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A nanocomposite made from hydroxyapatite (HAP) and silver nanoparticles (AgNPs), namely HAP-4.5 wt% AgNPs, is reported. HAP was prepared using a wet precipitation technique, and AgNPs were made by reducing silver nitrate with glucose in basic medium. HAP, AgNPs and HAP-4.5 wt% AgNPs composite were characterized by X-ray diffraction (XRD), SEM - energy dispersive X-ray spectroscopy (EDS) and different imagistic methods: TEM and AFM. The antibacterial effect of the HAP-4.5 wt% AgNPs nanocomposite was tested using diffusion technique in nutritive agar on two pathogenic species, one Gram-negative (Salmonella typhimurium) and one Gram-positive (Bacillus cereus) and promising results were obtained. This hydroxyapatite-silver nanocomposite can be employed as a potential antimicrobial coating for dental and orthopedic implants, or they can be utilized such as bone cements in clinical procedures. [ABSTRACT FROM AUTHOR]

Due to the ions in its structure, that have a variety of important roles in bone metabolism, forsterite (FS, Mg2SiO4) is a promising candidate for orthopedic and dental applications. This paper studies forsterite synthesized through two methods, namely sol-gel (FSsg) and precipitation (FSpp), based on a thermodynamic approach. Therefore, the precursor gel and precipitate were analyzed through thermal gravimetric (TG), differential thermal gravimetric (DTG) and differential scanning calorimetric (DSC) analysis. The FSsg and FSpp powders were characterized by X-ray powder diffraction (XRD) and atomic force microscopy (AFM). XRD reveals that the synthesized forsterite is of high crystallinity. As is evidenced by AFM, the average size of the nanoparticles is around 40 nm for FSsg and 30 nm for FSpp. The potential reaction mechanisms for the two synthesis routes were also established. [ABSTRACT FROM AUTHOR]

The stability and solubility of curcumin, CCM, can be enhanced by complexation with whey protein concentrate (WPC). The CCM-WPC of 1:1 and 1:0.5 molar ratio complexes were encapsulated by two methods, namely spray drying (SD) and freeze drying (FD). The major objective of this work is to determine the stability and solubility of the CCM-WPC complexes encapsulated by SD and FD method. The X-ray diffraction and thermogravimetric analysis were performed on raw CCM and WPC, and on their complexes. The changes in thermal degradation and in crystallinity suggest the formation of these CCMWPC complexes. Scanning electron microscopy images showed that the used methods influenced the morphology and the properties of the formed complexes. The stability and solubility of curcumin are enhanced by complexation in both encapsulation methods. However, comparing the used molar ratio and drying methods, the results are various. The solubility of samples obtained by FD method was higher than in the case of the SD method, which can explain the difference of their morphology (FD samples are more amorphous than SD samples). The antioxidant property of curcumin and its protein-complexes compared to vitamin C showed that CCM and its complexes have a lower IC50 value than vitamin C, i.e., the antioxidant effect of CCM is higher. The addition of WPC improved the antioxidant activity of CCM, probably due to its encapsulation in the protein. Our results suggest that the 1CCM-1WPC_SD complex is the best antioxidant from these studied CCM-WPC complexes. [ABSTRACT FROM AUTHOR]

In this study, the ions release of physiological elements from pure stoichiometric hydroxyapatite, HAP, and from multi-substituted hydroxyapatite, ms-HAPs, containing 1.5%Mg, 0.2%Zn, 0.2%Si and 5 %Sr, noted HAPc-5%Sr, and from HAPc-10%Sr, in water and in simulated body fluid, SBF, was studied by inductively coupled plasma optical emission spectrometry, ICP-OES, both in static and simulated dynamic regimes. The HAP and ms-HAP nanoparticles, NPs, were prepared by wet chemical precipitation and lyophilized powders were physicochemical characterized as presented elsewhere. The in vitro cations and anions release mechanism was investigated by applying a modified Higuchi model, which fits well the experimental results, particularly for simulated dynamic conditions. The predominant role of diffusion in the release of ions from the hydroxyapatites was confirmed. The sustained ions release from these nanomaterials recommends the investigated ms-HAPs for therapeutic applications. [ABSTRACT FROM AUTHOR]

