The present invention discloses a conductive composite sheet for use as an electrochemical sensor or a biosensor. The conductive composite sheet comprises a bacterial cellulose derived from a coconut gel or nata de coco grown in a static culture that is allowed to age, season or degrade to change color from opaque white to transparent brown due to relatively reduced crystallinity, and to have intermolecular bonds partially broken, wherein the static culture is maintained at a pH of 2-5 throughout a culturing period; and a conductive material functionalized with an OH group integrated with the said aged bacterial cellulose, wherein the conductive material is intertwined or entangled with the bacteria cellulose thereof through the broken intermolecular bonds by way of sonication in water, wherein the conductive material is mixed with the bacteria cellulose at a ratio of 3:1.