Biofunctional hybrid structures—cell–silicon hybrids for applications in biomedicine and bioinformatics

Microbial lipases and their industrial applications: a comprehensive review

Lipases are very versatile enzymes, and produced the attention of the several industrial processes. Lipase can be achieved from several sources, animal, vegetable, and microbiological. The uses of microbial lipase market is estimated to be USD 425.0 Million in 2018 and it is projected to reach USD 590.2 Million by 2023, growing at a CAGR of 6.8% from 2018. Microbial lipases (EC 3.1.1.3) catalyze the hydrolysis of long chain triglycerides. The microbial origins of lipase enzymes are logically dynamic and proficient also have an extensive range of industrial uses with the manufacturing of altered molecules. The unique lipase (triacylglycerol acyl hydrolase) enzymes catalyzed the hydrolysis, esterification and alcoholysis reactions. Immobilization has made the use of microbial lipases accomplish its best performance and hence suitable for several reactions and need to enhance aroma to the immobilization processes. Immobilized enzymes depend on the immobilization technique and the carrier type. The choice of the carrier concerns usually the biocompatibility, chemical and thermal stability, and insolubility under reaction conditions, capability of easy rejuvenation and reusability, as well as cost proficiency. Bacillus spp., Achromobacter spp., Alcaligenes spp., Arthrobacter spp., Pseudomonos spp., of bacteria and Penicillium spp., Fusarium spp., Aspergillus spp., of fungi are screened large scale for lipase production. Lipases as multipurpose biological catalyst has given a favorable vision in meeting the needs for several industries such as biodiesel, foods and drinks, leather, textile, detergents, pharmaceuticals and medicals. This review represents a discussion on microbial sources of lipases, immobilization methods increased productivity at market profitability and reduce logistical liability on the environment and user.

Measuring fluorescence-lifetime and bio-impedance sensors for cell based assays using a network analyzer integrated circuit

Cell culture assays for therapeutic drug screening today are fully automated. Vitality of the cells is monitored by different sensors. For such a system, we propose a new reader unit, which is capable of reading two different fluorescent sensors and electrical impedance in 24-well-plates. Main goals are to reduce cost, complexity and size while achieving a similar performance as the existing reader unit. To achieve this, measurement electronics and signal paths for frequency domain fluorescence and bio-impedance measurement are combined. Central component is an integrated circuit for impedance spectroscopy. A new compact and economic optical setup is developed to read two different sensor spots on the bottom of the well. Measurement errors introduced by different components like DFT leakage, and frequency dependent signal delays are evaluated and compensated. A set of commercially available fluorescence sensor spots is used to verify the read out performance. The results are usable, with noise slightly higher than commercial readers. To verify the impedance measurement accuracy, measurements of known resistances are conducted. In the relevant impedance and frequency range for biological applications a suitable accuracy is achieved. Due to the higher sampling rate of the new reader, the higher noise can be reduced through averaging. The new system is significantly smaller and cheaper to manufacture than commercially available devices.

Application of algae-biosensor for environmental monitoring

Environmental problems including water and air pollution, over fertilization, insufficient wastewater treatment and even ecological disaster are receiving greater attention in the technical and scientific area. In this paper, a method for water quality monitoring using living green algae (Chlorella Kessleri) with the help of the intelligent mobile lab (IMOLA) is presented. This measurement used two IMOLA systems for measurement and reference simultaneously to verify changes due to pollution inside the measurement system. The IMOLA includes light emitting diodes to stimulate photosynthesis of the living algae immobilized on a biochip containing a dissolved oxygen microsensor. A fluid system is used to transport algae culture medium in a stop and go mode; 600s ON, 300s OFF, while the oxygen concentration of the water probe is measured. When the pump stops, the increase in dissolved oxygen concentration due to photosynthesis is detected. In case of a pollutant being transported toward the algae, this can be detected by monitoring the photosynthetic activity. Monitoring pollution is shown by adding emulsion of 0,5mL of Indonesian crude palm oil and 10mL algae medium to the water probe in the biosensor.

Automated platform for sensor-based monitoring and controlled assays of living cells and tissues

Cellular assays have become a fundamental technique in scientific research, pharmaceutical drug screening or toxicity testing. Therefore, the requirements of technical developments for automated assays raised in the same rate. A novel measuring platform was developed, which combines automated assay processing with label-free high-content measuring and real-time monitoring of multiple metabolic and morphologic parameters of living cells or tissues. Core of the system is a test plate with 24 cell culture wells, each equipped with opto-chemical sensor-spots for the determination of cellular oxygen consumption and extracellular acidification, next to electrode-structures for electrical impedance sensing. An automated microscope provides the optical sensor read-out and allows continuous cell imaging. Media and drugs are supplied by a pipetting robot system. Therefore, assay can run over several days without personnel interaction. To demonstrate the performance of the platform in physiologic assays, we continuously recorded the kinetics of metabolic and morphologic parameters of MCF-7 breast cancer cells under the influence of the cytotoxin chloroacetaldehyde. The data point out the time resolved effect kinetics over the complete treatment period. Thereby, the measuring platform overcomes problems of endpoint tests, which cannot monitor the kinetics of different parameters of the same cell population over longer time periods.

