In vitro characterization of a biocompatible composite based on poly(3-hydroxybutyrate)/hydroxyapatite nanoparticles as a potential scaffold for tissue engineering.

The use of regeneration scaffolds has been a promising strategy in the bone tissue engineering area. Among the materials available for this purpose the poly(3-hydroxybutyrate) - PHB stands out for its adequate biocompatibility and osteoinduction capacity. Hydroxyapatite, in turn, has as its main characteristics its ability to increase bioactivity and cell proliferation. Thus, the objective of the present study was to obtain PHB composites with nanohydroxyapatite (Hap) (0.05%, 0.20%, and 0.50%) and evaluate the microstructure, thermal and mechanical properties and molecular dynamics. Besides that, in vitro biological properties such as wettability, cell viability and adhesion of L929 fibroblasts cells, enzymatic degradation and radiographic contrast were evaluated. The results indicate a weak interaction between Hap and PHB, however, the dispersion states of the nanoparticles can influence crystallization and thermal stability. Through the evaluation of the mechanical behavior was verified a harder behavior with the Hap addition. The wettability of the systems showed a tendency to increase with the addition of nanoparticles. All systems presented high values of viability and cell adhesion, the latter being more pronounced for systems containing Hap. The nanoparticles acted as a barrier slowing the rate of enzymatic degradation and contributed to the increase in radiographic contrast. The results obtained indicate that the systems are promising for application in tissue engineering.

Polyvinylpyrrolidone/Montmorillonite/Zinc Oxide Bionanosystems Prepared by Spray Drying.

In this study, microparticles of bionanomaterials were obtained by polyvinylpyrrolidone, montmoril-lonite, and zinc oxide bionanosystems produced through solution intercalation technique combined with a spray-drying process, aiming for possible application as drug delivery systems. The final microparticles obtained were evaluated in terms of their production yield, which varies between 39.2% and 56.9%. Thermal analysis showed no major changes in Tg of the nanocomposites, compared to the pure PVP polymer. Scanning electron microscopy analysis revealed a pseudo-spherical shape and confirmed the micrometric size of the microparticles. Transmission electron microscopy analysis corroborated the embedding of montmorillonite and ZnO within the polymer phase. Nuclear magnetic resonance and X-rays diffraction were used to study the nanoparticles dispersion, indicating a predominant intercalated morphology. This study suggests that the applied methodology is suitable for the high yields synthesis of nanocomposites PVP based microparticles with uniform size and shape, which can be promising for the production of a new drug delivery system.

Single-shot measurement of solids and liquids T1 values by a small-angle flip-flop pulse sequence.

We propose the small-angle flip-flop (SAFF) pulse sequence as an alternative procedure for the rapid measurement of the 1 H spin-lattice relaxation time in the laboratory frame (T1 ) of solid and liquid substances, in a time-domain NMR experiment. Based on the original flip-flop pulse sequence, this technique allows the fast estimation of T1 values of samples that require minutes to hours of acquisition time if traditional pulse sequences are employed. We have applied SAFF to different substances, with T1 ranging from microseconds up to seconds, including natural clays, polymers, and organic and inorganic solvents. We also demonstrate the potential of the pulse sequence in the real-time monitoring of dynamic processes, such as the conformational changes of polymeric materials during heating. The results we obtained with SAFF are comparable with those acquired with the inversion-recovery pulse sequence, with the addition of several benefits. This pulse sequence obeys steady-state and magnetization-conserving principles, making it possible to dismiss the need for relaxation delay times of the order of 5T1 . SAFF has shown high sensitivity in the resolution of individual components of T1 in multiexponential systems and can be easily integrated to well-established pulse sequences, such as Magic Sandwich Echo and Carr-Purcell-Meiboom-Gill, for the single-shot determination of T1 and T2 or T2* .

Preparation of Poly(D,L-lactic-co-glycolic acid) Nanoparticles Through Solvent Displacement and Structural Evaluation Using Time-Domain Nuclear Magnetic Resonance.

