Sammaiah Thota
University of Massachusetts Lowell
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Publication
Featured researches published by Sammaiah Thota.
Journal of Medicinal Chemistry | 2012
Min Wang; Liyi Huang; Sulbha K. Sharma; Seaho Jeon; Sammaiah Thota; Felipe F. Sperandio; Suhasini Nayka; Julie Chang; Michael R. Hamblin; Long Y. Chiang
Novel water-soluble decacationically armed C(60) and C(70) decaiodide monoadducts, C(60)- and C(70)[>M(C(3)N(6)(+)C(3))(2)], were synthesized, characterized, and applied as photosensitizers and potential nano-PDT agents against pathogenic bacteria and cancer cells. A high number of cationic charges per fullerene cage and H-bonding moieties were designed for rapid binding to the anionic residues displayed on the outer parts of bacterial cell walls. In the presence of a high number of electron-donating iodide anions as parts of quaternary ammonium salts in the arm region, we found that C(70)[>M(C(3)N(6)(+)C(3))(2)] produced more HO(•) than C(60)[>M(C(3)N(6)(+)C(3))(2)], in addition to (1)O(2). This finding offers an explanation of the preferential killing of Gram-positive and Gram-negative bacteria by C(60)[>M(C(3)N(6)(+)C(3))(2)] and C(70)[>M(C(3)N(6)(+)C(3))(2)], respectively. The hypothesis is that (1)O(2) can diffuse more easily into porous cell walls of Gram-positive bacteria to reach sensitive sites, while the less permeable Gram-negative bacterial cell wall needs the more reactive HO(•) to cause real damage.
Journal of Materials Chemistry | 2010
Long Y. Chiang; Prashant A. Padmawar; Joy E. Rogers-Haley; Grace So; Taizoon Canteenwala; Sammaiah Thota; Loon-Seng Tan; Kenneth P.H. Pritzker; Ying-Ying Huang; Sulbha K. Sharma; Divya Kurup; Michael R. Hamblin; Brian J. Wilson; Augustine Urbas
We report the synthesis of a new class of photoresponsive C(60)-DCE-diphenylaminofluorene nanostructures and their intramolecular photoinduced energy and electron transfer phenomena. Structural modification was made by chemical conversion of the keto group in C(60)(>DPAF-C(n)) to a stronger electron-withdrawing 1,1-dicyanoethylenyl (DCE) unit leading to C(60)(>CPAF-C(n)) with an increased electronic polarization of the molecule. The modification also led to a large bathochromic shift of the major band in visible spectrum giving measureable absorption up to 600 nm and extended the photoresponsive capability of C(60)-DCE-DPAF nanostructures to longer red wavelengths than C(60)(>DPAF-C(n)). Accordingly, C(60)(>CPAF-C(n)) may allow 2γ-PDT using a light wavelength of 1000-1200 nm for enhanced tissue penetration depth. Production efficiency of singlet oxygen by closely related C(60)(>DPAF-C(2) (M)) was found to be comparable with that of tetraphenylporphyrin photosensitizer. Remarkably, the (1)O(2) quantum yield of C(60)(>CPAF-C(2) (M)) was found to be nearly 6-fold higher than that of C(60)(>DPAF-C(2) (M)), demonstrating the large light-harvesting enhancement of the CPAF-C(2) (M) moiety and leading to more efficient triplet state generation of the C(60)> cage moiety. This led to highly effective killing of HeLa cells by C(60)(>CPAF-C(2) (M)) via photodynamic therapy (200 J cm(-2) white light). We interpret the phenomena in terms of the contributions by the extended π-conjugation and stronger electron-withdrawing capability associated with the 1,1-dicyanoethylenyl group compared to that of the keto group.
Molecules | 2012
Sammaiah Thota; Min Wang; Seaho Jeon; Satyanarayana Maragani; Michael R. Hamblin; Long Y. Chiang
We designed and synthesized two analogous pentacationic [60]fullerenyl monoadducts, C60(>ME1N6+C3) (1) and C60(>ME3N6+C3) (2), with variation of the methoxyethyleneglycol length. Each of these derivatives bears a well-defined number of cationic charges aimed to enhance and control their ability to target pathogenic Gram-positive and Gram-negative bacterial cells for allowing photodynamic inactivation. The synthesis was achieved by the use of a common synthon of pentacationic N,N′,N,N,N,N-hexapropyl-hexa(aminoethyl)amine arm (C3N6+) having six attached propyl groups, instead of methyl or ethyl groups, to provide a well-balanced hydrophobicity–hydrophilicity character to pentacationic precursor intermediates and better compatibility with the highly hydrophobic C60 cage moiety. We demonstrated two plausible synthetic routes for the preparation of 1 and 2 with the product characterization via various spectroscopic methods.
