Kajian terhadap tanah liat bentonit dan kaolin sebagai perisai sinaran

Plumbum (Pb) merupakan perisai sinaran yang utama bagi mengurangkan dedahan sinaran gama. Pb mempunyai bilangan atom dan ketumpatan yang tinggi. Walau bagaimanapun, Pb adalah bersifat toksik, sangat berat serta mempunyai tahap penyerapan neutron yang sangat rendah. Justeru, perisai sinaran dengan ciri-ciri yang ideal seperti ringan dan berkeupayaan tinggi dalam menghalang sinaran sedang giat diterokai. Antara perisai yang sedang dikaji pada masa kini ialah yang diperbuat daripada tanah liat. Tanah liat mempunyai ciri-ciri takat lebur yang tinggi, kestabilan termokimia dan kekuatan mekanik pada suhu yang tinggi. Ciri-ciri ini menjadikan tanah liat berpotensi sebagai perisai sinaran. Justeru, kajian ini dijalankan bagi menentukan perincian unsur, nilai pekali pengecilan serta perbandingan nilai ketebalan kesetaraan plumbum untuk tanah liat (iaitu bentonit dan kaolin). Perincian unsur tanah liat ditentukan daripada analisis pembelauan sinar-X (XRD) dan mikroskop imbasan medan elektron (FESEM). Ujian pembakaran tanah liat dilakukan pada suhu ~1000 oC bagi melihat sebarang perubahan terhadap sifat fizikal dan kimia tanah liat. Sementara itu, ujian bagi penentuan pekali pengecilan dilakukan menggunakan sumber sinaran gama dan sinar-X. Hasil analisis menunjukkan tiada perubahan yang ketara bagi sifat kimia dan fizikal tanah liat selepas ujian pembakaran. Berdasarkan pekali pengecilan, tanah liat jenis bentonit mempunyai nilai pekali pengecilan yang lebih tinggi berbanding kaolin dengan hampir 90% pengurangan dos berjaya diperoleh. Akhir sekali, analisis ketebalan kesetaraan plumbum menunjukkan nilai kesetaraan bagi bentonit adalah tinggi berbanding kaolin. Kesimpulannya, tanah liat bentonit menunjukkan keupayaan pengurangan dos yang tinggi untuk digunakan sebagai perisai sinaran

Effect of gamma irradiation on the physical stability of DPPC liposomes

Unilamellar liposomes composed of dipalmitoylphosphatidylcholine (DPPC) were prepared by the reverse-phase evaporation method and extrusion through a polycarbonate membrane filter. Liposomes at 0.7 mg/mL lipid concentration in deionized water were exposed to gamma irradiation at a dose in the range 0.5 to 25 kGy. Gamma irradiation of liposomes resulted in the degradation of DPPC lipids into free fatty acids, lysophosphatidylcholine and 1,2-palmitoyl-phosphatidic acid (DPPA). The effect of gamma irradiation towards the physical stability of liposomes was investigated by means of dynamic light scattering (DLS), transmission electron microscopy (TEM) and zeta potential analysis. From the DLS analysis, no significant changes were observed in the hydrodynamic size of liposomes. TEM images indicate that the liposomes surface became smoother and rounder as higher irradiation doses were applied. Zeta potential analysis showed that gamma irradiation of DPPC liposomes at radiation doses as low as 0.5 kGy resulted in a drastic rise in the magnitude of the zeta potential. The results also demonstrate that gamma irradiation of liposomes suspension enhanced the overall stability of liposomes. Hence, it can be concluded that gamma irradiation on DPPC liposomes may potentially produce liposomes with higher stability

Radiation-induced grafting of acrylic acid onto expanded poly(tetrafluoroethylene) membranes

Expanded poly(tetrafluoroethylene) (ePTFE) is currently being applied in facial reconstruction surgery. One requirement for the use of ePTFE membranes in soft tissue replacements is establishment of a well-bonded interface with the surrounding bone. However, ePTFE is classified as bioinert, thus lacking in biomimetic properties which may result in poor osseointegration at the bone-implant interface. Thus, the introduction of functional groups onto the polymer surface was carried out in the current study using radiation induced grafting of acrylic acid (AA) yielding graft yields of up to 40%. This resulted in reducing the hydrophobicity (advancing contact angle reduced from 116 to 92°). XPS revealed that the grafted PAA was highly crosslinked. The effects of grafting conditions (dose, monomer concentration, as well as solvent) on the grafting outcome were evaluated. Grafting of tertbutyl acrylate (tBA) was investigated but low graft yields were obtained and this was shown to be unaffected by the solvent used during the grafting process. The mechanical properties of the AA grafted membranes were altered significantly and were dependent on the testing conditions (wet or dry

