Novel micromachined silicon sensor for continuous glucose monitoring

The Need to Pair Molecular Monitoring Devices with Molecular Imaging to Personalize Health

By enabling the non-invasive monitoring and quantification of biomolecular processes, molecular imaging has dramatically improved our understanding of disease. In recent years, non-invasive access to the molecular drivers of health versus disease has emboldened the goal of precision health, which draws on concepts borrowed from process monitoring in engineering, wherein hundreds of sensors can be employed to develop a model which can be used to preventatively detect and diagnose problems. In translating this monitoring regime from inanimate machines to human beings, precision health posits that continual and on-the-spot monitoring are the next frontiers in molecular medicine. Early biomarker detection and clinical intervention improves individual outcomes and reduces the societal cost of treating chronic and late-stage diseases. However, in current clinical settings, methods of disease diagnoses and monitoring are typically intermittent, based on imprecise risk factors, or self-administered, making optimization of individual patient outcomes an ongoing challenge. Low-cost molecular monitoring devices capable of on-the-spot biomarker analysis at high frequencies, and even continuously, could alter this paradigm of therapy and disease prevention. When these devices are coupled with molecular imaging, they could work together to enable a complete picture of pathogenesis. To meet this need, an active area of research is the development of sensors capable of point-of-care diagnostic monitoring with an emphasis on clinical utility. However, a myriad of challenges must be met, foremost, an integration of the highly specialized molecular tools developed to understand and monitor the molecular causes of disease with clinically accessible techniques. Functioning on the principle of probe-analyte interactions yielding a transducible signal, probes enabling sensing and imaging significantly overlap in design considerations and targeting moieties, however differing in signal interpretation and readout. Integrating molecular sensors with molecular imaging can provide improved data on the personal biomarkers governing disease progression, furthering our understanding of pathogenesis, and providing a positive feedback loop toward identifying additional biomarkers and therapeutics. Coupling molecular imaging with molecular monitoring devices into the clinical paradigm is a key step toward achieving precision health.

Functionalized microneedles for continuous glucose monitoring

Microneedles (MNs) have been established as promising medical devices as they are minimally invasive, cause less pain, and can be utilized for self-administration of drugs by patients. There has been rapid development in MNs for transdermal monitoring and diagnostic systems, following the active research on fabrication methods and applications for drug delivery. In this paper, recent investigations on bio-sensing using MNs are reviewed in terms of the applicability to continuous glucose monitoring system (CGMS), which is one of the main research focuses of medical engineering technologies. The trend of the functionalized MNs can be categorized as follows: (i) as a sensing probe, and (ii) as a biological fluid collector. MNs as in vivo sensors are mainly integrated or coated with conductive materials to have the function as electrodes. MNs as fluid collectors are given a certain geometrical design, such as a hollow and porous structure aided by a capillary action or negative pressure, to extract the interstitial fluids or blood for ex vivo analysis. For realization of CGMS with MNs, a long-term accurate measurement by the MN-based sensing probe or a fluidic connection between the MN-based fluid collector and the existing microfluidic measurement systems should be investigated.

Microelectronics-based biosensors dedicated to the detection of neurotransmitters: a review

Dysregulation of neurotransmitters (NTs) in the human body are related to diseases such as Parkinson's and Alzheimer's. The mechanisms of several neurological disorders, such as epilepsy, have been linked to NTs. Because the number of diagnosed cases is increasing, the diagnosis and treatment of such diseases are important. To detect biomolecules including NTs, microtechnology, micro and nanoelectronics have become popular in the form of the miniaturization of medical and clinical devices. They offer high-performance features in terms of sensitivity, as well as low-background noise. In this paper, we review various devices and circuit techniques used for monitoring NTs in vitro and in vivo and compare various methods described in recent publications.

Saliva-based biosensors: noninvasive monitoring tool for clinical diagnostics

Saliva is increasingly recognised as an attractive diagnostic fluid. The presence of various disease signalling salivary biomarkers that accurately reflect normal and disease states in humans and the sampling benefits compared to blood sampling are some of the reasons for this recognition. This explains the burgeoning research field in assay developments and technological advancements for the detection of various salivary biomarkers to improve clinical diagnosis, management, and treatment. This paper reviews the significance of salivary biomarkers for clinical diagnosis and therapeutic applications, with focus on the technologies and biosensing platforms that have been reported for screening these biomarkers.

