Apatite Nanoparticles Research Articles

Fabrication of highly porous biodegradable biomimetic nanocomposite as advanced bone tissue scaffold

Development of bioinspired or biomimetic materials is currently a challenge in the field of tissue regeneration. In-situ 3D biomimetic microporous nanocomposite scaffold has been developed using a simple lyophilization post hydrothermal reaction for bone healing applications. The fabricated 3D porous scaffold possesses advantages of good bonelike apatite particles distribution, thermal properties and high porous interconnected network structure. High dispersion bonelike apatite nanoparticles (NPs) rapidly nucleated and deposited from surrounding biological minerals within chitosan (CTS) matrices using hydrothermal technique. After that, freeze-drying method was applied on the composite solution to form the desired porous 3D architecture. Interestingly, the porosity and pore size of composite scaffold were not significantly affected by the particles size and particles content within the CTS matrix. Our results demonstrated that the compression modulus of porous composite scaffold is twice higher than that of plain CTS scaffold, indicating a maximization of the chemical interaction between polymer matrix and apatite NPs. Cytocompatibility test for MC3T3-E1 pre-osteoblasts cell line using MTT-indirect assay test showed that the fabricated 3D microporous nanocomposite scaffold possesses higher cell proliferation and growth than that of pure CTS scaffold. Collectively, our results suggest that the newly developed highly porous apatite/CTS nanocomposite scaffold as an alternative of hydroxyapatite/CTS scaffold may serve as an excellent porous 3D platform for bone tissue regeneration.

Protein-Nanoparticle Hydrogels That Self-assemble in Response to Peptide-Based Molecular Recognition.

Recently, supramolecular hydrogels assembled through nonspecific interactions between polymers and nanoparticles (termed PNP systems) were reported to have rapid shear-thinning and self-healing properties amenable for cell-delivery applications in regenerative medicine. Here, we introduce protein engineering concepts into the design of a new family of PNP hydrogels to enable direct control over the polymer-nanoparticle interactions using peptide-based molecular recognition motifs. Specifically, we have designed a bifunctional peptide that induces supramolecular hydrogel assembly between hydroxy apatite nanoparticles and an engineered, recombinant protein. We demonstrate that this supramolecular assembly critically requires molecular recognition, as no assembly is observed in the presence of control peptides with a scrambled amino acid sequence. Titration of the bifunctional peptide enables direct control over the number of physical cross-links within the system and hence the resulting hydrogel mechanical properties. As with previous PNP systems, these materials are rapidly shear-thinning and self-healing. As proof-of-concept, we demonstrate that these materials are suitable for therapeutic cell delivery applications in a preclinical murine calvarial defect model.

Hydroxyapatite nanocrystals as a smart, pH sensitive, delivery system for kiteplatin.

Hydroxyapatite (HA) nanocrystals are important inorganic constituents of biological hard tissues in vertebrates and have been proposed as a bone substitute or a coating material for prostheses in biomedicine. Hydroxyapatite is also amenable for its capacity to bind to a great variety of biomolecules and therapeutic agents. As drug carriers, apatite nanoparticles also have the advantage of pH dependent solubility and low toxicity. Thus HA nanoparticles are negligibly soluble at physiological pH but their dissolution is accelerated at lower pH such as that typically found in the vicinity of tumors. In the present study we have investigated the adsorption on and the release from biomimetic HA nanoparticles of two platinum derivatives of cis-1,4-diaminocyclohexane ([PtX2(cis-1,4-DACH)], X2 = Cl2 (1) and 1,1-cyclobutanedicarboxylate (CBDCA, 2)). The first of the two compounds proved to be active against colon cancer cells also resistant to oxaliplatin. The release has been investigated as a function of pH to mimic the different physiological environments of healthy tissues and tumors, and the in vitro cytotoxicity of the releasates from the HA matrices has been assessed against various human cancer cell lines. The results fully confirmed the potential of 1-loaded HA nanoparticles as bone-specific drug delivery devices.