In vitro mineralisation of grafted ePTFE membranes carrying carboxylate groups

mineralisation in simulated body fluid (SBF) of synthetic polymers continues to be an important area of research as the outcomes cannot be predicted. This study evaluates a series of ePTFE membranes grafted with carboxylate-containing copolymers, specifically using acrylic acid and itaconic acid for grafting. The samples differ with regards to graft density, carboxylate density and polymer topology. The type and amount of mineral produced in 1.5\ua0×\ua0SBF was dependent on the sample characteristics as evident from XPS, SEM/EDX, and FTIR spectroscopy. It was found that the graft density affects the mineral phases that form and that low graft density appear to cause co-precipitation of calcium carbonate and calcium phosphate. Linear and branched graft copolymer topology led to hydroxyapatite mineralisation whereas crosslinked graft copolymers resulted in formation of a mixture of calcium-phosphate phases. This study demonstrates that mineralisation outcomes for carboxylate-containing graft copolymers are complex. The findings of this study have implications for the design of bioactive coatings and are important for understanding the bone-biomaterial interface

Synteza polimerów szczepionych nanocząstkami złota z wykorzystaniem promieniowania gamma

The research focused on the synthesis of polytetrafluoroethylene (PTFE) grafted with gold nanoparticles (AuNP). The Turkevich method, one of the common techniques of AuNP synthesis, was used to obtain an AuNP solution with a nanoparticle size of 20 nm. The PTFE-AuNP samples were subsequently irradiated and the absorbed doses were 0.5, 2, 5, 10 and 20 kGy. It was noticed that samples irradiated with 0.5 and 2 kGy were less stable and less concentrated than samples irradiated with higher doses due to aggregation and formation of precipitation after 30 days.W artykule omówiono technikę syntezy poli(tetrafluoroetylenu) (PTFE) szczepionego nanocząstkami złota (AuNP). Metodą Turkevicha, jedną z powszechnie stosowanych technik syntezy AuNP, uzyskano roztwór AuNP o wielkości cząstek 20 nm. Próbki roztworu PTFE-AuNP były następnie naświetlane promieniowaniem gamma; zaabsorbowane dawki promieniowania wyniosły 0,5, 2, 5, 10 oraz 20 kGy. Stwierdzono, że w przypadku dawek 0,5 i 2 kGy roztwór był mniej stabilny, a stężenie nanocząstek było niższe niż w przypadku wyższych dawek. Wiązało się to z agregacją i precypitacją nanocząstek po upływie 30 dni od naświetlania

Grafting of acrylic acid-co-itaconic acid onto ePTFE and characterization of water uptake by the graft copolymers

Expanded polytetrafluoroethylene, ePTFE, is an attractive material for use as the implant in facial reconstruction surgery because it is bioinert; however, its low surface energy does not facilitate a strong interfacial bond with bone and thus for some applications the surfaces need to be modified to enhance their bone-integration properties. The surface modification of ePTFE membranes with copolymers of acrylic acid (AA) and itaconic acid (IA) using in situ gamma radiation induced grafting has been studied. Solutions with AA mole fractions ranging from 0.4 to 1.0 have been investigated. Graft yields of 35-50% with water uptakes of greater than 300% were obtained using 3 mol L-1 aqueous solutions of the monomers and a total incident dose of 10 kGy. The grafts were characterized by Fourier transform infrared and X-ray photoelectron spectroscopy analyses and the compositional microstructure of the grafted copolymers was investigated. The water uptake by the grafted membranes displayed a complex dependence on polymer chemistry and topology. (C) 2014 Wiley Periodicals, Inc

Protein adsorption to poly(tetrafluoroethylene) membranes modified with grafted poly(acrylic acid) chains

Protein adsorption to biomaterial surfaces is important for the function of such materials with anchorage-dependent cell adhesion requiring the presence of adsorbed proteins. The current study evaluated five solid surfaces with poly(acrylic acid) (PAA) grafted from the surface of a poly(tetrafluoroethylene) membrane with respect to the adsorption of serum albumin (SA), lactoferrin (Lf), and lysozyme (Lys) from a phosphate buffer and NaCl solution or water for specific combinations. With the use of x-ray photoelectron spectroscopy, the relative amounts and protein layer thickness were evaluated. SA adsorption was governed by ionic repulsive forces and hydrophobic interactions as evidenced from an increase in the protein adsorption at lower pH (6.5 compared to 7.4) and a correlation with surface coverage when water (pH 6.5) was used as the medium. The adsorption of Lf and Lys followed similar trends for all samples. In general, ionic attractive forces dominated and a strong correlation of increasing protein adsorption with the PAA chain length was evident. This study concluded that all surfaces appear suitable for use in biomaterial applications where tissue ingrowth is desired and that the enhanced protein adsorption in a medium with high ionic strength (e.g., biological fluid) correlates with the PAA chain length rather than the surface coverage