Angela Kinoshita

Natural rubber latex used as drug delivery system in guided bone regeneration (GBR)

In this work, we propose natural rubber latex (NRL) membranes as a protein delivery system. For this purpose Bovine Serum Albumin (BSA) was incorporated into the latex solution for in vitro protein delivery experiments. Different polymerization temperatures were used, from -10 to 27 °C, in order to control the membrane morphology. These membranes were characterized by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), as well as the Lowry Method to measure the BSA release. SEM and AFM microscopy analysis showed that the number, size and distribution of pores in NRL membranes can be varied, as well as its overall morphology. We have found that the morphology of the membrane is the predominant factor for higher protein release, compared with pore size and number of pores. Results demonstrated that the best drug-delivery system was the membrane polymerized at RT (27 °C), which does release 66% of its BSA content for up to 18 days. Our results indicate that NRLb could be used in the future as an active membrane that could accelerate bone healing in GBR.

Latex use as an occlusive membrane for guided bone regeneration

Latex extracted from Hevea brasiliensis was used as an occlusive membrane for guided bone regeneration. Twenty-four rabbits were divided in two groups: treated and control group. Critical size bone defects (2 cm × 1 cm) were surgically made in the rabbit calvarium. Two latex membranes were implanted in each animal of the treated group, whereas the control defect was filled only with autogenous blood clot. After 15, 30, 60, and 120 days, animals from each group were euthanized, and the samples with regenerated bone were removed. No signs of allergy or rejection were noticed around the calvarial bone defect of the treated group. In the histological analysis, no foreign body inflammatory reaction was observed in the adjacent tissues in contact with the membranes demonstrating that latex can be used at injured sites as an aid in the healing process. Histological analysis, digital radiography, and electron spin resonance were used to evaluate the progress of bone repair. The results show significant differences between groups (p < 0.05) suggesting that latex membranes accelerates healing in critical bone defects.

Metronidazole release using natural rubber latex as matrix

Natural Rubber Latex (NRL) can be used successfully in controlled release drug delivery due to their excellent matrix forming properties. Recently, NRL has shown to stimulate angiogenesis, cellular adhesion and the formation of extracellular matrix, promoting the replacement and regeneration of tissue. A dermatological delivery system comprising a topically acceptable, inert support impregnated with a metronidazole (MET) solution was developed. MET 2-(2- methyl- 5-nitro- 1H- imidazol- 1-yl) ethanol, has been widely used for the treatment of protozoa and anaerobic bacterial infections. MET is a nitroimidazole anti-infective medication used mainly in the treatment of infections caused by susceptible organisms, particularly anaerobic bacteria and protozoa. In a previous study, we have tested NRL as an occlusive membrane for GBR with promising results. One possible way to decrease the inflammatory process, it was incorporated the MET in NRL. MET was incorporated into the NRL, by mixing it in solution for in vitro protein delivery experiments. The solutions of latex and MET were polymerized at different temperatures, from -100 to 40 °C, in order to control the membrane morphology. SEM microscopy analysis showed that the number, size and distribution of pores in NRL membranes varied depending on polymerization temperature, as well as its overall morphology. Results demonstrated that the best drug-delivery system was the membrane polymerized at -100 °C, which does release 77,1% of its MET content for up 310 hours.

Clinical applications of alanine/electron spin resonance dosimetry.

This paper discusses the clinical applications of electron spin resonance (ESR) dosimetry focusing on the ESR/alanine system. A review of few past studies in this area is presented offering a critical overview of the challenges and opportunities for extending this system into clinical applications. Alanine/ESR dosimetry fulfills many of the required properties for several clinical applications such as water-equivalent composition, independence of the sensitivity for the energy range used in therapy and high precision. Improvements in sensitivity and the development of minidosimeters coupled with the use of a spectrometer of higher microwave frequency expanded the possibilities for clinical applications to the new modalities of radiotherapy (intensity-modulated radiation therapy and radiosurgery) and to the detection of low doses such as those present in some radiological image procedures.

