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Catalyst free silica templated porous carbon nanoparticles from bio-waste materials

Kumar A, Hegde G, Manaf SA, Ngaini Z, Sharma KV

Chem Commun (Camb), 2014 Oct 28;50(84):12702-5.
PMID: 25100105 DOI: 10.1039/c4cc04378b

Porous Carbon Nanoparticles (PCNs) with well-developed microporosity were obtained from bio-waste oil palm leaves (OPL) using single step pyrolysis in nitrogen atmosphere at 500-600 °C in tube-furnace without any catalysis support. The key approach was using silica (SiO2) bodies of OPL as a template in the synthesis of microporous carbon nanoparticles with very small particle sizes of 35-85 nm and pore sizes between 1.9-2 nm.
Click chemistry approach: regioselective one-pot synthesis of some new 8-trifluoromethylquinoline based 1,2,3-triazoles as potent antimicrobial agents

Garudachari B, Isloor AM, Satyanarayana MN, Fun HK, Hegde G

Eur J Med Chem, 2014 Mar 3;74:324-32.
PMID: 24486415 DOI: 10.1016/j.ejmech.2014.01.008

Three series of 8-trifluoromethylquinoline based 1,2,3-triazoles derivatives (5a-c, 6a-d and 7a-c) were synthesized by multi-step reactions by click chemistry approach. Synthesized compounds were characterized by spectral studies and X-ray analysis. The final compounds were screened for their in-vitro antimicrobial activity by well plate method (zone of inhibition). Compounds 5c, 6b, 8b, 11 and 12 were found to be active against tested microbial strains. The results are summarized in Tables 5 and 6.
Synthesis and biological evaluation of novel substituted 1,3,4-thiadiazole and 2,6-di aryl substituted imidazo [2,1-b] [1,3,4] thiadiazole derivatives

Chandrakantha B, Isloor AM, Shetty P, Fun HK, Hegde G

Eur J Med Chem, 2014 Jan;71:316-23.
PMID: 24321835 DOI: 10.1016/j.ejmech.2013.10.056

A new series of N-[5-(4-(alkyl/aryl)-3-nitro-phenyl)-[1,3,4-thiadiazol-2-yl]-2,2-dimethyl-propionamide 4 (a-l) and 6-(4-Methoxy-phenyl)-2-(4-alkyl/aryl)-3-nitro-phenyl)-Imidazo [2,1-b] [1,3,4] thiadiazole 6 (a-l) were synthesized starting from 5-(4-Fluoro-3-nitro-phenyl)-[1,3,4] thiadiazole-2-ylamine. The synthesized compounds were characterized by IR, NMR, mass spectral and elemental analysis. All the compounds were tested for antibacterial and antifungal activities. The antimicrobial activities of the compounds were assessed by well plate method (zone of inhibition). Compounds 4a, 4c and 6e, 6g displayed appreciable activity at the concentration 0.5-1.0 mg/mL.
Chiral Polymorphic Hydrazine-based Asymmetric Liquid Crystal Trimers with Resorcinol as Linking Group

Goh YP, Yam WS, Yip FW, Hegde G

Curr Org Synth, 2021;18(4):352-365.
PMID: 33530909 DOI: 10.2174/1570179418666210202123935

INTRODUCTION: This is the first report on chiral polymorphic hydrazine-based asymmetric liquid crystal trimers, 1-[4'-(4''-(5-Cholesteryloxy)carbonyl)butyloxy]-3-[N-benzylideneoxy-N'-(4'''-decyloxybenzylidene) hydrazine] butyloxybenzenes, and 1-[4'-(4''-(10-cholesteryloxy)carbonyl)nonyloxy]-3-[N-benzylideneoxy-N'-(4'''- decyloxybenzylidene)hydrazine]butyloxybenzenes., in which the hydrazine and cholesterol arms were connected via two flexible methylene spacers (n = 3-12 units and m = 4 or 9, respectively) to the central resorcinol core.
MATERIALS AND METHODS: FT-IR, 1D and 2D NMR spectroscopy, and CHN microanalysis were used to elucidate the structures of the trimers. Differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction were used to study the transitional and phase properties of the trimers, which were length and spacer parity dependent. Trimers with short spacer length in the cholesteryl arm, m = 4 showed an interesting phase sequence of BP/N*-TGBA*-SmA*.
RESULTS AND DISCUSSION: The TGBA* phase was sensitive to spacer length as it was only observed in trimers with short ester linkage. For the long analogues, m = 9, characteristic visible reflection and a much simpler phase sequence with only N* and SmA* phases were observed.
CONCLUSION: The X-ray diffraction measurements revealed that layer periodicities of the SmA* phase were approximately half the estimated all-trans molecular length (d/L ≈ 0.44-0.52), thus suggesting that the molecules are either strongly intercalated or bent.
New para-substituted non-symmetric isoflavones for their fast photo-switching ability: synthesis and their liquid crystal characterization

