Yazar "Bhethanabotla, Venkat R." seçeneğine göre listele

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    Biofilm inhibition and bacterial eradication by C-dots derived from polyethyleneimine-citric acid
    (Elsevier B.V., 2022) Abraham, Wakeem L.; Demirci, Şahin; Wypyski, Madison S.; Ayyala, Ramesh S.; Bhethanabotla, Venkat R.; Lawson, Louise B.; Şahiner, Nurettin
    Protonable polyethyleneimine (PEI) and citric acid (CA) based C-dots were prepared via a hydrothermal process, yielding particles with a hydrodynamic diameter of ~100 and ~80 nm, and zeta potential of ? 2.3 ± 0.1 and + 23.4 ± 0.2 mV for PEI-CA C-dots and their protonated form, respectively. Treating Staphylococcus aureus with these C-dots resulted in a statistically significant reduction in bacterial growth, specifically growth in the planktonic phase as well as in the development of bacterial biofilm when compared to untreated (p < 0.05). When 24 h matured S. aureus biofilms were treated with C-dots, a significant disruption and dispersion of bacteria from the existing biofilms was noted as compared to untreated (p < 0.05). Other Gram-positive microorganisms (B. cereus, S. epidermidis, S. pyogenes) and Gram-negative (P. mirabilis, E. coli, and P. aeruginosa) were also susceptible to the antimicrobial activity of the PEI-CA C-dots with significant inhibition of bacterial growth noted for all organisms after C-dot treatment. Only for B. cereus, S. epidermidis, and P. aeruginosa was this reduction in total growth reflected in decreased planktonic growth. However, biofilm formation by all organisms was reduced significantly upon treatment with the C-dots, including those for which planktonic growth was not impacted. © 2022 Elsevier B.V.
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    Carbon Tetrafluoride, Oxygen, and Air RF Plasma Modified Low-Density Polyethylene and Polydimethylsiloxane
    (Springer, 2023) Polat, Osman; Bhethanabotla, Venkat R.; Ayyala, Ramesh S.; Şahiner, Nurettin
    Low-density polyethylene (LDPE) and polydimethylsiloxane (silicone or PDMS) were exposed to low-pressure air, oxygen (O2), and carbon tetrafluoride (CF4) plasma to modify their surfaces. Plasma power and irradiation time were varied to determine the optimal yield for the water contact angle (θ). For both polymers, the CF4 plasma treatment resulted in the fluorination of the surfaces corroborated by FT-IR and XPS analysis, while small changes in the corresponding θ could be observed. For the O2 and air plasma treatment, the θ values of LDPE were reduced from 100° to around 60°. The changes in surface free energies (SFE) were compared for pre- and post-plasma gas treatment for both polymers and their stability under different aging conditions e.g., air, vacuum, and in water were investigated. The SFE of silicone was increased with the O2 plasma treatment from 10 to 75 mN/m and remained stable in water. Whereas the SFE of LDPE was indifferent to all storing conditions and stable up to 168 h. Also, while the SFE for the CF4 plasma-treated silicone remained almost unchanged, for the LDPE it was decreased to 15 from 35 mN/m. The wettability studies under different conditions e.g., different pH, NaCl, and BSA concentrations affirmed that they can be potentially used for biomedical applications. Finally, the multiple successive gas plasma treatment of LDPE and silicone were done up to 6 times to attain the θ values in the desired range e.g., about 120° to 30° for LDPE and 120° to 13° for silicone.
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    Degradable poly(catechin) nanoparticles as a versatile therapeutic agent
    (Taylor and Francis Ltd., 2021) Suner, Selin S.; Şahiner, Mehtap; Mohapatra, Subhra; Ayyala, Ramesh S.; Bhethanabotla, Venkat R.; Şahiner, Nurettin
    Poly(catechin) (p(CAT)) nanoparticles (NPs), 173 +/- 4 nm was prepared as a therapeutic agent with hydrolytic degradability affording sustainable CAT release over 20 d at carcinogenic conditions, pH 5.5 and 37.5 degrees C. Cell viability studies on MC38 colon cancer cells revealed the anticancer potential of p(CAT) NPs with 691 mu g/mL IC50 value while being well-tolerated by nonmalignant CCD841 CoN colon cells at 72 h incubation-time. P(CAT) NPs showed effective antioxidant capacity with 241 +/- 7 and 456 +/- 54 mu g/mL of GA equivalency of total phenol content (TPC), and total flavonoid content (TFC) values and 1.19 +/- 0.8 mu mol/g Trolox equivalent antioxidant capacity by 2,2'-Azino-bis-(3-ethylbenzothioazoline-6-sulfonic acid (ABTS(center dot+)) scavenging assay.
