Development of dip-strip sucrose sensors: Application of plant invertase immobilized in chitosan–guar gum, gelatin and poly-acrylamide films

In present work, chitosan, guar gum, gelatin and poly-acrylamide hydrogels were tested for plant invertase immobilization. Acid invertase was extracted and partially purified from watermelon fruit (Cirullus vulgaris) with specific activity of 834 units mg−1. Immobilization of invertase was carried out in composite matrices of chitosan–guar gum, gelatin and poly-acrylamide with immobilization efficiency of 93%, 85% and 74% respectively. Scanning electron microscope analysis of blank and immobilized enzyme films was carried out to reveal their surface morphology. Enzyme dip-strips were designed to evaluate sucrose concentration from different aqueous samples. Response time for chitosan–guar gum invertase, gelatin invertase and poly-acrylamide invertase dip-strips was found to be 7, 10 and 12 min, respectively. Detection limit for sucrose using chitosan–guar gum invertase dip-strip was 1 × 10−8 M, while poly-acrylamide invertase dip-strip and gelatin-invertase strip had same limit of detection of 1 × 10−7 M for sucrose. All three dip-strip systems showed concentration dependent response for sucrose in the range of 1 × 10−7–1 × 10−3 M. Operational stability and storage stability for the sensors were checked after each use. The dip-strips were also employed for sucrose estimation from sugar factory samples. The results concluded that the designed dip-strips ensure fast and easy detection of sucrose with good accuracy and reliability.