Continuous Glucose Monitoring CGM

As previously noted, medical devices are developed and marketed under strict regulatory requirements to ensure safety and efficacy. The transcutaneous nature of the minimally invasive CGM systems on the market and in development creates additional requirements on the materials, processes, packaging, and delivery of the devices. In vitro diagnostic devices are considered to be a subclass of medical devices, and a separate EU regulation (98/79EC) applies. In contrast to in vitro diagnostic devices, medical devices need, e.g., a biocompatibility assessment, and for invasive sensors also sterilization, disinfection requirements apply. As such, the materials used in the constmction of the transcutaneous part of the sensor, and the complete sensor itself, must be biocompatible in the sense that the sensor exhibits no toxicity toward the surrounding tissue. 

ISO 10993 standard family regulates the testing required for a determination of biocompatibility for tissue contact devices. Cytotoxicity testing is a basic requirement for the biocompatibility assessment. The cytotoxicity assay requires the elution of the sensor with physiological saline and the evaluation of the effect of the eluate on living cells. This can be critical for enzymes which are not properly immobilized, plasticizers in substrates or membrane layers, and the often-used reference electrode material silver/silver chloride. Also relevant for CGM sensors, but not addressed by the elution test, is the effect of the enzymatic reaction in the sensor in the absence of polarization of the sensor. First-generation sensors which 

The regulatory requirements for biocompatibility and sterihty increase the time and cost of product development for CGM sensors, as all materials and sensors to be used in any experimental programs or clinical trials must be evaluated and satisfy the requirements of the standards. 

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Tsujino D, Utsunomiya K (2014) Continuous glucose monitoring (CGM). Rinsho byori 62 (l) 53-59... 

Gai M, Merlo I, Dellepiane S, Cantaluppi V, Leonard G, Fop F, Guaiena C, Grass G, Biancone L (2014) Glycemic pattern in diabetic patients on hemodialysis. Continuous Glucose Monitoring (CGM) analysis. Blood Purif 38(l) 68-73... 

Home glucose test strips were able to reach the market two decades before the first continuous glucose monitors. This points to the tremendous challenges faced in the development of CGM. Following the long and colorful development of the technology will make it easier to understand the present systems. 

The first of these methods was the first explored by researchers [64, 90-94], and after 30 years of effort, there is finally a continuous glucose monitoring system (CGMS), which is currently marketed by MiniMed (Silmar, CA, USA). Up to now, it has only been used by healthcare professionals [95]. The system employs an approach similar to a Holter monitor, 72-h implantation, automatic glucose measurement every 5 min, and a 2-week data-storage capability. The sensor is a tiny electrode inside a small needle that is introduced under the skin. Once inserted, only the sensor remains under the skin and a thin cable connects the sensor to a pager-sized glucose monitor. 

The CGMS (Continuous Glucose Monitoring System), a device... 

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