Enzyme nanoarchitectonics: organization and device application

Fabrication of ultrasmall functional machines and their integration within ultrasmall areas or volumes can be useful for creation of novel technologies. The ultimate goal of the development of ultrasmall machines and device systems is to construct functional structures where independent molecules operate as independent device components. To realize exotic functions, use of enzymes in device structures is an attractive solution because enzymes can be regarded as efficient machines possessing high reaction efficiencies and specificities and can operate even under ambient conditions. In this review, recent developments in enzyme immobilization for advanced functions including device applications are summarized from the viewpoint of micro/nano-level structural control, or nanoarchitectonics. Examples are roughly classified as organic soft matter, inorganic soft materials or integrated/organized media. Soft matter such as polymers and their hybrids provide a medium appropriate for entrapment and encapsulation of enzymes. In addition, self-immobilization based on self-assembly and array formation results in enzyme nanoarchitectures with soft functions. For the confinement of enzymes in nanospaces, hard inorganic mesoporous materials containing well-defined channels play an important role. Enzymes that are confined exhibit improved stability and controllable arrangement, which are useful for formation of functional relays and for their integration into artificial devices. Layer-by-layer assemblies as well as organized lipid assemblies such as Langmuir-Blodgett films are some of the best media for architecting controllable enzyme arrangements. The ultrathin forms of these films facilitate their connection with external devices such as electrodes and transistors. Artificial enzymes and enzyme-mimicking catalysts are finally briefly described as examples of enzyme functions involving non-biological materials. These systems may compensate for the drawbacks of natural enzymes, such as their instabilities under harsh conditions. We believe that enzymes and their mimics will be freely coupled, organized and integrated upon demand in near future technologies.

A MEMS differential viscometric sensor for affinity glucose detection in continuous glucose monitoring

Micromachined viscometric affinity glucose sensors have been previously demonstrated using vibrational cantilever and diaphragm. These devices featured a single glucose detection module that determines glucose concentrations through viscosity changes of glucose-sensitive polymer solutions. However, fluctuations in temperature and other environmental parameters might potentially affect the stability and reliability of these devices, creating complexity in their applications in subcutaneously implanted continuous glucose monitoring (CGM). To address these issues, we present a MEMS differential sensor that can effectively reject environmental disturbances while allowing accurate glucose detection. The sensor consists of two magnetically driven vibrating diaphragms situated inside microchambers filled with a boronic-acid based glucose-sensing solution and a reference solution insensitive to glucose. Glucose concentrations can be accurately determined by characteristics of the diaphragm vibration through differential capacitive detection. Our in-vitro and preliminary in-vivo experimental data demonstrate the potential of this sensor for highly stable subcutaneous CGM applications.

Microfluidic Device with Integrated Glucose Sensor for Cell-Based Assay in Toxicology

We have developed a cell-based assay platform using a microfluidic device integrating a glucose sensor into a cell culture device with closed-loop perfusion. Online measurement of cell kinetic change associated with cell status change was achieved by measuring glucose concentration change in the device with a cell exposed to a toxic material. The cell-based assay platform, which is integrated with a sensor and a perfusion system, was expected to improve measurement accuracy and efficiency, leading to the discovery of new tools in such wide-ranging fields as drug discovery, life sciences, and medical research.

A review of smart homes- present state and future challenges

In the era of information technology, the elderly and disabled can be monitored with numerous intelligent devices. Sensors can be implanted into their home for continuous mobility assistance and non-obtrusive disease prevention. Modern sensor-embedded houses, or smart houses, cannot only assist people with reduced physical functions but help resolve the social isolation they face. They are capable of providing assistance without limiting or disturbing the resident's daily routine, giving him or her greater comfort, pleasure, and well-being. This article presents an international selection of leading smart home projects, as well as the associated technologies of wearable/implantable monitoring systems and assistive robotics. The latter are often designed as components of the larger smart home environment. The paper will conclude by discussing future challenges of the domain.

