Functionalized Calcium Phosphate Nanoparticles for Biomedical Application

The Antioxidant Supplementation with Filipendula ulmaria Extract Attenuates the Systemic Adverse Effects of Nanosized Calcium Phosphates in Rats

The aim of this study was to investigate and compare the systemic toxicity of three nanosized calcium phosphates (CaPs): hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) in rats. Since those metallic compounds are widely used as bone replacement materials, including their use in oral surgery, CaPs were applied (per os) equimollary (17.8 mg/kg, 11 mg/kg, and 9.65 mg/kg b.w., respectively) for 30 days in order to mimic the previously described release rate from dental composites. Also, we employed antioxidant supplementation with Filipendula ulmaria (FU) extract. All the applied CaPs significantly increased serum calcium, triglycerides, LDL, and LDH, while serum levels of testosterone and LH declined, with no alterations in the liver enzymes. The evaluation of oxidative stress markers (in the liver, kidney, and testicle) showed an increase in TBARS values, while SOD and CAT activities and GSH levels were significantly reduced. The relative gene expression of Bax and Bcl-2 was shifted to proapoptotic action, accompanied by intense characteristic histological changes in architecture in all investigated organs. The toxic effects were most prominent in groups treated by ACP. FU administration attenuated the majority of nanosized CaP-induced adverse effects, thus recommending this therapeutic approach to minimize nano-CaP systemic toxicities.

The Antioxidant Supplementation with Filipendula ulmaria Extract Attenuates the Systemic Adverse Effects of Nanosized Calcium Phosphates in Rats

The aim of this study was to investigate and compare the systemic toxicity of three nanosized calcium phosphates (CaPs): hydroxyapatite (HA), tricalcium phosphate (TCP), and amorphous calcium phosphate (ACP) in rats. Since those metallic compounds are widely used as bone replacement materials, including their use in oral surgery, CaPs were applied (per os) equimollary (17.8 mg/kg, 11 mg/kg, and 9.65 mg/kg b.w., respectively) for 30 days in order to mimic the previously described release rate from dental composites. Also, we employed antioxidant supplementation with Filipendula ulmaria (FU) extract. All the applied CaPs significantly increased serum calcium, triglycerides, LDL, and LDH, while serum levels of testosterone and LH declined, with no alterations in the liver enzymes. The evaluation of oxidative stress markers (in the liver, kidney, and testicle) showed an increase in TBARS values, while SOD and CAT activities and GSH levels were significantly reduced. The relative gene expression of Bax and Bcl-2 was shifted to proapoptotic action, accompanied by intense characteristic histological changes in architecture in all investigated organs. The toxic effects were most prominent in groups treated by ACP. FU administration attenuated the majority of nanosized CaP-induced adverse effects, thus recommending this therapeutic approach to minimize nano-CaP systemic toxicities.

Prolonged release of bone morphogenetic protein-2 in vivo by gene transfection with DNA-functionalized calcium phosphate nanoparticle-loaded collagen scaffolds

In the combination of scaffolds immersed in growth factor solutions, the release of growth factors mainly depends on scaffold degradation. However, the release of bone morphogenetic protein (BMP)-2 at an appropriate concentration during the stage of tissue regeneration would enhance bone regeneration. To achieve this condition, the present study was performed to investigate the effects of scaffolds combined with gene transfection using non-viral vectors. Nanohydroxyapatite-collagen (nHAC) scaffolds cross-linked with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC) or ascorbic acid/copper chloride, and a collagen scaffold (Terdermis®) were prepared, loaded with BMP-2-encoding plasmid DNA-functionalized calcium phosphate nanoparticles (CaP), naked plasmid DNA, or BMP-2 solution, and implanted in rats. The yield of released BMP-2 and its releasing period, respectively, were larger and longer from the scaffolds loaded with CaP than from those incubated with BMP-2 solution. In addition, the alkaline phosphatase activity induced by the CaP-loaded scaffolds was higher. Histological analysis showed that released BMP-2 could be observed on the macrophages or multinuclear giant cells surrounding the nHAC fragments or collagen fibres. TRAP-positive or OCN-positive sites were observed in all groups and a mineralization area was observed in the Terdermis®/CaP sample. The present study demonstrates that gene transfection by scaffold loaded with CaP gene transfer vectors induces a larger yield of BMP-2 for a longer period than by scaffolds loaded with BMP-2 solution or naked plasmid.

