Programmable graphene-based microfluidic sensor for DNA detection

This study presents the development of a lab-on-a-chip (LoC) by integrating a graphene field-effect transistor (FET) chip with a programmable microfluidic device for DNA detection. The real-time biochemical events on the graphene FET chip were monitored through Dirac voltage shift data from the portable graphene curve reader with changes dependent on the fluidic flow into the sensing interface by a fully automated programmable microfluidic system. High sensitivity with high reliability can be obtained with a nine-graphene sensor layout on a single chip. The portable graphene curve reader also provides a tunable electrical parameter setup and straightforward data acquisition. Fluidic control was performed through a multi-position valve, allowing sequential commands for liquid injection into the polydimethylsiloxane (PDMS) flow cell mounted on the sensing chip. The flow cell design with impinging jet geometry and the microfluidic system packaging offer high precision and portability as a less laborious and low-cost sensing setup. The merged system allows for various functionalities, including probe DNA (pDNA) immobilization, a blocking step, and DNA hybridization with stable signal output autonomously, even in a long-run experimental setup. As a DNA sensor, the proposed prototype has demonstrated a high sensitivity of ~44 mV/decade of target DNA concentration, with an outstanding limit of detection (LoD) of ~0.642 aM, making it one of the most sensitive sensors reported up to date. The programmable device has demonstrated essential versatilities for biomolecular detection in a fully portable and automated platform.This research is supported by PORTGRAPHE-Control of Port and Douro Wines authenticity using graphene DNA sensors project co-funded by Fundação para a Ciência e a Tecnologia (FCT) Portugal (PTDC/BIA-MOL/31069/2017) and the ERDF through COMPETE2020 (POCI-01–0145-FEDER-031069). One of the authors (Telma Domingues) acknowledges a Ph.D. grant from Fundação para a Ciência e a Tecnologia (FCT) Portugal (SFRH/BD/08181/2020). FCT partially supported University of Minho´s research in the Strategic Funding UIDB/04650/2020

PENGEMBANGAN SENSOR pH BERBASIS BACTERIAL CELLULOSE (Acetobacter xylinum) DAN NANOPARTIKEL EMAS (Au Nanostars) SEBAGAI DETEKTOR KEASAMAN SUSU

Saat ini, perkembangan teknologi yang menuju teknologi smart sensor terus berkembang pesat. Biosensor muncul sebagai alat analisis yang sangat efisien untuk pengukuran resolusi tinggi. Kebutuhan akan metode analisis yang cepat, akurat, efektif, efisien dan mudah terus meningkat. Dalam penelitian ini, pengukuran analitis menggunakan potentiostat. Metode Cyclic Voltametry (CV) berbasis biosensor ini diharapkan dapat mengukur keasaman susu lebih cepat, akurat dengan proses fabrikasi sederhana. Penelitian ini dibagi menjadi 3 tahap yaitu penelitian pendahuluan, penelitian utama dan penelitian lebih lanjutan. Penelitian pendahuluan yang dilakukan adalah untuk mengetahui dampak paparan sinar UV pada hidrofilisitas ITO. Selain itu, penelitian pendahuluan ini bertujuan untuk menentukan karakteristik ITO sebelum dan sesudah pemaparan sinar UV. Penelitian utama yang dilakukan adalah untuk mengetahui pengaruh waktu pertumbuhan bacterial cellulose (BC) terhadap karakter morfologi dan kristalinitas permukaan elektroda. Penelitian lebih lanjut dilakukan untuk menentukan respon pH. Hasil penelitian ini menunjukkan bahwa durasi pertumbuhan selulosa BC mempengaruhi kinerja elektroda yang dimodifikasi dan sifat elektrokimia yang berkaitan dengan permukaan aktif elektro. Struktur biosintesis selanjutnya diterapkan untuk sensor pH melalui analisis CV dan digunakan untuk deteksi keasaman dalam sampel susu. Sensor fabrikasi dipertimbangkan untuk memiliki potensi sebagai platform berbiaya rendah dan mudah dibuat untuk penyaringan kualitas susu. Kata kunci : bacterial cellulose (BC), indium tin oxide, Au Nanostars, Cyclic Voltametry (CV), kualitas susu

Influence of the electrolyte salt concentration on DNA detection with graphene transistors