Mesoscopically ordered bone mimetic nanocomposites

Event Abstract Back to Event Mesoscopically ordered bone mimetic nanocomposites Martin Andersson1, Wenxiao He1 and Anand K. Rajasekharan1 1 Chalmers University of Technology, Chemistry and Chemical Engineering, Sweden Introduction: Bone provides protection and support for the movements of our body through its excellent load-bearing properties. Though the macrostructure differs depending on bone type, the nanostructure of natural bone universally comprises collagen fibrils possessing periodic gaps, within which elongated bone apatite nanoparticles are aligned and embedded. To synthetically reproduce the complexity of bone has been proven challenging, and the fact that simple mixing of proteins, such as collagen 1, with precipitated apatite crystals does not form materials having mechanical properties even close to that of bone, clearly demonstrates that the hierarchical arrangement of the structure is of outmost importance. Figure 1(A) Formation and nanostructure of bone and our biomimetic composite. (B) SAXS scattering confirms presence of order and anisotropy in composite. (C) TEM image shows alignment of HA nanocrystals with the material. Methods: Herein we demonstrate a novel, synthetic approach, highly inspired by the architecture of natural bone, to design mechanically stable nanocomposites incorporating aligned apatite nanocrystals. To mimic the nanostructure of natural bone, we first combine molecular self-assembly and intermolecular crosslinking to create resilient polymeric matrices with long-range periodicity; then we employ compartmentalized mineral growth via a transient amorphous phase for the biomimetic formation of bone-like apatite, see Fig. 1. Results and Discussion: Small angle X-ray scattering (SAXS) data of the nanocomposite confirmed the presence of meso-ordered (hexagonal) structure with long-range anisotropy of the nanocomposite similar to bone (Figure 1B)[1]. Moreover electron microscopy images of grounded composites show alignment of the HA nanoparticles due to the orientation from the PLC matrix (Figure 1C)[1]. The nanoscale confinements within the polymeric matrices controled the phase purity of calcium phosphates. When CaP is precipitated in confinements of sizes 11-27 nm, multiple phases including acidic polymorphs coexisted. Contrastingly, confinements smaller than 10 nm produced phase pure ACPs, which on aging converted to nanocrystalline apatite[2]. A general hypothesis is proposed that in absence of chemical control, confinements might need to be smaller than naturally occurring ones to control the mineral phase purity in both synthetic and biological systems. The results also provide an insight into designing biomaterials with an ordered structure and high mineral content while maintaining chemical homogeneity. Mechanically, the composite showed compressive strength of 3-4 MPa, which is comparable to cancellous bone, an important result for further developing the implant. Current work focuses on developing the composite with a 3-D hierarchical structure and a porous network for functioning as a scaffold. Conclusion: Molecular self-assembly of synthetic polymers can be used to form mesoscopically ordered polymer-apatite nanocomposites having similar apatite chemistry and a highly ordered nanostructure inspired from bone. We acknowledge the Swedish Research Council, Nano-Sphere Centre/Formas and the Wallenberg Foundation through their Wallenberg Academy Fellow Program for financial support. We also thank MAX-lab (Lund, Sweden) for the allocation of beam time and assistance with SAXS measurements

Biomimetic Apatite-Based Functional Nanoparticles as Promising Newcomers in Nanomedicine: Overview of 10 Years of Initiatory Research

Biomimetic calcium phosphate apatites, analogous to bone mineral, may now be produced synthetically. Their intrinsic biocompatibility and the nanometer dimensions of their constitutive crystals not only allow one to envision applications in bone tissue regeneration, but also in other medical fields such as nanomedicine, and in particular in view of cell diagnosis. In this mini-review, we look back at 10 years of our dedicated research, and summarize the main advances made in terms of preparation, physical-chemical characterizations and biological evaluations of colloidal formulations of biomimetic apatite-based nanoparticles, which we illustrate here with the angle of cancer diagnosis. The confirmed exceptional biocompatibility of these engineered nanoparticles, associated to the possibility to confer them luminescence properties by way of controlled lanthanide doping, and their capacity to be internalized by cells, including with cancer cell addressing abilities (shown here as a proof of concept), underline that biomimetic apatite-based colloidal nanoparticles are particularly promising for nanomedicine applications, for example related to diseased cells diagnosis. Multidisciplinary research on these functional nanoparticles, initiated as described here, has now generated emulation in the scientific community where the concept of apatite nanoparticles for nanomedicine is being, gratifyingly, appropriated.

