Nanosized bioceramic particles could function as efficient gene delivery vehicles with target specificity for the spleen

Synthesis, Characterization, Functionalization and Bio-Applications of Hydroxyapatite Nanomaterials: An Overview

Hydroxyapatite (HA) is similar to natural bone regarding composition, and its structure favors in biomedical applications. Continuous research and progress on HA nanomaterials (HA-NMs) have explored novel fabrication approaches coupled with functionalization and characterization methods. These nanomaterials have a significant role in many biomedical areas like sustained drug and gene delivery, bio-imaging, magnetic resonance, cell separation, and hyperthermia treatment due to their promising biocompatibility. This review highlighted the HA-NMs chemical composition, recent progress in synthesis methods, characterization and surface modification methods, ion-doping, and role in biomedical applications. HA-NMs have a substantial role as drug delivery vehicles, coating material, bone implant, coating, ceramic, and composite materials. Here, we try to summarize an overview of HA-NMs with the provision of future directions.

Development of novel gene carrier using modified nano hydroxyapatite derived from equine bone for osteogenic differentiation of dental pulp stem cells

Hydroxyapatite (HA) is a representative substance that induces bone regeneration. Our research team extracted nanohydroxyapatite (EH) from natural resources, especially equine bones, and developed it as a molecular biological tool. Polyethylenimine (PEI) was used to coat the EH to develop a gene carrier. To verify that PEI is well coated in the EH, we first observed the morphology and dispersity of PEI-coated EH (pEH) by electron microscopy. The pEH particles were well distributed, while only the EH particles were not distributed and aggregated. Then, the existence of nitrogen elements of PEI on the surface of the pEH was confirmed by EDS, calcium concentration measurement and fourier transform infrared spectroscopy (FT-IR). Additionally, the pEH was confirmed to have a more positive charge than the 25 kD PEI by comparing the zeta potentials. As a result of pGL3 transfection, pEH was better able to transport genes to cells than 25 kD PEI. After verification as a gene carrier for pEH, we induced osteogenic differentiation of DPSCs by loading the BMP-2 gene in pEH (BMP-2/pEH) and delivering it to the cells. As a result, it was confirmed that osteogenic differentiation was promoted by showing that the expression of osteopontin (OPN), osteocalcin (OCN), and runt-related transcription factor 2 (RUNX2) was significantly increased in the group treated with BMP-2/pEH. In conclusion, we have not only developed a novel nonviral gene carrier that is better performing and less toxic than 25 kD PEI by modifying natural HA (the agricultural byproduct) but also proved that bone differentiation can be effectively promoted by delivering BMP-2 with pEH to stem cells.

Interplay between surface chemistry and osteogenic behaviour of sulphate substituted nano-hydroxyapatite

Surface potential and chemical compositions of the bioceramics are the core of therapeutic effect and are key factors to trigger the interfacial interactions with surrounding hard and soft tissues to repair and regeneration. Ionic substitution in hydroxyapatite (Hap) lattice significantly influences the zeta potential from -16.46 ± 0.66 mV to -6.01 ± 0.68 mV as well as an average nano-rod length from ~40 nm to ~26 nm with respect to SO₄^2- ion content. Moreover, the surface chemistry of Hap is mainly inter-related to SO₄^2- substitution rate at PO₄^2- site. Specifically, nano-sized feature with lowered negative surface potential influences the protein adsorption via their weak repulsive or attractive forces. Bovine serum albumin (BSA) and lysozyme (LSZ) adsorption studies confirmed the increased affinity to active binding sites of Hap's surface. Further, SO₄^2- ion substituted Hap (SNHA) showed improved in vitro biomineralization activity and alkaline phosphatase activity. Expression of osteogenic biomarkers such as collagen I, V, osteopontin and osteocalcin were evaluated in Saos-2 and MC3T3-E1 cells. Gene expression of these markers was influenced by SO₄^2- ion content in Hap (maximum with 10SNHA). Altogether, these data emphasizes that chemical composition and surface properties are dominant aspect in bioceramic development towards bone regeneration.

Effect of Zirconium oxide nanoparticle on serum level of testosterone and spermatogenesis in the rat: An experimental study

BACKGROUND

Zirconium nanoparticles are used as health agents, pharmaceutical carriers, and in dental and orthopedic implants.

