ABSTRACT Polymeric nanoparticles have demonstrated a great potential for biomedical application, especially in drug delivery systems acting as nanocarriers. The polymers obtained from living organisms, known as biopolymers, are promising materials for these purposes since they present biodegradability, biocompatibility and low immunogenicity, which are features required for in vivo applications. In this work, polymeric nanoparticles were prepared from mixtures of biopolymers such as chitosan, collagen and gelatin by ionic reticulation with sodium tripolyphosphate. Picric acid as a model drug was encapsulated into the nanoparticles. Chitosan of 50.4 kDa of molecular weight and 81 % of deacetylation degree was prepared through the deacetylation and depolymerization of chitin extracted from squid pens (Loligo sp). The composition, size distribution, and surface charge of the prepared nanoparticles were evaluated. Moreover, the influence of the nanoparticles mass and picric acid concentration were analyzed during the loading process by determining of the loaded content and the incorporation efficiency. Maximum loaded contents of picric acid were 7.16 % and 6.45 % for chitosan/gelatin nanoparticles and chitosan/collagen nanoparticles, respectively. In vitro release tests showed a quick picric acid release in chitosan/gelatin nanoparticles. The nanoparticles prepared with collagen took longer time to release the picric acid. Kinetic studies, using mathematical models, revealed that the release takes place through a diffusion mechanism.

RESUMEN Las nanopartículas poliméricas han demostrado un gran potencial para aplicaciones biomédicas, especialmente en sistemas de liberación de fármacos actuando como nanocargadores. Los polímeros obtenidos de organismos vivos, conocidos como biopolímeros, son materiales interesantes para estos propósitos desde que presentan biodegradabilidad, biocompatibilidad y baja inmunogenicidad, en cual tiene características requeridas para aplicaciones in vivo. En este trabajo, nanopartículas poliméricas fueron preparados a partir de mezclas de biopolímeros como el quitosano, colágeno y gelatina por reticulación iónica con tripolifosfato de sodio. Quitosano de 50,4 kDa de masa molar y 81 % de grado de desacetilación fue preparado a través de la desacetilación y despolimerización de la quitina extraída a partir de pluma de calamar (Loligo sp). La composición, distribución de tamaño y carga superficial de las nanopartículas preparadas también fue evaluada. Además, la influencia de la masa de las nanopartículas y la concentración de ácido pícrico durante el proceso de cargado fue analizado mediante la determinación del contenido cargado y la eficiencia de la incorporación. El máximo contenido cargado de ácido pícrico fue de 7.16% y 6.45% para nanopartículas de quitosano/gelatina y quitosano/colágeno, respectivamente. Los ensayos de liberación in vitro mostraron una rápida la liberación de ácido pícrico en las nanopartículas de quitosano/gelatina. Las nanopartículas preparadas con colágeno liberaron el ácido pícrico en mayor tiempo. Los estudios cinéticos usando modelos matemáticos mostraron que la liberación se lleva a cabo por un mecanismo de difusión.

Biomaterials with the hydroxyapatite and biopolymers such as chitosan derived of crustaceans are is an alternative for bone repair. Carbon nanotubes have been a focus of interest because they can ameliorate the biomechanical properties of biomaterials. The objective of this study was to evaluate these materials in the repair of cranial defects in rats. The animals were divided in groups: without implant (G1), implanted with the chitosan/carbon nanotube membrane (G2), and chitosan/nanotube membrane mineralized with hydroxyapatite (G3). The animals were sacrificed 5 weeks after surgery and the skulls were removed for analysis of the defect area. The results showed absence of chronic inflammatory and little bone neoformation in the defect area of all groups. In G2 and G3 there was lack of reabsorption of the biomaterial that were encapsulated by connective tissue. In conclusion, the biomaterials were biocompatible, but their specific physicochemical properties did not indicate a considerable osteoregenerative capacity.

