Jutaan manusia mati disebabkan ketiadaan dan ketidakbolehcapaian kemudahan diagnostik terutamanya dalam mengawal penyakit-penyakit penting, yang mana membawa kepada pembangunan biopenderia yang progresif. Malangnya, pengoksidaan secara langsung analit sasaran pada elektrod terdedah bagi biopenderia adalah proses tidak boleh balik dan memerlukan upaya lebih yang tinggi, menyebabkan kotoran elektrod dan kepekaan yang rendah. Elektrod yang terubahsuai membran nilon-6 telah dicadangkan untuk mengatasi masalah ini. Sebagai satu immunocerakin, tindakbalas biokimia antara analit sasaran dan tawanan berlaku pada permukaan membran nilon-6, kemudian diterjemahkan kepada isyarat rintangan yang boleh diukur. Kajian ini menjelaskan ciri morfologi bagi nilon-6 sebagai membran penjerapan protin dan pengaruh mereka dalam antaramuka pengecaman biologi. Membran nilon-6 disintesis melalui penyongsangan fasa kering dengan kepekataan berbeza bagi polimer nilon-6 dalam julat 16 wt. % hingga 28 wt. % dan pelbagai jenis bahan tambah (air dan metanol) dalam larutan ‘dope’. Membran nilon-6 yang dibangunkan, N-16B, dengan 16 wt. % nilon-6 polimer dan metanol sebagai bukan pelarut telah memperlihatkan kelajuan sisi penyumbuan yang terpantas (1.07 mm/saat) dan kapasiti penjerapan protin yang sangat baik, (1,650.00 + 85.84 μg/cm3). Kajian semasa mendedahkan kepentingan morfologi membran yang mempengaruhi kepekaan dan keberkesanan peranti pengesan imun. Isu kestabilan dalam penjerapan biomolekul telah diatasi dengan mengintegrasi glutaradehid (GA) ke atas membran nilon-6 sebelum penjerapan protin. Kajian awal telah dijalankan untuk mengkaji kesan masa inkubasi, pH dan kepekatan GA pada pengikatan protin ke atas polimer nilon-6. Keadaan optimum bagi integrasi GA ditemui pada 40 minit masa inkubasi, pH 7.5 dan 1 wt. % kepekatan GA. Analisis statistik dengan program rekabentuk silang dilakukan dan keadaan integrasi GA optimum dari analisis statistik didapati pada 25 wt. % bagi polimer nilon-6, 75 wt.% campuran pelarut + tak larut, pH 9.0 dan 70 minit masa inkubasi. Keputusan eksperimen menunjukkan bahawa GA sebagai penyambung lintang pada keadaan optimum mampu mencapai sangkutan GA yang lebih baik untuk penjerapan protin yang terakhir. Kajian lanjut telah meneroka penyediaan polianilina-ferum (III) oksida (PANI/Fe2O3) yang konduktif yang berfungsi sebagai pemindaharuh isyarat elektrik, untuk menukar interaksi elektrokimia kepada satu isyarat ketahanan yang dapat diukur. PANI disintesis melalui pempolimeran beroksida bagi monomer anilina (AM) dengan kehadiran ammonium persulfat (APS). 0.2 M kepekatan AM and 1:3 nisbah sukatan AM:APS didapati menghasilkan PANI dengan tindakbalas konduktiviti ionik yang tertinggi pada 7.565 + 0.262 mS/cm. Kajian telah mengkaji semula aspek menarik bagi keadaan yang berlainan oleh PANI sebagai satu bahan konduktif yang penting untuk peranti elektronik/elektrik. Seterusnya, penderia amperometri berasaskan-membran telah dipasang dan aktiviti elektrokimia antara asid askorbat (AA, analit sasaran) dan askorbat oksidase (analit tawanan) telah dinilai. Had pengesanan bagi penderia didapati pada 5.77 mM dan pemalar Michaelis-Menten (Km) dikira sebanyak 26.76 mM. Tindakbalas bagi spektroskopi galangan elektrokimia (EIS), voltammetry kitaran (CV) dan voltammograms denyutan kebezaan (DPV) dijalankan untuk menganalis dua lapis elektrokimia ke atas elektrod kerja. Membran nilon-6 yang dibangunkan telah menyediakan satu pelantar pengesanan yang menjanjikan untuk pembinaan penderia dan sesuai untuk aplikasi praktikal dalam analisis farmaseutikal atau klinikal dan tanaman pertanian.
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Millions of people die due to the unavailability and inaccessible of diagnostics facilities especially in controlling crucial diseases, which led to the progressive development of biosensor. Unfortunately, direct oxidation of target analyte at the bare electrode of a biosensor is an irreversible process and requires a high overpotential, resulted in electrode fouling and low sensitivity. Nylon-6 membrane modified electrodes have been proposed to overcome this problem. As an immunoassay, the biochemical reaction between target and capture analyte takes place on the surface of the nylon-6 membrane, then translated to measurable resistance signal. The present study elucidates the morphology characteristic of nylon-6 as protein immobilization membrane and their influences in biological recognition interface. The nylon-6 membranes were synthesized via dry phase inversion with different concentration of nylon-6 polymer in a range of 16 wt. % to 28 wt.% and different types of additives (water and methanol) in dope solution. The developed nylon-6 membrane, N-16B, with 16 wt. % nylon-6 polymer and methanol as non-solvent had demonstrated the fastest lateral wicking speed (1.07 mm/sec) and excellent protein immobilization capacity (1,650.00 + 85.84 μg/cm3). The current study revealed the importance of membrane morphology that affects the sensitivity and effectiveness of an immuno-sensing device. The stability issue in biomolecule immobilization has been overcomed by integrating glutaraldehyde (GA) onto nylon-6 membrane prior to protein immobilization. The preliminary study was carried out to study the effect of incubation time, pH and concentration of GA on protein binding of the nylon-6 polymer. The optimum conditions of GA integration were found at 40 minutes of incubation time, pH 7.5 and 1 wt. % of GA concentration. Statistical analysis using crossed design programme was performed and the optimum GA integration conditions from the statistical analysis were found at 25 wt. % of the nylon-6 polymer, 75 wt. % of mixture solvent + nonsolvent, pH 9.0 and 70 minutes of incubation time. The experimental results showed that the GA as a cross-linker reagent at optimum conditions was able to achieve better GA attachment for latter protein immobilization. Further study has been explored on the preparation of conductive polyaniline-iron oxide (PANI/Fe2O3) that served as the electrical signal transducer, to convert the electrochemical interactions to a measurable resistance signal. PANI was synthesized via oxidative polymerization of aniline monomer (AM) in the presence of ammonium persulfate (APS). 0.2 M concentration of AM and 1:3 volume ratio of AM:APS were found to produce PANI logged with the highest ionic conductivity response at 7.565 + 0.262 mS/cm. The study had reviewed the interesting aspect of different state of PANI as one of the important conducting material for electronic/electrical devices. Subsequently, a membrane-based amperometric sensor was assembled and electrochemical activities ascorbic acid (AA, target analyte) and ascorbate oxidase (capture analyte) were evaluated. The detection limit of the sensor was found at 5.77 mM and the Michaelis–Menten constant (Km) was calculated as 26.76 mM. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammograms (DPV) responses were carried out to analyze the electrochemical double layer on the working electrode. The developed nylon-6 membrane has provided a promising detection platform for sensor construction and suitable for practical application in pharmaceutical or clinical analysis and agricultural crops.
Development of electrochemical biosensor based on nylon-6 membrane_Roswani Shaimi_K4_2019_MYMY