Evaluation of glucose sensitive affinity binding assay entrapped in fluorescent dissolved‐core alginate microspheres

Abstract

The feasibility of dissolved-core alginate-templated fluorescent microspheres as "smart tattoo" glucose biosensors was investigated in simulated interstitial fluid (SIF). The sensor works on the principle of competitive binding and fluorescence resonance energy transfer. The sensor consists of multilayer thin film coated alginate microspheres incorporating dye-labeled glucose receptor and competing ligand within the partially dissolved alginate core. In this study, different approaches for the sensing and detection chemistry were studied, and the response of encapsulated reagents was compared with the solution-phase counterparts. The glucose sensitivity of the encapsulated TRITC-Con A/FITC-dextran (500 kDa) assay in DI water was estimated to be 0.26%/mM glucose while that in SIF was observed to be 0.3%/mM glucose. The glucose sensitivity of TRITC-apo-GOx/FITC-dextran (500 kDa) assay was estimated to be 0.33%/mM glucose in DI water and 0.5%/mM glucose in SIF and both demonstrated a response in the range of 0-50 mM glucose. Therefore, it is hypothesized that the calcium ion concentration outside the microsphere (in the SIF) does not interfere with the response sensitivity. The sensor response was observed to exhibit a maximum response time of 120 s. The system further exhibited a sensitivity of 0.94%/mM glucose with a response in range of 0-50 mM glucose, using near-infrared dyes (Alexa Fluor-647-labeled dextran as donor and QSY-21-conjugated apo-GOx as acceptor), thereby making the sensor more amenable to in vivo use, when implanted in scattering tissue.

Glucose oxidase stabilization against thermal inactivation using high hydrostatic pressure and hydrophobic modification

“…The most successful commercial application is the GOx-based biosensor used to measure blood glucose of individuals suffering from diabetes. Environmental factors play important roles in enhancing the thermal stability of enzymes including pH (Caves et al, 2011), and the presence of metal ions (Li et al, 2013), polyelectrolytes (Chaudhary et al, 2009;Srivastava et al, 2005), and small organic molecules that are involved in maintaining osmotic pressure in the cell (Timson et al, 2013;Zancan and Sola-Penna, 2005). Environmental factors play important roles in enhancing the thermal stability of enzymes including pH (Caves et al, 2011), and the presence of metal ions (Li et al, 2013), polyelectrolytes (Chaudhary et al, 2009;Srivastava et al, 2005), and small organic molecules that are involved in maintaining osmotic pressure in the cell (Timson et al, 2013;Zancan and Sola-Penna, 2005).…”

“…However, the short operational life due to the lack of stability of the enzyme is a major limitation that has reduced the availability of commercial GOx biosensors (Altikatoglu et al, 2010) and other enzyme biosensor for continuous measurement of analytes. Environmental factors play important roles in enhancing the thermal stability of enzymes including pH (Caves et al, 2011), and the presence of metal ions (Li et al, 2013), polyelectrolytes (Chaudhary et al, 2009;Srivastava et al, 2005), and small organic molecules that are involved in maintaining osmotic pressure in the cell (Timson et al, 2013;Zancan and Sola-Penna, 2005). Glucose oxidase stability has been improved by using several techniques including immobilization (Bouin and Hultin, 1982;Rauf et al, 2006), protein engineering , and reaction medium engineering (Kalisz et al, 1997).…”

Preclinical Evaluation of Poly(HEMA-co-acrylamide) Hydrogels Encapsulating Glucose Oxidase and Palladium Benzoporphyrin as Fully Implantable Glucose Sensors

“…[13][14][15] Demonstrations of potential hydrogel sensor formats over the years have included poly(ethylene glycol)-based microspheres and fibers [13][14][15] and includes a variety of hollow polymeric capsules and various nanocomposite particulate systems using other encapsulating materials. [16][17][18][19][20] Utilizing these unique properties of hydrogels in a fully implantable CGM may circumvent repetitive tissue trauma and infection associated with the percutaneous nature of traditional CGM devices in vivo. 9,21 Used in medical devices for decades, one of the most widely studied and well-characterized hydrogels for biomedical applications is poly (2-hydroxyethyl methacrylate) (pHEMA).…”

Nanosensors and nanomaterials for monitoring glucose in diabetes

“…Upon removal of glucose, this process is reversed as both components are contained inside the nanofilm; thus, this is a reversible sensor. Later work expanded this concept to alginate microspheres [71]. Importantly, this work makes use of near-infrared fluorophores, which offers an advantage for in vivo application, as background signal from tissue and biological fluids is minimized, allowing easier imaging through the skin.…”