Mahbuba Jannat - Academia.edu (original) (raw)

Papers by Mahbuba Jannat

Ph.DDOCTOR OF PHILOSOPHY (FOE

ACS Applied Materials & Interfaces, 2020

Millifluidic devices decorated with enzymes have been used for enzymatic reactions in continuous ... more Millifluidic devices decorated with enzymes have been used for enzymatic reactions in continuous processes, but low enzymatic activity and enzyme leaching remain as challenges. Herein, we develop a strategy to embed cross-linked enzyme aggregates (CLEAs) on the surfaces of millifluidic devices to achieve higher enzymatic activity and better stability. Catalase was chosen as a model enzyme to degrade H2O2 in wastewater samples. Firstly, CLEA of catalase (153±10 nm) was formed by simultaneous precipitation and crosslinking with 25.0 wt % acetonitrile containing 0.025 wt % glutaraldehyde in a millifluidic device. To immobilize CLEA, we first swell a piece of plastic tubing by using 5.0 wt % acetonitrile and then immerse it in an aqueous solution with 5.0 wt % (3-Aminopropyl) triethoxysilane (APTES) and 5.0 wt % Dextran polyaldehyde (DPA) subsequently. After CLEA is absorbed inside the expanded polymer network of the tubing, the tubing is tightened by using vacuum to secure the immobilized CLEA. The millifluidic device decorated with CLEA of catalase has total activity of 660 U for degradation of H2O2, and it shows good stability under a flow rate of 200 µL/min. The tubing can be used to degrade 0.1 wt % H2O2 solution continuously for 3 h or remove 2 wt % residual H2O2 in wastewater for 2 h. The technique is general enough and can be applied to other types of enzymes for continuous enzymatic reactions.

AIP Conference Proceedings, 2019

Plastic is made from wide range of synthetic or semi-synthetic organic compounds that are malleab... more Plastic is made from wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects. The yearly use of plastics in Bangladesh has grown to 12,00,000 metric tons in 2018. A part of it is recycled but Bangladesh still generates 8,00,000 tons of plastic wastes every year. Disposal of plastic is of great environmental concern now-a-days, as it seizes centuries to decompose if left at its own. Conversion of waste plastic to fuel oil mitigates both plastic pollution problem and fuel crisis. This study focuses on the thermal degradation of polypropylene plastic wastes by pyrolysis process without any catalyst to produce fuel oil. A small scale batch type set up was built to perform thermal degradation of plastic. Polypropylene plastic wastes were cleaned, shredded and pyrolysed from 300-400°C for 60 minutes in this setup. The yield products were liquid fuel oil, gas and black solid plastic residue. These pyrolysed products were collected and characterized by different experimental and analytical methods. The conversion efficiency of oil achieved by the set up was 78% by mass. 73% plastic waste volume reduction was obtained by converting it into fuel oil from solid waste. Equivalent energy output calculated from measured heating value of pyrolytic oil which was obtained from 60 minutes pyrolysis was 12.8MJ/kg. Properties of the fuel oil produced such as-calorific value, viscosity, density, flash point and water content were measured and all of these properties were found to be very close to that of diesel and octane.The products obtained have potential values for further use as fuel oil, lubricating oil, diesel supplement etc which may provide solution as alternative energy resource.

Sensors and Actuators B: Chemical, 2019

Abstract Protease inhibitors are essential drug molecules which can be used for treatments of pro... more Abstract Protease inhibitors are essential drug molecules which can be used for treatments of protease-related diseases. Herein, we report an LC-based protease inhibition assay built inside a millifluidic device. This assay can be used to study the inhibition efficiency and reversibility of pefabloc (a serine protease inhibitor) against proteases. LC is employed for the detection of peptide fragments produced from protease activity inside the millifluidic device. LC gives a bright spot when the amount of peptide fragment exceeds a minimum value. By using this assay, we find that IC50 value of pefabloc for the immobilized protease is 0.45 mg/mL, which is lower than the IC50 value of pefabloc (0.90 mg/mL) obtained in a homogeneous assay. Moreover, proteases can be immobilized on the millifluidic device to build a heterogeneous protease assay. In this assay, pefabloc blocks the immobilized protease irreversibly after 60 min, which is longer than that in a homogenous protease assay. This reversibility study provides useful information about the transition period of pefabloc from reversible to irreversible inhibition. This protease inhibition assay is potentially useful for high throughput screening of unknown proteases and their inhibitor in a small sample volume. Moreover, this method can be used for dosage test of novel drug molecules which are protease inhibitors.

