An in vivo study on the reaction of hydroxyapatite-sol injected into blood

Nanoparticles based on MIL-101 metal-organic frameworks as efficient carriers of therapeutic188Re radionuclide for nuclear medicine

Nuclear medicine presents one of the most promising modalities for efficient non-invasive treatment of a variety of cancers, but the application of radionuclides in cancer therapy and diagnostics is severely limited by their nonspecific tissue accumulation and poor biocompatibility. Here, we explore the use of nanosized metal-organic frameworks (MOFs) as carriers of radionuclides to order to improve their delivery to tumour. To demonstrate the concept, we prepared polymer-coated MIL-101(Cr)-NH2MOFs and conjugated them with clinically utilized radionuclide188Re. The nanoparticles demonstrated high loading efficacy of radionuclide reaching specific activity of 49 MBq mg-1. Pharmacokinetics of loaded MOFs was investigated in mice bearing colon adenocarcinoma. The biological half-life of the radionuclide in blood was (20.9 ± 1.3) h, and nanoparticles enabled it to passively accumulate and retain in the tumour. The radionuclide delivery with MOFs led to a significant decrease of radioactivity uptake by the thyroid gland and stomach as compared with perrhenate salt injection, which is beneficial for reducing the side toxicity of nuclear therapy. The reported data on the functionalization and pharmacokinetics of MIL-101(Cr)-NH2for radionuclide delivery unveils the promising potential of these MOFs for nuclear medicine.

A Photoacoustic Contrast Agent for miR-21 via NIR Fluorescent Hybridization Chain Reaction

Nucleic acids are well-established biomarkers of cancer with immense value in diagnostics and basic research. However, strategies to monitor these species in tissue can be challenging due to the need for amplification of imaging signal from low analyte concentrations with high specificity. Photoacoustic (PA) imaging is gaining traction for molecular imaging of proteins, small biomolecules, and nucleic acids by coupling pulsed near-infrared (NIR) excitation with broadband acoustic detection. This work introduces a PA nucleic acid contrast agent that harnesses NIR fluorophore and quencher-tagged hybridization chain reaction (HCR) for signal amplification. This HCR probe was designed to enable contact quenching between NIR dye-quencher pairs by coercing their direct alignment when miR-21, a microRNA cancer biomarker, is detected. The probe demonstrated a ratiometric PA limit of detection of 148 pM miR-21, sequence specificity against one- and two-base mutations, and selectivity over other microRNAs. It was further tested in live human ovarian cancer (SKOV3) and noncancerous (HEK 293T) cells to exemplify in situ PA activation based on differences in endogenous miR-21 regulation (p = 0.0002). The probe was lastly tested in tissue mimicking phantoms to exemplify sustained contrast in centimeter-range depths and 85.3% photostability after 15 min of laser irradiation. The probe's miR-21-specific activation and its ability to maintain contrast in biologically relevant absorbing and scattering media support its consideration for live-cell PA microscopy and potential cancer diagnostics. Results from this probe also underscore the combined detection power between ratiometric PA signaling and strand amplification for more sensitive DNA-based PA sensors.

Modulation of bone turnover aberration: A target for management of primary osteoporosis in experimental rat model

Osteoporosis is a skeletal degenerative disease characterised by abnormal bone turnover with scant bone formation and overabundant bone resorption. The present approach was intended to address the potency of nanohydroxyapatite (nHA), chitosan/hydroxyapatite nanocomposites (nCh/HA) and silver/hydroxyapatite nanoparticles (nAg/HA) to modulate bone turnover deviation in primary osteoporosis induced in the experimental model. Characterisation techniques such as TEM, zeta-potential, FT-IR and XRD were used to assess the morphology, the physical as well as the chemical features of the prepared nanostructures. The in vivo experiment was conducted on forty-eight adult female rats, randomised into 6 groups (8 rats/group), (1) gonad-intact, (2) osteoporotic group, (3) osteoporotic + nHA, (4) osteoporotic + nCh/HA, (5) osteoporotic + nAg/HA and (6) osteoporotic + alendronate (ALN). After three months of treatment, serum sclerostin (SOST), bone alkaline phosphatase (BALP) and bone sialoprotein (BSP) levels were quantified using ELISA. Femur bone receptor activator of nuclear factor-kappa B (NF-κB) ligand (RANKL) and cathepsin K (CtsK) mRNA levels were evaluated by quantitative RT-PCR. Moreover, alizarin red S staining was applied to determine the mineralisation intensity of femur bone. Findings in the present study indicated that treatment with nHA, nCh/HA or nAg/HA leads to significant repression of serum SOST, BALP and BSP levels parallel to a significant down-regulation of RANKL and CtsK gene expression levels. On the other side, significant enhancement in the calcification intensity of femur bone has been noticed. The outcomes of this experimental setting ascertained the potentiality of nHA, nCh/HA and nAg/HA as promising nanomaterials in attenuating the excessive bone turnover in the primary osteoporotic rat model. The mechanisms behind the efficacy of the investigated nanostructures involved the obstacle of serum and tissue indices of bone resorption besides the strengthening of bone mineralisation.