Titanium implants are highly resistant to external forces and have affordable prices but the contact between Ti metal and surrounding native tissue could provoke an immunological response. The developing of biomimetic coating onto the Ti surface proves to be a smart choice to enhance the osseointegration and ensure an optimal healing process, due to the creation of nanostructured biomaterials like those in native bone. Thus, we designed a composite coating based on multi-substituted hydroxyapatite (noted ms-HAP or HAPc) nanoparticles, NPs, doped with essential elements: Mg, Zn and Si, functionalized with collagen type 1 (COL), embedded into poly lactic acid, PLA, matrix, and finally covered with COL layer to achieve biomimetic structures. Thin layers of biomimetic composite were self-assembled onto Ti surface via dip-coating method. Both, initial and coated Ti implants were investigated by atomic force microscopy (AFM), which allows surface investigation at high resolution of nano-level. COL amount in composite might self-assemble as COL fibers assuring a biomimetic structure, characterized by important features, like suitable porosity to facilitate the delivery of nutrients to osteoblasts and proper nano-topography and surface roughness to promote cell adhesion and proliferation. The outermost layer is of pure collagen which could assure a natural attachment to the bone tissue promoting osseo-integration. [ABSTRACT FROM AUTHOR]

Silver nanoparticles (AgNPs) were synthesized by chemical reduction method, using different reducing systems. The interaction of AgNPs and vancomycin hydrochloride (V) was investigated by UV-Vis spectroscopy, and their tendency to form AgNP@V associations or complexes was identified in colloidal solutions. Moreover their affinity to self-assembly and aggregate is also examined. This behavior is important and decisively influences the antimicrobial effect of AgNP@V complexes. [ABSTRACT FROM AUTHOR]

The wet chemical synthesis of silver nanoparticles (AgNPs) by reduction of silver nitrate with sodium citrate, tannic acid, and their mixture is reported. The obtained silver nanoparticles were investigated by UV-Vis spectroscopy, scanning transmission electron microscopy (STEM), and atomic force microscopy (AFM) images and their antibacterial effect against Escherichia coli was assessed. [ABSTRACT FROM AUTHOR]

Nanostructured hydroxyapatite (HAP) and three multiple substituted HAPs, containing Mg, Zn, Sr and Si were synthesized by a wet precipitation method The presence of the HAP lattice as unique crystalline phase was established by XRD and by FTIR spectroscopy. The chemical composition was confirmed by SEM-EDX. The TEM, SEM and AFM imaging showed the morphology of these biomaterials. The elements release in water and in simulated body fluid (SBF) was monitored in time from 1 to 90 days, by using inductively coupled plasma optical emission spectrometry (ICP-OES). The results are important for the future use of these hydroxyapatite biomaterials, as bone substitutes or coatings on metallic implants, able to release essential physiological elements, both in vitro and in vivo, with great impact in orthopedics and dentistry. [ABSTRACT FROM AUTHOR]

The thermal stability over time of the pure and multisubstituted hydroxyapatite (HAP) pastes, doped with magnesium, silicon, strontium and zinc, synthesized using aqueous precipitation method were investigated by thermal analyses (TG-DTA). Results show high thermal stability of pure and multidoped hydroxyapatite pastes, up to 1000 oC and even after ageing for 1 year, making these pastes promising nano materials for medical applications. [ABSTRACT FROM AUTHOR]

HAP powder of a low crystallinity and rather large specific surface area was synthesized by an environmentally friendly, cost effective precipitation method, and characterized by XRD, FTIR, and BET isotherms. TEM and AFM are used to envisage the surface of HAP nano particles, showing a high porosity of this ceramic powder. It was used for the removal of metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) from mine wastewater. Metal contents in the initial and treated samples were quantified by inductively coupled plasma atomic emission spectrometry and high-resolution continuum source atomic absorption spectrometry. By the use of HAP, an efficient removal of all metals was ensured. The increase of Ca2+ ions content in the treated water suggests an ion exchange mechanism. [ABSTRACT FROM AUTHOR]