Synthesis and preliminary in vivo evaluation of well-dispersed biomimetic nanocrystalline apatites labeled with positron emission tomographic imaging agents.

In recent years, biomimetic synthetic apatite nanoparticles (AP-NPs), having chemical similarity with the mineral phase of bone, have attracted a great interest in nanomedicine as potential drug carriers. To evaluate the therapeutic perspectives of AP-NPs through the mechanisms of action and organs they interact with, the noninvasive monitoring of their in vivo behavior is of paramount importance. To this aim, here the feasibility to radiolabel AP-NPs ("naked" and surface-modified with citrate to reduce their aggregation) with two positron emission tomographic (PET) imaging agents ([(18)F]NaF and (68)Ga-NO2AP(BP)) was investigated. [(18)F]NaF was used for the direct incorporation of the radioisotope into the crystal lattice, while the labeling by surface functionalization was accomplished by using (68)Ga-NO2AP(BP) (a new radio-metal chelating agent). The labeling results with both tracers were fast, straightforward, and reproducible. AP-NPs demonstrated excellent ability to bind relevant quantities of both radiotracers and good in vitro stability in clinically relevant media after the labeling. In vivo PET studies in healthy Wistar rats established that the radiolabeled AP-NPs gave significant PET signals and they were stable over the investigated time (90 min) since any tracer desorption was detected. These preliminary in vivo studies furthermore showed a clear ability of citrated versus naked AP-NPs to accumulate in different organs. Interestingly, contrary to naked AP-NPs, citrated ones, which unveiled higher colloidal stability in aqueous suspensions, were able to escape the first physiological filter, i.e., the lungs, being then accumulated in the liver and, to a lesser extent, in the spleen. The results of this work, along with the fact that AP-NPs can be also functionalized with targeting ligands, with therapeutic agents, and also with metals for a combination of different imaging modalities, make AP-NPs very encouraging materials for further investigations as theranostic agents in nanomedicine.

Synthesis and modification of apatite nanoparticles for use in dental and medical applications

Summary Synthesised hydroxyapatite (HAp) exhibits excellent biocompatibility, making it an ideal candidate for use as a hard tissue substitute material. Nanoscale-size effects and surface phenomena impart HAp nanoparticles with unique properties compared to the conventional-sized HAp ceramics. Modification of HAp is also important for regulating its physiochemical properties. In this review, methods of HAp synthesis and modification, and various applications of HAp nanoparticles for dental and medical treatment are discussed.

Innovative delivery of siRNA to solid tumors by super carbonate apatite.

RNA interference (RNAi) technology is currently being tested in clinical trials for a limited number of diseases. However, systemic delivery of small interfering RNA (siRNA) to solid tumors has not yet been achieved in clinics. Here, we introduce an in vivo pH-sensitive delivery system for siRNA using super carbonate apatite (sCA) nanoparticles, which is the smallest class of nanocarrier. These carriers consist simply of inorganic ions and accumulate specifically in tumors, yet they cause no serious adverse events in mice and monkeys. Intravenously administered sCA-siRNA abundantly accumulated in the cytoplasm of tumor cells at 4 h, indicating quick achievement of endosomal escape. sCA-survivin-siRNA induced apoptosis in HT29 tumors and significantly inhibited in vivo tumor growth of HCT116, to a greater extent than two other in vivo delivery reagents. With innovative in vivo delivery efficiency, sCA could be a useful nanoparticle for the therapy of solid tumors.

