A multilayered optical sensing patch, for the measurement of conditions, such as pH, oxygen level, etc, within containers, is provided. The multilayered optical sensing patch of the present invention is comprised of a heat sealable polymer substrate layer, and a polymeric sensing membrane later attached thereto. The polymer sensing membrane layer is formed of a porous polymer support membrane, and an optical sensing composition (comprising a reactive indicator) covalently bonded thereto. The heat sealable polymer substrate layer is capable of being securely bonded to the inner layer of bioreactor bags, as well as the porous polymer support substrate layer. Further, the porous polymer support membrane layer provides a firm supporting structure for the polymeric sensing layer, thereby protecting the optical sensing composition disposed therein from degradation/damage.