This study compares a wound dressing based on bacterial cellulose/collagen (BC/COL) hydrogel in rat dorsum with commercial collagenase ointment and untreated wound. The hydrogel was characterized by Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier transformed - Infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). According to the In vivo test and macroscopic evaluation, BC/COL hydrogel showed a better repair of wounds and promoted statistically significant differences of tissue repair between treatments on the 7th day after surgery. Better quality, quantity and orientation evaluation of collagen fibers (p=0.0001) were observed in the BC/COL hydrogel and collagenase ointment groups in relation to the control group. The BC/COL hydrogel promoted better wound healing than collagenase and the control group, therefore, it can be considered a potential wound dressing for skin regeneration.

Biomaterials are used as a promising alternative to bone grafts, including bioceramics whose composition resembles that of bone and fibrin sealants due to their hemostatic properties. The objective was to evaluate the repair of cranial defects in 40 rats, grafted with hydroxyapatite and a new fibrin sealant derived from snake venom. The animals were divided into four groups: C (control, no graft); Ha (hydroxyapatite); FS (fibrin sealant), and HaFS (hydroxyapatite and fibrin sealant). The animals were euthanized 2 and 6 weeks after surgery and wound area were submitted to analysis. After 2 weeks, immature bone was formed from the borders of the defect and in groups Ha and HaFS, few hydroxyapatite particles were surrounded by new bone. After 6 weeks, the new bone was mature and surrounded several hydroxyapatite particles, without connective tissue interposition and the volume of new bone was higher in HaFS group. The hydroxyapatite in combination with the new fibrin sealant accelerates bone repair.

Objetivou-se, neste trabalho, obter biomembranas de colágeno tratadas em solução alcalina por 72 horas (GE), a partir de centros tendinosos diafragmáticos de equinos e comparar sua biocompatibilidade com membranas conservadas em solução de glicerina a 98% (GG) e membranas não tratadas (GC). As membranas foram implantadas na fáscia interna do músculo reto do abdome de equinos e retiradas, juntamente com os tecidos adjacentes, aos sete, 63 e 126 dias pós-operatórios para a preparação de lâminas histológicas. O estudo histomorfométrico das lâminas revelou processo inflamatório mais intenso para os implantes GG e CC e cicatrização mais rápida para os implantes GE. Concluiu-se que as biomembranas colagênicas tratadas em solução alcalina são mais biocompatíveis do que biomembranas conservadas em glicerina 98%.

The objective of this research was obtain collagen biomembranes treated in alkaline solution for 72 hours (GE) from tendineous diaphragmatic center of equines and compare its biocompatibility with membranes preserved in a glycerin solution 98% (GG) and membranes do not treated (GC). The membranes were implanted in the internal fascia of recto abdominis muscle of equines and removed, with adjacent tissues, seven, 63 and 126 days postoperative for the preparation of histological slides. The histomorphometric study revealed more intense inflammatory process to GG and CC implants and faster healing for GE implants. It was concluded that the collagen biomembranes treated in alkaline solution is more biocompatible than biomembranes preserved in 98% glycerin.

The effect of different propionaldehyde ratios on the properties of bis-GMA-based comonomers and copolymers diluted with propoxylated bis-GMA (CH3bis-GMA) was evaluated. Five experimental comonomers were prepared combining bis-GMA with CH3bis-GMA and propionaldehyde at 0, 2, 8, 16, 24 mol%. Light polymerization was effected with the use of 0.2 wt. (%) each of camphorquinone and N,N-dimethyl-p-toluidine. Resin degrees of conversion (%DC) were evaluated by FT-IR spectrophotometry and Tg by Differential Scanning Calorimeter. Complex viscosity (η*), the effect of temperature on η*, and Microhardness (H) for dry and wet samples were also determined. Data were analyzed by Student's t-test, one-way ANOVA and Tukey-Kramer test (α = 0.05). The group with 24 mol% additive had a significant increase in %DC and H, and the lowest comonomer Tg and η*. No remarkable variation was noted in copolymers Tg s. All resins presented Newtonian behavior of viscosity, which linearly decreased with increased temperature. The η* decreased sigmoidally as the additive ratio increased.