Advanced Materials Research Vol. 829

Abstract: In this study, localized heating of homogenous spherical copper nanoparticles surrounded by water on exposure to short laser pulses is investigated. We are intended to estimate the maximum temperatures of nanoparticles by calculating the absorption efficiency and absorbed energy with some radii in the range 1-50 nm at the laser wavelengths of 248 and 633 nm using Mie theory. The dependency of the melting temperature of nanoparticles upon the particle size is also considered. Our calculations show the appropriate laser wavelength and nanoparticle size which are preferred for large area heating, localized heating without thermal damage or completely localized destroying of small amount of species and polymeric materials modification. The significant temperature rising and the heat transfer to the immediate vicinity is of exceptional interest in selective cell targeting, diagnosis and therapeutic applications, surface modification, and particle removing below damage threshold energy of surrounding media.

Abstract: Today, hydroxyapatite hollow nanopowders have attracted the attention of researchers as a reliable option for drug and protein delivery systems. In this study, nanohydroxyapatite powders with different morphologies were successfully synthesized via wet chemical precipitation method. Elongated rice-shape and semi-spherical nanopowders with hollow structures were synthesized using CTAB and the mixture of cetyltrimethylammonium bromide (CTAB) and polyethylene glycol (PEG) as surfactants respectively. The properties of these nanopowders were charecterized by means of scanning electron microscopy, x-ray diffraction, fourier transform infrared spectroscopy and nitrogen adsorption experiments. The results showed that using CTAB as a surfactant not only can alter the morphology of the HAp nanopowders but also it can have a significant effect on the structure of them, so that by using CTAB and mixture of CTAB and PEG, nanoporous HAp nanopowders were acquired. Moreover, the analysis of nitrogen adsorption showed a higher average surface area for CTAB synthesized HAp in comparison to CTAB/PEG synthesized nanopowder. The amount of live cells adjacent to the HAp suspensions in PBS (50, 100, 200 mg/L) was evaluated by MTT experiment. The results of MTT assay showed the ascending cell proliferation trend for spherical nanopowders by an increment in suspension concentration, while this trend was descending for rice-shape nanopwders.

Abstract: Our goal is to develop methoxy poly (ethylene glycol) (m-PEG) decorated, glycine capped magnetic nanoparticles (MNPs) with proper physicochemical characteristics including particle size and magnetic property. MNP were synthesized by a biocompatible chemical co-precipitation of Mn²⁺ and Fe³⁺ in a sodium hydroxide solution. In order to covalently modify nanoparticles surface by previously prepared m-PEG aldehyde, glycine was used as linker. X-ray diffraction analysis showed successful formation of pure nanocrystalline single phase of Mn-Ferrite and FT-IR spectroscopy approved that m-PEG and glycine were covalently bound to nanoparticles surface. Particle size study showed significant change after modification. In addition, the Vibrating sample magnetometry was done for measuring the magnetic properties (Ms: 52 emu/g) and showing the superparamagnetism behavior.

Abstract: nanobiocomposites are a new class of hybrid materials composed of nanosized filler (nanofiller) incorporated into a bio-based matrix. Such an association between eco-friendly biopolymers and nanoobjects, with the aim to obtain synergic effects, is one of the most innovating routes to enhance the properties of these bio-matrices. In recent years, there has been an increasing interest in Starch as an inexpensive and renewable source has been used as a filler for environmentally friendly plastics for about two decades. However, the poor mechanical properties of starch based biopolymers, leads to use of nanoparticles as reinforcing materials. In the present study, the influence of a combination of a novel plasticizer (formamide) and a traditional plasticizer (glycerol) on the mechanical characteristic of the TPS (thermoplastic starch)-nanoclay compounds has been investigated and the results were compared with thermoplastic starches plasticized by glycerol only. The biodegradable nanocomposites were produced via melt extrusion processing and the samples for mechanical properties were originated by injection molding. The tests performed after two weeks keeping the samples in polyethylene bags. In this study, tensile strength, elongation at break and Young's Modulus were evaluated. Furthermore, the morphologies of samples were studied using a transmission optical microscope. This research showed that using a combination of glycerol and formamide reduce the Young's Modulus and improve the flexibility which can be useful in some applications.

Abstract: A nanoparticle polymer has been developed as a potential platform for drug delivery. Chitosan nanoparticles were prepared with tripolyphosphate (TPP) by the ionic crosslinking method. The particle size of chitosan nanoparticles was in the range of 190-250 nm and encapsulation efficiencies of levothyroxine were 85%. The particle size was determined by photon correlation spectroscopy (PCS). Shape and surface morphology were determined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). They revealed fairly spherical shape of nanoparticles. A non-invasive way to deliver drugs to the deepest parts of the human body is ultrasound. To study how ultrasound causes levothyroxine to be released from chitosan nanoparticles, cumulative release was examined. In this report, we explore the effect of ultrasound and tripolyphosphate (TPP) concentration on release behavior of levothyroxine from chitosan nanoparticles. The drug release from chitosan nanoparticles was enhanced using the ultrasound wave.