OBJECTIVE

This studyaimed to investigate the effects of Zirconium oxide nanoparticles on the process of spermatogenesis in rat.

MATERIALS AND METHODS

In this experimental study, 32 male Wistar rats (150-200 gr), with range of age 2.5 to 3 months were used and divided into four groups of eight per each. The control group received 0.5 ml of distilled water and the three experimental groups received 50, 200, and 400 ppm doses of Zirconium oxide nanoparticles solution over a 30-day period, respectively. At the end of the experiment, tissue sections were taken from the testis and stained with hematoxylin-eosin. Serum concentration of testosterone was measured by enzyme-linked immunosorbent assay.

RESULTS

In the experimental group receiving 400 ppm Zirconium oxide nanoparticles, the number of Spermatogonia cells (p ≤ 0.01), Spermatocytes (p ≤ 0.01), Spermatids (p ≤ 0.001), and sertoli and Leydig cells (p ≤ 0.05) showed a significant decrease compared to the control group. Serum testosterone concentration did not change significantly in all experimental groups receiving Zirconium oxide nanoparticles compared to the control group. Experimental group received 400 ppm Zirconium oxide nanoparticles shrinkage of seminal tubules and reduced lumen space compared to control group.

CONCLUSION

Zirconium oxide nanoparticles are likely to damage the testes by increasing Reactive oxygen species production and free radicals.

Bismuth-Based Nanomaterials: Recent Advances in Tumor Targeting and Synergistic Cancer Therapy Techniques

Despite all of the efforts in the field of cancer therapy, the heterogeneous properties of tumor cells induce an insufficient therapeutic outcome when treated with conventional monotherapies, necessitating a shift in cancer treatment from monotherapy to combination therapy for complete cancer treatment. Multifunctional bismuth (Bi)-based nanomaterials (NMs) with therapeutic functions hold great promise for the fields of cancer diagnosis and therapy based on their low toxicity, X-ray sensitive capabilities, high atomic number, near-infrared driven semiconductor properties, and low cost. Herein, a comprehensive review of recent advances in various medicinal aspects of Bi-based NMs is presented including: evaluation of in-tumor site accumulation, tumor targeting, and therapeutic performance, as well as the characteristics, benefits, and shortcomings of Bi-based NM-mediated major monotherapies. In addition, the cooperative enhancement mechanisms between two or more of these monotherapies are described in detail to address common challenges in cancer therapy, such as multidrug resistance, hypoxia, and metastasis. Finally, this review opens new insights into the design of multimodal synergistic therapies for potential future clinical applications of Bi-based NMs.

Spleen selective enhancement of transfection activities of plasmid DNA driven by octaarginine and an ionizable lipid and its implications for cancer immunization

Efficiently delivering plasmid DNA (pDNA) to the spleen is particularly significant for DNA immunization. However, increasing the efficiency of gene expression in spleen cells for achieving a therapeutic effect remains a serious challenge. An ideal spleen-targeted system should avoid liver uptake and should efficiently transfect specific functional spleen cells. Here, we report on pDNA nanocarriers with enhanced transfection in spleen cells driven by synergism between an octaarginine (R8) peptide and YSK05; a pH-responsive ionizable lipid. A double-coating design is essential for enhancing spleen selective transfection which is significantly affected by the total amount of lipid and the composition of the outer coat. The optimized R8/YSK system shows a high gene expression in the spleen with a high spleen/liver ratio and a surprising ability to target spleen B cells. Compared to other organs, the high spleen activity cannot be explained based on the amount of pDNA delivered to each organ, indicating that the system is extremely efficient in transfecting spleen cells. The system can be used in cancer immunization where a strong anti-tumor effect was observed in mice immunized with the R8/YSK system encapsulating antigen-encoding pDNA. The R8/YSK system holds great promise for future applications in the field of DNA vaccination.