Nanostructured hydroxyapatite (HAP) and silicon substituted hydroxyapatites (HAP-Si), with 0.47 and 2.34 wt% Si, were prepared by wet precipitation method. Their structure was investigated by X rays diffraction (XRD), FTIR spectroscopy, energy dispersive X ray (EDX) spectroscopy and their images were obtained by TEM, SEM and AFM. Their behavior in water and SBF was investigated by inductively coupled plasma optical emission spectrometry (ICP-OES) for an immersion time from 1 to 90 days. While Ca and P release from HAP is very low, the presence of Si enhances greatly their release in water, along with a continuous and long lasting Si release. In simulated body fluid, SBF, Ca, P and Mg are removed from the solution, by the formation of a new HAP enriched in Mg, while silicon is released as in water. Thus, Si doped HAP might have advantageous applications as bone and tooth materials. [ABSTRACT FROM AUTHOR]

Principal component analysis (PCA) and cluster analysis (CA) were applied to classify 20 natural amino acids. We selected 18 characteristics, properties available from literature, as a basis for the classification. The correlations between these characteristics and their classification were investigated, as well as the classification of the amino acids. The results are presented as score plots of the first 3 principal components and as dendrograms obtained by clustering analysis. The resulting classification is consistent with the chemical behavior of amino acids and their mutual substitution possibilities in peptides and proteins. [ABSTRACT FROM AUTHOR]

In order to obtain a low crystalline nanohydrxyapatite (HAP), suitable for biomedical application, a new synthesis procedure was developed, based on the aqueous precipitation method, at room temperature, without any additives. Accordingly, lyophilized HAP powders, both calcined and non calcined, were prepared, and characterized by XRD, TEM and AFM imaging, FTIR spectroscopy, zeta potential and BET measurements. The results confirmed HAP as the only phase present. The high porosity of this nanomaterial is attained. The nanoparticle size and shape as well as the crystallinity degree of the obtained HAP samples were also determined. [ABSTRACT FROM AUTHOR]

This study reports the synthesis of new porous nanohydroxyapatites (HAPs) substituted with different Zn contents (HAP_Zn) employing calcium and zinc nitrates and diammonium hydrogen phosphate as precursors. The synthesis was conducted in the presence of a surfactant, L-asparagine, for controlling the pore size distribution and morphology of obtained nanopowders, using a co-precipitation route. Thus a new approach leading to HAP_Zn nanopowders with improved nucleation and crystallization ability was developed. After maturation treatment of dispersions and filtration, the precipitate was lyophilized and ground. Part of the samples was calcined at 300°C for 1 h. The zinc content in the nanoHAPs varies from 0.2 to 10 wt% (substitution degree of Ca by Zn from 0.3 to 15.8 mole %). XRD investigations indicated HAP as the unique phase present and the nanostructured nature of the obtained HAPs. FTIR spectra also confirmed the presence of HAP structure. TEM, SEM, and AFM images showed the morphology of the HAP_Zn samples. BET analysis led to the characterization of specific surface area and porosity for the samples. The new nanopowders are designed to be used in orthopedic surgery, particularly for the treatment of osteoporosis and as bone substitutes, and in dentistry for remineralization of enamel. [ABSTRACT FROM AUTHOR]

Ceramic porous disks made of hydroxyapatite, HAP, loaded with silver ions and nitroxoline (5-nitro-8-hydroxyquinoline, NHQ) are used in vitro against pathogens, such as Staphylococcus aureus. HAP powder was synthesized by a wet chemical method, and its phase purity and nanocrystalline structure were assessed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Disk samples of HAP were prepared and impregnated with Ag+ ions and NHQ solutions. A strong antimicrobial activity of all samples was assessed by the diffusion assay in vitro against Staphylococcus aureus. Through the development of the optimal composition of these biomaterials, this approach might hold potential applications for antimicrobial coating, bone tissue engineering scaffolds and biomedical devices. [ABSTRACT FROM AUTHOR]

A complex nano-hydroxyapatite (HAP) with.0.6 wt% Mg, 0.2 wt% Zn and 0.2 wt% Si was synthesized by the precipitation method. Composites of HAP with collagen (HAP-COL), HAP with chitosan (HAP-CHI) and HAP-COL-CHI were also prepared. The obtained biomaterials were characterized by X-ray diffraction (XRD), FTIR and FT-Raman spectroscopy, and by transmission electron microscopy (TEM) imaging. These biocomposites are potentially useful for hard tissue repairs and orthopedic applications [ABSTRACT FROM AUTHOR]

