Fiber-optic pH detection in small volumes of biosamples

Area of Science:

• Plant biology and biophysics
• Analytical chemistry and sensor technology

Background:

• Understanding plant physiological processes often requires accurate pH measurements.
• Microscopic pH determination in plant samples is challenging with conventional methods.
• Fiber-optic probes offer a potential solution for in-situ measurements.

Purpose of the Study:

• To develop and validate a novel fiber-optic sensing probe for microscopic plant pH measurements.
• To measure the pH of plant xylem exudate using the developed probe.
• To assess the accuracy and range of the developed sensing probe.

Main Methods:

• Fabrication of V-taper fiber-optic probes with diameters as small as 8 μm.
• Coating probe tips with pH-sensitive dye (HPTS) and a reference dye (Ru-phen dichloride) in a xerogel matrix.
• Utilizing ratiometric fluorescence intensity measurements for pH determination.
• Validating results with conventional electrochemical pH measurements.

Main Results:

• The V-taper probes enabled fluorescence signal delivery from microscopic detection sites.
• The probes demonstrated sensitivity to pH in the range of 6.0 to 9.0.
• Measurement errors were approximately 0.2 pH units in the 6-9 range and 0.5 pH units in the 5-6 range.
• Successful in vivo and in vitro pH measurements of small plant xylem exudate volumes (~6 μl) were achieved.

Conclusions:

• Novel V-taper fiber-optic probes are effective for microscopic pH measurements of plant xylem exudate.
• The developed sensing system provides accurate and reliable pH data for small biological samples.
• This technology has potential applications in botanical research for understanding plant physiology.