Application of hydroxyapatite nanoparticles in tumor-associated bone segmental defect

Hydroxyapatite (HA) has been widely applied in bone repair because of its superior biocompatibility. Recently, a proliferation-suppressive effect of HA nanoparticles (n-HA) against various cancer cells was reported. This study was aimed at assessing the translational value of n-HA both as a bone-regenerating material and as an antitumor agent. Inhibition of tumor growth, prevention of metastasis, and enhancement of the survival rate of tumor-bearing rabbits treated with n-HA were demonstrated. Activated mitochondrial-dependent apoptosis in vivo was confirmed, and we observed that a stimulated immune response was involved in the n-HA-induced antitumor effect. A porous titanium scaffold loaded with n-HA was fabricated and implanted into a critical-sized segmental bone defect in a rabbit tumor model. The n-HA-releasing scaffold not only showed a prominent effect in suppressing tumor growth and osteolytic lesion but also promoted bone regeneration. These findings provide a rationale for using n-HA in tumor-associated bone segmental defects.

Can nano-hydroxyapatite permeate the oral mucosa? A histological study using three-dimensional tissue models

Nano-hydroxyapatite is used in oral care products worldwide. But there is little evidence yet whether nano-hydroxyapatite can enter systemic tissues via the oral epithelium. We investigated histologically the ability of two types of nano-hydroxyapatite, SKM-1 and Mi-HAP, to permeate oral epithelium both with and without a stratum corneum, using two types of three-dimensional reconstituted human oral epithelium, SkinEthic HGE and SkinEthic HOE respectively with and without a stratum corneum. Both types of nano-hydroxyapatite formed aggregates in solution, but both aggregates and primary particles were much larger for SKM-1 than for Mi-HAP. Samples of each tissue model were exposed to SKM-1 and Mi-HAP for 24 h at concentrations ranging from 1,000 to 50,000 ppm. After treatment, paraffin sections from the samples were stained with Dahl or Von Kossa stains. We also used OsteoSense 680EX, a fluorescent imaging agent, to test for the presence of HAP in paraffin tissue sections for the first time. Our results for both types of nano-hydroxyapatite showed that the nanoparticles did not penetrate the stratum corneum in SkinEthic HGE samples and penetrated only the outermost layer of cells in SkinEthic HOE samples without stratum corneum, and no permeation into the deeper layers of the epithelium in either tissue model was observed. In the non-cornified model, OsteoSense 680EX staining confirmed the presence of nano-hydroxyapatite particles in both the cytoplasm and extracellular matrix of outermost cells, but not in the deeper layers. Our results suggest that the stratum corneum may act as a barrier to penetration of nano-hydroxyapatite into the oral epithelium. Moreover, since oral epithelial cell turnover is around 5–7 days, superficial cells of the non-keratinized mucosa in which nanoparticles are taken up are likely to be deciduated within that time frame. Our findings suggest that nano-hydroxyapatite is unlikely to enter systemic tissues via intact oral epithelium.

