KAJIAN TEORETIS RELASI DISPERSI BAHAN BERINDEKS BIAS NEGATIF

Tetapan dielektrik ε dan permeabilitas μ merupakan kuantitas karakteristik dasar yang mampu merefleksikan interaksi antara gelombang elektromagnetik dan bahan. Penjalaran gelombang elektromagnetik pada bahan dengan indeks bias negatif (NIM, Negative Index Materials) memunculkan beberapa sifat – sifat elektrodinamika yang berbeda dibandingkan dengan penjalarannya pada medium berindeks bias positif. Dalam kajian ini dilakukan penelusuran secara teoritis perumusan relasi dispersi pada bahan berindeks bias negatif. Struktur dari susunan resonator cincin bercelah (Split Ring Resonator, SRR) dan susunan kawat logam tipis digunakan untuk merealisasikan bahan berindeks bias negatif. Dari relasi dispersinya, SRR memberikan kontribusi pada permeabilitas negatif sedangkan susunan kawat logam tipis memberikan kontribusi pada permitivitas negatif

Polyvinyl alcohol/Polyvinylpyrrolidone/Chitosan Nanofiber Scaffold with Hydroxyapatite from Sand Lobster Shells (Panulirus homarus) for Bone Tissue Engineering

In this work, nanofiber scaffold membrane polyvinyl alcohol (PVA)/polyvinylpyrrolidone (PVP)/Chitosan (CS)/hydroxyapatite (HAp) from sand lobster (SL; Panulirus homarus) shells have successfully synthesized to mimic the extracellular matrix (ECM) nanoscale in the native bone. HAp was synthesized by co-precipitation method with Ca/P was 1.67, then nanofiber membrane PVA/PVP/CS/HAp was synthesized by electrospinning method. Nanofiber solution was prepared from PVA 10% (w/v) polymer solution that dissolved in the distilled water, then the PVP/CS 15% (w/v) polymer solution was dissolved in acetic acid 1% (v/v) separately. The PVA polymer solution and PVP/CS solution were mixed with a ratio of 8.5: 1.5 (v/v). HAp dispersed into mixture solution with variation concentration 0, 1, 3, and 5 wt%. The composite solution was put into a 10 ml syringe with a hole diameter = 0.5 mm. Electrospinning was carried out at a 10 kV voltage, the flow rate at 0.1 ml/h, and the distance between the collector to the tip was 12 cm. Nanofiber scaffold membrane was characterized using SEM, FTIR, and XRD. The addition of HAp into the fiber showed incorporation into nanofiber with small agglomeration in the concentration of HAp at 1, 3, and 5 wt%. Based on the physicochemical analysis, the nanofiber scaffold PVA/PVP/CS/HAp 5 wt% with a fiber diameter of 0.328 ± 0.049 μm has the most potential to be used for bone tissue engineering

TELAAH KUANTUM PERANAN POTENSIAL ELEKTROMAGNETIKA DALAM DINAMIKA PARTIKEL BERMUATAN DAN VISUALISASI GRAFISNYA

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Fabrication of antibacterial bone scaffold based on carbonate-substituted hydroxyapatite containing magnesium from black sea urchin (Arbacia lixula) shells reinforced with polyvinyl alcohol and gelatin

Carbonate-substituted hydroxyapatite containing magnesium (Mg–C-HAp) was introduced through dissolution-precipitation treatment of hydroxyapatite containing magnesium (Mg-HAp) based on a black sea urchin (arbacia lixula) shells as novel biogenic materials. Based on chemical composition analysis, the Mg–C-HAp formed A- and B-type CHAp, which contained high carbonate ions. The Ca/P ratio of Mg–C-HAp was 1.707, very close to the biological bone apatite of 1.71. The Mg content in Mg–C-HAp was also relatively high, with the Mg/(Ca + Mg) ratio of 0.139, which is beneficial for antibacterial agents. The morphology of Mg–C-HAp showed particles with nanosize that provide a large surface area of ion promotion. The antibacterial test revealed that the Mg–C-HAp performed high antibacterial activity against Pseudomonas aeruginosa. The Mg–C-HAp-based porous scaffolds were then fabricated using the freeze-drying method with variations of polyvinyl alcohol (PVA) and gelatin fraction. According to the physicochemical analysis, the addition of PVA and gelatin in the scaffold structure decreased the crystallinity of the Mg–C-HAp/PVA/Gel scaffold. This lower crystallinity indicates high biodegradability, which is good for new bone growth. The macropores of the Mg–C-HAp/PVA/Gel scaffold were appropriate for new bone and blood vessel formation. The micropores of the Mg–C-HAp/PVA/Gel scaffold can be a medium for cells to grow. The microporosity of the Mg–C-HAp/PVA/Gel scaffold was also suitable for cell nutrient promotion. The compressive strength of the Mg–C-HAp/PVA/Gel scaffold was sufficient for bone regeneration. The Mg–C-HAp/PVA/Gel scaffold demonstrated high antibacterial activity against P. aeruginosa, so the Mg–C-HAp/PVA/Gel scaffold can maintain the role of Mg and carbonate content for antibacterial purposes. The good physicochemical, mechanical, and antibacterial properties of the Mg–C-HAp/PVA/Gel scaffold represented its suitable characteristics for antibacterial bone scaffolds

Green synthesis of CoFe2O4/ZnS composite nanoparticles utilizing Moringa Oleifera for magnetic hyperthermia applications

The development of targeted cancer therapies is crucial to reducing harmful patient side effects. The incorporation of magnetic and fluorescent nanoparticles as heat mediators in magnetic hyperthermia is a novel and efficient strategy. This study investigated the potential of CoFe2O4/ZnS composite nanoparticles, successfully fabricated using a green synthesis method with Moringa oleifera leaf extract, as magnetic hyperthermia agents. X-ray diffraction spectra demonstrated the existence of the CoFe2O4 cubic spinel ferrite and ZnS cubic zinc-blend phases in the composite nanoparticles. The average particle sizes of CoFe2O4 and CoFe2O4/ZnS were 12 and 17 nm, respectively. The peak at 1406-1411 cm−1 indicated the incorporation of ZnS on the surfaces of the CoFe2O4/ZnS composite nanoparticles through the SO functional group. The UV–visible spectra showed that the bandgap increased from 3.7 to 4.5 eV with increasing ZnS content. Magnetic property studies indicated that the coercivity and saturation magnetization of the CoFe2O4/ZnS composite nanoparticles were lower than those of the CoFe2O4 nanoparticles but still showed ferromagnetic characteristics. Heating properties were investigated by measuring the specific absorption rate (SAR) in an alternating magnetic field at various ZnS contents. The SAR of the CoFe2O4 composite nanoparticles was 85.7 mW/g while that of the CoFe2O4/ZnS composite nanoparticles increased from 87.8 to 132.9 mW/g with increasing ZnS content. Results indicate that green-synthesized CoFe2O4/ZnS composite nanoparticles are promising candidates for magnetic hyperthermia applications in cancer therapy