Yuvaraj AR, Yam WS, Chan TN, Goh YP, Hegde G

Spectrochim Acta A Mol Biomol Spectrosc, 2015 Jan 25;135:1115-22.
PMID: 25173529 DOI: 10.1016/j.saa.2014.08.009

The first example of non-symmetric isoflavone-based fast photo-switchable liquid crystals with different functional groups at the terminal position were synthesized and characterized. Polarizing optical microscopy study revealed that the compounds showed least ordered nematic phase. Optical photo switching study exhibited very fast photoisomerization effect in solution. The E-Z and Z-E conversion occurred around 3-5s and 40-700 s respectively. This is also the first example of para-substituted non-symmetric isoflavone liquid crystals exhibiting very fast photo switching property in solution. Argument based on non-symmetrical behaviour might be the reason for the observed behaviour.
Fulltext 4-{(E)-2-[4-(But-3-en-1-yl-oxy)phen-yl]diazen-1-yl}benzoic acid

Rahman ML, Kwong HC, Mohd Yusoff M, Hegde G, Mohamed Tahir MI, Rahman MZ

Acta Crystallogr Sect E Struct Rep Online, 2012 Oct 1;68(Pt 10):o2958.
PMID: 23125741 DOI: 10.1107/S1600536812038718

The title compound, C(17)H(16)N(2)O(3), has an E conformation about the azobenzene (-N=N-) linkage. The benzene rings are twisted slightly with respect to each other [6.79 (9)°], while the dihedral angle between the plane through the carb-oxy group and the attached benzene ring is 3.2 (2)°. In the crystal, mol-ecules are oriented with the carb-oxy groups head-to-head, forming O-H⋯O hydrogen-bonded inversion dimers. These dimers are connected by C-H⋯O hydrogen-bonds into layers lying parallel to the (013) plane.
Fulltext 1-[4-(Prop-2-en-1-yl-oxy)benz-yl]-2-[4-(prop-2-en-1-yl-oxy)phen-yl]-1H-benzimidazole

Rahman ML, Kwong HC, Mohd Yusoff M, Hegde G, Mohamed Tahir MI

Acta Crystallogr Sect E Struct Rep Online, 2012 Dec 1;68(Pt 12):o3311-2.
PMID: 23476157 DOI: 10.1107/S160053681204559X

In the title compound, C26H24N2O2, the benzimidazole ring system is almost planar [maximum displacement = 0.025 (1) Å] and makes dihedral angles of 80.48 (5) and 41.57 (5)° with the benzene rings, which are inclined to one another by 65.33 (6)°. In the crystal, mol-ecules are linked via C-H⋯π and weak π-π inter-actions [centroid-centroid distance = 3.8070 (7) Å and inter-planar distance = 3.6160 (5) Å].
Carbon nanospheres derived from Lablab purpureus for high performance supercapacitor electrodes: a green approach

Ali GAM, Divyashree A, Supriya S, Chong KF, Ethiraj AS, Reddy MV, et al.

Dalton Trans, 2017 Oct 17;46(40):14034-14044.
PMID: 28979958 DOI: 10.1039/c7dt02392h

Carbon nanospheres derived from a natural source using a green approach were reported. Lablab purpureus seeds were pyrolyzed at different temperatures to produce carbon nanospheres for supercapacitor electrode materials. The synthesized carbon nanospheres were analyzed using SEM, TEM, FTIR, TGA, Raman spectroscopy, BET and XRD. They were later fabricated into electrodes for cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy testing. The specific capacitances were found to be 300, 265 and 175 F g-1in 5 M KOH electrolyte for carbon nanospheres synthesized at 800, 700 and 500 °C, respectively. These are on a par with those of prior electrodes made of biologically derived carbon nanospheres but the cycle lives were remarkably higher than those of any previous efforts. The electrodes showed 94% capacitance retention even after 5200 charge/discharge cycles entailing excellent recycling durability. In addition, the practical symmetrical supercapacitor showed good electrochemical behaviour under a potential window up to 1.7 V. This brings us one step closer to fabricating a commercial green electrode which exhibits high performance for supercapacitors. This is also a waste to wealth approach based carbon material for cost effective supercapacitors with high performance for power storage devices.
Functionalized Carbon Nano-scale Drug Delivery Systems From Biowaste Sago Bark For Cancer Cell Imaging