An amperometric glucose biosensor constructed by immobilizing glucose oxidase on titanium-containing mesoporous composite material of no. 41 modified screen-printed electrodes

We have constructed a glucose biosensor by immobilizing glucose oxidase (GOD) on titanium-containing MCM-41 (Ti-MCM-41) modified screen-printed electrodes. The strategy of the sensing method is to monitor the extent of the decrease of the reduction current of O2 upon adding glucose at a selected potential. The detection can be done at the applied potential of -0.50 V and can efficiently exclude the interference from commonly coexisted substances. The constructed sensor has a high sensitivity to glucose (5.4 mA M(-1) cm(-2)) and a linear response range of 0.10-10.0 mM. The detection limit is 0.04 mM at a signal-to-noise ratio of 3. The sensor also shows high stability and remains its catalytic activity up to 60 degrees C. The biocompatibility of Ti-MCM-41 means that this immobilization matrix not only can be used for immobilizing GOD but also can be extended to other enzymes and bioactive molecules, thus providing a promising platform for the development of biosensors.

Recent progress in analytical instrumentation for glycemic control in diabetic and critically ill patients

Implementing strict glycemic control can reduce the risk of serious complications in both diabetic and critically ill patients. For this reason, many different analytical, mainly electrochemical and optical sensor approaches for glucose measurements have been developed. Self-monitoring of blood glucose (SMBG) has been recognised as being an indispensable tool for intensive diabetes therapy. Recent progress in analytical instrumentation, allowing submicroliter samples of blood, alternative site testing, reduced test time, autocalibration, and improved precision, is comprehensively described in this review. Continuous blood glucose monitoring techniques and insulin infusion strategies, developmental steps towards the realization of the dream of an artificial pancreas under closed loop control, are presented. Progress in glucose sensing and glycemic control for both patient groups is discussed by assessing recent published literature (up to 2006). The state-of-the-art and trends in analytical techniques (either episodic, intermittent or continuous, minimal-invasive, or noninvasive) detailed in this review will provide researchers, health professionals and the diabetic community with a comprehensive overview of the potential of next-generation instrumentation suited to either short- and long-term implantation or ex vivo measurement in combination with appropriate body interfaces such as microdialysis catheters.

Health care applications based on mobile phone centric smart sensor network

This paper presents the MIMOSA architecture and development platform to create Ambient Intelligence applications. MIMOSA achieves this objective by developing a personal mobile-device centric architecture and open technology platform where microsystem technology is the key enabling technology for their realization due to its low-cost, low power consumption, and small size. This paper focuses the demonstration activities carried out in the field of health care. MIMOSA project is a European level initiative involving 15 enterprises and research institutions and universities.

Flexible biosensors on spirally rolled micro tube for cardiovascular in vivo monitoring

New flexible biosensors on a spirally rolled micro tube have been designed, fabricated and characterized for microcatheter-based cardiovascular in vivo monitoring. With this new microfabrication method, sensors, wires and circuits can be fabricated first on the flexible polymer substrate (Kapton film) and then rolled spirally to make micro tubes with different diameters. This approach provides a unique method for mounting multiple sensors on both the inside and outside the tube. So, the new spirally rolled polymer tube flexibly conceives physical, biomedical and physiological microsensors, elevating most problems arisen from wiring and assembling of microsensors in conventional microcatheters. As a demonstration vehicle, we fabricated glucose biosensors on the 25 microm thick Kapton film first, then the film was spirally rolled to make a polymer micro tube with the glucose sensors on the inside wall of the tube. To verify the performance of the spirally rolled glucose biosensor, we characterized it both in a planar unrolled and rolled conditions and compared their performances. The spirally rolled glucose sensors showed good performance in the typical glucose concentration range in human blood from 60 mg/dL to 120 mg/dL with different rolled diameters at different working temperature.

Computer-aided continuous drug infusion: setup and test of a mobile closed-loop system for the continuous automated infusion of insulin

For a diabetes mellitus patient, tight control of glucose level is essential. Results are reported of an investigation of the suitability of existing wearable continuous insulin infusors controlled and adjusted by a control algorithm using continuous glucose measurements as input to perform the functionality of an artificial pancreas. Special attention was given to the development of a continuous glucose monitor and to evaluate which quality of input data is necessary for the control algorithm. In clinical trials, it was found that for patients in a controlled environment an autonomously regulating control algorithm leads to an improved adjustment of patient glucose values and less overall insulin infusion as compared with the best fixed preprogrammed insulin infusion profiles of standard pump therapy. For the limited number of cases studied here, functionality of the control algorithm could tolerate some delay between the actual glucose values in the patient interstitial fluid and the algorithm input of up to 30 min. A quasicontinuous glucose measurement delivering actual glucose values every 5-10 min seems to be suited to control an artificial pancreas.