Self assemblies of mixed cholesterol (CHO) and dimyristoyl phosphatidyl choline (DMPC) monolayers spread at the air/water interface were prepared and investigated by compression isotherms using Langmuir technique (LT). By means of the Langmuir-Blodgett technique (LBT), these self assemblies were transferred on solid support (e.g. glass optically polished) and were characterized by atomic force microscopy (AFM) imaging technique. This investigation demonstrates that rather strong interactions between these lipid molecules, DMPC and CHO molecules, lead to well defined two-dimensional stable nanostructures characterized by low surface roughness. These lipid self assemblies could have practical applications for biosensors fabrication. They also occur within natural membranes representing the lipid matrix where in vivo the protein molecules are embedded or adsorbed. [ABSTRACT FROM AUTHOR]

Maize and potato starch samples were investigated by three scanning electron microscopy techniques (secondary electron imaging, Everhart Thornley secondary electron detection, backscattered electron imaging) at different magnifications. The starch granules were visualized and their shapes, surface morphology and size were revealed. From the SEM images the size distribution of the granules was inferred and compared for the different samples. These investigations will contribute to the characterization of native starches as raw materials for the production of biodegradable plastics. [ABSTRACT FROM AUTHOR]

Atomic force microscopy (AFM) was used to reveal the micro and nanostructure of maize starch granules from Romanian cultivar. The size, shape and surface morphology of the native maize starch granules are shown by AFM observations. Numerous structures, protrusions (particles), pores or depressions and cracks were found on the surface of maize starch granules and they have a broad range of sizes. The occurrence of small spherical protrusions might be related with the highly branched amylopectin molecules in substantial agreement with the amylopectin blocklets model. The larger particles were also visualized, representing different associations of amylopectin and amylose and other granule surface components as previously discussed. The existence of rather smooth regions with low surface roughness and rougher zones on the starch granules is confirmed. [ABSTRACT FROM AUTHOR]

The phase behaviour of cholesterol (CHO) and dimyristoyl phosphatidyl choline (DMPC) monolayers at the air/water interface was investigated by surface pressure measurements using Langmuir technique. Compression isotherms and isobars as functions of composition were represented, and the surface compressibility modulus was calculated, in order to characterize the physical states of the monolayers. At a constant lateral surface pressure, the monolayers were transferred by Langmuir-Blodgett technique (LBT) from air-water interface on solid supports and further studied by atomic force microscopy (AFM). This study shows that the strong interactions between DMPC and CHO lead to well defined twodimensional nanostructures, which can have practical applications for biosensors fabrication. Also, this type of nanostructures seems plausible to occur in natural membranes and thus, can influence the protein distribution and protein function in vivo. [ABSTRACT FROM AUTHOR]

The surface topography of erythrocyte membrane was imaged with the atomic force microscope (AFM), operating in tapping mode, and the effect of desferal (deferoxamine mesylate: DFO) at various concentrations on the cell membrane was investigated. The normal (control) human erythrocytes, without DFO, showed a clear concave form. After the incubation of fresh blood with increasing DFO concentrations, from 5 ×10- 7 M to 5 × 10- 3 M, a progressive increase in both concave depth and surface roughness of erythrocytes were observed. Further, the AFM images indicated that the particles (granules) of the cell surface nanostructure increased with the increasing DFO concentrations. This increase of surface granules is due to the aggregation of lipid nanoparticles and lipid domain formation, induced by DFO. The data are in substantial agreement with our previously published results obtained on lipid membrane models in the presence of DFO. Besides domain formation, the pore formation within human erythrocyte membrane was observed in the presence of desferal. The DFO effect on lipid membranes might be also associated with the modification of both the conformation and the aggregation of membrane proteins, probably leading to an increased permeability of cell membrane. [ABSTRACT FROM AUTHOR]

Silver nanoparticles of about 6 nm average size were prepared by reduction of an aqueous silver nitrate solution with sodium citrate and characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). The interaction of this aqueous colloidal silver solution with the α-lipoic acid solution in ethanol was investigated. The changes in the optical spectra and the TEM images suggest the adsorption of lipoic acid molecules onto the silver nanoparticles and the self assembly of the particles in three dimensional aggregates. [ABSTRACT FROM AUTHOR]