Sensors and Actuators B: Chemical, 2018

Abnormal protease activities are associated with cancers, vascular diseases and Alzheimer disease... more Abnormal protease activities are associated with cancers, vascular diseases and Alzheimer diseases. Therefore, detection of protease activities has become increasingly important in recent years. Herein, we report a semi-quantitative, liquid crystal (LC)-based protease assay for naked-eye detection of protease activity. In this assay, casein molecules are cleaved by proteases into small peptide fragments, which can be quantified either by using Lowry's method or using LC. In the latter, peptide fragments adsorb on a solid surface and disrupt LC to produce a bright spot for naked-eye detection. The bright spot is observed only when the surface-adsorbed peptide density exceeds a critical value. In the assay, a major challenge is how to separate undigested casein and remaining protease from peptide fragments to prevent their interferences with LC. To overcome this issue, trichloroacetic acid (TCA) is added to precipitate casein and proteases. By using the assay, we are able to detect 10 ng/mL of protease (activity 7.23 U/mg protease, R 2 = 0.991) or 6.5 g/mL of peptide fragments. Finally, a continuous protease assay is developed to minimize manual sampling and reduce errors in kinetic studies.

Langmuir, 2018

Immobilized enzymes can be used to catalyze biochemical reactions in a batch process, however, it... more Immobilized enzymes can be used to catalyze biochemical reactions in a batch process, however, it is more difficult to use them in a continuous process. Herein, we develop an enzyme immobilization technique for flexible tubing surfaces, which can be used to catalyze biochemical reactions in a continuous process. In this technique, the tubing is first treated with (3-aminopropyl) triethoxysilane (APTES) at 50 o C and baked at 100 o C in a vacuum to form a network of reactive amine functional group on the inner tubing surface. Subsequently, dextran polyaldehyde (DPA), a polymeric cross-linker, is used to immobilize crude protease extract and catalase for hydrolyzing casein and degrading H 2 O 2 , respectively, in a continuous process. The immobilized proteases are highly stable even after a long-term storage at 4 o C. After 12 weeks of storage, 90% of the original protease activity can be preserved. Meanwhile, the immobilized catalase is able to degrade 0.1 % H 2 O 2 solution flowing at 5 µL/min. The immobilization technique is potentially useful for bioassays and industrial wastewater treatments when continuous processes are preferred.

Ph.DDOCTOR OF PHILOSOPHY (FOE

ACS Applied Materials & Interfaces, 2020

Millifluidic devices decorated with enzymes have been used for enzymatic reactions in continuous ... more Millifluidic devices decorated with enzymes have been used for enzymatic reactions in continuous processes, but low enzymatic activity and enzyme leaching remain as challenges. Herein, we develop a strategy to embed cross-linked enzyme aggregates (CLEAs) on the surfaces of millifluidic devices to achieve higher enzymatic activity and better stability. Catalase was chosen as a model enzyme to degrade H2O2 in wastewater samples. Firstly, CLEA of catalase (153±10 nm) was formed by simultaneous precipitation and crosslinking with 25.0 wt % acetonitrile containing 0.025 wt % glutaraldehyde in a millifluidic device. To immobilize CLEA, we first swell a piece of plastic tubing by using 5.0 wt % acetonitrile and then immerse it in an aqueous solution with 5.0 wt % (3-Aminopropyl) triethoxysilane (APTES) and 5.0 wt % Dextran polyaldehyde (DPA) subsequently. After CLEA is absorbed inside the expanded polymer network of the tubing, the tubing is tightened by using vacuum to secure the immobilized CLEA. The millifluidic device decorated with CLEA of catalase has total activity of 660 U for degradation of H2O2, and it shows good stability under a flow rate of 200 µL/min. The tubing can be used to degrade 0.1 wt % H2O2 solution continuously for 3 h or remove 2 wt % residual H2O2 in wastewater for 2 h. The technique is general enough and can be applied to other types of enzymes for continuous enzymatic reactions.