Therapeutic Implications of Orally Delivered Immunomodulatory Oligonucleotides

DNA has multiple and complex effects on the immune system. Bacterial DNA contains immunostimulatory CpG motifs that trigger cells expressing Toll-like receptor 9 (TLR9) to proliferate, mature, and support T helper type 1 (Th1)-biased immune responses (reviewed in ref. 1). This response confers a selective advantage to the host by improving resistance to infection. In contrast, mammalian DNA contains sequence motifs that downregulate the immune system. Synthetic oligodeoxynucleotides that mimic this inhibitory activity (iODNs) slow or prevent the development of inflammatory and autoimmune diseases, consistent with the release of DNA from dying host cells inhibiting autoaggressive immune responses (reviewed in ref. 2). As reported in this issue, Wang et al. break new ground in the study of immunomodulatory ODNs by showing that the severity of chemically induced atopic dermatitis can be reduced by oral delivery of iODNs and worsened by CpG ODNs.3

Monoclonal antibody-targeted fluorescein-5-isothiocyanate-labeled biomimetic nanoapatites: a promising fluorescent probe for imaging applications.

Multifunctional biomimetic nanoparticles (NPs) are acquiring increasing interest as carriers in medicine and basic research since they can efficiently combine labels for subsequent tracking, moieties for specific cell targeting, and bioactive molecules, e.g., drugs. In particular, because of their easy synthesis, low cost, good biocompatibility, high resorbability, easy surface functionalization, and pH-dependent solubility, nanocrystalline apatites are promising candidates as nanocarriers. This work describes the synthesis and characterization of bioinspired apatite nanoparticles to be used as fluorescent nanocarriers targeted against the Met/hepatocyte growth factor receptor, which is considered a tumor associated cell surface marker of many cancers. To this aim the nanoparticles have been labeled with Fluorescein-5-isothiocyanate (FITC) by simple isothermal adsorption, in the absence of organic, possibly toxic, molecules, and then functionalized with a monoclonal antibody (mAb) directed against such a receptor. Direct labeling of the nanoparticles allowed tracking the moieties with spatiotemporal resolution and thus following their interaction with cells, expressing or not the targeted receptor, as well as their fate in vitro. Cytofluorometry and confocal microscopy experiments showed that the functionalized nanocarriers, which emitted a strong fluorescent signal, were rapidly and specifically internalized in cells expressing the receptor. Indeed, we found that, once inside the cells expressing the receptor, mAb-functionalized FITC nanoparticles partially dissociated in their two components, with some mAbs being recycled to the cell surface and the FITC-labeled nanoparticles remaining in the cytosol. This work thus shows that FITC-labeled nanoapatites are very promising probes for targeted cell imaging applications.

A glucose carbonate apatite complex exhibits in vitro and in vivo anti-tumour effects.

Tumour targeting nanotechnology has recently made therapeutic progress and several therapeutic nanoparticles have been approved for clinical application. However, an ideal nanotechnology based therapeutic for solid tumours, particularly for systemic administration, still remains a challenge in clinical cancer therapy. We previously reported a pH sensitive in vivo delivery system of doxorubicin, or microRNA, using carbonate apatite (CA) nanoparticles. To further explore utility of CA in cancer therapy, we attempted to transport excess glucose into tumour cells by conjugating glucose (Glc) to the nanoparticle. Despite the non-toxicity of CA and Glc, the complex (CA-[Glc]) exhibited an unexpected anti-cancer effect in vitro and in vivo. CA-[Glc] significantly reduced the growth of colon cancer cell lines. Intravenous injections successfully suppressed solid tumour growth. In mice and monkeys, intravenously injected CA-[Glc] complex resulted in no serious abnormalities in body weight or blood chemistry. Because cancer cells intensively metabolise glucose than normal cells, treatment of cancer using glucose seems paradoxical. However, with the aid of CA, this safe and ‘sweet’ complex may be a novel anti-cancer reagent.