RSC Advances | 2015
Hardeep Singh Gill; Sammaiah Thota; Lian Li; Akshay Kokil; Ravi Mosurkal; Jayant Kumar
Photovoltaic performance enhancement of fullerene based solar cells was achieved upon exposure to near-infrared (NIR) laser pulses. The solar cells were fabricated with poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) under ambient conditions. The cells were then post-treated with NIR femto-second laser pulses at 800 nm for different intervals of time. An enhancement of 50% in the power conversion efficiency was achieved for the devices with 15 minutes of NIR laser irradiation compared to that of the control device. The enhancement in the power conversion efficiency is attributed to the formation of a covalent linkage between P3HT and PCBM as suggested by Matrix-assisted laser desorption/ionization time of flight mass spectroscopic analysis on a blend of a thiophene oligomer and PCBM before and after NIR laser exposure.
Journal of Electronic Materials | 2018
Ezaz Hasan Khan; Sammaiah Thota; Yiwen Wang; Lian Li; Eugene Wilusz; Richard M. Osgood; Jayant Kumar
Aqueous vitamin C solution has been used as an environment-friendly reducing agent for tuning the thermoelectric properties of p-toluenesulfonate-doped poly(3,4-ethylenedioxythiophene) (PEDOT-Tos) films. The de-doping of the PEDOT-Tos films by aqueous vitamin C solutions led to a decrease in the electrical conductivity of the films. The measured ultraviolet-visible-near-infrared and x-ray photoelectron spectra clearly indicated the reduction in the oxidation level from 37 to 23% when the PEDOT-Tos films were treated with 5% (w/v) aqueous vitamin C solutions. An increase in the Seebeck coefficient was measured, resulting in an increase in the figure-of-merit (ZT). A 42% increase in ZT was determined for the 5% aqueous vitamin C solution-treated PEDOT-Tos films with respect to that of the untreated films.
Journal of Macromolecular Science, Part A | 2010
Sammaiah Thota; Seaho Jeon; Min Wang; Long Y. Chiang
A design of novel hydrophilic tetracationic dumbbell-shaped [60]fullerene nanostructures was made by balancing the hydrophilicity and hydrophobicity characteristics of the fullerene adduct for their potential application as photodynamic sensitizers in the PDT treatment. A sequential protection-deprotection reaction pathway was applied for the functional differentiation between primary and secondary amine moieties of pentaethylene hexamine. Synthesis of the target molecule involves two key steps of unsymmetrical esterification and amidation of malonic acid and subsequent fullerenation. The synthetic strategy was accomplished using mild reaction conditions in the intermediate molecule preparation and led a moderate overall product yield.
Journal of Macromolecular Science, Part A | 2009
Ken Kokubo; Sammaiah Thota; Hsing-Lin Wang; Long Y. Chiang
The structural analysis of the first [60]fullerenyl 1,38-bisadduct having the almost perpendicular angle between two addends was performed based on the simulation of 13C-NMR spectral line patterns using the DFT calculation at the B3LYP/6-31G* level of the theory. Among seven closely related model regioisomers of C60(CH3)2 applied in the calculation, we confirmed that the 1,38-bisadduct and 1,4-bisadduct, being the most plausible regioisomers in a structure showing an approximate consistency of spectral line profiles, match with that of the experimentally obtained spectrum.
Journal of Macromolecular Science, Part A | 2009
Sammaiah Thota; Ken Kokubo; Loon-Seng Tan; Long Y. Chiang
In our effort to enhance the cross section of simultaneous multiphoton absorption of C60-based photonic nanomaterials, a novel highly luminescent tris-fluorenyl ring-interconnected chromophore tris-DPAF-C9 was designed and synthesized using a C 3 symmetrical triaminobenzene core as the synthon. The structural moiety bears a close resemblance to that of 2-diphenylamino-9,9-dialkylfluorenyl attachment in the previously studied C60(> DPAF-Cn)x. The product tris-DPAF-C9 was fully characterized by NMR, UV, IR, and MALDI-TOF MS spectroscopic methods. Based on the molecular energy calculation at MOPAC PM3 level, it suggested the presence of two possible cis/trans stereoisomers on the configuration of fluorenyl moieties. Consequently, a lower heat formation (ΔH f) of 19.9 kcal/mol was found for the tris-cis C9-isomer as the favorable one vs 47.9 kcal/mol for the bis-mono-trans C9-isomer.
Sensors and Actuators B-chemical | 2015
Hardeep Singh Gill; Sammaiah Thota; Lian Li; Haizhou Ren; Ravi Mosurkal; Jayant Kumar
Tetrahedron | 2014
Joshna Chittigori; Abhishek Kumar; Lian Li; Sammaiah Thota; Akshay Kokil; Lynne A. Samuelson; Daniel J. Sandman; Jayant Kumar