Selective vancomycin detection using optical fibre long period gratings functionalised with molecularly imprinted polymer nanoparticles

Abstract

An optical fibre long period grating (LPG) sensor modified with molecularly imprinted polymer nanoparticles (nanoMIPs) for the specific detection of antibiotics is presented. The operation of the sensor is based on the measurement of changes in refractive index induced by the interaction of nanoMIPs deposited onto the cladding of the LPG with free vancomycin (VA). The binding of nanoMIPs to vancomycin was characterised by a binding constant of 4.3 ± 0.1 × 10(-8) M. The lowest concentration of analyte measured by the fibre sensor was 10 nM. In addition, the sensor exhibited selectivity, as much smaller responses were obtained for high concentrations (∼700 μM) of other commonly prescribed antibiotics such as amoxicillin, bleomycin and gentamicin. In addition, the response of the sensor was characterised in a complex matrix, porcine plasma, spiked with 10 μM of VA.

Figure 1

TS of the LPG measured in air: black line, before APTMS deposition, and red line, after APTMS deposition

Figure 2

(a) Evolution of the TS of the APTMS-coated optical fibre LPG during the deposition of 1wt % GA, measured in solution at different interval times: black line, before GA deposition; red line, 15 min; and green line, 1 h after GA deposition; (b) TS measured in air: black line, before GA deposition, and red line, after GA deposition;

Figure 3

(a), TS of the nano-MIP coated LPG measured in air after exposure to VA concentrations ranging from 10 nM to 700 μM; (b), Dependence of the transmission at the centre of the resonance band corresponding to coupling to the LP₀₁₉ mode (square) and wavelength shift of the resonance band corresponding to coupling to the LP₀₁₈ mode (circle) on the concentration of VA. The red and black lines are fits using the Langmuir adsorption isotherm. The inset shows the logarithmic dependence of transmission at the centre of the resonance band corresponding to coupling to the LP₀₁₉ mode on VA concentration.

Figure 3

(a), TS of the nano-MIP coated LPG measured in air after exposure to VA concentrations ranging from 10 nM to 700 μM; (b), Dependence of the transmission at the centre of the resonance band corresponding to coupling to the LP₀₁₉ mode (square) and wavelength shift of the resonance band corresponding to coupling to the LP₀₁₈ mode (circle) on the concentration of VA. The red and black lines are fits using the Langmuir adsorption isotherm. The inset shows the logarithmic dependence of transmission at the centre of the resonance band corresponding to coupling to the LP₀₁₉ mode on VA concentration.

Figure 4

TS of the nano-MIP coated LPG, measured in air before (black line) and after exposure to, porcine plasma (red line) and porcine plasma spiked with 10 μM of VA (green line)

Figure 5

TS of the nano-MIP-coated LPG, measured in air after exposure to, VA (670 μM) (red line), amoxicillin (690 μM) (green line); bleomycin (706 μM) (blue line) and gentamicin (690 μM) (magenta line).

Scheme 1

Schematic illustration of the molecular imprinting procedure.

Scheme 2

Schematic illustration of the chemicals used for detection and selectivity tests: (a) vancomycin (VA); (b) amoxicillin; (c) bleomycin and (d) gentamicin.

Scheme 3

Schematic illustration of the protocol used to immobilize nanoMIPs