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    Fungal Keratitis Treatment Using Drug-Loaded Hyaluronic Acid Microgels
    (Amer Chemical Soc, 2022) Ayyala, Ramesh S.; Sağbaş Suner, Selin; Bhethanabotla, Venkat R.; Şahiner, Nurettin
    microgels using conjugation and encapsulation drug-loading techniques were utilized in the treatment of fungal keratitis. Natamycin (NAT) and amphotericin B (AMB) drugs were chemically linked to HA microgels by employing a chemical coupling agent to obtain conjugated (C-) HA:NAT and HA:AMB microgels. Also, these drugs were loaded into the HA microgel network during HA microgel preparation to attain encapsulated (E-) HA:NAT and HA:AMB microgels. The conjugation of drug molecules was confirmed by FT-IR spectra of bare and drugloaded HA microgels. It was determined that the AMB loading amount was about 4-fold higher for E-HA:AMB in comparison to C-HA:AMB microgels. Furthermore, the antifungal activity of drug conjugated and encapsulated HA:NAT and HA:AMB microgels was tested on Fusarium sp. and compared with the effect of bare drug molecules as control for up to 15 days of incubation time by means of the disc diffusion technique. The antifungal activity of 200 mu L at 20 mg/mL concentration of C-HA:NAT and C-HA:AMB microgels was not found to effectively inhibit Fusarium sp. growth after 1 day of incubation, whereas the same concentration of E-HA:NAT and E-HA:AMB microgels totally killed Fusarium sp. for up to 15 days. These E-HA:NAT and E-HA:AMB microgels show no cytotoxicity on the L929 fibroblast cells up to 1000 mu g/ mL concentration, whereas the free drug molecules destroy the cells even at 100 mu g/mL concentration.
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    Low-pressure plasma treated polycarbonate and polymethyl methacrylate (PMMA) sheets with different surface patterns to change their surface properties
    (Elsevier B.V., 2023) Gizer, S. Görkem; Bhethanabotla, Venkat R.; Ayyala, Ramesh S.; Şahiner, Nurettin
    Low-pressure plasmas of carbon tetrafluoride (CF4), oxygen (O2), and air were used to treat the surfaces of polycarbonate (PC) and polymethyl methacrylate (PMMA) to achieve a variety of surface attributes, such as hydrophilicity, hydrophobicity, and surface free energy. Patterns of straight line, triangular and square shapes with different sizes e.g., 0.5 mm, 0.75 mm, and 1 mm dimensions as templates were constructed from stainless-steel sheets with a thickness of 1 mm, via laser cutter, were used to induce the corresponding shape of the functionality on PC and PMMA surfaces during plasma gas treatment were also investigated. The untreated PC and PMMA surfaces have a contact angle (θ) value of 70°±0.47° and 77°±0.80°, respectively. As expected upon CF4 plasma treatment, their contact angle values were increased to 109.04°±0.35° and 105.76°±0.61°, respectively; whereas the air plasma treated surfaces became more hydrophilic with the contact angle values of 29.34°±0.14° and 43.99°±0.22°, correspondingly. Moreover, O2 plasma treated surfaces became more hydrophilic with the contact angle values of 25.32°±0.77° for PC and 39.94°±2.05° for PMMA. Also, surface free energy (SFE) values were decreased to 11±0.87 mN/m from 41.16±0.42 mN/m for PC and to 12.11±1.53 mN/m from 35.93±1.12 mN/m for PMMA upon CF4 treated surfaces. Furthermore, SFE values were increased to 57.59±1.12 and 62.13±1.15 mN/m for PC and PMMA after air plasma treatment. PC surface's, advancing and receding contact angles were determined as 101.48°±0.33° and 65.60°±0.11° respectively for 34.77°±0.50° slide-off angles. Moreover, the advancing and receding contact angles for PMMA were found as 93°±0.64° and 61.60°±1.19°, respectively with a sliding angle of 24.49°±1.14°. X-ray Photoelectron Spectroscopy (XPS) analysis results confirmed the fluorination and oxidation of both PC and PMMA after CF4 and O2 plasma treatments, individually. PC and PMMA surfaces were treated multiple times with CF4 and Air, Air and CF4, O2 and CF4, and CF4 and O2 plasmas in succession. After multiple treatment, PC and PMMA surfaces contact angle values were decreased as low as 10.62°±0.88° and 14.96°±0.2°, respectively.