Experimental study of TNF-α receptor gene transfection by ultrasound-targeted microbubble destruction to treat collagen-induced arthritis in rats in vivo

Ultrasound-targeted microbubble destruction (UTMD) is a novel method for gene transfection. The aim of the present study was to identify the most suitable method of tumor necrosis factor (TNF)-α receptor (TNFR) gene transfection using UTMD for systemically treating a rat model of collagen-induced arthritis (CIA). Plasmids encoding the TNFR and enhanced green fluorescent protein (EGFP) with or without microbubbles were locally injected into the skeletal muscle and synovial membrane of CIA rats. The rats were divided into the following 6 groups: i) Group 1, plasmid + microbubble + ultrasound (muscle group); ii) group 2, plasmid + microbubble + ultrasound (joint group); iii) group 3, plasmid + ultrasound; iv) group 4, plasmid + microbubble; v) group 5, plasmid only and; vi) group 6, untreated controls. Rats were sacrificed at 2, 4 and 8 weeks of treatment. The transfection efficiency of the plasmids in the muscle or synovium was observed by fluorescence microscopy. Arthritis scores were calculated and serum levels of TNF-α were measured prior to and following treatment. Bilateral ankle joints were obtained and stained to observe synovial inflammation and the expression of TNF-α. EGFP expression was detected in all treated groups at each time point, and the fluorescence intensity of groups 1 and 2 was significantly greater than that of the other groups (P<0.05). For groups 1 and 2, the reductions in joint scores and serum levels of TNF-α were significant compared with the other groups (P<0.05). The number of synovial inflammatory cells and the synovial expression of TNF-α presented similar results among all experimental groups and no significant difference was observed between groups 1 and 2. Therefore, the results of the present study suggest that UTMD significantly enhanced the efficiency of TNFR gene transfection in the muscle and inflamed synovium of rats with. Regardless of whether the transfected TNFR gene was injected into the muscle or joint, it was continuously expressed in the rats for at least 8 weeks, which may improve arthritic symptoms and reduce the levels of inflammatory factors in the synovial tissues and peripheral blood.

Plasmid-Templated Control of DNA-Cyclodextrin Nanoparticle Morphology through Molecular Vector Design for Effective Gene Delivery

Engineering self-assembled superstructures through complexation of plasmid DNA (pDNA) and single-isomer nanometric size macromolecules (molecular nanoparticles) is a promising strategy for gene delivery. Notably, the functionality and overall architecture of the vector can be precisely molded at the atomic level by chemical tailoring, thereby enabling unprecedented opportunities for structure/self-assembling/pDNA delivery relationship studies. Beyond this notion, by judiciously preorganizing the functional elements in cyclodextrin (CD)-based molecular nanoparticles through covalent dimerization, here we demonstrate that the morphology of the resulting nanocomplexes (CDplexes) can be tuned, from spherical to ellipsoidal, rod-type, or worm-like nanoparticles, which makes it possible to gain understanding of their shape-dependent transfection properties. The experimental findings are in agreement with a shift from chelate to cross-linking interactions on going from primary-face- to secondary-face-linked CD dimers, the pDNA partner acting as an active payload and as a template. Most interestingly, the transfection efficiency in different cells was shown to be differently impacted by modifications of the CDplex morphology, which has led to the identification of an optimal prototype for tissue-selective DNA delivery to the spleen in vivo.

Inhibition of prostate cancer RM1 cell growth in vitro by hydroxyapatite nanoparticle‑delivered short hairpin RNAs against Stat3

The present study investigated the effect of signal transducer and activator of transcription 3 (Stat3) interference on RM1 prostate cancer cell viability in vitro, using plasmid‑based Stat3 specific short hairpin RNA (sh‑Stat3) delivered by hydroxyapatite nanoparticles (HAP). HAP carrying sh‑Stat3 plasmids were transfected into tumor cells. MTT assays were used to measure RM1 cell viability 24 and 48 h following transfection, and the apoptosis rate and cell cycle phase distribution were determined by flow cytometry. Stat3 mRNA expression levels were measured by reverse transcription‑quantitative polymerase chain reaction and Stat3, Cyclin D1, B cell lymphoma 2 apoptosis regulator (Bcl‑2), vascular endothelial growth factor (VEGF), Bcl‑2 associated X apoptosis regulator (Bax) and cleaved‑caspase‑3 protein expression levels were detected using western blot analysis. The results demonstrated that HAP‑delivered sh‑Stat3 significantly decreased RM1 cell viability through the promotion of cell cycle arrest and apoptosis. Stat3 mRNA and protein expression levels were significantly downregulated in RM1 cells. Bcl‑2, VEGF and Cyclin D1 were also significantly downregulated, but cleaved‑caspase‑3 and Bax mRNA and protein expression levels were significantly upregulated. HAP‑delivered sh‑Stat3 decreased RM1 cell viability in vitro, and HAP assisted plasmid‑based delivery of shRNA into tumor cells. The present results suggest that HAP may be a useful method for successful shRNA delivery into tumors.