Transfection system of amino-functionalized calcium phosphate nanoparticles: in vitro efficacy, biodegradability, and immunogenicity study

Many methods have been developed in order to use calcium phosphate (CaP) for delivering nucleotides into living cells. Surface functionalization of CaP nanoparticles (CaP NPs) with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane was shown recently to achieve dispersed NPs with a positive surface charge, capable of transfection (Chem. Mater. 2013, 25 (18), 3667). In this study, different crystal structures of amino-modified CaP NPs (brushite and hydroxyapatite) were investigated for their interaction in cell culture systems in more detail. Qualitative (confocal laser scanning microscopy) and quantitative (flow cytometry) transfection experiments with two cell lines showed the higher transfection efficacy of brushite versus hydroxyapatite. The transfection also revealed a cell type dependency. HEK293 cells were easier to transfect compared to A549 cells. This result was supported by the cytotoxicity results. A549 cells showed a higher degree of tolerance toward the CaP NPs. Further, the impact of the surface modification on the interaction with macrophages and complement as two important components of the innate immune system were considered. The amine surface functionalization had an effect of decreasing the release of proinflammatory cytokines. The complement interaction investigated by a C3a complement activation assay did show no significant differences between CaP NPs without or with amine modification and overall weak interaction. Finally, the degradation of CaP NPs in biological media was studied with respect to the two crystal structures and at acidic and neutral pH. Both amino-modified CaP NPs disintegrate within days at neutral pH, with a notable faster disintegration of brushite NPs at acidic pH. In summary, the fair transfection capability of this amino functionalized CaP NPs together with the excellent biocompatibility, biodegradability, and low immunogenicity make them interesting candidates for further evaluation.

The role of Carboxydothermus hydrogenoformans in the conversion of calcium phosphate from amorphous to crystalline state

Two previously unknown modes of biomineralization observed in the presence of Carboxydothermus hydrogenoformans are presented. Following the addition of NaHCO₃ and the formation of an amorphous calcium phosphate precipitate in a DSMZ medium inoculated with C. hydrogenoformans, two distinct crystalline solids were recovered after 15 and 30 days of incubation. The first of these solids occurred as micrometric clusters of blocky, angular crystals, which were associated with bacterial biofilm. The second solid occurred as 30–50 nm nanorods that were found scattered among the organic products of bacterial lysis. The biphasic mixture of solids was clearly dominated by the first phase. The X-ray diffractometry (XRD) peaks and Fourier transform infrared spectroscopy (FTIR) spectrum of this biphasic material consistently showed features characteristic of Mg-whitlockite. No organic content or protein could be identified by dissolving the solids. In both cases, the mode of biomineralization appears to be biologically induced rather than biologically controlled. Since Mg is known to be a strong inhibitor of the nucleation and growth of CaP, C. hydrogenoformans may act by providing sites that chelate Mg or form complexes with it, thus decreasing its activity as nucleation and crystal growth inhibitor. The synthesis of whitlockite and nano-HAP-like material by C. hydrogenoformans demonstrates the versatility of this organism also known for its ability to perform the water-gas shift reaction, and may have applications in bacterially mediated synthesis of CaP materials, as an environmentally friendly alternative process.

Functionalized ceramics for biomedical, biotechnological and environmental applications

Surface functionalization has become of paramount importance and is considered a fundamental tool for the development and design of countless devices and engineered systems for key technological areas in biomedical, biotechnological and environmental applications. In this review, surface functionalization strategies for alumina, zirconia, titania, silica, iron oxide and calcium phosphate are presented and discussed. These materials have become particularly important concerning the aforementioned applications, being not only of great academic, but also of steadily increasing human and commercial, interest. In this review, special emphasis is given to their use as biomaterials, biosensors, biological targets, drug delivery systems, implants, chromatographic supports for biomolecule purification and analysis, and adsorbents for toxic substances and pollutants. The objective of this review is to provide a broad picture of the enormous possibilities offered by surface functionalization and to identify particular challenges regarding surface analysis and characterization.

New developments in polymer-controlled, bioinspired calcium phosphate mineralization from aqueous solution

The polymer-controlled and bioinspired precipitation of inorganic minerals from aqueous solution at near-ambient or physiological conditions avoiding high temperatures or organic solvents is a key research area in materials science. Polymer-controlled mineralization has been studied as a model for biomineralization and for the synthesis of (bioinspired and biocompatible) hybrid materials for a virtually unlimited number of applications. Calcium phosphate mineralization is of particular interest for bone and dental repair. Numerous studies have therefore addressed the mineralization of calcium phosphate using a wide variety of low- and high-molecular-weight additives. In spite of the growing interest and increasing number of experimental and theoretical data, the mechanisms of polymer-controlled calcium phosphate mineralization are not entirely clear to date, although the field has made significant progress in the last years. A set of elegant experiments and calculations has shed light on some details of mineral formation, but it is currently not possible to preprogram a mineralization reaction to yield a desired product for a specific application. The current article therefore summarizes and discusses the influence of (macro)molecular entities such as polymers, peptides, proteins and gels on biomimetic calcium phosphate mineralization from aqueous solution. It focuses on strategies to tune the kinetics, morphologies, final dimensions and crystal phases of calcium phosphate, as well as on mechanistic considerations.