Rare Earth Doped Apatite Nanomaterials for Biological Application

In most biological analyses, a sensitive detection technique is primarily dependent on the fluorescence labeling agent. New generation of fluorophores called rare earth doped apatite nanoparticle (REAnp) has the ability to emit near infrared radiations which are of low absorptivity by tissue chromophores and especially suitable for biological system imaging. Moreover, bioapatite is demonstrated to be an excellent candidate for biomedical applications because of its biocompatibility, biodegradability, and bioactivity. During recent years a lot of efforts have been made for achievement of REAnp for medical diagnostics and targeted therapeutics applications. In this review, we discuss the significance of REAnps in biological systems, different root of synthesis, and biological applications. Also we discuss the future studies for the effective biological applications of REAnps.

Abstract 5382: A breakthrough in application of a drug delivery nanoparticle system for therapy and diagnosis of solid tumor

Abstract Introduction: Nanoparticle systems are usually designed to deliver the incorporated molecular to tumors. However, we found an interesting breakthrough in conducting the super carbonate apatite (sCA) nanoparticles itself. So far we have introduced the sCA as an in vivo pH sensitive delivery system of doxorubicin (PLoS ONE 8(4): e60428. 2013) or siRNA, which simply consist of inorganic ions and quickly accumulate specifically in tumors yet yield no serious adverse events in mice and monkeys. Intravenously administered sCA-siRNA markedly accumulated in the tumor cells at 90 min and survivin-siRNA delivered by sCA significantly inhibited in vivo tumor growth, compared with the two other in vivo commercially available delivery reagents, Invivofectamine 2.0 and Atelocollagen. In this study, we confirmed a unique characteristic of sCA itself, not as a drug delivery system. Empty sCA alone markedly enhanced the uptake of low molecular chemicals into tumor cells in vitro and in vivo. Methods: Doxorubicin (DXR), fluorouracil (5-FU), oxaliplatin (L-OHP) and indocyanine green (ICG) are used as low molecular chemicals. Cellular uptake of doxorubicin was analyzed by flow cytometry using a BD FACS Aria II instrument (BD Biosciences). Cell viability was examined by WST-8 assay (Dojindo). As for the in vivo tumor imaging assay, sCA and ICG were simultaneously administered via the separate routes to the mice bearing colon cancer HT29; sCA was administered i.v. (intravenously) and ICG was administered i.p. (intraperitoneally). Mice were imaged under anesthesia using IVIS (PerkinElmer) for ex vivo and in vivo imaging. Results and Discussions: Empty sCA itself enhanced the uptake and cytotoxic effect of anti-cancer agents in vitro, although sCA itself was not toxic. The flow cytometric analysis showed the mean florescence index (MFI: 2186) of the cells, first treated with sCA for 24 h and then treated with DXR for another 24 h, was higher than the MFI (1684) of the cells directly treated with DXR for 24 h. The IC50 (μM; mean ± SD) of 5-FU and L-OHP in colon cancer HCT116 were 47.6 ± 10.0 and 31.3 ± 2.2, whereas the IC50 of both drugs in the sCA pre-treated cells for 24 h were 11.7 ± 2.0 and 3.70 ± 1.1, respectively. Furthermore, the empty sCA itself also improved the efficacy of in vivo tumor imaging by ICG, even when ICG and sCA were administered through the separate routes; sCA was administered i.v. and ICG was administered i.p.. We should mention that we had not been able to incorporate ICG into sCA nanoparticles before this experiment. Time course studies showed that ICG levels in tumors with treatment of sCA plus ICG were significantly higher throughout the examined time points than those treated with ICG alone (P = 0.0142 for 4 h, P = 0.0139 for 8 h, P = 0.0433 for 12 h, P = 0.0304 for 24 and 48 h). Conclusion: Our data suggest that sCA itself, while designed as an in vivo delivery device, can facilitate entrance of low molecular chemicals into tumor cells in vitro and in vivo. Citation Format: Xin Wu, Hirofumi Yamamoto, Mamoru Uemura, Taishi Hata, Junichi Nishimura, Ichiro Takemasa, Tsunekazu Mizushima, Yuichiro Doki, Masaki Mori. A breakthrough in application of a drug delivery nanoparticle system for therapy and diagnosis of solid tumor. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5382. doi:10.1158/1538-7445.AM2014-5382