A Novel Approach of Synthesizing and Evaluating the Anticancer Potential of Silver Oxide Nanoparticles in vitro

Background: Development of novel strategies to kill cancer by sparing normal cells is of utmost importance. Apart from their known antimicrobial activity, only limited information has been recorded regarding the antitumor potential of biocompatible silver oxide nanoparticles (AgONPs). There is a need to evaluate the anticancer potential of biocompatible AgONPs in vitro. Methods: A new approach of utilizing the leaf extract of Excoecaria agallocha was used to synthesize AgONPs. This was then characterized by ultraviolet-visible spectrophotometry, nanoparticle-tracking analysis, and ζ-potential analysis. Cytotoxicity and apoptotic potential were evaluated with an MTT assay and an annexin V-binding assay against the murine melanoma (B16F10), murine colon cancer (CT26), murine lung adenocarcinoma (3LL), and murine Ehrlich ascites carcinoma (EAC) cell lines. Cellular localization of AgONPs was evaluated on fluorescence microscopy. Results: UV peaks at 270 and 330 nm indicated the formation of nanoparticles (NPs) and the NP-tracking analyzer revealed them to have a size of 228 nm. AgONPs exerted initial cytotoxicity, specifically against all the experimental malignant cells by sparing the normal cell lines. Moreover, AgONPs exert apoptosis equally on all the malignant cells in vitro and ex vivo. This cytotoxicity possibly occurs via the nuclear translocation of AgONPs as analyzed in B16F10 cells. Conclusions: AgONPs utilizing natural sources would be a new medicinal approach against a broad spectrum of malignancy.

Recent advances in the synthesis, functionalization and biomedical applications of hydroxyapatite: a review

Hydroxyapatite (HA) is a member of the Ca apatite family.

Mesoporous bioactive glasses: Relevance of their porous structure compared to that of classical bioglasses

In the last decade, the development of third generation bioceramics for Bone Tissue Regeneration has experienced significant progress with the emergence of a new generation of nanostructured materials named mesoporous bioactive glasses (MBG). This new generation of materials, also known as “templated glasses”, presents chemical compositions similar to those of conventional bioactive sol–gel glasses and the added value of an ordered mesopore arrangement. This article shows an indepth comparative study of the ordered porous structures of MBGs compared to conventional glasses (melt and solgel) andhowthese properties influence the bioactivity process. Moreover, the possibility to tailor the textural and structural properties of these nanostructured materials by an exhaustive control of the different synthesis parameters is also discussed. A brief overview regarding the possibility of using these materials as controlled drug delivery systems and as starting materials for the fabrication of 3D scaffolds for bone tissue regeneration is also given.

Effect of particle surface charge on drug uptake

In this paper, it aims to build the relationship of statically electric interaction between the surface charge of a particle drug and cellular uptake. The statically electric theory is applied to study the change of wetting between the drug particle and the cell, a factor that enhanced uptake of cells induced by particle’s surface charge is introduced, then it is formulated according to Kelvin theory for dissolving of solid particle in liquid. It is found that the change of contact angle between the surface charged particle drug and the cell can be detected if the Zeta potential reaches to 6 mV in water like solution, an increase of about 11.1% for the uptake could be obtained for a polymer particle with molar mass

Delivery system for DNAzymes using arginine-modified hydroxyapatite nanoparticles for therapeutic application in a nasopharyngeal carcinoma model

DNAzymes are synthetic, single-stranded, catalytic nucleic acids that bind and cleave target mRNA in a sequence-specific manner, and have been explored for genotherapeutics. One bottleneck restricting their application is the lack of an efficient delivery system. As an inorganic nanomaterial with potentially wide application, nano-hydroxyapatite particles (nHAP) have attracted increasing attention as new candidates for nonviral vectors. In this study, we developed an nHAP-based delivery system and explored its cellular uptake mechanisms, intracellular localization, and biological effects. Absorption of arginine-modified nanohydroxyapatite particles (Arg-nHAP) and DZ1 (latent membrane protein 1 [LMP1]-targeted) reached nearly 100% efficiency under in vitro conditions. Using specific inhibitors, cellular uptake of the Arg-nHAP/DZ1 complex was shown to be mediated by the energy-dependent endocytosis pathway. Further, effective intracellular delivery and nuclear localization of the complex was confirmed by confocal microscopy. Biologically, the complex successfully downregulated the expression of LMP1 in nasopharyngeal carcinoma cells. In a mouse tumor xenograft model, the complex was shown to be delivered efficiently to tumor tissue, downregulating expression of LMP1 and suppressing tumor growth. These results suggest that Arg-nHAP may be an efficient vector for nucleic acid-based drugs with potential clinical application.