Ultrasonic synthesis of hydroxyapatite in non-cavitation and cavitation modes

The size control of materials is of great importance in research and technology because materials of different size and shape have different properties and applications. This paper focuses on the synthesis of hydroxyapatite in ultrasound fields of different frequencies and intensities with the aim to find the conditions which allow control of the particles size. The results are evaluated by X-ray diffraction, Transmission Electron Microscopy, morphological and sedimentation analyses. It is shown that the hydroxyapatite particles synthesized at low intensity non-cavitation regime of ultrasound have smaller size than those prepared at high intensity cavitation regime. The explanation of observed results is based on the idea of formation of vortices at the interface between phosphoric acid and calcium hydroxide solution where the nucleation of hydroxyapatite particles is taken place. Smaller vortices formed at high frequency non-cavitation ultrasound regime provide smaller nucleation sites and smaller resulting particles, compared to vortices and particles obtained without ultrasound. Discovered method has a potential of industrial application of ultrasound for the controlled synthesis of nanoparticles.

Multifunctional Polymer-Coated Carbon Nanotubes for Safe Drug Delivery

Though progress in the use carbon nanotubes in medicine has been most encouraging for therapeutic and diagnostic applications, any translational success must involve overcoming the toxicological and surface functionalization challenges inherent in the use of such nanotubes. Ideally, a carbon nanotube-based drug delivery system would exhibit low toxicity, sustained drug release, and persist in circulation without aggregation. We report a carbon nanotube (CNT) coated with a biocompatible block-co-polymer composed of poly(lactide)-poly(ethylene glycol) (PLA-PEG) to reduce short-term and long-term toxicity, sustain drug release of paclitaxel (PTX), and prevent aggregation. The copolymer coating on the surface of CNTs significantly reduces in vitro toxicity in human umbilical vein endothelial cells (HUVEC) and U-87 glioblastoma cells. Moreover, coating reduces in vitro inflammatory response in rat lung epithelial cells. Compared to non-coated CNTs, in vivo studies show no long-term inflammatory response with CNT coated with PLA-PEG (CLP) and the surface coating significantly decreases acute toxicity by doubling the maximum tolerated dose in mice. Using polymer coatings, we can encapsulate PTX and release over one week to increase the therapeutic efficacy compared to free drugs. In vivo biodistribution and histology studies suggests a lower degree of aggregation in tissues in that CLP accumulate more in the brain and less in the spleen than the CNT-PLA (CL) formulation.

Recent advances in research applications of nanophase hydroxyapatite

Hydroxyapatite, the main inorganic material in natural bone, has been used widely for orthopaedic applications. Due to size effects and surface phenomena at the nanoscale, nanophase hydroxyapatite possesses unique properties compared to its bulk-phase counterpart. The high surface-to-volume ratio, reactivities, and biomimetic morphologies make nano-hydroxyapatite more favourable in applications such as orthopaedic implant coating or bone substitute filler. Recently, more efforts have been focused on the possibility of combining hydroxyapatite with other drugs and materials for multipurpose applications, such as antimicrobial treatments, osteoporosis treatments and magnetic manipulation. To build more effective nano-hydroxyapatite and composite systems, the particle synthesis processes, chemistry, and toxicity have to be thoroughly investigated. In this Minireview, we report the recent advances in research regarding nano-hydroxyapatite. Synthesis routes and a wide range of applications of hydroxyapatite nanoparticles will be discussed. The Minireview also addresses several challenges concerning the biosafety of the nanoparticles.

Aminopropyltriethoxysilane-mediated surface functionalization of hydroxyapatite nanoparticles: synthesis, characterization, and in vitro toxicity assay

BACKGROUND

We report on aminopropyltriethoxysilane (APTS)-mediated surface modification of nanohydroxyapatite with different surface functional groups for potential biomedical applications. In this study, nanohydroxyapatite covalently linked with APTS (n-HA-APTS) was reacted with acetic anhydride or succinic anhydride to produce neutralized (n-HA-APTS. Ac) or negatively charged (n-HA-APTS.SAH) nanohydroxyapatite, respectively. Nanohydroxyapatite formed with amine, acetyl, and carboxyl groups was extensively characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, (1)H nuclear magnetic resonance spectroscopy, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy, and zeta potential measurements.

RESULTS

In vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide colorimetric assay revealed that the slight toxicity of the amine-functionalized n-HA-APTS could be eliminated by post-functionalization of APTS amines to form acetyl and carboxyl groups. Blood compatibility assessment demonstrated that the negligible hemolytic activity of the pristine nanohydroxyapatite particles did not appreciably change after APTS-mediated surface functionalization.