Abstract 4460: Super carbonate apatite as simplified systemic nanoparticle carrier for therapy of solid tumors

Abstract Introduction: RNA interference technology is underway in clinical trials for limited diseases. RNAi technology for solid tumors, especially in systemic administration, still faces hurdles and has not emerged on the clinical stage. Here we introduce an in vivo pH sensitive delivery system of siRNA and microRNA using super carbonate apatite (sCA) nanoparticles (mean size: 10 nm), which simply consist of inorganic ions. In order to show the therapeutic superiority of the sCA system over currently available in vivo siRNA delivery systems, we perform further experiments comparing the sCA system with Invivofectamine 2.0 (IF) and Atelocollagen (Atelo). Finally we examine the toxicity of sCA nanoparticle system in mice and monkeys. Methods: To assess the bio-distribution of fluorescently labeled siRNA in normal organs and tumor tissues, we used the IVIS Spectrum CT system (PerkinElmer) and fluorescence microscopy. In addition, the multiphoton live imaging system (SP5; Leica) and light sheet fluorescence microscopy (Carl Zeiss) were employed for detailed analysis and clear visualization of extravasation and intracellular distribution of fluorescent siRNA in tumor cells. To examine therapeutic potential of the sCA system, we administered survivin siRNA in pre-established HCT116 tumor mice models. Results & Discussions: Ex vivo imaging analysis using IVIS Spectrum CT showed that the fluorescence of sCA-siRNA was highly accumulated into the tumors as early as 90 min. Light sheet fluorescence microscopy revealed that sCA-siRNA accumulated in the cytoplasm of HCT116 cells with considerable green fluorescence signals at 4 h after intravenous injection. On the other hand, IF-siRNA and Atelo-siRNA did not accumulate in tumor cells. sCA-survivin-siRNA exhibited anti-tumor effects on day 11 and the tumor volume of mice treated with sCA-survivin-siRNA was significantly smaller than in mice treated with sCA-control-siRNA (P = 0.0008), IF-survivin-siRNA (P = 0.0028), or Atelo-survivin-siRNA (P = 0.0046) on day 18. For in vivo safety, we carried out a toxicity study by intravenous injection of sCA to mice. Blood chemistry tests and HE stained sections of the liver, kidney and spleen showed no physiologically significant difference between the saline and sCA treated groups. To aim the final goal of therapy and diagnosis of human tumors, we made up approximately 70-fold sCA of that administered in mouse per injection and administered it to monkeys on 4 consecutive days (n = 3). Consequently intravenous administer of sCA did not cause any serious adverse events in monkeys. Conclusion: We have demonstrated a highly efficient in vivo siRNA delivery system targeting solid tumor models, which is characterized as 10 nm minimal particle size and quick accumulation in tumors, thus it can realize to deliver abundant intact siRNA into tumor cells. Citation Format: Hirofumi Yamamoto, Xin Wu, Susumu Miyazaki, Mamoru Uemura, Taishi Hata, Junichi Nishimura, Ichiro Takemasa, Tsunekazu Mizushima, Yuichiro Doki, Masaki Mori. Super carbonate apatite as simplified systemic nanoparticle carrier for therapy of solid tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4460. doi:10.1158/1538-7445.AM2014-4460

PH-sensitive carbonate apatite nanoparticles as DNA vaccine carriers enhance humoral and cellular immunity

