In a complex field such as bio-molecular diagnostics it is significant to know the behaviour of molecules in each assay before they are available for real time testing on devices. With numerous deadly diseases around mankind, behaviour of bio-molecules associated with each of these diseases becomes a first priority for the molecular diagnostics. The purpose of this review is to highlight the behaviour of enzymatic molecules using vibrations in conjunction with Micro-Electro-Mechanical Systems (MEMS) structures, which can be used as a diagnostic tool in a rapidly growing field of medical discipline. The authors introduce piezo-electric actuators in the experimental set-up that is used to accelerate the enzymatic molecular reaction in minute quantities of the reactant. The discussion for the above method is well supported by a body of literature from both biomedical and mechanical engineering. These enzymes are made to interact with their respective anti-bodies, whose reaction can be detected using many methods among which fluorescence spectroscopy is of preference and further detected using specific MEMS structures whose changes are detected through optical means. The results described here are intended to give a methodological approach to the creation of device in the future in the medical field for the detection of bio-molecules. Experimental results include pictures taken during shaking with piezo-electric stacks; fluorescence spectrometer results confirming a reaction between the enzyme and its anti-body and the biochemical reaction-taking place on the surface of the cantilever beams. The intent of this review is to better understand the behaviour of an enzymatic molecule under the influence of vibrations. With insight into the principles underlying the operation of the vibration experiment, the results could help to evaluate the value of a device that could be used in the molecular diagnostics in a simpler, faster and less expensive way.
Medical applications often require the detection of specific peptides that are indicators of patients' specific medical conditions. The identification of such peptides is to some extent cumbersome and requires specialized equipment, specialized personnel and the results of the test may come as false negative or false positive. This paper presents the experimental results that directed towards the developments of a device and measurement system that is precisely detecting the reaction time between a peptide and a corresponding reaction match. A series of reaction signatures are identified and presented in the paper. Besides, SEM analysis of the peptides after the reaction confirms the existence of the signatures as the ones recorded by the authors. The proposed device could be miniaturized and a potential solution of the optical-based measurement system is presented and discussed. Serious challenges such as packaging or peptide manipulation are also discussed. The configuration of the sensing element is essential in producing the desired sensitivity of the device. A sensitivity analysis is carried out to prove that concentrations of fraction of ppm are detectable through this method.
Diagnosis and monitoring of critical diseases such as acute myocardial infarction (AMI) require a quantitative analysis of biological molecules. A high-throughput identification of these biological molecules can be generated by using micro-electro-mechanical systems (MEMS) structures like simple cantilever beams, which respond to the intermolecular forces resulting from binding these molecules. Biochemical markers like troponin C are considered the primary markers for myocardial injury and have generated considerable interest. A 26-residue lytic membrane protein of bee venom melittin (ME) is chosen to interact with rabbit skeletal muscle troponin C (TnC) on the surface of the cantilever beams. An optical beam deflection method is employed to identify the enzymatic reaction on the surface of the cantilever due to these proteins. Identification of these proteins is also done using fluorescence spectroscopy (FS) to compliment the optical monitored deflection method. A second set of proteins like horse raddish peroxide (HRP) and hydrogen peroxide (H2O2) are applied to atomic force microscopy (AFM) cantilever beams to study their behavior under the enzymatic reactions of proteins. Identification of these proteins is done using Fourier transform infrared spectroscopy (FTIR). An analytical model of the cantilever beam is developed, and its mode shapes are studied by employing orthogonal polynomials in the classic Rayleigh-Ritz method. The surface stress caused by the enzymatic reaction of the proteins that leads to pure bending on the top surface of the cantilever is evaluated. The information provided by the experimental and analytical modeling reported in this work will be useful in the development of a portable biosensor for the detection of AMI.
