Search

Hydroxyapatite (HA) has attracted wide attention for medical application due to its biocompatibility and bioactivity. However, the infection problems of HA remain among the leading reasons for implantation failure. Thus, it is urgent to endow HA biomaterials with antibacterial activity. Herein, the high antibacterial activity was achieved by introducing trace Mn3+ and H vacancy couples in HA through a facile heat-treatment strategy in air. The theoretical results indicated that Mn3+ was preferentially substituted for the Ca(2) site in the HA structure with a charge-compensating H vacancy appearing at the adjacent OH− site. The antibacterial tests showed that Mn-HA possessed antibacterial activity towards both E. coli and S. aureus with trace Mn content at the ppm level, and implied that Mn3+ and centers may play an important role in the antibacterial process. The Mn3+ and couples in Mn-HA, serving as oxidative and reductive centers respectively, could then collectively participate in the CoQ/CoQH2 redox cycling and synergistically facilitate the accumulation of CoQ˙− and ROS radicals. This enhanced ROS production was the main factor to endow Mn-HA with efficient antibacterial activity. Moreover, the in vitro bioactivity assay showed that Mn-HA materials exhibited enhanced osteogenic activity and good biocompatibility. Therefore, this work not only provides a feasible method to control the oxidation state of Mn elements in HA, but also proposes a novel trace Mn3+-doped HA for potential applications in tissue engineering. [ABSTRACT FROM AUTHOR]

Si3N4:Al microbelts with tunable bandgap energy and resultant yellow-orange phosphors are prepared through a facile direct nitridation method. The bandgap energy of Si3N4:Al microbelts has been gradually trimmed from 2.58 eV to 2.67, 2.74 and 2.85 eV by regulating the Si/Al molar ratio from 1000 : 1 to 50 : 1. Si3N4:Al:Eu phosphors display a wide emission ranging from 500 to 800 nm when excited by a 450 nm blue LED light source. The crystal structure of Si3N4:Al microbelts is of the α-Si3N4 phase as characterized by X-ray diffraction, high-resolution TEM and crystal models. Si3N4:Al microbelts grow along the (012) stacking direction in a low doping concentration case and grow along the (011) stacking direction in a high doping concentration case. Theoretical calculation results show that Al prefers to occupy the low energy interstitial sites in the (012) plane. There are more substitutional sites in the (011) plane occupied by Al in the high doping concentration case with increasing the bandgap energy of Si3N4:Al. Warm white light emission has been achieved by precoating Si3N4:Al:Eu phosphors onto a blue LED chip, whose correlated color temperature (CCT) can be tailored from 3000 K to 6500 K by altering the phosphor amount, indicating a promising potential application of Si3N4:Al:Eu phosphors in warm white LEDs. [ABSTRACT FROM AUTHOR]

Fluorine plays an important role in dental protection and formation of enamel materials, however the intrinsic effect of fluorine on the formation mechanism of fluoridated hydroxyapatite still needs to be known. In this work, pure fluoridated hydroxyapatite (FHA) with a hierarchical architecture was produced by a simple one-pot method using CaF2, Ca(OH)2 and Ca(H2PO4)2·H2O. It was found that the hierarchical fluoridated hydroxyapatite showed a unique orientation structure and different phase transformation mechanism compared with hydroxyapatite (HA). In the phase transition process from DCPD (CaHPO4·2H2O, brushite) to DCPA (CaHPO4, monetite), and then to FHA, hierarchical FHA was formed with the c-axis-oriented nanowires perpendicular to the planes of DCPA plates. More importantly, the crystal orientation relationship between FHA and DCPA was found for the first time to be FHA [010]//DCPA [001] and FHA (001)//DCPA (010), which is quite different from the crystal orientation relationship of HA [1̅10]//DCPA [110] and HA (1̅12)//DCPA (112). It was found that the phase transition process from (100)DCPA to (100)FHA was occurred with a good crystal lattice match. F− on (100)FHA had a small ionic radius and high electronegativity, decreased the crystal lattices of (100)FHA and might enhance their negativity and reactivity. This result may help better understand the effect of fluorine on the crystal growth process of natural enamel and the preparation of pure FHA with a hierarchical architecture is informative for the synthesis of enamel-like biomaterials. [ABSTRACT FROM AUTHOR]

Tumor hypoxia is a negative prognostic factor in cancer radiotherapy, due in part to its role in causing resistance to radiotherapy. It has attracted extensive critical attention to radiation sensitizers by using active oxygen to improve radiotherapy outcome. Active oxygen delivery functional materials are promising candidates to transport active oxygen to tumor cells. Herein, we report an oxygen delivery functional material by using hollow mesoporous silica nanoparticles (HMSNs) as carriers, synthesizing sodium percarbonate (SPC) in the channels and cavity of HMSNs (SPC@HMSNs) and coating polyacrylic acid (PAA) on the functional materials (SPC@HMSNs–PAA). SPC@HMSNs–PAA could release more SPC in a simulated tumor acidic microenvironment (pH ∼ 6.5), which can provide oxygen to improve radiotherapy outcome even under low energy X-ray irradiation. The events induce obvious overproduction of reactive oxygen radicals to kill cancer cells with a significant effect. Meanwhile, no obvious cytotoxicity was observed when SPC@HMSNs–PAA applied alone. The radiosensitization of SPC@HMSNs–PAA on cancer cells, even exposure to low-energy X-ray irradiation, may suggest promising application in radiotherapy. [ABSTRACT FROM AUTHOR]

Tumor hypoxia is a negative prognostic factor in cancer radiotherapy, due in part to its role in causing resistance to radiotherapy. It has attracted extensive critical attention to radiation sensitizers by using active oxygen to improve radiotherapy outcome. Active oxygen delivery functional materials are promising candidates to transport active oxygen to tumor cells. Herein, we report an oxygen delivery functional material by using hollow mesoporous silica nanoparticles (HMSNs) as carriers, synthesizing sodium percarbonate (SPC) in the channels and cavity of HMSNs (SPC@HMSNs) and coating polyacrylic acid (PAA) on the functional materials (SPC@HMSNs-PAA). SPC@HMSNs-PAA could release more SPC in a simulated tumor acidic microenvironment (pH ∼ 6.5), which can provide oxygen to improve radiotherapy outcome even under low energy X-ray irradiation. The events induce obvious overproduction of reactive oxygen radicals to kill cancer cells with a significant effect. Meanwhile, no obvious cytotoxicity was observed when SPC@HMSNs-PAA applied alone. The radiosensitization of SPC@HMSNs-PAA on cancer cells, even exposure to low-energy X-ray irradiation, may suggest promising application in radiotherapy.

Excessive free radicals are noxious for living organisms and lead to cell death. Destruction of malignant cells by reactive free radicals has been widely used in cancer treatment. A key consideration is how to allow targeted free radical attack on cancer cells and avoid unwanted side-effects. Herein, we develop an efficient intracellular free radical generation strategy against cancer cells by delivering active ingredients into cancer cells, where free radicals are selectively generated by a lysosomal bioactivation process. Artesunate (ART), which is non-toxic to normal cells, was chosen as the free radical source and transported into cells with a hollow mesoporous silica-based delivery system (ART@HMS). To selectively activate the ART@HMS inside cancer cells, a high-bioactive Fe/O cluster-mesoporous silica nanosystem (Fe/O-MSN) was elaborately prepared. Under the bioactivation of the lysosome, the low-dose ART@HMS together with biocompatible Fe/O-MSN induced significant intracellular generation of toxic free radicals and efficient death of cancer cells. This selective intracellular free radical generation strategy is encouraging for its development into an effective low-cost cancer therapy.