Liquid-gated Graphene Field-Effect Transistors (GFET) are ultrasensitive bio-detection platforms carrying out the graphene’s exceptional intrinsic functionalities. Buffer and dilution factor are prevalent strategies towards the optimum performance of the GFETs. However, beyond the Debye length (λD), the role of the graphene-electrolytes’ ionic species interactions on the DNA behavior at the nanoscale interface is complicated. We studied the characteristics of the GFETs under different ionic strength, pH, and electrolyte type, e.g., phosphate buffer (PB), and phosphate buffer saline (PBS), in an automatic portable built-in system. The electrostatic gating and charge transfer phenomena were inferred from the field-effect measurements of the Dirac point position in single-layer graphene (SLG) transistors transfer curves. Results denote that λD is not the main factor governing the effective nanoscale screening environment. We observed that the longer λD was not the determining characteristic for sensitivity increment and limit of detection (LoD) as demonstrated by different types and ionic strengths of measuring buffers. In the DNA hybridization study, our findings show the role of the additional salts present in PBS, as compared to PB, in increasing graphene electron mobility, electrostatic shielding, intermolecular forces and DNA adsorption kinetics leading to an improved sensitivity.This research is supported by PORTGRAPHE-Control of Port and DouroWines authenticity using graphene DNA sensors project co-funded by FCT (PTDC/BIA-MOL/31069/2017) and the ERDF through COMPETE2020 (POCI-01-0145-FEDER-031069)

Attomolar detection of hepatitis C virus core protein powered by molecular antenna-like effect in a graphene field-effect aptasensor

Biosensors based on graphene field-effect transistors have become a promising tool for detecting a broad range of analytes. However, their performance is substantially affected by the functionalization protocol. In this work, we use a controlled in-vacuum physical method for the covalent functionalization of graphene to construct ultrasensitive aptamer-based biosensors (aptasensors) able to detect hepatitis C virus core protein. These devices are highly specific and robust, achieving attomolar detection of the viral protein in human blood plasma. Such an improved sensitivity is rationalized by theoretical calculations showing that induced polarization at the graphene interface, caused by the proximity of covalently bound molecular probe, modulates the charge balance at the graphene/aptamer interface. This charge balance causes a net shift of the Dirac cone providing enhanced sensitivity for the attomolar detection of the target proteins. Such an unexpected effect paves the way for using this kind of graphene-based functionalized platforms for ultrasensitive and real-time diagnostics of different diseases.EU Graphene Flagship funding (Grant Graphene Core3 881603), the Ministerio de Ciencia e Innovación of Spain: PID2020-113142RB-C21, the European Structural Funds via FotoArt-CM project (P2018/NMT-4367) and the Portuguese Foundation for Science and Technology (FCT) via the Strategic Funding UIDB/04650/2020. Work at CAB was funded by the Spanish Ministerio de Ciencia e Innovación (MICINN) grant no. PID2019-104903RB-I00 and the Spanish Agencia Estatal de Investigación (AEI) Project no. MDM-2017-0737 - Unidad de Excelencia “María de Maeztu,” and it also benefits from the interdisciplinary framework provided by CSIC through “LifeHUB.CSIC” initiative (PIE 202120E047-CONEXIONES-LIFE). CIBERehd is funded by Instituto de Salud Carlos III (ISCIII). A.N. is supported by the predoctoral fellowship PRE-CAB-BIOMOLECULAS 2 from INTA. B.T-V. is supported by the predoctoral fellowship TS17/16 from INTA and by the CSIC “Garantía Juvenil” contract CAM19_PRE_CAB_001 funded by Comunidad de Madrid (CAM). FCT supports T.D. and P.C. under Ph.D. grants SFRH/BD/08181/2020 and SFRH/BD/128579/2017. M.M. would like to thank Comunidad de Madrid for the predoctoral grant IND2020/BIO-17523. P.A. and C.B. also acknowledge the support provided by La Caixa Foundation through Project LCF/PR/HR21/52410023. L. V. would like to thank Comunidad de Madrid (TRANSNANOAVANSENS program: S2018-NMT-4349) and E.V. García-Frutos for her assistance during the AFM experiments

Attomolar detection of hepatitis C virus core protein powered by molecular antenna-like effect in a graphene field-effect aptasensor