To demonstrate the potential of pH-sensitive carbonate apatite (CO3Ap) nanoparticles as DNA vaccine carriers to enhance vaccination efficacy, we examined the humoral and cellular immune responses of C57BL/6 mice immunized with the plasmid expression vector pCI-neo encoding the full-length soluble ovalbumin (OVA) (pCI-neo-sOVA), pCI-neo-sOVA/CO3Ap complexes, or pCI-neo/CO3Ap complexes as a control. Mice immunized with a low dose of pCI-neo-sOVA-loaded CO3Ap (10μg) produced ex vivo splenocyte proliferation after stimulation with CD8 T-cell but not CD4 T-cell epitopes and a delayed-type-hypersensitivity reaction more efficiently than mice in the other groups. Furthermore, mice receiving this immunization generated the same levels of OVA-specific antibodies and interferon (IFN)-γ secretion after CD8 T-cell and CD4 T-cell epitope challenges as those in mice treated with 100μg of free pCI-neo-sOVA, whereas mice injected with a high dose of pCI-neo-sOVA-loaded CO3Ap (100μg) or with control plasmids produced negligible levels of OVA-specific antibodies or IFN-γ. Therefore, our results showed that 10μg of pCI-neo-sOVA delivered by CO3Ap strongly elicited humoral and cellular immune responses. This study is the first to demonstrate the promising potential of CO3Ap nanoparticles for DNA vaccine delivery.

Iron-doped apatite nanoparticles for improvement of phage therapy

Interest in phage therapy is currently on the rise. As bacterial strains become more and more resistant to antibiotic treatment, research into improved and alternative methods for treating bacterial disease becomes increasingly pertinent. Bacteriophages, or simply phage, are bacteria-specific viruses that provide an alternative treatment in addition to possessing biological traits that allow them avoid bacterial resistance. The authors have found specific apatite nanoparticles exhibit an unprecedented effect on phage infections in vitro. Through the addition of 30% iron-doped apatite nanoparticles (IDANPs) to phage in solution, bacterial death zone (plaque) totals increase up to 128% higher than phage alone. These results are therefore of great interest for antibacterial applications. Extensive investigations and characterization evaluations of these IDANPs and mechanisms involved are an ongoing focus and effort of our researchers. In this article, the authors describe and document the in vitro and characterization results they have amassed thus far.

Integration and bioactivity of hydroxyapatite grown on carbon nanotubes and graphene oxide

We report on the growth of non-stoichiometric nanocrystalline hydroxyapatite (nHAp) with a composition similar to natural bone by a wet-chemical in-situ precipitation route on carbon nanotubes (CNTs) with different degrees of oxygen functionalities and on graphene oxide (GO). Both, functionalization degree and morphology of CNTs and GO appear as critical parameters controlling the shape and crystallinity of the self-assembled nHAp nanoparticles in the corresponding composite materials. Crystalline nHAp nanoparticles with rod-like morphology were achieved for moderately oxidized CNTs and for GO. On CNTs these grow along the CNT’s axis while on GO they form a compact layer. In both cases enhanced nHAp integration onto the respective carbon support is obtained. In vitro bioactivity of the prepared composites exhibits a fast apatite biomineralization process, induced by the presence of nHAp. Depending on its crystalline size and dispersion degree remineralization of the apatite nanoparticles takes place through the inclusion of PO43− and CO32− by ion exchange. Importantly, during the stage of bioactivity the integration degree of nHAp nanoparticles on the carbon nanostructures alters with time, evidencing the potential of GO as valuable bioceramic support material.

Mineralization and drug release of hydroxyapatite/poly(l-lactic acid) nanocomposite scaffolds prepared by Pickering emulsion templating

