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- MakaleAçık Erişim2026Scopus SJRQ2Investigation of structural, optical and optoelectronic properties of eumelanin pigment
Aksoy Pehlivanoglu, Seval; Bayram, Sinan
In this work, the structural, morphological and optical properties of the eumelanin film fabricated on an FTO substrate were first investigated. Then, the effects of illumination intensitiy on the optoelectronic properties of the device fabricated on p-Si substrate (Eumelanin/p-Si) were investigated. The deposited film was identified as polycrystalline from the XRD pattern. The crystallite size was found to be approximately 13 nm. Surface morphology analysis of the film was carried out using atomic force microscopy (AFM) measurements. The surface roughness value (Rq) of the film was determined to be 55.7 nm. The film’s transmittance in the visible region is approximately 83%. The average refractive index in the visible region was calculated to be 1.39. The value of the eumelanin film was determined using both the Tauc technique and the Kubelka-Munk function. The direct and indirect optical bandgaps of eumelanin were calculated using both the Tauc method and the Kubelka-Munk function. The calculated direct and indirect optical bandgap values are, respectively, 2.79 eV and 1.96 eV for the Tauc method, and 2.65 eV and 1.79 eV for the Kubelka-Munk method. The electronic parameters of Eumelanin/p-Si heterostructure were derived from its characteristics. The charge transport mechanisms controlling the diode behavior of the eumelanin/p-Si structure were investigated and analyzed using the power law relationship. measurements performed at various illumination intensities indicated that the device exhibited photoconductive behavior. All the results obtained from this study demonstrate the potential of eumelanin/p-Si device to be used in photonic applications.
- MakaleAçık Erişim2023Scopus SJRQ1Exploring the Charge Transport of a Natural Eumelanin for Sustainable Technologies
Paulin, João V.; Bayram, Sinan; Graeff, Carlos F. O.; Bufon, Carlos C. B.
Eumelanin, the main quinone-based biomaterial of the melanin family of compounds, is emerging as a model for medical and sustainable electronic interfaces due to its biocompatibility, biodegradability, and transducing abilities. The study utilizes current-voltage measurements and impedance/dielectric spectroscopy under a controlled hydration atmosphere to investigate the charge transport of eumelanin produced from the S. parvus BSB49 strain. We show no differences in the electrical response in highly hydrated conditions compared to the standard synthetic eumelanin. Hence, our findings provide the groundwork to assess the potential use of this natural eumelanin in sustainable organic (bio)electronic applications.
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İncele - MakaleAçık Erişim2022Scopus SJRQ3A comparative characterization study between fungal and bacterial eumelanin pigments
Bayram, Sinan
Melanins are the most common and the most enigmatic natural pigments in the nature that found in many different taxa group such as bacteria, yeasts, fungi, insects, plants, reptiles, birds and mammals. These biological macromolecules are highly complex cross-linked, heterogeneous biopolymers and composed of polymerized phenolic and/or indolic compounds. Recently, interest in these ubiquitous biopolymers has been increasing considerably in many different areas such as medicine, pharmacology, cosmetics, organic electronic and optoelectronics because of their versatile properties. In this study, four different extracellular eumelanin pigments (two bacterial eumelanins and two fungal eumelanins) were characterized by different spectrometric techniques such as FT-IR, XRD, NMR and UV-vis. In XRD analyzes, purified fungal and bacterial eumelanin pigments were characterized by giving a wide peak at about 22o with an angle of 2θ. Furthermore, in the 1 H NMR spectra of these biopolymers, it was observed that all pigments have signals in both aromatic and aliphatic regions. In addition to these analyzes, nanostructures of these biopolymers were characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Finally, eumelanin pigment producer microorganisms were molecularly characterized. 16 S rDNA and 18 S rDNA sequence analysis results of these microorganisms (Streptomyces fulvissimus MPPS4, Streptomyces xiamenensis MPPS6, Aspergillus niger MPPF16 and Aspergillus terreus MPPF25) were deposited in NCBI GenBank® database with accession number MT825594, MT973972, MW652652 and MW652653 respectively.
