A biosensing device for continuous monitoring of an analyte in a fluid matrix, the device comprising: an electromagnetic excitation element, a biosensing surface, an opposing surface, a separation component, a light collection optics, a light sensor, an image recording and analysis system, and an excitation control system; wherein the separation component is connected to the biosensing surface and to the opposing surface, forming a concave gap region between the biosensing surface and the opposing surface, such that the biosensing surface and the opposing surface are opposite to each other and have a separation of at most 1 mm, wherein the biosensing surface and opposing surface both have lengths of at most 3 mm; wherein the electromagnetic excitation element and the light sensor are positioned on opposite sides of the gap region; wherein the excitation control system provides control signals to the electromagnetic excitation element to produce electromagnetic signals; wherein the electromagnetic excitation element is optically coupled to the biosensing surface, and wherein the biosensing surface comprises biosensing particles sensitive to the electromagnetic signals from the electromagnetic excitation element, wherein an optical response of the biosensing particles to the electromagnetic signals is adapted to change in the presence of an analyte in the gap region; wherein the light collection optics couple light emitted from the biosensing particles on the biosensing surface to the light sensor; wherein the light sensor and light collection optics are positioned outside of the concave gap region; wherein the image recording and analysis system is connected to the light sensor and processes light signals from the biosensing particles to determine presence or absence or concentration of the analyte in the fluid matrix. an electromagnetic excitation element, a biosensing surface, an opposing surface, a separation component, a light collection optics, a light sensor, an image recording and analysis system, and an excitation control system; wherein the separation component is connected to the biosensing surface and to the opposing surface, forming a concave gap region between the biosensing surface and the opposing surface, such that the biosensing surface and the opposing surface are opposite to each other and have a separation of at most 1 mm, wherein the biosensing surface and opposing surface both have lengths of at most 3 mm; wherein the electromagnetic excitation element and the light sensor are positioned on opposite sides of the gap region; wherein the excitation control system provides control signals to the electromagnetic excitation element to produce electromagnetic signals; wherein the electromagnetic excitation element is optically coupled to the biosensing surface, and wherein the biosensing surface comprises biosensing particles sensitive to the electromagnetic signals from the electromagnetic excitation element, wherein an optical response of the biosensing particles to the electromagnetic signals is adapted to change in the presence of an analyte in the gap region; wherein the light collection optics couple light emitted from the biosensing particles on the biosensing surface to the light sensor; wherein the light sensor and light collection optics are positioned outside of the concave gap region; wherein the image recording and analysis system is connected to the light sensor and processes light signals from the biosensing particles to determine presence or absence or concentration of the analyte in the fluid matrix.