Biodegradable and bioactive nanocomposite (NC) biomaterials with controlled microstructures and able to deliver special drugs have gained increasing attention in bone tissue engineering. In this study, the hydroxyapatite (HAp)/poly(l-lactic acid) (PLLA) NC scaffolds were facilely prepared using solvent evaporation from templating Pickering emulsions stabilized with PLLA-modified HAp (g-HAp) nanoparticles. Then, in vitro mineralization experiments were performed in a simulated body fluid (SBF) to evaluate the bioactivity of the NC scaffolds. Moreover, in vitro drug release of the NC scaffolds using anti-inflammatory drug (ibuprofen, IBU) as the model drug was also investigated. The results showed that the NC scaffolds possessed interconnected pore structures, which could be modulated by varying the g-HAp nanoparticle concentration. The NC scaffolds exhibited excellent bioactivity, since they induced the formation of calcium-sufficient, carbonated apatite nanoparticles on the scaffolds after mineralization in SBF for 3 days. The IBU loaded in the NC scaffolds showed a sustained release profile, and the release kinetic followed the Higuchi model with diffusion process. Thus, solvent evaporation based on Pickering emulsion droplets is a simple and effective method to prepare biodegradable and bioactive porous NC scaffolds for bone repair and replacement applications.

Synthetic apatite nanoparticles as a phosphorus fertilizer for soybean (Glycine max).

Some soluble phosphate salts, heavily used in agriculture as highly effective phosphorus (P) fertilizers, cause surface water eutrophication, while solid phosphates are less effective in supplying the nutrient P. In contrast, synthetic apatite nanoparticles could hypothetically supply sufficient P nutrients to crops but with less mobility in the environment and with less bioavailable P to algae in comparison to the soluble counterparts. Thus, a greenhouse experiment was conducted to assess the fertilizing effect of synthetic apatite nanoparticles on soybean (Glycine max). The particles, prepared using one-step wet chemical method, were spherical in shape with diameters of 15.8 ± 7.4 nm and the chemical composition was pure hydroxyapatite. The data show that application of the nanoparticles increased the growth rate and seed yield by 32.6% and 20.4%, respectively, compared to those of soybeans treated with a regular P fertilizer (Ca(H2PO4)2). Biomass productions were enhanced by 18.2% (above-ground) and 41.2% (below-ground). Using apatite nanoparticles as a new class of P fertilizer can potentially enhance agronomical yield and reduce risks of water eutrophication.

P0059 Induction of apoptosis in breast cancer cells through combined intracellular delivery of a tumour-suppressor gene and small interfering RNAs against growth factor receptor and anti-apoptotic genes

Background The mechanisms underlying the development of breast cancer are complex and vary among individual tumours. These mechanisms include genetic and epigenetic alterations and resulting changes in the activity of signalling pathways. Current treatment strategies for metastatic breast cancer (MBC) depend upon patient and tumour classification; menopausal status, hormone receptor status, and HER2 status can all be considered, as can site of metastatic disease (bone or soft tissue). The choice of treatment in metastatic disease usually involves systemic endocrine therapy or cytotoxic chemotherapy, with an anti-HER2 agent when appropriate. Novel agents are needed because many of the current therapies have limitations. These include drug resistance, lack of target receptor expression in tumours (e.g., only 25% of breast cancer tumours have HER2 expression), lack of specificity, and relatively small improvements in survival. Advances in the understanding of the aetiology and biology of breast cancer have identified key targets among the multiple signalling pathways involved in the development, growth, and survival of breast cancer cells. As such, targeted therapies are among the most promising new agents for the treatment of breast cancer. Methods The main objective of the project is the restoration of p53 activity and the silencing of HER2, EGFR, and IGF1 genes through the delivery of normal p53 gene and specific validated siRNA, respectively, using carbonate apatite nanoparticles both in vitro and in vivo. Concurrently, the sensitivity of breast cancer cells to the traditional anti-cancer drugs, such as doxorubicin, cisplatin, and paclitaxel will be tested following individually and combined delivery p53 gene and the siRNAs against both growth factor receptor genes and anti-apoptotic genes. Findings The in vitro analysis of siRNAs together and in combination with p53 and anticancer drugs helped to identify potential targets for the treatment of breast cancer. Interpretation Preclinical studies in animal models of breast cancer should be done through tumour-targeted delivery of siRNA in combination with passively diffusible anti-cancer drugs and p53.