AtıfScopus16WoS13OpenAlex14İncele - BildiriYalnız künye2022Scopus SJRQ2Ultrasonicate-assisted preparation of eumelanin-loaded nano/microparticles based on polylactide stereocomplex
Putri, Oceu Dwi; Petchsuk, Atitsa; Bayram, Sinan; Opaprakasit, Pakorn
The utilization of ultrasonication in the preparation of polymeric nano/microparticles has attracted vast attention due to its simplicity with low cost and high energy efficiency. The occurrence of acoustic cavitation generated by the ultrasonication process can enhance droplet disintegration, allowing the improved stability of emulsions. In this study, eumelanin-loaded nano/microparticles were prepared by employing polylactide stereocomplex (sc-PLA) formed by blending of poly(D-lactide-caprolactone-D-lactide), P(DLA-b-CL-b-DLA), triblock copolymer with linear poly(L-lactide), PLLA. The particles were prepared through an oil in water emulsion (O/W) technique followed by a solvent evaporation. The effect of ultrasonication on the encapsulation efficiency and physicochemical properties of the nano/microparticles was evaluated. The results showed that ultrasonication treatment could control nano/microparticles' shape, size, and size distribution, which enhanced the particle stability and the entrapment efficiency of eumelanin. Particle size distribution of ultrasound-assisted nano/microparticles was in a range of 0.38–135 μm, while those without ultrasonication had a broader distribution from 0.38–153 μm. Higher zeta potential was also observed in the ultrasound-assisted nano/microparticles, reflecting their higher suspension stability. The ultrasonication treatment led to higher eumelanin encapsulation efficiency (46.6%) with higher thermal stability and crystallinity, promoted by the formation of higher contents of the stereocomplex crystallites. The results confirm that ultrasonicate-assisted emulsification can be effectively used to fabricate the functional eumelanin-loaded nano/microparticles.
AtıfScopus5OpenAlex3İncele - MakaleAçık Erişim2022Scopus SJRQ1Eumelanin protects the liver against diethylnitrosamine-induced liver injury
Altındağ, Fikret; Boğokşayan, Seda; Bayram, Sinan
This study aims to evaluate in vivo protective effects of eumelanin (EU) on diethylnitrosamine (DEN)-induced liver injury. Wistar albino male rats were divided into 6 groups (n = 6), Control, DMSO, DEN, DEN + EU10, DEN + EU15, and DEN + EU20. Animals in the DEN group were injected i.p a single dose of 200 mg/kg DEN, DEN + EU10 group was given 10 mg/kg EU, DEN + EU15 group was given 15 mg/kg, DEN + EU20 group was given 20 mg/kg EU for a week. The results showed that there was no significant difference in vessel volume density between the groups. Inflammatory cell infiltration, hydropic degeneration, and necrotic cells were observed in the DEN group, and these histopathological changes were significantly reduced in all treatment groups. Although there was a low intensity of PAS-positive staining in the DEN groups, moderate staining was observed in the treatment groups. While Caspase-3, PCNA, TNF-α, and IL-6 expressions increased in the DEN group, their expressions decreased in the EU-treated groups. DEN increased AST, ALT, and MDA levels and decreased CAT levels. In particular, the EU10 dose significantly improved these parameters. The present study revealed that eumelanin has protective effects against DEN-induced liver injury.
AtıfScopus9WoS8OpenAlex10İncele - MakaleAçık Erişim2020Scopus SJRQ2Bioproduction, structure elucidation and in vitro antiproliferative effect of eumelanin pigment from Streptomyces parvus BSB49
Bayram, Sinan; Dengiz, Cagatay; Gerçek, Yusuf Can; Cetin, Idil; Topcul, Mehmet R.
In this study, the structure of the purified extracellular eumelanin pigment isolated from Streptomyces spp. was elucidated by detailed analysis via two different spectroscopic techniques (FT-IR and NMR). In vitro antiproliferative effects of eumelanin were evaluated on HeLa cell line. These experiments were carried out with the evaluation of the parameters including cell viability, cell index, and mitotic index. With the cell viability and cell index, IC50 concentration of eumelanin was determined as 10 μM. This result showed that the IC50 concentration of eumelanin decreased the values of cell viability, cell index and mitotic index. These changes are statistically significant (p ' 0.01). The ability of the dissolved eumelanin (250 μg mL−1) to scavenge free radicals was determined via DPPH and ABTS and was shown to be about 87.73% and 75.2%, respectively, compared with standard antioxidants. It was observed that dry weights of eumelanin yield among the selected strains ranged from 160 to 240 mg L−1. The strain with the highest production potential was selected for 16S rDNA sequence analysis and, accordingly, the selected strain BSB49 was identified as Streptomyces parvus and the sequence analysis results were deposited in NCBI under accession number MK894155.
AtıfScopus47WoS40OpenAlex48İncele