The Construction And In-vivo Application Of Ratiometric Photoelectrochemical Microsensors

Photoelectrochemical（PEC）sensing has been developing quickly in recent years,while its in vivo application is still in the infancy.The complexity of biological environment poses a high challenge to specificity and reliability of PEC sensing.The purpose of this thesis is to achieve the reliable PEC analysis in vivo.Start from solving the key problem of low reliability of in-situ PEC analysis.We were committed to expanding electrochemical channel to achieve ratiometric PEC sensing.Two kinds of ratiometric PEC sensors were constructed based on the small molecule organic semiconductor（SMOS）of light absorption capability at two different wavelengths as well as lanthanide doped nanoparticles（Ln NPs）multiple light gives ability,respectively.It is expected to promote the practical application of PEC microsensor in biomedicine.The specific contents are as follows:（1）We herein proposed the concept of SMOS-based ratiometric PEC sensing making use of the structural flexibility as well as readily tunable energy band of SMOS.The light absorption ability at two different wavelengths of SMOS is easily regulated by analyte.Xanthene skeleton-based Cy OH was prepared as photoactive molecule,and its absorption band and corresponding PEC output can be modulated by an intramolecular charge transfer process.As such,the target mediated shift of absorption opened the opportunity to construct ratiometric PEC sensor.A proof-of-concept probe Cy OThiols was synthesized and assembled on Ti wire electrode（Ti WE）to prepare a highly selective microsensor for thiols.Under two monochromatic laser excitation（808nm and 750 nm）,Cy OThiols/Ti WE offered a ratiometric signal(j₈₀₈/j₇₅₀)which exhibited pronounced capacity to offset disturbance of environmental factors,guaranteeing its reliability for application in vivo.The ratiometric PEC sensor achieved the observation of bio-thiols release induced by cytotoxic edema and fluctuations of thiols in drug-induced epilepsy in living rat brains.（2）Ratiometric photoelectrochemical（PEC）sensing is a promising tool for in vivo analysis due to the merits of high reliability and favorable sensitivity.It is difficult to develop the ratiometric PEC sensor mainly due to the difficulty in introducing an additional internal reference channel.Herein,we broke through this limitation with Lanthanide-doped nanoparticles（Ln NPs）mediated multiple optical inputs,which provide a flexible platform for designing ratiometric or multichannel PEC sensors.In which,electrochemical channels are distinguished by the energy transfer approach of lanthanide ions.H₂S was chosen as a proof-of-concept target and a ratiometric PEC microsensor Cy-Cl@Ln NPs/Cd Te/OFCM was built.In which the dye Cy-Cl both functions as the recognition unit for H₂S and modulator for ratiometric upconversion fluorescence（UCF）of Ln NPs through the internal filtration effect.The sole signal reporting unit（SRU）Cd Te quantum dots（Cd Te QDs）act as the photon collectors of the ratiometric UCF for output ratiometric photocurrent signal(j₈₀₈/j₉₇₅)through in-situ PEC reaction.The UCF under 808-nm excitation was dependent on the concentration of H₂S and serves as the photocurrent’s modulators,while the UCF under 975-nm or1550-nm excitation served as the trigger of reference.An implantable integrated optical fiber based-microelectrode OFCM was developed for in vivo PEC analysis,so as to break through the limitation of light penetration in living body.The as-fabricated Cy-Cl@Ln NPs/Cd Te/OFCM allows monitoring of H₂S fluctuations at the nmol level and shows good adaptive ability in vivo that assists the first observation of increase of H₂S induced by increased intracranial pressure（ICP）in living rats.