CONCLUSION

APTS-mediated functionalization of nanohydroxyapatite with different surface groups may be useful for further functionalization of nanohydroxyapatite with biologically active materials, thereby providing possibilities for a broad range of biomedical applications.

Characteristics of functionalized nano-hydroxyapatite and internalization by human epithelial cell

Hydroxyapatite is the main inorganic component of biological bone and tooth enamel, and synthetic hydroxyapatite has been widely used as biomaterials. In this study, a facile method has been developed for the fabrication of arginine-functionalized and europium-doped hydroxyapatite nanoparticles (Arg-Eu-HAP). The synthesized nanoparticles characterized by transmission electron microscopy, X-ray diffractometry, Fourier transform infrared, and Zeta potential analyzer. Its biological properties with DNA binding, cell toxicity, cell binding and intracellular distribution were tested by agarose gel electrophoresis assay, flow cytometry, and fluorescence microscope and laser scanning confocal microscope. The synthesized Arg-Eu-HAP could effectively bind DNA without any cytotoxicity and be internalized into the cytoplasm and perinuclear of human lung epithelial cells.

Effect of hydroxyapatite nanoparticles on the growth and p53/c-Myc protein expression of implanted hepatic VX2 tumor in rabbits by intravenous injection

AIM: To evaluate the effect of hydroxyapatite nano-particles (Nano HAP) by intravenous injection on the inhibition of implanted hepatic VX₂ tumor growth in rabbits and cell p53/c-Myc protein expression.

METHODS: 60 hepatic VX₂ tumor-bearing rabbits was randomly divided into five groups. Nano HAP collosol 20 mg/kg, 40 mg/kg, 5-FU solutions 20 mg/mL, mixed liquor of 5-FU solution 20 mg/mL and Nano HAP collosol 20 mg/kg were infused by vein, normal saline conducted as the control. The general state, weight, liver function and gross tumor volume were detected dynamically. The expression of p53 and c-Myc gene protein in tumor tissue was detected by immunohistochemistry methods.

RESULTS: The growth of implanted hepatic VX₂ tumors was significantly inhibited in all therapy groups, 3 wk after the injection, the tumor control rates in Nano HAP collosol groups were 25.5% and 32.5% respectively, and the gross tumor volumes were obviously less than that of control group. (24.81 ± 5.17 and 22.73 ± 4.23 vs 33.32 ± 5.26, P < 0.05). The tumor control rate of 5-FU group was 43.7% (18.74 ± 4.40 vs 33.32 ± 5.26, P < 0.05), but the general state of the animals after injection aggravated; and the adverse reaction in the drug combination group obviously decreased. Due to the effect of Nano HAP, the positive expression of tumor associated the mutated p53 and c-Myc in tumor tissue was decreased obviously compared with the control group.

CONCLUSION: Nano HAP has evident inhibitory action on rabbit implanted hepatic VX₂ tumor in vivo, which may be the result of decreasing the expression of the mutated p53 and c-myc, and drug combination can obviously decrease the adverse reaction of 5-FU.

Cardiovascular changes after pulmonary embolism from injecting calcium phosphate cement

Concerns have been raised that the use of calcium phosphate (CaP) cements for the augmentation of fractured, osteoporotic bones may aggravate cardiovascular deterioration in the event of pulmonary cement embolism by stimulating coagulation. The aim of the present study was therefore to investigate the cardiovascular changes after pulmonary embolism of CaP cement using an animal model. In 14 sheep, 2.0 mL CaP or polymethylmethacrylate cement were injected intravenously. Cardiovascular parameters and antithrombin levels were monitored until 60 min postinjection. Postmortem, lungs were subjected to CT scanning, and 3D reconstruction of the cement was performed. Intravenous injection of CaP cement resulted in a more severe increase in pulmonary arterial pressure and decrease in arterial blood pressure. Disintegration of the CaP cement seemed to be the reason for the more severe reaction. There was no evidence of thromboembolism. Disintegration of CaP cement in circulating blood does not only compromise the mechanical properties, but also represents a risk of cardiovascular complications. Reliable cohesion of CaP cements in an aqueous environment is essential for clinical applications such as osteoporotic bone augmentation.