This study presents the development of a lab-on-a-chip (LoC) by integrating a graphene field-effect transistor (FET) chip with a programmable microfluidic device for DNA detection. The real-time biochemical events on the graphene FET chip were monitored through Dirac voltage shift data from the portable graphene curve reader with changes dependent on the fluidic flow into the sensing interface by a fully automated programmable microfluidic system. High sensitivity with high reliability can be obtained with a nine-graphene sensor layout on a single chip. The portable graphene curve reader also provides a tunable electrical parameter setup and straightforward data acquisition. Fluidic control was performed through a multi-position valve, allowing sequential commands for liquid injection into the polydimethylsiloxane (PDMS) flow cell mounted on the sensing chip. The flow cell design with impinging jet geometry and the microfluidic system packaging offer high precision and portability as a less laborious and low-cost sensing setup. The merged system allows for various functionalities, including probe DNA (pDNA) immobilization, a blocking step, and DNA hybridization with stable signal output autonomously, even in a long-run experimental setup. As a DNA sensor, the proposed prototype has demonstrated a high sensitivity of ~44 mV/decade of target DNA concentration, with an outstanding limit of detection (LoD) of ~0.642 aM, making it one of the most sensitive sensors reported up to date. The programmable device has demonstrated essential versatilities for biomolecular detection in a fully portable and automated platform.This research is supported by PORTGRAPHE-Control of Port and Douro Wines authenticity using graphene DNA sensors project co-funded by Fundação para a Ciência e a Tecnologia (FCT) Portugal (PTDC/BIA-MOL/31069/2017) and the ERDF through COMPETE2020 (POCI-01–0145-FEDER-031069). One of the authors (Telma Domingues) acknowledges a Ph.D. grant from Fundação para a Ciência e a Tecnologia (FCT) Portugal (SFRH/BD/08181/2020). FCT partially supported University of Minho´s research in the Strategic Funding UIDB/04650/2020

Gold nanospikes formation on screen-printed carbon elec-trode through electrodeposition method for non-enzymatic electrochemical sensor

In this study, we reported the construction of Gold Nanospike (AuNS) structures on the surface of screen-printed carbon electrode (SPCE) used for non-enzymatic electrochemical detection. This modification was prepared with a one-step electrodeposition method by controlling the electrodeposition parameters, such as applied potential and deposition time, via Constant Potential Amperometry (CPA). Those parameters and precursor solution concentration were varied to investigate the optimum electrodeposition configuration. The results confirmed that AuNS were homogenously deposited and well-dispersed on the working electrode surface of SPCE. The AuNS-modified SPCE was implemented as a non-enzymatic sensor toward dopamine and could enhance the electrocatalytic ability compared with the bare SPCE. Further examination shows that the sensing performance of the AuNS-modified SPCE produced an increase in electrochemical surface area (ECSA) at 17.25 times higher than the bare electrode, a sensitivity of 0.056 µA mM−1 cm−2 with a wide linear range of 0.2–50 µM and a detection limit of 0.33 µM. In addition, AuNS-modified SPCE can selectively detect dopamine among other interfering analytes such as ascorbic acid, urea, and uric acid, which commonly coexist in the body fluid. This work demonstrated that AuNS-modified SPCE is a prospective sensing platform for non-enzymatic dopamine detection

Surface Plasmon Resonance Optical Sensor: A Review on Light Source Technology

The notion of surface plasmon resonance (SPR) sensor research emerged more than eight decades ago from the first observed phenomena in 1902 until the first introduced principles for gas sensing and biosensing in 1983. The sensing platform has been hand-in-hand with the plethora of sensing technology advancement including nanostructuring, optical technology, fluidic technology, and light source technology, which contribute to substantial progress in SPR sensor evolution. Nevertheless, the commercial products of SPR sensors in the market still require high-cost investment, component, and operation, leading to unaffordability for their implementation in a low-cost point of care (PoC) or laboratories. In this article, we present a comprehensive review of SPR sensor development including the state of the art from a perspective of light source technology trends. Based on our review, the trend of SPR sensor configurations, as well as its methodology and optical designs are strongly influenced by the development of light source technology as a critical component. These simultaneously offer new underlying principles of SPR sensor towards miniaturization, portability, and disposability features. The low-cost solid-state light source technology, such as laser diode, light-emitting diode (LED), organic light emitting diode (OLED) and smartphone display have been reported as proof of concept for the future of low-cost SPR sensor platforms. Finally, this review provides a comprehensive overview, particularly for SPR sensor designers, including emerging engineers or experts in this field