through traditional coprecipitation method, by using the mixture of water and polyethylene glycol (volume ratio is 3:1) as solvent. The relationship between particle size and hydrothermal treatment conditions (i.e., time and temperature) had been systematically investigated, and the results indicate that the particle size can be precisely controlled between 70 and 300 nm. Elemental C/H/N and inductive coupled plasma (ICP) analysis indicated that different hydrothermal treatment almost has no effect on compositions of the nanohybrids. X-ray diffraction (XRD) patterns and fourier transform infrared spectroscopy (FTIR) investigations manifested the successful intercalation of MTX anions. MTX/LDHs particles exhibited hexagonal platelet morphology with round corner, due to the adsorption of MTX anions on positively charged LDHs surface. In addition, the crystallinity of MTX/LDHs increased with the particle diameters and the thermal stability of MTX anions was enhanced by holding together with LDHs layers. The in vitro release showed that bigger particles have much longer release duration, and the bioassay tests indicated that bigger particles are more efficient in the suppression of the tumor cells.

•MTX/LDHs were first synthesized by mechanochemical–hydrothermal method.•The molar ratio of the reactants has significant influence on final products.•The release process can be divided into two stages.•The properties of intercalation compounds are comparable to those obtained from standard method.In this context, the methotrexatum/layered double hydroxides (MTX/LDHs) intercalation compounds have been synthesized by a mechanochemical–hydrothermal method, which involves a grinding process and subsequent hydrothermal treatment. The influence of R (molar ratio of Mg2+ to Al3+ to MTX) values on the structure and morphology of the intercalation compounds and their release properties were investigated systematically. The resulting compounds were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), inductively coupled plasma (ICP), thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis. All the results indicate that R value has significant influence on the intercalation of MTX anions into LDH interlayer and the optimal R value is 2:1:0.5. Furthermore, four dissolution–diffusion kinetic models were used to fit the in vitro release of MTX from LDH layers. The release process can be divided into two stages: firstly surface diffusion and secondly intraparticle diffusion. The study also revealed that the properties of the intercalation compounds is comparable to that obtained from standard methods such as co-precipitation method, but with time, solvent and energy saving.

The influence of zeta potential, altered by the pH value in synthesis, on the property of glutamic acid (Glu for short)/LDH compounds has been studied. It was found that the layer charges increased first then decreased as the pH value increased, and the layer charge had prominent effect on the properties of the samples. The crystallinity degree and the interlayer spacing increased gradually and the morphology changed from tubular or fibrous to platelet structure as the layer charge increased. And a model has been proposed to explain how pH values in the synthesis influence the LDH compound property by altering their layer charges.

In this paper, we found that the variation content of Fe3+ in the Fe–Al–Mg hydrotalcite-like compounds (HTlc) and the change of R values (R = WHTlc/WMT) will influence the thixotropic and viscoelastic properties of HTlc/sodium montmorillonite (MT) suspensions. With increasing the content of Fe3+ in the HTlc samples, the storage modulus (G′) and the loss modulus (G″) of the HTlc/MT suspensions will increase gradually, meaning that the structure strength of the HTlc/MT suspension increases with increasing of Fe3+ content in the HTlc samples. Similar results have been found in studying the influence of R values: the structure strength of the suspensions will increase with increasing of R values. Special emphasis has been laid on the phenomenon of thixotropy. With the gradual increase of the structure strength in the HTlc/MT suspension, the thixotropic types will change accordingly. The mechanism has been emphatically discussed in this paper.

The novel rheological properties of the hydrotalcite-like compound (HTlc)/sodium montmorillonite (MT) suspensions were investigated. The influence of the weight ratio of HTlc to MT (R) on the microstructure of the suspensions was examined emphatically. As increasing of R values, the structure strength increased gradually. Moreover, significant deviation from the Cox-Merz rule was observed in the HTlc/MT systems, which proved the formation of the network structure. The mechanism of “dispersion particles-steric network-dense network” was used to explain the complicated phenomena in these complex suspensions.

A novel platform making up of methotrexate intercalated layered double hydroxide (MTX/LDH) hybrid doped with gold nanoparticles (NPs) may have great potential both in chemo-photothermal therapy and the simultaneous drug delivery. In this paper, a promising platform of Au@PDDA-MTX/LDH was developed for anti-tumor drug delivery and synergistic therapy. Firstly, Au NPs were coated using Layer-by-Layer (LbL) technology by alternate deposition of poly (diallyldimethylammonium chloride) (PDDA) and MTX molecules, and then the resulting core-shell structures (named as Au@PDDA-MTX) were directly conjugated onto the surface of MTX/LDH hybrid by electrostatic attraction to afford Au@PDDA-MTX/LDH NPs. Here MTX was used as both the agent for surface modification and the anti-tumor drug for chemotherapy. The platform of Au@PDDA-MTX/LDH NPs not only had a high drug-loading capacity, but also showed excellent colloidal stability and interesting pH-responsive release profile. In vitro drug release studies demonstrated that MTX released from Au@PDDA-MTX/LDH was relatively slow under normal physiological pH, but it was enhanced significantly at a weak acidic pH value. Furthermore, the combined treatment of cancer cells by using Au@PDDA-MTX/LDH for synergistic hyperthermia ablation and chemotherapy was demonstrated to exhibit higher therapeutic efficacy than either single treatment alone, underscoring the great potential of the platform for cancer therapy.A new strategy was proposed to fabricate a kind of complex platform for synergistic therapy. Firstly, MTX molecules were firstly bound or adsorbed onto the surface of Au to form stable Au-MTX NPs. Further, Au@PDDA-MTX structure was built up by LbL technology with MTX adsorbed outside. At last, negatively-charged Au@PDDA-MTX NPs were directly conjugated onto the surface of positively-charged MTX/LDH hybrid to build up Au@PDDA-MTX/LDH platform.Download high-res image (112KB)Download full-size image