Gold Nanostructures-Assembled Electrospun Films For The Colorimetric And Photothermal Point-of-Care Testing (POCT) Toward Disease-Related Biomarkers And Bacteria

Accurate,sensitive and selective detection of disease markers,viruses and bacterial pathogens is of great significance to people’s lives and health,especially the development of more convenient colorimetric visualization and photothermal imaging detection technology,which is more novel in point-of-care testing（POCT）.At present,researchers have developed a variety of biosensors for the detection of biological proteins,neural markers and bacterial pathogens.However,these biosensors have some shortcomings,such as using expensive instruments,requiring special inspectors,complicated processes and time-consuming,which limit the widespread use of biosensors in POCT.In addition,the visual detection of light and heat provides good conditions for the preparation of portable biosensor.Therefore,it is very necessary to develop a POCT technology for biological proteins,neurobiomarkers and bacterial pathogens.For this reason,based on the electrostatic interaction between gold nanostructures（gold nanorods,gold bipyramids）and electrospun fiber films,gold nanorods and gold bipyramids were assembled on electrospun fiber membranes.Using the unique localized surface plasmon resonance（LSPR）characteristics of gold nanostructures,a series of visual POCT techniques for disease markers,biological enzymes and Escherichia coli were developed.The main three research works are as follows:1.Target-induced tripedal G-quadruplex DNAzyme for multicolor visual point-of-care testing of biomarkers using Au nanorods-decorated electrospun nanofibrous filmsThe visually colorimetric technique do not require expensive analytical equipment,which are of great significance in establishing more novel POCT techniques for the accurate detection of analytes.In order to better meet the needs of the field of POCT,it is necessary and meaningful to build a multi-color solid sensing platform.In this work,a target-induced TGD for multicolor visual POCT of PSA proteins by using Au NRs-decorated electrospun nanofibrous films signal output elements was constructed.First,tripod hemin/G-quadruplex DNAzyme with excellent Horseradish peroxidase.（HRP）activity was produced by the target trigger and catalytic hairpin assembly（CHA）.The tripedal DNAzyme structure can promote the degradation of H₂O₂into hydroxyl radicals（·OH）as a strong oxidants to oxidize3,3’,5,5’-tetramethylbenzidine（TMB）into TMB⁺.Under acid condition,TMB⁺continue to convert into TMB²⁺,which can etch the Au NRs,resulting in the blue shift of the longitudinal surface plasmon resonance（LSPR）absorption peak of Au NRs.Finally,the corrosion of Au NRs generate abundant color variations with the increasing PSA concentration.In order to achieve the POCT mode,the wet Au NRs-decorated electrospun nanofibrous films were employed to detect PSA by visual effect.This proposed strategy exhibited palpable visual effect by naked eyes near the cutoff values of 4.0 and 10.0 ng/m L,which could be beneficial for identifying the levels of PSA in blood serum to prospec-tively achieve the early diagnosis and prognosis evaluation.2.Preparation of acetylcholinesterase-responsive multicolor Au NBPs/PEI/PVA electrospun fiber membranes and visual screening of their enzyme inhibitorsThe detection of acetylcholinesterase（ACh E）and the screening of its inhibitors are of great significance for the diagnosis and treatment of nervous system diseases.In this study,Au NBPs was modified on PEI/PVA electrospun fiber membrane,and a simple,rapid,reproducible and multi-color response electrospun sensor membrane was prepared,and it was applied to the visual detection of ACh E and the visual screening of enzyme inhibitors.thiocholine（TCh）is produced by hydrolyzing acetylthiocholine（ATCh）with ACh E.The strong reducibility of sulfhydryl groups in TCh decomposes Fe OOH,releasing a large number of Fe²⁺,Fe²⁺and H₂O₂as Fenton-like reagents,and the generated·OH corrodes Au NBPs,leading to the blue shift of local surface plasmon resonance（LSPR）absorption peak of Au NBPs.With the increase of ACh E,the degree of blue shift increases,and the color of its liquid phase gradually changes from orange red to blue.Similarly,the color of the electrospun fiber membrane modified by Au NBPs changes obviously.When ACh E inhibitor is introduced into the analytical system,the activity of ACh E is inhibited,the TCh content produced is reduced,and the ability to decompose Fe OOH is also reduced,which leads to the reduction of the degree of Fe²⁺catalyzing H₂O₂production and·OH corrosion of Au NBPs.Finally,the LSPR blue shift of Au NBPs colloidal solution is not obvious.Therefore,under the LED lamp,the colored electrospun fiber film is photographed with a mobile phone,and the RGB value of the electrospun fiber film is read through the"color recognizer"APP software.Based on this,a multi-color visual sensing membrane was constructed to monitor ACh E activity and visually screen enzyme inhibitors（donepezil hydrochloride,rivastigmine tartrate,berberine hydrochloride）.This method can screen drugs that inhibit ACh E by changing the color of electrospun membrane,which provides a convenient method for screening ACh E inhibitors.3.Enzyme-induced colorimetric and photothermal dual-mode analysis techniques for point-of-care testing ofβ-galactosidase and bacteriaUltra-sensitive,rapid and accurate detection ofβ-galactosidase（β-Gal）and bacterial pathogens is very important for public safety and improving the survival rate of patients.Escherichia coli can produceβ-Gal,soβ-Gal has been widely used to monitor the concentration of Escherichia coli.In this study,the dual-mode real-time detection ofβ-Gal and bacteria was realized by using the unique LSPR of Au NBPs and the strong electric field characteristics at the tip of the double cone,resulting in colorimetric and photothermal effects.In the research system,the prepared six-membered cyclic Co OOH can oxidize I^-to I₂,and the generated I₂has the effect of corroding Au NBPs,and the LSPR absorption peak of Au NBPs shifts blue from 844nm to about 640 nm after corrosion,and the solution color changes from orange-red to blue.Whenβ-Gal is present,β-Gal hydrolyzes with the substrate p-aminophenylβ-D-galactopyranoside（PAPG）to form p-aminophenol（PAP）,PAP reduced Co OOH to Co²⁺,and there was a decrease in the amount of I^-converted to I₂,and the degree of corrosion of Au NBPs decreased.With the gradual increase ofβ-Gal concentration,the degree of Au NBPs being corroded also showed a gradual decrease,leading to a decrease in the blue shift of the LSPR absorption peak of Au NBPs.The color of the solution changed gradually from blue,green,brownish-orange,to orange-red as the concentration ofβ-Gal increased from low to high.The assembly of Au NBPs onto electrospun fiber membranes showed a similar effect.In the same detection system,because of the photothermal properties of Au NBPs in the NIR region,irradiation of Au NBPs solution and Au NBPs/PEI/PVA electrospun fiber membranes with 808 nm near-infrared light increases the temperature with increasingβ-Gal concentration,Conversely,sinceβ-Gal concentration is very low,less PAP is generated and the ability to decompose Co OOH is weak,which facilitates the conversion of I^-to I₂,the longitudinal plasma absorption of Au NBPs is gradually displaced from the near-infrared region（844 nm）to the visible region（640 nm）,leading to a decrease in temperature.In this study,the temperature value and heat map can also be observed by combining the mobile phone with the U-disk infrared thermal imager,which is used for the colorimetric and photothermal dual-mode point-of-care testing ofβ-Gal and bacteria.This method provides a new method for the detection ofβ-Gal and bacteria,and has great application prospect in its early diagnosis.