The present study obtained coated poly(lactic-co-glycolic acid) nanoparticles using the solvent displacement method aiming to evaluate the effect of the polymer concentration in the pharmaceutical formulations' and polymer properties. Nanosuspensions were evaluated by fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), zeta potential (ZP), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and time-domain nuclear magnetic resonance (TD-NMR). Uniform nanoparticles could be obtained using this method and higher polymer concentrations led to an increase in particle size and negatively charged surfaces were observed. However typical PLGA halo was observed in XRD, diffractograms revealed the Pluronic chains behavior when PLGA concentration changed. Additionally, samples' spin-lattice relaxation times, dipolar interaction and correlation times were evaluated using time-domain nuclear magnetic resonance (TD-NMR), which revealed the interference of PLGA chain packing when Pluronic was incorporated as well as Pluronic chains organization and its behavior around the particle.

Nanoradiopharmaceuticals for breast cancer imaging: development, characterization, and imaging in inducted animals.

Monoclonal antibodies as polymeric nanoparticles are quite interesting and endow this new drug category with many advantages, especially by reducing the number of adverse reactions and, in the case of radiopharmaceuticals, also reducing the amount of radiation (dose) administered to the patient. In this study, a nanoradiopharmaceutical was developed using polylactic acid (PLA)/polyvinyl alcohol (PVA)/montmorillonite (MMT)/trastuzumab nanoparticles labeled with technetium-99m (99mTc) for breast cancer imaging. In order to confirm the nanoparticle formation, atomic force microscopy and dynamic light scattering were performed. Cytotoxicity of the nanoparticle and biodistribution with 99mTc in healthy and inducted animals were also measured. The results from atomic force microscopy showed that the nanoparticles were spherical, with a size range of ~200-500 nm. The dynamic light scattering analysis demonstrated that over 90% of the nanoparticles produced had a size of 287 nm with a zeta potential of -14,6 mV. The cytotoxicity results demonstrated that the nanoparticles were capable of reaching breast cancer cells. The biodistribution data demonstrated that the PLA/PVA/MMT/trastuzumab nanoparticles labeled with 99mTc have great renal clearance and also a high uptake by the lesion, as ~45% of the PLA/PVA/MMT/trastuzumab nanoparticles injected were taken up by the lesion. The data support PLA/PVA/MMT/trastuzumab labeled with 99mTc nanoparticles as nanoradiopharmaceuticals for breast cancer imaging.

Evaluation of the Influence of Modified TiO2 Particles on Polypropylene Composites.

This article reports the preparation of composites and nanocomposites of polypropylene and titanium dioxide particles, with our without surface modification, to obtain photodegradable or photostable materials with less severe environmental impacts. The modification of the titanium dioxide was carried out in the laboratory using propionic acid to improve the interaction of titanium dioxide with the polymer matrix. The composites and nanocomposites were prepared by melt extrusion using a single-screw extruder. The materials obtained were characterized by nuclear magnetic resonance relaxometry, X-ray diffraction, Raman spectroscopy, thermogravimetric analysis and mechanical analysis (tension). The results showed that the surface modification of the titanium dioxide particles promoted their better dispersion, distribution and interaction with the polypropylene matrix, generating a nanocomposite material. The NMR relaxometry results showed that the modified particles changed the molecular dynamics, indicating the formation of nanocomposites. In the Raman spectra, peaks related to the titanium dioxide only appeared at a concentration of 1%, and there was an inversion between crystalline and amorphous phase regions in the samples with the organophilic titanium dioxide, indicating the formation of a nanocomposite. The best modified PP/TiO2 compositions were those containing 0.25 and 0.50% modified TiO2 particles. The incorporation of the titanium dioxide particles, in rutile form, promoted photostabilization of the composites and nanocomposites at all ratios, and the composition containing 0.50% modified TiO2 presented the best photostabilization.

The effect of the Nb2O5 dispersion on ethylene vinyl acetate to obtain ethylene vinyl acetate/Nb2O5 nanostructured materials.

This work investigated the effect of niobium pentoxide nanoparticles (Nb2O5) on the molecular organization of an ethylene vinyl acetate copolymer (EVA) matrix containing 28% vinyl acetate groups, according to their dispersion and distribution in the polymer matrix. Due to niobium pentoxide's characteristics and properties, it may interfere in the chemical and UV resistance, as well as in the EVA mechanical properties, increasing mechanical resistance. The EVA/Nb2O5 nanocomposite films, with Nb2O5 varying from 0.25 to 1% in relation to the total EVA mass, were prepared by solution casting. The Nb2O5 was well dispersed with the use of ultrasound. These films were mainly characterized by X-ray diffraction and low-field nuclear magnetic resonance through relaxometry, in order to obtain responses on the structural organization and molecular dynamic, respectively, and consequently to understand the effect of the nanoparticles on the EVA matrix. The results showed that the addition of Nb2O5 to the EVA matrix caused changes in its crystallinity and molecular mobility, due to the new interactions formed by the good dispersion of nanoparticles and also their distribution in the EVA matrix, changing the copolymer characteristics due to the formation of a new material.

