Miniaturized all fiber probe for optical coherence tomography and pH detection of biological tissue

Abstract

We present a novel all‐fiber probe with 710‐μm outside diameter for combined optical coherence tomography and pH detection. In cancer surgery, a significant challenge is how to completely remove the malignant tumor without cutting too much normal tissue. The difference between cancer tissue and normal tissue not only lies in morphology and structure but also in tissue pH, where malignant tissue has a lower pH. This dual‐modality probe combined optical coherence tomography and pH detection of biological tissue, is expected to determine whether the tissue is cancerous quickly and accurately. The probe utilizes a typical three‐segment structure (double‐clad fiber ‐ no‐core fiber ‐ graded‐index fiber). We obtained a lateral resolution of ~10.6 μm, a working distance of ~506 μm and a pH measurement accuracy of 0.01 pH unit for the probe. The performance of the all‐fiber probe was verified through an ex vivo experiment using the porcine brain specimen.

Double-Clad Fiber-Based Multifunctional Biosensors and Multimodal Bioimaging Systems: Technology and Applications

“…[66] Monolithic all-fiber needle probe with GRIN lens [27] Imaging and pH change monitoring of lactic acid producing oocytes.…”

“…A tilted surface can be added to obtain a side-viewing configuration. Such designs can be achieved through bonding micro-elements, such as cylindrical rods and gradient-index (GRIN) lenses [ 24 ], using an all-fiber implementation by directly splicing the DCF to given lengths of no-core fiber (NCF) (or multimode fiber (MMF)) and GRIN fiber ( Figure 2 A) [ 25 , 26 , 27 ] or using a ball lens (polished or intact) that has been produced by melting a section of NCF ( Figure 2 B) [ 28 , 29 , 30 ]. A free-space arrangement using discrete micro-optics elements ( Figure 2 C) can also be used.…”

“…DCF-based pH measurements have been realized by either injecting a pH-sensitive dye into some biological sample [ 27 ] or by attaching a pH sensor onto the fiber tip (as shown in Figure 4 ) [ 47 ]. The simplest method for pH detection via a DCF is by injecting the solution of a pH indicator into the biological tissue [ 27 ]. The fluorescence signal can then be detected by a DCF or a GRIN-NCF-DCF fiber assembly (as shown in Figure 2 A).…”

“…Commercially available ratiometric pH indicators, such as seminaphthorhodafluor (SNARF) [ 27 , 47 ] or 5,6-carboxynapthofluorescein (CNF) [ 48 ], were utilized in previous DCF-based pH sensing studies. SNARF can be excited at 520–540 nm.…”

Ex-Vivo Measurement of the pH in Aqueous Humor Samples by a Tapered Fiber-Optic Sensor

“…The first fiber-optic pH sensor, described more than 40 years ago by Peterson et al, was developed for pH measurement in blood [ 5 ]. Recently, applications of fiber-optic sensors were described for pH measurement in brain tissue [ 6 ], lungs [ 7 , 8 , 9 ], bladder and kidneys [ 10 , 11 ], oocytes [ 12 ], blood and subcutaneous tissue [ 13 , 14 ], breast tissue [ 15 ] and in lung cancer cells [ 16 ].…”