Abdul Manaf SA, Hegde G, Mandal UK, Wui TW, Roy P

Curr Drug Deliv, 2017;14(8):1071-1077.
PMID: 27745545 DOI: 10.2174/1567201813666161017130612

BACKGROUND: Nano-scale carbon systems are emerging alternatives in drug delivery and bioimaging applications of which they gradually replace the quantum dots characterized by toxic heavy metal content in the latter application.
OBJECTIVE: The work intended to use carbon nanospheres synthesized from biowaste Sago bark for cancer cell imaging applications.
METHODS: This study synthesised carbon nanospheres from biowaste Sago bark using a catalyst-free pyrolysis technique. The nanospheres were functionalized with fluorescent dye coumarin-6 for cell imaging. Fluorescent nanosytems were characterized by field emission scanning electron microscopy-energy dispersive X ray, photon correlation spectroscopy and fourier transform infrared spectroscopy techniques.
RESULTS: The average size of carbon nanospheres ranged between 30 and 40 nm with zeta potential of -26.8 ± 1.87 mV. The percentage viability of cancer cells on exposure to nanospheres varied from 91- 89 % for N2a cells and 90-85 % for A-375 cells respectively. Speedy uptake of the fluorescent nanospheres in both N2a and A-375 cells was observed within two hours of exposure.
CONCLUSION: Novel fluorescent carbon nanosystem design following waste-to-wealth approach exhibited promising potential in cancer cell imaging applications.
Carbon nanomaterial properties help to enhance xylanase production from recombinant Kluyveromyces lactis through a cell immobilization method

Abdul Manaf SA, Mohamad Fuzi SFZ, Low KO, Hegde G, Abdul Manas NH, Md Illias R, et al.

Appl Microbiol Biotechnol, 2021 Nov;105(21-22):8531-8544.
PMID: 34611725 DOI: 10.1007/s00253-021-11616-0

Carbon nanomaterials, due to their catalytic activity and high surface area, have potential as cell immobilization supports to increase the production of xylanase. Recombinant Kluyveromyces lactis used for xylanase production was integrated into a polymeric gel network with carbon nanomaterials. Carbon nanomaterials were pretreated before cell immobilization with hydrochloric acid (HCl) treatment and glutaraldehyde (GA) crosslinking, which contributes to cell immobilization performance. Carbon nanotubes (CNTs) and graphene oxide (GO) were further screened using a Plackett-Burman experimental design. Cell loading and agar concentration were the most important factors in xylanase production with low cell leakage. Under optimized conditions, xylanase production was increased by more than 400% compared to free cells. Immobilized cell material containing such high cell densities may exhibit new and unexplored beneficial properties because the cells comprise a large fraction of the component. The use of carbon nanomaterials as a cell immobilization support along with the entrapment method successfully enhances the production of xylanase, providing a new route to improved bioprocessing, particularly for the production of enzymes. KEY POINTS: • Carbon nanomaterials (CNTs, GO) have potential as cell immobilization supports. • Entrapment in a polymeric gel network provides space for xylanase production. • Plackett-Burman design screen for the most important factor for cell immobilization.
Emergence of nanomaterials as potential immobilization supports for whole cell biocatalysts and cell toxicity effects

Abdul Manaf SA, Mohamad Fuzi SFZ, Abdul Manas NH, Md Illias R, Low KO, Hegde G, et al.

Biotechnol Appl Biochem, 2021 Dec;68(6):1128-1138.
PMID: 32969042 DOI: 10.1002/bab.2034

The traditional approach of fermentation by a free cell system has limitations of low productivity and product separation that need to be addressed for production enhancement and cost effectiveness. One of potential methods to solve the problems is cell immobilization. Microbial cell immobilization allows more efficient up-scaling by reducing the nonproductive growth phase, improving product yield and simplifying product separation. Furthermore, the emergence of nanomaterials such as carbon nanotubes, graphene, and metal-based nanomaterials with excellent functional properties provides novel supports for cell immobilization. Nanomaterials have catalytic properties that can provide specific binding site with targeted cells. However, the toxicity of nanomaterials towards cells has hampered its application as it affects the biological system of the cells, which cannot be neglected in any way. This gray area in immobilization is an important concern that needs to be addressed and understood by researchers. This review paper discusses an overview of nanomaterials used for cell immobilization with special focus on its toxicological challenges and how by understanding physicochemical properties of nanomaterials could influence the toxicity and biocompatibility of the cells.