Determination of dynamic doxorubicin-EC50 value in an automated high-content workstation for cellular assays

To overcome the problems of endpoint tests routinely required for EC50 determination, we utilized a novel automated high-content workstation and calculated a time-resolved EC50 value of MCF-7 mamma carcinoma cells treated with a pharmacologic agent. Measuring parameters were the cellular oxygen consumption and the extracellular acidification. These parameters were detected in real-time and label free with optochemical sensor spots in a modified 24-well sensor plate. In particular, the objective was to compare the measuring data of the workstation with a classical standard resazurin cell assay and to transfer the benefit of continuously recorded metabolic data of the workstation to practical time-resolved information about the effect of the applied active reagent (doxorubicin). MCF-7 cells were treated with a broad range of doxorubicin concentrations (100 μM to 1 nM) over 24 h and cellular activities were investigated with both, the resazurin assay and the automated workstation. Twenty-four hours after treatment, the resazurin assay showed an EC50 value (6.3 μM) which was about one decade above the value obtained from oxygen consumption rate (0.37 μM) and extracellular acidification rate (0.72 μM), measured with the workstation. Presumably, the differences are due to the different metabolic nature and regulation behind these measuring parameters. By polynomial fitting of continuously recorded metabolic data, we were able to point out a dynamic, time-resolved EC50 characteristic for different time points. The workstation is a powerful tool to record in vitro kinetic data of pharmacologic effects in vital cells in an automated experimental run.

The use of digital signal processors (DSPs) in real-time processing of multi-parametric bioelectronic signals

In many cases of bioanalytical measurement, calculation of large amounts of data, analysis of complex signal waveforms or signal speed can overwhelm the performance of microcontrollers, analog electronic circuits or even PCs. One method to obtain results in real time is to apply a digital signal processor (DSP) for the analysis or processing of measurement data. In this paper we show how DSP-supported multiplying and accumulating (MAC) operations, such as time/frequency transformation, pattern recognition by correlation, convolution or filter algorithms, can optimize the processing of bioanalytical data. Discrete integral calculations are applied to the acquisition of impedance values as part of multi-parametric sensor chips, to pH monitoring using light-addressable potentiometric sensors (LAPS) and to the analysis of rapidly changing signal shapes, such as action potentials of cultured neuronal networks, as examples of DSP capability.

Poly(dimethylsiloxane) thin films as biocompatible coatings for microfluidic devices: cell culture and flow studies with glial cells

Oxygen plasma treatment of poly(dimethylsiloxane) (PDMS) thin films produced a hydrophilic surface that was biocompatible and resistant to biofouling in microfluidic studies. Thin film coatings of PDMS were previously developed to provide protection for semiconductor-based microoptical devices from rapid degradation by biofluids. However, the hydrophobic surface of native PDMS induced rapid clogging of microfluidic channels with glial cells. To evaluate the various issues of surface hydrophobicity and chemistry on material biocompatibility, we tested both native and oxidized PDMS (ox-PDMS) coatings as well as bare silicon and hydrophobic alkane and hydrophilic oligoethylene glycol silane monolayer coated under both cell culture and microfluidic studies. For the culture studies, the observed trend was that the hydrophilic surfaces supported cell adhesion and growth, whereas the hydrophobic ones were inhibitive. However, for the fluidic studies, a glass-silicon microfluidic device coated with the hydrophilic ox-PDMS had an unperturbed flow rate over 14 min of operation, whereas the uncoated device suffered a loss in rate of 12%, and the native PDMS coating showed a loss of nearly 40%. Possible protein modification of the surfaces from the culture medium also were examined with adsorbed films of albumin, collagen, and fibrinogen to evaluate their effect on cell adhesion.

Simultaneous measurement of cellular respiration and acidification with a single CMOS ISFET

In vivo, the pH value and oxygen partial pressure are the most important physico-chemical parameters in the microenvironment of human tissues. In vitro, the extracellular acidification rate of cell cultures is an indicator of global cellular metabolism, while the rate of oxygen consumption is a measure of mitochondrial activity. Earlier approaches had the disadvantage that these two values had to be measured with two separate sensors at different loci within the tissue or cell culture. Furthermore, conventional Clark-type oxygen sensors are not very compatible for miniaturisation, making it impossible to measure at small cell volumes or even at the single cell level. We have, therefore, developed an ISFET based sensor structure which is able to measure both pH and oxygen partial pressure. This sensor structure was tested in vitro for simultaneous records of cellular acidification and respiration rates at the same site within the cell culture. This sensor is manufactured by a CMOS-process.