Abstract: The use of biomaterials in bone tissue engineering newly has been developed. They are biocompatible material which are reabsorbed in body and replaced with newly formed tissue. Bioactive glass scaffolds will be appropriate candidates if pore morphology, size and structures are controlled. Scaffolds with nanostructure will provide these goals. In this research bioglass powder was synthesized with sol-gel method to achieve nanostructure powder. The glass powder was characterized with transmission electron microscope (TEM). Scaffolds were prepared with combination of bioglass powder and sugar as porogen followed by pressing at 80 MPa then sintering at 1050 oC. The morphology of sintered scaffolds was characterized with scanning electron microscope (SEM) and porosity was measured with density method. Mechanical properties were assessed with compressive strength. The TEM results show that synthesized powder has particle size about 25 nm. The SEM results show that nanopores and macropores are connectively distributed in whole part of scaffolds. The compressive strength of scaffolds was 0.8 MPa. Overall, the scaffold is suggested that is appropriate alternative for bone tissue engineering.

Abstract: High purity Cadmium (Cd) metal was used as raw material and placed in a microwave susceptor. an evaporation/oxidation process occurs under exposure to microwave in less than 2 minutes. Then, Evaporated cadmium reacted with oxygen and cadmium oxide was collected on the inner surface of a glassy container that was placed a few centimeters above the susceptor. Morphological and structural information of As-synthesized CdO nanopowder, were investigated via SEM and X-ray diffraction (XRD) spectroscopy. The antibacterial activities of different concentration of the CdO nanoparticles were tested by treating Escherichia coli (Gram negative) cultures with CdO nanoparticles. The Study indicates that cadmium oxide nanoparticles show effective antibacterial activity toward the gram-negative bacterium E. coli. Electrochemical properties of as-synthesized powder were investigated via linear and two vertex cyclic voltammetery in the presence of ethanol, a pair of Oxidation/reduction peaks were achieved.

Abstract: Nowadays, nanocarriers possess growing interest for medical usage such as photodynamic therapy. Conjunction of these nanoparticles with photosensitising drugs leads to more cellular uptake, higher photocytotoxicty, higher biocompatibility and more selectivity. Previous papers conclude that the 50 nm size nanoparticles give the highest cellular uptake for the purpose of photodynamic therapy. In this paper the gold nanoparticles were synthesized based on TurkevichFrens method. Moreover, methylene blue as a relevant photosensitiser was conjugated to achieved AuNPs. The spectrometric results of UV-visible and Fourier Transform Infrared spectroscopy (FTIR) as well as Atomic Force Microscopy (AFM) emphasis on the presence of MB sensitizers connected to resulting 50 nm gold nanoparticles.

Abstract: Functionalization of Multiwalled Carbon Nanotubes (MWCNTs) for biological applications was considered. For this purpose, the pristine MWCNTs (pMWCNTs) are covalently aminated using p-amino benzoic acid and phosphoric acid without shortening of pMWCNTs. The grafted amine groups on the sidewall of pMWCNTs are useful as initiator for grafting of polymer chains on the sidewall of aminated MWCNTs (MWCNT-NH₂). The PLLA homopolymer chains grafted covalently from the sidewall of aminated MWCNTs successfully. The FT-IR spectra revealed that the amine groups and the PLLA chains grafted form the sidewall of pMWCNTs strongly. The fluoroscopy test results shows that the pMWCNTs and aminated MWCNTs have not any significant photoluminescence (PL) effect at 350 nm excitation. The MWCNT-g-PLLAs exhibit an extremely strong visible emission at 404 nm and 429 nm. These results may be ascribed to the contribution of oxygen vacancies and defects at the end chain of grafted PLLA chains on the sidewall of MWCNTs that created by Sn atoms of initiator during polymerization on the sidewall of MWCNTs. The oxygen vacancies usually act as radiative centers in the PL process. In addition, The MWCNT-g-PLLAs enhance the PL of neat PLLA. The PL of composites slightly diminishes with blue shift during in-vitro degradation. As mentioned above, the MWCNT-g-PLLAs are the functionalized MWCNTs that applicable in the field of medicine. Due to biocompatible and biodegradable molecular groups on the sidewall of MWCNTs, it is predictable that the MWCNT-g-PLLAs will pass all exams for its application in medicine.

Abstract: The aim of this study was to evaluate the interaction of bioactive and biodegradable poly (lactide-co-glycolide)/bioactive glass (PBG) nanocomposite coating with bone and human adipose-derived stem cells (hASC) in vivo and in vitro, respectively. Sol-gel derived 58S bioactive glass (BG) nanoparticles and 50/50wt% poly (lactic acid)/poly (glycolic acid) (PLGA) were used to prepare the coating. The nanocomposite coating was characterized by SEM, XRD, and AFM. Mechanical stability of the prepared nanocomposite coating was studied during intramed­ullary implantation of coated Kirschner wires (k-wires) into rabbit tibiae. Titanium mini-screws coated with PBG nanocompoite coating was implanted intramedullary in rabbit tibia. Bone tissue interaction with the prapared nanocomposite coating was evaluated 30 and 60 days after surgery. The effect of PBG nanocomposite coating on the attachment and viability of human adipose-derived stem cells (hASCs) was investigated. Results showed that PBG nanocomposite coating remained stable on the K-wires with a minimum of 96% of the original coating mass. Tissue around the coated implants showed no adverse reactions to the coating. Woven and trabecular bone formation were observed around the coated samples with a minimum inflammatory reaction. The hASCs showed excellent attachment and viability on the PBG nanocomposite coating. It was concluded that PBG nanocomposite coating provides an ideal surface for bone formation and stem cells attachment and it could be used as a candidate for coating the dental and orthopedic implants.