Mouse lymphatic endothelial cell targeted probes: anti-LYVE-1 antibody-based magnetic nanoparticles

Purpose

To investigate the specific targeting property of lymphatic vessel endothelial hyaluronan receptor-1 binding polyethylene glycol-coated ultrasmall superparamagnetic iron oxide (LYVE-1-PEG-USPIO) nanoparticles to mouse lymphatic endothelial cells (MLECs).

Methods

A ligand specific target to lymphatic vessels was selected by immunohistochemical staining on the sections of a Lewis subcutaneous transplanted tumor. The z-average hydrodynamic diameter (HD), zeta potential, and the relaxivity of PEG-USPIO and LYVE-1-PEG-USPIO nanoparticles were determined with a laser particle analyzer and magnetic resonance T₂ spin echo sequence, respectively. Prussian blue staining and transmission electron microscopy (TEM) of nanoparticle labeled cells were performed to determine the nanoparticles’ binding form. Magnetic resonance imaging (MRI) was performed in vitro to evaluate the signal enhancement on the T₂ spin echo sequence of the nanoparticle labeled cells. The iron content of the labeled cells after the Prussian blue staining and MRI scanning was determined by atomic absorption spectroscopy (AAS).

Results

The anti-LYVE-1 antibody was used as the specific ligand to synthesize the target probe to the MLECs. The mean z-average HDs of the LYVE-1-PEG-USPIO and PEG-USPIO nanoparticles were 57.42 ± 0.31 nm and 47.91 ± 0.73 nm, respectively, and the mean zeta potentials of the LYVE-1-PEG-USPIO and PEG-USPIO nanoparticles were 12.38 ± 4.87 mV and 2.57 ± 0.83 m V, respectively. The relaxivities of the LYVE-1-PEG-USPIO and PEG-USPIO nanoparticles were 185.48 mM⁻¹s⁻¹ and 608.32 mM⁻¹s⁻¹. Cells binding nanoparticles were visualized as blue granules in the Prussian blue staining. The TEM results of the labeled cells showed the specific localization of nanoparticles. The AAS results of labeled cells after the Prussian blue staining and MRI scanning showed that the LYVE-1-PEG-USPIO nanoparticles had good binding selectivity for MLECs. MRI results indicated that the PEG-USPIO and LYVE-1-PEG-USPIO nanoparticles could generate contrast on T₂-weighted imaging, and the correlation between R₂ and the iron content of the labeled cells was significantly positive.

Conclusion

This study demonstrated that LYVE-1-PEG-USPIO nanoparticles might potentially be used as an MRI contrast agent for targeting MLECs, and the magnetic properties of LYVE-1-PEG-USPIO nanoparticles were suitable for MRI.

Intraperitoneal delivery of nanoparticles for cancer gene therapy

Nanoparticle-based gene delivery systems may be more efficient for administration of therapeutic genes to solid tumors and cancer metastases, owing to the numerous advantages in terms of enhanced tissue penetrability, improved cellular uptake and targeted gene delivery to the cells of interest compared with other gene delivery systems. Intraperitoneal (IP) delivery of therapeutic agents offers special merits because of the anatomical situation of peritoneum for local cancer therapy. Via the IP administration route, it is possible to target the therapeutic agents exactly to the target cells and protect healthy tissues outside the peritoneal cavity from side effects. IP delivery could be applicable for the treatment of disorders of organs in the peritoneal cavity covered with peritoneum and subperitoneal connective tissue, including cancers such as ovarian and gastric. The goal of this article is to review the current state of IP delivery of nanoparticles for cancer gene therapy.