AIP Conference Proceedings, 2019

Plastic is made from wide range of synthetic or semi-synthetic organic compounds that are malleab... more Plastic is made from wide range of synthetic or semi-synthetic organic compounds that are malleable and so can be molded into solid objects. The yearly use of plastics in Bangladesh has grown to 12,00,000 metric tons in 2018. A part of it is recycled but Bangladesh still generates 8,00,000 tons of plastic wastes every year. Disposal of plastic is of great environmental concern now-a-days, as it seizes centuries to decompose if left at its own. Conversion of waste plastic to fuel oil mitigates both plastic pollution problem and fuel crisis. This study focuses on the thermal degradation of polypropylene plastic wastes by pyrolysis process without any catalyst to produce fuel oil. A small scale batch type set up was built to perform thermal degradation of plastic. Polypropylene plastic wastes were cleaned, shredded and pyrolysed from 300-400°C for 60 minutes in this setup. The yield products were liquid fuel oil, gas and black solid plastic residue. These pyrolysed products were collected and characterized by different experimental and analytical methods. The conversion efficiency of oil achieved by the set up was 78% by mass. 73% plastic waste volume reduction was obtained by converting it into fuel oil from solid waste. Equivalent energy output calculated from measured heating value of pyrolytic oil which was obtained from 60 minutes pyrolysis was 12.8MJ/kg. Properties of the fuel oil produced such as-calorific value, viscosity, density, flash point and water content were measured and all of these properties were found to be very close to that of diesel and octane.The products obtained have potential values for further use as fuel oil, lubricating oil, diesel supplement etc which may provide solution as alternative energy resource.

Sensors and Actuators B: Chemical, 2019

Abstract Protease inhibitors are essential drug molecules which can be used for treatments of pro... more Abstract Protease inhibitors are essential drug molecules which can be used for treatments of protease-related diseases. Herein, we report an LC-based protease inhibition assay built inside a millifluidic device. This assay can be used to study the inhibition efficiency and reversibility of pefabloc (a serine protease inhibitor) against proteases. LC is employed for the detection of peptide fragments produced from protease activity inside the millifluidic device. LC gives a bright spot when the amount of peptide fragment exceeds a minimum value. By using this assay, we find that IC50 value of pefabloc for the immobilized protease is 0.45 mg/mL, which is lower than the IC50 value of pefabloc (0.90 mg/mL) obtained in a homogeneous assay. Moreover, proteases can be immobilized on the millifluidic device to build a heterogeneous protease assay. In this assay, pefabloc blocks the immobilized protease irreversibly after 60 min, which is longer than that in a homogenous protease assay. This reversibility study provides useful information about the transition period of pefabloc from reversible to irreversible inhibition. This protease inhibition assay is potentially useful for high throughput screening of unknown proteases and their inhibitor in a small sample volume. Moreover, this method can be used for dosage test of novel drug molecules which are protease inhibitors.

Sensors and Actuators B: Chemical, 2018

Abnormal protease activities are associated with cancers, vascular diseases and Alzheimer disease... more Abnormal protease activities are associated with cancers, vascular diseases and Alzheimer diseases. Therefore, detection of protease activities has become increasingly important in recent years. Herein, we report a semi-quantitative, liquid crystal (LC)-based protease assay for naked-eye detection of protease activity. In this assay, casein molecules are cleaved by proteases into small peptide fragments, which can be quantified either by using Lowry's method or using LC. In the latter, peptide fragments adsorb on a solid surface and disrupt LC to produce a bright spot for naked-eye detection. The bright spot is observed only when the surface-adsorbed peptide density exceeds a critical value. In the assay, a major challenge is how to separate undigested casein and remaining protease from peptide fragments to prevent their interferences with LC. To overcome this issue, trichloroacetic acid (TCA) is added to precipitate casein and proteases. By using the assay, we are able to detect 10 ng/mL of protease (activity 7.23 U/mg protease, R 2 = 0.991) or 6.5 g/mL of peptide fragments. Finally, a continuous protease assay is developed to minimize manual sampling and reduce errors in kinetic studies.

Langmuir, 2018

Immobilized enzymes can be used to catalyze biochemical reactions in a batch process, however, it... more Immobilized enzymes can be used to catalyze biochemical reactions in a batch process, however, it is more difficult to use them in a continuous process. Herein, we develop an enzyme immobilization technique for flexible tubing surfaces, which can be used to catalyze biochemical reactions in a continuous process. In this technique, the tubing is first treated with (3-aminopropyl) triethoxysilane (APTES) at 50 o C and baked at 100 o C in a vacuum to form a network of reactive amine functional group on the inner tubing surface. Subsequently, dextran polyaldehyde (DPA), a polymeric cross-linker, is used to immobilize crude protease extract and catalase for hydrolyzing casein and degrading H 2 O 2 , respectively, in a continuous process. The immobilized proteases are highly stable even after a long-term storage at 4 o C. After 12 weeks of storage, 90% of the original protease activity can be preserved. Meanwhile, the immobilized catalase is able to degrade 0.1 % H 2 O 2 solution flowing at 5 µL/min. The immobilization technique is potentially useful for bioassays and industrial wastewater treatments when continuous processes are preferred.