Plasmonic photothermic and stem cell therapy of atherosclerotic plaque as a novel nanotool for angioplasty and artery remodeling

BACKGROUND

Some modern angioplasty techniques drastically affect the geometry of the plaque and the lumen, but have some inherent clinical and technical limitations.

METHODS

A total of 101 Yucatan miniature swine were allocated to the three following groups (34 pigs into 60/15- to 70/40-nm silica-gold nanoparticles (NPs), 34 swine into ferromagnetic group with iron-bearing NPs and delivery in hand of magnetic fields, and 33 in a sirolimus stenting control). Animals in the nanogroup were subdivided further into four subsets according to the delivery approach: (1) Intracoronary infused circulating stem progenitor cells (SPCs), including SP(+) (side population) cells, (2) intracoronary infused, ultrasound-mediated, albumin-coated, gas-filled microbubbles, (3) CD73(+)105(+) SPCs in the composition of a bioengineered on-artery patch (cardiac surgery), (4) CD73(+)CD105(+) SPCs engrafted by manual subadventitial injection (cardiac surgery). NPs were detonated with a microwatt near-infrared (NIR) laser (821 nm, 35-44 W/cm(2) for 7 min of exposure).

RESULTS

Changes of the total atheroma volume (TAV; mm(3)) immediately after the laser irradiation at month 6 in the nanoshell, ferromagnetic, and control groups were -7.54%/-22.92%, -9.7%/-16.84%, and -10.5%/-7.06% (p<0.01), respectively, and in the subsets reached -2.79%/-21.92%, -6.26%/-15.24%, -4.6%/-31.21%, -16.5%/-23.3% (p<0.05), respectively. Some cases of atherothrombosis and distal embolism (23.5%) were documented only in the microbubbles subset. The impact of the therapy on the nonorganic part of the plaque-antiinflammative and antiapoptotic effects, signs of neovascularization, and restoration of artery function-were predominant in the observed subsets with SPCs (p<0.01).

CONCLUSION

Nanoburning, especially in combination with stem cell technologies, is a very challenging technique for altering advanced plaque and holds the promise of revolutionizing state-of-the-art interventional cardiology, assuring destruction of plaque and functional restoration of the vessel wall. It could potentially become the current mechanical and pharmacological treatment.

Calcium phosphate ceramic systems in growth factor and drug delivery for bone tissue engineering: a review

Calcium phosphates (CaPs) are the most widely used bone substitutes in bone tissue engineering due to their compositional similarities to bone mineral and excellent biocompatibility. In recent years, CaPs, especially hydroxyapatite and tricalcium phosphate, have attracted significant interest in simultaneous use as bone substitute and drug delivery vehicle, adding a new dimension to their application. CaPs are more biocompatible than many other ceramic and inorganic nanoparticles. Their biocompatibility and variable stoichiometry, thus surface charge density, functionality, and dissolution properties, make them suitable for both drug and growth factor delivery. CaP matrices and scaffolds have been reported to act as delivery vehicles for growth factors and drugs in bone tissue engineering. Local drug delivery in musculoskeletal disorder treatments can address some of the critical issues more effectively and efficiently than the systemic delivery. CaPs are used as coatings on metallic implants, CaP cements, and custom designed scaffolds to treat musculoskeletal disorders. This review highlights some of the current drug and growth factor delivery approaches and critical issues using CaP particles, coatings, cements, and scaffolds towards orthopedic and dental applications.

Synthetic pathways to make nanoparticles fluorescent

In biosciences, it is often necessary to follow the pathway of nanoparticles within cells or tissues. The nanoparticles can be used as labeled sensors which may, e.g., address functionalities within a cell, carry other specific agents like drugs or be magnetic for tumor thermotherapy. In the context of nanotoxicology, the fate of a given nanoparticle is of interest. As many methods in cell biology are based on fluorescence detection, there is a strong demand to make nanoparticles fluorescent. Different ways to introduce fluorescence are reviewed and exemplified with typical kinds of nanoparticles, i.e. polymers, silica and calcium phosphate.