The comparative immunotoxicity of mesoporous silica nanoparticles and colloidal silica nanoparticles in mice

BACKGROUND

Mesoporous silica (MPS) nanoparticles (NPs), which have a unique pore structure and extremely large surface area and pore volume, have received much attention because of their biomedical application potential. Using MPS NPs for biomedical devices requires the verification of their biocompatibility because the surface area of NPs is one of the most important determinants of toxicity, including the cellular uptake and immune response. We have previously reported that the cytotoxicity and inflammation potential of MPS NPs have been shown to be lower than those of general amorphous colloidal silica (Col) NPs in macrophages, but the low cytotoxicity does not guarantee high biocompatibility in vivo. In this study, we compared the in vivo immunotoxicity of MPS and Col NPs in the mouse model to define the effects of pore structural conditions of silica NPs.

MATERIALS AND METHODS

Both MPS and Col NPs (2, 20, and 50 mg/kg/day) were intraperitoneally administered in female BALB/c mice for 4 weeks, and clinical toxicity, lymphocyte population, serum IgG/IgM levels, and histological changes were examined.

RESULTS

There was no overt sign of clinical toxicity in either MPS- or Col-treated mice. However, MPS NPs led to significant increases in liver and spleen weight and splenocyte proliferation. Mice treated with MPS NPs showed altered lymphocyte populations (CD3(+), CD45(+), CD4(+), and CD8(+)) in the spleen, increased serum IgG and IgM levels, and histological changes. Despite slight changes in lymphocyte populations in the spleen, Col NPs did not alter other immunological factors.

CONCLUSION

The results indicate that in vivo exposure to MPS NPs caused more damage to systemic immunity than that of Col NPs through the dysregulation of the spleen. The results for in vivo data are inconsistent with those for in vitro data, which show lower cytotoxicity for MPS NPs. These results suggest the importance of verifying biocompatibility both in vitro and in vivo during the design of new nanomaterials.

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.

Size-dependent transfection efficiency of PEI-coated gold nanoparticles

Gold nanoparticles (Au NPs) are promising vectors for gene delivery applications. In order to gain insight on the influence of particle size on cell transfection, Au NPs were combined with poly(ethylenimine) (PEI) to prepare two sets of PEI-coated Au NPs having particle-size distributions centered at about 6 nm (<10nm Au-PEI NPs) or 70 nm (<100 nm Au-PEI NPs), respectively. Au-PEI NPs were coupled to a variety of plasmids carrying reporter or suicide genes to prepare Au-PEI NPs/DNA complexes, and human osteosarcoma Saos-2 cells were used to investigate the performance of the Au-PEI NPs as transfection vectors in serum-containing media. The conjugates of DNA with both types of Au-PEI NPs were found to be negatively charged. In spite of the electrostatic repulsion that occurs between the surface of the cell and the surface of the plasmid-conjugated NPs, cell internalization was observed for both kinds of Au-PEI NPs. Cells were efficiently transfected with complexes derived from <10 nm Au-PEI NPs, but not with the <100 nm Au-PEI NPs. Large aggregates of NPs associated with DNA were found in endocytic vesicles of cells incubated with <100 nm Au-PEI NPs, while the success of the smaller Au-PEI NPs as transfection vectors was related to their lower agglomeration state inside cells and to endosomal escape of DNA.

The role of surface charge on the uptake and biocompatibility of hydroxyapatite nanoparticles with osteoblast cells

The objective of this study is to evaluate the effect of hydroxyapatite (HAP) nanoparticles with different surface charges on the cellular uptake behavior and in vitro cell viability and proliferation of MC3T3-E1 cell lines (osteoblast). The nanoparticles' surface charge was varied by surface modification with two carboxylic acids: 12-aminododecanoic acid (positive) and dodecanedioic acid (negative). The untreated HAP nanoparticles and dodecanoic acid modified HAP nanoparticles (neutral) were used as the control. X-ray diffraction (XRD) revealed that surface modifications by the three carboxylic acids did not change the crystal structure of HAP nanoparticles; Fourier transform infrared spectroscopy (FT-IR) confirmed the adsorption and binding of the carboxylic acids on the HAP nanoparticles' surfaces; and zeta potential measurement confirmed that the chemicals successfully modified the surface charge of HAP nanoparticles in water based solution. Transmission electron microscopy (TEM) images showed that positively charged, negatively charged and untreated HAP nanoparticles, with similar size and shape, all penetrated into the cells and cells had more uptake of HAP nanoparticles with positive charge compared to those with negative charge, which might be attributed to the attractive or repulsive interaction between the negatively charged cell membrane and positively/negatively charged HAP nanoparticles. The neutral HAP nanoparticles could not penetrate the cell membrane due to their larger size. MTT assay and LDH assay results indicated that as compared with the polystyrene control, greater cell viability and cell proliferation were measured on MC3T3-E1 cells treated with the three kinds of HAP nanoparticles (neutral, positive, and untreated), among which positively charged HAP nanoparticles showed the strongest improvement for cell viability and cell proliferation. In summary, the surface charge of HAP nanoparticles can be modified to influence the cellular uptake of HAP nanoparticles and the different uptake also influences the behavior of cells. These in vitro results may also provide useful information for investigations of HAP nanoparticle applications in gene delivery and intracellular drug delivery.