Evaluation of a high dose to a finger from a 60Co accident

Abstract— Electron spin resonance and fluorescence in situ hybridization were used to evaluate the dose to the finger of a worker who accidentally touched a radiotherapy 60Co therapy source in November 1995. In September 1999, the middle finger was amputated. We estimated the dose to the bone of the finger to be 6.4 ± 0.5 Gy using the electron spin resonance additive dose method and a corrected dose of about 20 ± 3 Gy could be inferred by translocation analysis in peripheral lymphocytes using the fluorescence in situ hybridization method. This retrospective dosimetry was performed for the victim 4 y after the accident, but the compatibility of the results obtained by physical and biological methods reinforce their validity, although in the case of partial-body exposure the biological method has limitations and demonstrates the need to find appropriate correction factors.

ESR dosimetry of 89Sr- and 153Sm-in bone

The radiation absorbed dose in the rabbit bone delivered by 153Sm-EDTMP (samarium ethylenediaminetetra methylene diphosphonic acid) and 89SRCl2 (strontium chloride) was measured by means of electron spin resonance (ESR). These radioisotopes are used in systemic radiotherapy for palliation of painful bone metastases. The knowledge of the dose is important in order to avoid side effects to the bone marrow. The ESR radiation dose signal was calibrated by the additive dose method using cobalt-60 gamma rays. For 153Sm-EDTMP, the bone doses in three rabbits were (4 +/- 2), (5 +/- 1) and (5 +/- 2) cGy kg/MBq. For 89SrCl2, a dose of (2 +/- 1) cGy kg/MBq was found in one rabbit.

Nitric oxide release using natural rubber latex as matrix

Received: March 16, 2011; Revised: June 16, 2011Nitric oxide (NO) is a diffusible messenger that has been involved in numerous physiological processes ranging from vasodilatation and antimicrobial properties to wound healing. The beneficial effects can be attributed to the role NO plays in angiogenesis, inflammation and tissue remodeling. In the present work, a polymeric device for the sustained site specific delivery of nitric oxide using a latex rubber matrix from

ESR dating of teeth from Brazilian megafauna

The study of radiation defects created in biomaterials, such as bone and teeth, can be used in dating with importance to palaeontology and archaeology. Two Stegomastodon teeth (AL1 and AL2) from north-eastern Brazilian megafauna were studied by electron spin resonance (ESR) spectroscopy. The samples were collected in Fazenda Ovo da Ema, (913349 / 3714965) UTM, Alagoas state, Brazil. The dating of these samples can contribute to the better knowledge of megafauna presence in this region as well as to the events associated to the extinction of these species.

An attempt to use sweeteners as a material for accident dosimetry.

In case of a radiological accident, it is important to determine the exposure to radiation of the general population. Several materials can be used to reconstruct the exposed dose. Tooth enamel has been studied for a long time, and now the procedures to determine the dose are well established for in vitro measurements. Many materials have been investigated by different techniques: sugar, wall bricks, roof tiles, plastics, watch glass, ruby present in watches, medicines carried by persons and shell button, among others. In this work an attempt is made to use sweeteners as a possible accident dosimeter material because they are becoming increasingly common. Sweeteners based on saccharine, cyclamate, stevia, and aspartame were acquired in local stores, and ESR spectrum was recorded before and after gamma irradiation. Spectrum simulation demonstrated that there are two main radicals with g = 2.0063, A = 1.6 mT, and g = 2.0048, A = 5 mT due to lactose. For the better characterization of spectroscopic and dosimetric properties of these materials, higher microwave frequency (K-band, &ngr; ∼ 24 GHz) was also employed. Experiments in X-band (&ngr; ∼ 9 GHz) showed that low dose levels of 500 mGy can be measured with this material, demonstrating the potential use of sweeteners for retrospective dosimetry.

ESR dating of a subfossil shell from Couve Island, Ubatuba, Brazil

The occurrence of subfossil material in bottom sediments of Couve Island, Ubatuba region, São Paulo State, is confirmed. The analyzed material consists of a bivalve shell that was dated by the electron spin resonance technique. By the additive irradiation method an archaeological absorbed dose of (25 +/- 5) Gy was obtained and calibration with other dating works in the same area allows the inference of an age of (25 +/- 5) x 10(2) years. The importance of this finding and its paleoecological implications could contribute to elucidating the nature of short-term environmental changes in the Brazilian coastline during the Holocene, as well as becoming an important tool to the understanding of the distribution and biological aspects of the bivalve fauna.