ABSTRACT
RESUMO Este estudo avaliou as propriedades físico-químicas envolvidas no processo de adsorção para subsidiar o potencial uso de biocarvão produzido com folhas secas de amendoeira-da-praia, Terminalia catappa, como remediador em águas contaminadas com metais. O biocarvão utilizado foi produzido por conversão à baixa temperatura e caracterizado por apresentar bandas de O-H, CH2, C-O e C-O-C; teores de 48,8% de carbono, 46,6% de oxigênio, 3,3% de hidrogênio e demais entre enxofre e nitrogênio; presença de macroporos e passado em peneira (100 mesh). Para o estudo, preparou-se um coquetel de radiotraçadores (Co-57, Mn-54 e Zn-65), que foi adicionado à água deionizada e massas de biocarvão com o objetivo de obter parâmetros tais como pH, tempo de equilíbrio e capacidade de adsorção por meio das isotermas de Langmuir e Freundlich. O detector de Germânio Hiperpuro foi utilizado para quantificar as atividades dos radiotraçadores por meio da técnica de espectroscopia gama para geração e tratamento de dados. Os resultados obtidos mostraram aumento na adsorção do pH 3,8 em diante e tempo de equilíbrio de 30 minutos ou mais. As isotermas de Langmuir e Freundlich construídas apresentaram bons ajustes, com valores de n maiores que 1, indicando preferência dos metais pelo material adsorvente. Além disso, levando-se em conta a competição pelos sítios ativos e a concentração inicial das soluções (ordem de picogramas), foram encontradas capacidades de adsorção de 1,273 ng.g-1 para o Zn-65, de 3.271 ng.g-1 para o Co-57 e de 9,026 ng.g-1 para o Mn-54.
ABSTRACT This study evaluated the physical-chemical properties of the adsorption process in biochar produced from dry leaves of beach-almond, Terminalia catappa, as a useful tool for remediation purposes in water contaminated with metals. The biochar was characterized by having: bands of O-H, CH2, C-O, and C-O-C; contents of 48.8% carbon, 46.6% oxygen, 3.3% hydrogen and the others between sulfur and nitrogen; the presence of macropores; and being sieved (100 mesh). Parameters such as pH, equilibrium time and adsorption capacity by the Langmuir and Freundlich isotherms were determined from experiments using a radiotracer cocktail (Co-57, Mn-54 and Zn-65) which was added to deionized water and a constants mass of biochar. The high-purity germanium detector (HPGe) was used to quantify the radiotracer activity by gamma spectroscopy. The results showed better adsorption from pH 3.8 and 30 minutes equilibrium time. The Langmuir and Freundlich isotherms had a good model fit, with n values higher than 1, and showed affinity between the metals and the biochar. The adsorption capacities of Zn-65, Co-57 and Mn-54 were 1.273 ng.g−1, 3.271 ng.g−1 and 9.026 ng.g−1, respectively.
ABSTRACT
OBJECTIVES: Conventional imaging methods are excellent for the morphological characterization of the consequences of osteonecrosis; however, only specialized techniques have been considered useful for obtaining functional information. To explore the affinity of radiotracers for severely devascularized bone, a new mouse model of isolated femur implanted in a subcutaneous abdominal pocket was devised. To maintain animal mobility and longevity, the femur was harvested from syngeneic donors. Two technetium-99m-labeled tracers targeting angiogenesis and bone matrix were selected. METHODS: Medronic acid and a homodimer peptide conjugated with RGDfK were radiolabeled with technetium-99m, and biodistribution was evaluated in Swiss mice. The grafted and control femurs were evaluated after 15, 30 and 60 days, including computed tomography (CT) and histological analysis. RESULTS: Radiolabeling achieved high (>95%) radiochemical purity. The biodistribution confirmed good blood clearance 1 hour after administration. For 99mTc-hydrazinonicotinic acid (HYNIC)-E-[c(RGDfK)2, remarkable renal excretion was observed compared to 99mTc-methylene diphosphonate (MDP), but the latter, as expected, revealed higher bone uptake. The results obtained in the control femur were equal at all time points. In the implanted femur, 99mTc-HYNIC-E-[c(RGDfK)2 uptake was highest after 15 days, consistent with early angiogenesis. Regarding 99mTc-MDP in the implant, similar uptake was documented at all time points, consistent with sustained bone viability; however, the uptake was lower than that detected in the control femur, as confirmed by histology. CONCLUSIONS: 1) Graft viability was successfully diagnosed using radiotracers in severely ischemic bone at all time points. 2) Analogously, indirect information about angiogenesis could be gathered using 999mTc-HYNIC-E-[c(RGDfK)2. 3) These techniques appear promising and warrant further studies to determine their potential clinical applications.
Subject(s)
Animals , Female , Mice , Bone-Implant Interface/physiology , Organotechnetium Compounds , Osteonecrosis/physiopathology , Peptides, Cyclic , Radiopharmaceuticals , Bone Transplantation , Diphosphonates , Disease Models, Animal , Femur/pathology , Femur/physiopathology , Isotope Labeling/methods , Neovascularization, Physiologic/physiology , Osteonecrosis/pathology , Reproducibility of Results , Time Factors , Tissue Survival/physiology , Tomography, X-Ray ComputedABSTRACT
After the development of two major techniques - SPECT (Single Photon Emission Computed Tomography) and PET (Positron Emission Tomography) to image the human subjects in a three-dimensional direction in the 1980s, many radiotracers have been used for functional neuroimaging. Still it would be very important study to develop selective radiotracers for functional neuroimaging. New radiotracers will help to expand the knowledge of neurotransmitter systems and of the genetic contribution to receptor or transporter availability. Neurotransmitter depletion-restoration studies, the distribution of brain functions and their modulation by neurotransmitter system aid in better understanding and limiting the side effects of drugs used as well as newly developed. In addition, these radiotracers will be thus very useful to gain a better understanding in biochemical and pharmacological interactions in living human. This review mentions the introduction of radioligands for the functional neuroimaging. Although significant progress has been achieved in the development of new PET and SPECT ligands for in vivo imaging of those receptors and transporters, there are continuous needs of new diagnostic radioligands.