Miniaturization and highly accurate detection technologies are key factors to advancing sensor performance and utility and the search for such technologies promises accomplishments with the advent of Micro Electro Mechanical Systems (MEMS) structures. MEMS is an enabling technology that can create integrated devices with mechanical, optical and electronic components. One of the fields where these micro-devices are successfully widespread is that of medical care where micro-machined cantilever sensors are found to be the ideal candidates for bio-sensing applications. These micro-machined cantilevers have been proposed as mechanical transducers for different sensing applications. These sensing surfaces are of interest in the development of novel cantilever-based biosensors. The fascinating aspect about these transducers is that they bend due to modifications in nano-mechanical interactions between neighboring molecules which curve the beam and that curvature can be optically detected. In this paper, PVDF-cantilevers are coated with 2 sets of antibody and antigen on one side, which respond with specific deflection signatures to each other and their intermolecular nano-mechanics bend the cantilever. The first set of antibody and antigen used here are rabbit skeletal muscle Troponin C (TnC) and Honey Bee Venom Melittin (ME) prepared in 50mM KCl and 50mM Tris-HCl buffer at a pH of 7.5 in a 1:1 ratio. The next set used were Horse Raddish Peroxide (HRP) and Hydrogen Peroxide (H2O2) prepared to get 10mg per 1ml of 0.1M Potassium Phosphate dibasic (K2HPO4) and diluted hydrochloric acid to get pH of 6.0. The optical system includes a laser source and a Position Sensitive Detector (PSD) which is used to readout deflections of the PVDF-cantilevers. The behavior of the cantilevers was also monitored with the enzymes under the influence of voltage. The classical problem of evaluating the tip deflection of the cantilever beam is analyzed involving the relation between movement recorded by the PSD, the tip deflection and angle of incidence. The combined results provide valuable information on the development of an optimizing sensing element that would enable life saving treatments of patients suffering from Acute Myocardial Infarction (AMI).
One of the major goals of biosensor technology is to detect and quantify in detail analytes with very high accuracy. To achieve this, much of the emphasis in sensor fabrication has been laid on antibody-antigen interaction. The consequence of this focus of enzyme biosensor studies is the development of critical techniques which can be extended in the detection of Acute Myocardial Infarction (AMI). Biosensors for AMI have attracted considerable interest in the last few years since the monitoring of a specific substance is central in enzymatic reactions. This interest has led to the investigation of biochemical markers of myocardial injury. These biomarkers facilitate the diagnosis and treatment of patients with AMI. Serial measurements of biochemical markers are now universally accepted as an important determinant in AMI diagnosis. Due to their high sensitivity and specificity over other biomarkers, the troponins are the markers of choice for the diagnosis or exclusion of AMI. The present techniques used in the identification of the troponins are lengthy and require large amount of specimen solution. The present research is directed towards the identification of optical detection procedures that are compatible to the miniaturization. In the present study an effort has been made to study the antigen-antibody reaction of rabbit skeletal muscle troponin C (TnC) and bee venom melittin (ME). Fluorescence energy transfer experiments were done to investigate the Ca 2+ -dependant interaction of TnC-ME in a 1:1 complex. Experiments were also conducted on TnC-ME binding at different ratios. These results validate the biosensor technology and illustrate how a biosensor can be developed based on the study of interaction between monoclonal antibody and antigen reaction in real time. The reported experimental results provide valuable information that will be useful in the development of a biosensor for the detection of AMI.
Biomedical applications of MOEMS are limited only by the humankind imagination. Precision measurements are minute amounts of biological material could be performed by optical means with a remarkable accuracy. Although available in medical laboratories, such analyzers are making their way directly to the users. Such an example is the test kit to detect the existence of cardiac enzymes in the blood stream. Apart from the direct users, the medical personnel will make use of such tools given the practicality of the kit. In a large proportion of patients admitted to hospital suspected of Acute Myocardial Infarction (AMI), the symptoms and electrocardiographic changes are inconclusive. This necessitates the use of biochemical markers of myocardial damage for correct exclusion or conformation of AMI. New cardiac-specific markers have recently been introduced into the detection of AMI. The cardiac troponins, because of their extraordinary high specificity for myocardial cell injury, have gained particular interest.
Experimental setup involves the use of a rectangle shaped AFM cantilevers, optical lenses, laser source, oscilloscope and a charged coupled device (CCD) to detect the cantilever deflection. When specific biomolecular binding occurs on one surface of a microcantilever beam, intermolecular nanomechanics bend the cantilever, which can be detected optically. Based upon the above concept, troponin I was detected optically by depositing it on the microcantilever containing anti-troponin I. The laser beam was directed on the cantilever and the deflection noted on the CCD.
Early enzymatic identification and confirmation is essential for diagnosis and prevention as in the case of Acute Myocardial Infarction (AMI). Biochemical markers continue to be an important clinical tool for the enzymatic detection. The advent of MEMS devices can enable the use of various microstructures for the detection of enzymes. In this study, the concept of MEMS is applied for the detection of enzyme reaction, in which microcantilevers undergo changes in mechanical behavior that can be optically detected when enzyme molecules adsorb on their surface. This paper presents the static behavior of microcantilevers under Horse Radish Peroxide (HRP) enzyme reaction. The reported experimental results provide valuable information that will be useful in the development of MEMS sensors for enzymatic detection. The surface stress produced due to enzyme reactions results in the bending of cantilevers as similar to the influencing of thermal stress in the cantilevers. This paper also reports the influence of thermal gradient on the microcantilevers.