In vitro labeling of hydroxyapatite minerals by an engineered protein

Biological and biomimetic synthesis of inorganics have been a major focus in hard tissue engineering as well as in green processing of advanced materials. Among the minerals formed by organisms, calcium phosphate mineralization is studied extensively to understand the formation of mineral-rich tissues. Herein, we report an engineered fusion protein that not only targets calcium phosphate minerals but also allows monitoring of biomineralization. To produce the bi-functional fusion protein, nucleotide sequence encoding combinatorially selected hydroxyapatite-binding peptides (HABP) was genetically linked to the 3' end of the open reading frame of green fluorescence protein (GFPuv) and successfully expressed in Escherichia coli. The fluorescence and binding activities of the bi-functional proteins were characterized by, respectively, using fluorescence microscopy and quartz crystal microbalance spectroscopy. The utility of GFPuv-HABP fusion protein was assessed for both time-wise monitoring of mineralization and the visualization of the mineralized tissues. We used an alkaline phosphatase-based reaction to control phosphate release, thereby mimicking biological processes, to monitor calcium phosphate mineralization. The increase in mineral amount was observed using the fusion protein at different time points. GFPuv-HABP1 was also used for efficient fluorescence labeling of mineralized regions on the extracted human incisors. Our results demonstrate a simple and versatile application of inorganic-binding peptides conjugated with bioluminescence proteins as bi-functional bioimaging molecular probes that target mineralization, and which can be employed to a wide range of biomimetic processing and cell-free tissue engineering.

Enhanced uptake of porous silica microparticles by bifunctional surface modification with a targeting antibody and a biocompatible polymer

Strategies were developed by which mesoporous microparticles were modified on their external surfaces with tetraethylene glycol (TEG), a protein, or both, leaving the pore surfaces available for modification with a separate moiety, such as a dye. Only particles bifunctionally modified with both TEG and a cell-specific antibody were taken up specifically by a targeted cancer cell line. In contrast to similarly functionalized nanoparticles, endocytosed microparticles were not contained within a lysosome.

Toxic and teratogenic silica nanowires in developing vertebrate embryos

Silica-based nanomaterials show promise for biomedical applications such as cell-selective drug delivery and bioimaging. They are easily functionalized, which allows for the conjugation or encapsulation of important biomolecules. Although recent in vitro studies suggested that silica-derived nanomaterials are nontoxic, in vivo studies of silica nanomaterial toxicity have not been performed. Using the embryonic zebrafish as a model system, we show that silica nanomaterials with aspect ratios greater than 1 are highly toxic (LD(50) = 110 pg/g embryo) and cause embryo deformities, whereas silica nanomaterials with an aspect ratio of 1 are neither toxic nor teratogenic at the same concentrations. Silica nanowires also interfere with neurulation and disrupt expression of sonic hedgehog, which encodes a key midline signaling factor. Our results demonstrate the need for further testing of nanomaterials before they can be used as platforms for drug delivery.

FROM THE CLINICAL EDITOR

Silica-based nanomaterials show promise for biomedical applications such as cell-selective drug delivery and bioimaging. Using an embryonic zebrafish model system silica nanomaterials with aspect ratios greater than one were found to be highly toxic; whereas silica nanomaterials with an aspect ratio of one are neither toxic nor teratogenic. These results demonstrate the need for testing "nanomaterials" before they can be used as platforms for drug delivery.