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    Nitrogen-Doped Arginine Carbon Dots and Its Metal Nanoparticle Composites as Antibacterial Agent
    (Mdpi, 2020) Sağbaş Suner, Selin; Şahiner, Mehtap; Ayyala, Ramesh S.; Bhethanabotla, Venkat R.; Şahiner, Nurettin
    Nitrogen (N)-doped arginine carbon dots (Arg CD) were successfully synthesized using arginine as the amine source and citric acid as the carbon source via a one-pot green synthesis microwave-assisted technique in 2 min. Ag and Cu nanoparticles (NP) were generated within N-doped Arg CDs as composite Arg-Ag CDs and Arg-Cu CDs to render enhanced antibacterial properties. TEM analysis revealed that Arg CDs are in graphitic structures withdspacing ranging from 0.5 nm to 10 nm. The minimum inhibition concentration (MIC) values of Arg CDs with 6.250 mg/mL were decreased by about 100-fold for Arg-Ag CDs and ten-fold for Arg-Cu CDs with 0.062 and 0.625 mg/mL MIC values againstStaphylococcus aureus(S. aureus). The highest antibacterial susceptibility was observed for the Arg-Ag CD composite with 0.125 and 0.312 mg/mL minimum bactericidal concentration (MBC) values against Gram negativeS. aureusand Gram positiveEscherichia coli(E. coli) bacteria strains, respectively. It was found that the metal NPs within Arg CDs significantly increased the antibacterial properties of CDs making them available in the treatment of infections caused by different bacterial species. Furthermore, Arg-Ag CD and Arg-Cu CD composites were tested for Acetylcholinesterase (AChE, E.C. 3.1.1.7) that break down acetylcholine (ACh) into choline and acetic acid leading to the loss of ACh which plays an essential role as neurotransmitter in Alzheimer disease. It was found that Arg-Cu CDs inhibited 74.9 +/- 0.8% and Arg-Ag CDs inhibited 52.1 +/- 3.8% of AChE at a 1.82 mg/mL concentration versus no inhibition for Arg-CD. Moreover, the chelating activity of Arg-Cu CDs and Arg-Ag CDs were tested for Fe(II) and it was found that almost 100% chelating was attained at 116 mu g composites versus no measurable chelation for bare Arg CDs, suggesting the potential neurodegenerative disease treatment properties of these composite CDs in the brain.
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    Rapid Pathogen Purge by Photosensitive Arginine-Riboflavin Carbon Dots without Toxicity
    (Mdpi, 2023) Sağbaş Suner, Selin; Bhethanabotla, Venkat R.; Ayyala, Ramesh S.; Şahiner, Nurettin
    Photo-activatable antipathogenic carbon dots (CDs) were prepared by carbonization of citric acid and arginine (Arg) via 3 min microwave treatment for use in the eradication of common microorganisms. Nitrogen-doped Arg CDs were spherical in shape with a size range of 0.5 to 5 nm. The Arg CDs were modified with fluorescent dyes, such as fluorescein sodium salt (FSS, as Arg-FSS) and riboflavin (RBF, as Arg-RBF), to improve antimicrobial potency by enhancing their application in photodynamic therapy. The modified Arg CDs afforded fluorescence emission properties at 520 nm in the green region in addition to excellent blue fluorescence intensity at 420 nm under 345 nm excitation upon their FSS and RBF conjugation, respectively. Although the cytotoxicity of Arg CDs was decreased for Arg-RBF CDs to 91.2 +/- 0.7% cell viability for fibroblasts, the Arg-based CDs could be safely used for intravenous applications at 1000 mu g/mL concentration. The Arg CDs showed broad-spectrum antimicrobial activity against common pathogens and the minimum inhibitory concentration of Arg CDs was almost two-fold decreased for the modified forms without UV light. However, faster and more effective antibacterial activity was determined for photosensitive Arg-RBF CDs, with total bacterial eradication upon UV-A light exposure for 30 min.
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    Versatile Fluorescent Carbon Dots from Citric Acid and Cysteine with Antimicrobial, Anti?biofilm, Antioxidant, and AChE Enzyme Inhibition Capabilities
    (Springer, 2021) Sağbaş Suner, Selin; Şahiner, Mehtap; Ayyala, Ramesh S.; Bhethanabotla, Venkat R.; Şahiner, Nurettin
    Nanostructured fuorescent particles derived from natural molecules were prepared by a green synthesis technique employing a microwave method. The precursors citric acid (CA) and cysteine (Cys) were used in the preparation of S- and N-doped Cys carbon dots (Cys CDs). Synthesis was completed in 3 min. The graphitic structure revealed by XRD analysis of Cys CDs dots had good water dispersity, with diameters in the range of 2–20 nm determined by TEM analysis. The isoelectric point of the S, N-doped CDs was pH value for 5.2. The prepared Cys CDs displayed excellent fuorescence intensity with a high quantum yield of 75.6±2.1%. Strong antimicrobial capability of Cys CDs was observed with 12.5 mg/mL minimum bactericidal concentration (MBC) against gram-positive and gram-negative bacteria with the highest antimicrobial activity obtained against Staphylococcus aureus. Furthermore, Cys CDs provided total bioflm eradication and inhibition abilities against Pseudomonas aeruginosa at 25 mg/mL concentration. Cys CDs are promising antioxidant materials with 1.3±0.1 μmol Trolox equivalent/g antioxidant capacity. Finally, Cys CDs were also shown to inhibit the acetylcholinesterase (AChE) enzyme, which is used in the treatment of Alzheimer’s disease, even at the low concentration of 100 μg/mL.