Mohammad Mosharraf Hossain

Toward the development of smart and low cost point-of-care biosensors based on screen printed electrodes

Abstract Screen printing technology provides a cheap and easy means to fabricate disposable electrochemical devices in bulk quantities which are used for rapid, low-cost, on-site, real-time and recurrent industrial, pharmaceutical or environmental analyses. Recent developments in micro-fabrication and nano-characterization made it possible to screen print reproducible feature on materials including plastics, ceramics and metals. The processed features forms screen-printed disposable biochip (SPDB) upon the application of suitable bio-chemical recognition receptors following appropriate methods. Adequacy of biological and non-biological materials is the key to successful biochip development. We can further improve recognition ability of SPDBs by adopting new screen printed electrode (SPE) configurations. This review covers screen-printing theory with special emphasis on the technical impacts of SPE architectures, surface treatments, operational stability and signal sensitivity. The application of SPE in different areas has also been summarized. The article aims to highlight the state-of-the-art of SPDB at the laboratory scale to enable us in envisaging the deployment of emerging SPDB technology on the commercial scale.

Vegetative propagation of Litsea monopetala, a wild tropical medicinal plant: Effects of indole-3-butyric acid (IBA) on stem cuttings

In this study we investigated the rooting ability and the growth performance of juvenile single-node leafy stem cuttings of Litsea monopetala (Roxb) Pers. collected from two mature mother trees preserved in the hill forest of Chittagong district, Bangladesh. The rooting ability of cuttings was studied under 0%, 0.1%, 0.2% and 0.4% indole-3-butyric acid (IBA) treatments. Significantly better rooting response (p ≤ 0.05) was observed with 0.1% IBA compared to control (0% IBA). The mean number of roots and the length of the longest root of cuttings in different treatments showed no significant difference (p≤0.05). After transfer into polythene bags from non-mist propagator, rooted cuttings treated with 0%, 0.1% and 0.2% IBA demonstrated the highest (100 ± 0.00%) survival capacity. The mean number of shoots developed in cuttings in the polythene bags in first three weeks varied significantly (p≤0.05) among the treatments. Effects of three fertilizer treatments, viz. T0 (no fertilizer), T1 (10g Urea, 20g TSP, 10g MOP dissolved in 1 L water) and T2 (10g Urea, 20g TSP, 10g MOP dissolved in 2 L water) on initial growth of stecklings were also measured over a 90-days period. The increment of leaf area of stecklings was significantly higher (p≤0.05) under T0 compared with that under T1 and T2 while the increment of stem length, collar diameter and root biomass varied insignificantly among different fertilizer treatments. The results suggest that rooting juvenile single-node leafy stem cuttings could be an effective mean of regenerating L. monopetala. The application of 0.1% IBA concentration is recommended for rooting of juvenile leafy stem cuttings and application of fertilizer appeared unnecessary for the subsequent growth of stecklings in polythene bags.

Trends and advances in food analysis by real-time polymerase chain reaction.

Analyses to ensure food safety and quality are more relevant now because of rapid changes in the quantity, diversity and mobility of food. Food-contamination must be determined to maintain health and up-hold laws, as well as for ethical and cultural concerns. Real-time polymerase chain reaction (RT-PCR), a rapid and inexpensive quantitative method to detect the presence of targeted DNA-segments in samples, helps in determining both accidental and intentional adulterations of foods by biological contaminants. This review presents recent developments in theory, techniques, and applications of RT-PCR in food analyses, RT-PCR addresses the limitations of traditional food analyses in terms of sensitivity, range of analytes, multiplexing ability, cost, time, and point-of-care applications. A range of targets, including species of plants or animals which are used as food ingredients, food-borne bacteria or viruses, genetically modified organisms, and allergens, even in highly processed foods can be identified by RT-PCR, even at very low concentrations. Microfluidic RT-PCR eliminates the separate sample-processing step to create opportunities for point-of-care analyses. We also cover the challenges related to using RT-PCR for food analyses, such as the need to further improve sample handling.

Effects of shifting cultivation on biological and biochemical characteristics of soil microorganisms in Khagrachari hill district, Bangladesh

We collected soil samples from two representative sites at Aatmile of Khagarachari hill district in Chittagong Hill Tracts. One of the sites was under shifting cultivation and the other an adjacent 13-year old teak plantation. Both sites were in the same physiographic condition and same aspect with parable soil type, which enabled us to measure the effects of shifting cultivation on soil micro-flora. We studied soil physicochemical properties and the biochemical and biological properties of soil microbes. Moisture and organic matter content as well as fungi and bacterial populations, both in surface and subsurface soils, were significantly (p ≤0.001) lower in shifting cultivated soils compared to soils not under shifting cultivation, i.e. the teak plantation site. The most abundant bacteria in surface (0–10 cm) and sub-surface (10–20 cm) soils under shifting cultivation were Pseudomonas diminuta and Shigella, respectively, while in corresponding soil layers of teak plantation, predominant microbes were Bacillus firmus (0–10 cm) and Xanthomonas (10–20 cm). The microbial population differences cannot be explained by soil texture differences because of the textural similarity in soils from the two sites but could be related to the significantly lower moisture and organic matter contents in soils under shifting cultivation.

