Liquid-gated field effect transistors based on single-walled carbon nanotubes : investigations of nanotubes-biomolecular interactions and ultra-sensitive biosensors

Detection and analysis of biomolecules is of paramount importance in the areas of medical diagnostics, environmental monitoring and defense which often requires rapid, low-cost, portable, and high-sensitivity analysis. In this thesis, an alternative approach to attain these attributes is demonstrated by employing single-walled carbon nanotubes (SWCNTs) based liquid-gated field-effect transistor (LGFET) with an integrated microfluidic channel. To address the need for a simple and robust fabrication step, a simple lamination process is described in this thesis for the production of the device which requires merely two materials: SWCNTs and poly (dimethyl siloxane) (PDMS), an elastomer. This uncomplicated production process, which involves soft lithography, alleviates the need for photolithography altogether, besides the initial requirement of mold preparation. The integrated microfluidic channel offers advantages, such as: controlled delivery of the liquid sample, minute requirement of sample volume, and ability to perform kinetic measurements amongst others. The biomolecular interaction is then studied in real-time and label-free fashion within the aqueous liquid environment by monitoring the conductance of the semiconducting carbon nanotubes network. The size similarity of the nanotubes with most biomolecules and electronic properties of SWCNT derived from its hollow geometry renders the SWCNTs a potential candidate for high-sensitivity biosensing. To gain understanding about the interaction between the biomolecules and the nanotubes, a series of experiments have been performed to study the interaction between Bovine Serum Albumin (BSA) protein and the nanotubes, with a focus given to the reciprocal effect of such interactions: protein conformation change and conductance of the LGFETs. The carboxylated nanotubes inflicted a large conformational change in the protein than its pristine counterpart, thus, resulting in differential signal level in the transistor based kinetic measurement.This observation underscores the importance of the precise surface chemistry of the nanotubes in developing a biosensor. The application of SWCNTs LGFET in biosensing was investigated in the detection of 2, 4-dichlorophenoxy acetic acid (2, 4-D) herbicide in both buffer solution and soil extract by employing competitive immunoassay. The study suggests that the size of the bioanalytes determines the type of protocol that can be employed for the kinetic detection. Additionally, the experiment also highlights that lower ionic-strength solution, such as soil extracts, helps in signal amplification thus facilitating detection limits down to femto-molar concentrations. A similar ionic-strength dependency of the signal level is also found in the successive experiments of adsorption of poly (L-Lysine) (PLL) in different ionic-strength solutions.DOCTOR OF PHILOSOPHY (MSE

IMPLEMENTASI CUSTOMER RELATIONSHIP MANAGEMENT (CRM) BERBASIS WEBSITE PADA CV. PERMATA DIGITAL PRINTING

Permata Digital Printing merupakan perusahaan yang bergerak di bidang digital printing dan advertising yang berpusat di Kota Denpasar. Saat ini belum menerapkan konsep CRM sehingga kurang maksimal dalam melayani pelanggan. Peningkatan pelayanan perlu dilakukan guna mencapai tujuan CRM dalam meningkatkan kepuasan pelanggan serta menjaga loyalitas pelanggan. Perancangan CRM menggunakan Metode CRM-IRIS dengan menganalisis kerangka organisasi,  strategi pelanggan, hubungan dengan pelanggan, serta merancang sistem CRM. Hasil analisis hubungan pelanggan ditemukan poin permasalahan yang diselesaikan dengan mengimplemantasikannya ke sistem CRM berbasis Website. Website ini mempunyai halaman admin dan halaman pelanggan dengan penggunaan yang berbeda. Hasil sistem tersebut kemudian diuji menggunakan Kuesioner SUS yang diberikan kepada Responden. Hasil website yang di rancang tersebut dapat memberikan solusi bagi perusahaan dalam menjaga loyalitas pelanggan dengan memberikan pelayanan yang maksimal. Kata kunci: CRM, Website, Metode CRM-IRIS, Kuesioner SUS, Digital Printing.Permata Digital Printing merupakan perusahaan yang bergerak di bidang digital printing dan advertising yang berpusat di Kota Denpasar. Saat ini belum menerapkan konsep CRM sehingga kurang maksimal dalam melayani pelanggan. Peningkatan pelayanan perlu dilakukan guna mencapai tujuan CRM dalam meningkatkan kepuasan pelanggan serta menjaga loyalitas pelanggan. Perancangan CRM menggunakan Metode CRM-IRIS dengan menganalisis kerangka organisasi,  strategi pelanggan, hubungan dengan pelanggan, serta merancang sistem CRM. Hasil analisis hubungan pelanggan ditemukan poin permasalahan yang diselesaikan dengan mengimplemantasikannya ke sistem CRM berbasis Website. Website ini mempunyai halaman admin dan halaman pelanggan dengan penggunaan yang berbeda. Hasil sistem tersebut kemudian diuji menggunakan Kuesioner SUS yang diberikan kepada Responden. Hasil website yang di rancang tersebut dapat memberikan solusi bagi perusahaan dalam menjaga loyalitas pelanggan dengan memberikan pelayanan yang maksimal. Kata kunci: CRM, Website, Metode CRM-IRIS, Kuesioner SUS, Digital Printing

Membraneless glucose/O2 microfluidic biofuel cells using covalently bound enzymes

International audienceWe developed a new covalent enzyme immobilization technique compatible with lithography processes. Carbon nanotube electrodes patterned on glass slides were used to create Y-shaped membraneless glucose/O(2) microfluidic biofuel cells. An original extremophilic laccase, CotA from Bacillus subtilis, was used in the cathodic compartment of these miniaturized biofuel cells

New Glycosidase Substrates for Droplet-Based Microfluidic Screening

Droplet-based microfluidics is a powerful technique allowing ultra-high-throughput screening of large libraries of enzymes or microorganisms for the selection of the most efficient variants. Most applications in droplet microfluidic screening systems use fluorogenic substrates to measure enzymatic activities with fluorescence readout. It is important, however, that there is little or no fluorophore exchange between droplets, a condition not met with most commonly employed substrates. Here we report the synthesis of fluorogenic substrates for glycosidases based on a sulfonated 7-hydroxycoumarin scaffold. We found that the presence of the sulfonate group effectively prevents leakage of the coumarin from droplets, no exchange of the sulfonated coumarins being detected over 24 h at 30 °C. The fluorescence properties of these substrates were characterized over a wide pH range, and their specificity was studied on a panel of relevant glycosidases (cellulases and xylanases) in microtiter plates. Finally, the β-d-cellobioside-6,8-difluoro-7-hydroxycoumarin-4-methanesulfonate substrate was used to assay cellobiohydrolase activity on model bacterial strains (<i>Escherichia coli</i> and <i>Bacillus subtilis</i>) in a droplet-based microfluidic format. These new substrates can be used to assay glycosidase activities in a wide pH range (4–11) and with incubation times of up to 24 h in droplet-based microfluidic systems