The structure of polycaprolactone-clay nanocomposites investigated by 1H NMR relaxometry.

Nanocomposites based on polycaprolactone (PCL), containing concentrations of 1, 3 and 5 wt% of sodium montmorillonite (NT-25) and organo-modified montmorillonite clay, with three different salts (Viscogel B7, Viscogel S4 and Viscogel B8), were prepared employing the solution intercalation method using chloroform. The PCL nanocomposites were characterized by relaxometry, through determination of the hydrogen spin-lattice relaxation times using low-field nuclear magnetic resonance (NMR). Conventional X-ray diffraction (XDR) was also used to measure the basal space of the nanoclay. The proton spin-lattice relaxation parameters showed that hybrid nanocomposites were formed, containing different parts of intercalated and exfoliated organoclay. The proton T1rhoH also indicated changes in the microstructure, organization and the molecular mobility of the hybrid materials. NMR relaxometry is a good way to evaluate nanomaterials because it provides complementary information, since it is measured in a different time scale. Furthermore, differential scanning calorimetry and thermogravimetric analysis were also used to investigate the crystallization and thermal behavior of the nanocomposites, respectively. All materials had low crystallization temperature (Tc) and the melting temperature (Tm) were very close to that of the PCL matrix, but the degree of crystallinity of the nanocomposites decreased. TGA analysis demonstrated that montmorillonite accelerates PCL's decomposition while unmodified montmorillonite has the opposite effect.

Evaluation of the influence of nanoparticles' shapes on the formation of poly(lactic acid) nanocomposites obtained employing the solution method.

PLA nanocomposites were prepared by adding organically modified montmorillonite clay (Viscogel B8) and a homoionic clay (NT25), as well as unmodified silica (A200) and modified organic silica (R972). All nanocomposites were obtained by the solution intercalation method using chloroform as a solvent. The materials obtained were essentially characterized by X-ray diffraction and low-field nuclear magnetic resonance relaxometry, through the measurement of proton spin-lattice relaxation time (LF-NMR). Both clays and silicas used to obtain the polymeric nanocomposites showed good dispersion in the polymeric matrix. The relaxation times were distinct for each type of nanoparticle used. The nanocomposite formed with homoionic clay, NT25, presented an increase in the relaxation data, indicating formation of intercalated nanocomposites, contrary to the action of the organoclay Viscogel B8, which preferentially formed an exfoliated nanocomposite. When unmodified and organo-modified silica were added to PLA, an increase in the relaxation time of the polymer matrix was observed. According to the relaxation data, the organosilica R972 dispersed better in the polymeric matrix and consequently interacted better than the A200.

Melatonin location in egg phosphatidylcholine liposomes: possible relation to its antioxidant mechanisms.

Although it is known that the antioxidant properties of melatonin can be modulated by its effect on membrane fluidity, there are few studies on this subject reported in the literature and they are controversial. In this study, viscosimetry and nuclear magnetic resonance (NMR) techniques were used to determine melatonin's effect and location on egg phosphatidylcholine bilayers mobility. Melatonin decreases the dynamic viscosity of the lipid dispersion. (31)P-NMR line width analysis indicated that melatonin induces a slight but uniform restriction of the lipid motional freedom in the polar head. However, melatonin changes in choline (13)C dynamics was only observed through chemical shift analysis. On the other hand, melatonin can induce an increase in the lipid nonpolar chain mobility, as observed by (13)C and (1)H relaxation time analysis. These results suggest the interfacial location of melatonin in the membrane. Additionally, the results of the analysis of the lipid (1)H-fitted exponential relaxation times suggest that melatonin promotes a molecular rearrangement of the bilayers. The melatonin effect and location in the lipid membrane may explain its antioxidant properties against lipid peroxidation induced by reactive species.