Conservation of a river for biodiversity and ecosystem services: the case of the Halda – the unique river of Chittagong, Bangladesh

ABSTRACT The Halda is the only tidal freshwater river in the world where major Indian carps spawn naturally. The river also serves as a source of drinking and irrigation water, a fishing ground and a means of water transportation. We investigated the biodiversity and ecosystem services of the Halda in the context of the conservation of this river in cooperation with river-dependent community and challenges thereof. The primary and secondary field data have been collected from relevant government and non-governmental organizations using both structured and semi-structured questionnaires. According to our calculations, the total economic worth of benefits derived from provisioning services of the Halda was approximately BDT (Bangladesh Taka) 1753 million. Irrigation and drinking water were the major contributors with BDT 1333 and 122 million, respectively. Carp spawning has lower primary economic worth (BDT 10 million) but it has a much bigger impact, as it supplies fish fries to the whole country. The river supports temporary and permanent livelihood for egg and fry collectors (approximately 2000), fishermen (approximately 350), boatmen (approximately 250), boat building and mending (approximately 150), sand quarrying (approximately 760), which creates a cumulative worth of BDT 283 million. The sustained flow of provisioning service from the Halda explains the willingness to contribute money (54 million) and time (average 6.6 hours/month) by local communities for conserving this river. Half of the respondents, though illiterate, have shown genuine concern about the future of the river. The sustainable flow of services and enhancement in their economic output require conservation and scientific management of the Halda. The community willingness and its dependence, as unearthed by our research, provides compelling ground for community-based conservation and management of the river. Future conservation projects and management plans for this river should involve local communities to avail their willingness to conserve this river while sustaining their livelihood through enhancement of economic output from it.

State of research on carbon sequestration in Bangladesh: a comprehensive review

ABSTRACT A deep interest is evident in carbon sequestration modeling in Bangladesh from the development of several allometric equations to estimate carbon sequestration by plants. It is linked to the evolving carbon offsetting approaches, for example, Clean Development Mechanism (CDM) and the REDD+, which require certifiable estimate of carbon captured by trees and forests. This review compiled a snapshot of state of the art in carbon modeling in Bangladesh. More than half of the published research focused on the development of allometric equations and forest carbon estimation. The comparison among available studies was challenging due to the use of different terminologies and assumptions and arbitrary combinations of parameters including age, topography, season, slope, crown diameter, etc. The spatial distribution of reports indicated narrow geographical focus outside forests in Chittagong and Sundarbans. Surprisingly, no attempts were evident to explore carbon stocks at the Chittagong Hill Tracts (CHTs) where majority of pristine forest areas of the country occurs. Bangladesh is likely to reforest the vast deforested areas in CHTs under CDM and REDD+ projects which requires extensive carbon modeling. Majority of the reports used conversion factor to calculate soil carbon instead of analytical estimation which might cause inaccurate estimation of soil carbon. Blue carbon assessment and policy implication of carbon studies are two areas where insufficient attention is evident. Bangladesh apparently needs to conduct wide-scale carbon modeling through the integration of GIS, remote sensing, etc to increase precision and accuracy of carbon stock assessments. .

CHAPTER 16:Isothermal DNA Amplification Strategies for Food Biosensors

Rapid, sensitive, and selective pathogen detection in food industry is of paramount importance for global health. Currently available diagnostic assays based on polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA), which are time-consuming, complex, and relatively expensive, are ill suited to meet the current requirements for pathogen detection in the food industry. Different isothermal amplification techniques are faster, more sensitive, and more robust compared to other standard pathogen detection methods. Modern techniques are based on molecular diagnostics integrated with various detection modalities such as bioanalytical, electrochemical, and luminescence techniques to ensure more sensitive and specific detection processes. Here, we review conventional and non-conventional techniques for pathogen detection on food industry. We focus mainly on nucleic acid detection integrated with electrochemical biosensors. In addition, the applications of nanoparticle biosensors and colorimetric sensors are reviewed. Lab-on-a-chip (LOC) devices based on design strategies utilizing isothermal amplification for pathogen detection are also discussed.