GUSTAVO HENRIQUE COSTAVARCA
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Resumo IPEN-doc 27329 The effects gamma radiation dose on the swelling capacity of PVP/lignin hydrogels dressings for wound treatment2019 - NOGUEIRA, K.M.; VARCA, J.O.; LIMA, C.S.A.; VARCA, G.; LUGAO, A.B.; FREITAS, L.F.Lignin is a carbon renewable source and has been widely explored in different areas in the last years, especially in the biomaterials field as dressings and other biomedical devices due its natural origin and low cost (1). Its chemical structure confers important properties to this macromolecule such as antioxidant capacity, UV protection and bactericidal activity (2,3). Polivinylpirrolidone (PVP) is a polymer widely applied for biomedical applications due to its relevant properties, such as the water absorption capacity, suitable mechanical properties for wound healing applications, and the capacity to originate hydrogels with different characteristics (4). Gamma radiation is a relevant option to produce biomedical devices, as the technology allows polymer crosslinking and sterilization in a single step (5). Two polymer solutions were prepared, PVP 10% (w, v) in distiled water (neutral pH) with poly(ethylene glycol) diacrylate (1.0% w/v) and lignin 6% (w, v) (pH > 13) and homogenized separately, until complete dissolution. The solutions were mixed in the follow ratios 95/5, 90/10 and 80/20, in which were added to a 2% (w, v) of agar and mixed at 70 ºC for 30 minutes. Samples were disposed in glass moulds and irradiated at 25, 50 and 100 kGy at dose rate of 5 kGy/h in a 60Co irradiator. Samples assessed by autoclave presented higher swelling than the PVP control, but lower gel fraction in comparison with the standard, except for formulation 90:10. Swelling and Gel Fraction were also evaluated by shaker at 37 ºC for 24 h. The results showed that the increase of dose decrease the swelling capacity and gel fraction decrease with the increase of lignin in the formulations. In general, the hydrogels irradiated at 25 and 50 kGy, except for formulation 80:20 at 25 kGy, presented good integrity and suitable results to be considered for the next steps of the study and are promising for biomedical application.Resumo IPEN-doc 27328 The presence or absence of ethanol in radiolytic synthesis medium leads to different kinds of hybrid papain-gold nanoparticles2019 - DE FREITAS, L.F.; DA CRUZ, C.C.; VARCA, G.; LUGAO, A.B.Gold nanoparticles are widely used for a plethora of applications, however, the short and long term environmental impacts of those nanoparticles when they reach the soil, rivers, and sea have just recently been taken into consideration. Novel synthetic routes have been developed without the use of toxic reducing or capping agents so that the products are biocompatible and environment-friendly, in the so-called Green Nanotechnology. One of these methods is the radiolytic synthesis using gamma radiation, which does not require the use of any reducing agent. Different conditions in the synthesis medium can lead to different products, therefore the aim of this study was to investigate the effect of the presence of ethanol on the nanoparticles generated via radiolysis using gamma radiation. The synthesis medium consisted on a mixture of NaAuCl4 (5 x 10-4 mol L-1), isopropanol (0.2 mol-1); and papain as a stabilizer and coating agent (1 mg mL-1), with or without the presence of 20% ethanol. The samples were irradiated with 10 kGy in a gamma multipurpose irradiator (60Co source) and stored at 4 ºC until use. Their hydrodynamic diameter and zeta potential was assessed with a Zetasizer Nano ZS90 device (Malvern Instruments UK), and images of transmission electron microscopy (TEM) were taken in order to observe the real size and morphology of the nanoparticles in a 40,000X magnification. The presence of ethanol indeed leads to different kinds of nanoparticles. Their hydrodynamic diameter was 8.773 ± 2.3 nm (papain-AuNPs without ethanol) and 9.976 ± 2.9 nm (papain- AuNPs with 20% ethanol), and their zeta potentials were 34.4 ± 4,2 mV and 25.3 ± 3.58 mV, respectively. The TEM images revealed that when ethanol is absent, the nanoparticles formed consist on a gold core (approximately 5 nm in diameter) with papain coating. When ethanol is present, though, the nanoparticles consist on a papain core (approximately 10 nm) decorated with smaller gold nanoparticles. In conclusion, both protocols lead to stable nanoparticles with good control of size, especially in the absence of ethanol, but according to the desired applications, ethanol can be useful for the generation of nanoparticles with higher enzymatic activity from papain, i.e. proteolytic and permeation-enhancing activities.Resumo IPEN-doc 27326 Natural polymer hydrogels with gold nanoparticles for bladder cancer chemotherapy delivery2019 - LIMA, C.S.A.; VARCA, G.; DE FREITAS, L.F.; VARCA, J.O.; LUGAO, A.B.The treatment of bladder cancer is done by transurethral resection for tumor removal, followed by immune or chemotherapy intravesical, according to the stage of the disease. The main objective of this work was to develop and characterize strategies to increase the residence time and specificity of chemotherapy through the application of hydrogels for chemotherapy and /or immunotherapy administration. Natural polymers gellan gum and microcrystalline cellulose were chosen to prepare the hydrogels as they are already widely used in the biomedical area due to characteristics such as the absence of toxicity, high biocompatibility, and biodegradability. Papain-coated gold nanoparticles were added to the gels to promote chemo or immunotherapeutic permeation. Preliminary stability assays were carried out to evaluate the compatibility between the polymeric matrices and the gold nanoparticles. The systems were characterized by Scanning Electron Microscopy, and Fourier Transform Infrared Spectroscopy. The results allowed the identification of the polymer groups present in the formulations, as well as the evaluation of the interactions between the hydrogel network and the nanoparticles. The formulations were suitable for the proposed application.Artigo IPEN-doc 25206 An overview of the synthesis of gold nanoparticles using radiation technologies2018 - FREITAS, LUCAS F. de; VARCA, GUSTAVO H.C.; BATISTA, JORGE G. dos S.; LUGAO, ADEMAR B.At a nano-level, optical properties of gold are unique and gave birth to an emerging platform of nanogold-based systems for diverse applications, because gold nanoparticle properties are tunable as a function of size and shape. Within the available techniques for the synthesis of gold nanoparticles, the radiolytic synthesis allows proper control of the nucleation process without the need for reducing agents, in a single step, combined or not with simultaneous sterilization. This review details and summarizes the use of radiation technologies for the synthesis and preparation of gold nanoparticles concerning fundamental aspects, mechanism, current pathways for synthesis and radiation sources, as well as briefly outlines final applications and some toxicity aspects related to nanogold-based systems.