Fluorescent Strips of Electrospun Fibers for Ratiometric Sensing of Serum Heparin and Urine Trypsin

Abstract

"Turn-on" or "turn-off" probes remain challenges in the establishment of sensitive, easily operated, and reliable methods for in situ monitoring bioactive substances. In the current study, electrospun fibrous strips are designed to provide straightforward observations of ratiometric color changes with the naked eye in the presence of serum heparin or urine trypsin. A tetraphenylethene (TPE) derivative is constructed and along with phloxine B is grafted on fibers, followed by protamine adsorption to induce static quenching of phloxine B and aggregation-induced emission of the TPE derivative. The presence of heparin or trypsin removes protamine to restore the fluorescence of phloxine B at 574 nm (I) and relieve the emission of the TPE derivative at 472 nm (I). The grafting densities of phloxine B and the TPE derivative are essential to achieve the optimal fluorescence-intensity ratio of I/I for the ratiometric detection of heparin and trypsin. Under illumination by an ultraviolet lamp, the fibrous mats turn from cyan to green in the presence of heparin at 0.4 U/mL and to a bright yellow at 0.8 U/mL, which is feasible in sensing serum heparin levels during postoperative and long-term care of patients after cardiovascular surgery. The protamine digestion results in similar color transitions with increasing trypsin levels up to 8 μg/mL, indicating the potential for monitoring urine trypsin levels of pancreas transplant patients. The color strips based on the ratiometric fluorescent response indicate advantages in lowering the detection limit and improving the accuracy and reproducibility, bearing great potential for a real-time and naked-eye detection of bioactive substances as self-test devices.

Recent advances in film-based fluorescence sensing

“…(a) Synthesis route for B-1 and its condensation reactions with different non-boron motifs; (b) recognition patterns of the saturated vapors of the tested VSOMs at 293 K obtained by collecting fluorescence intensity variations of the sensors (S1 to S8). Note: the Arabic numerals in the figure stand for different chemicals: specifically, methane (1), ethane(2), propane (3), n-butane (4), n-pentane (5), n-hexane (6), n-heptane(7), n-octane(8), nnonane (9), n-decane(10), methanol (11), toluene(12), diethyl ether (13), benzene(14), acetone(15), ethanol(16), THF(17), DCM(18), TCM(19) and water(20). (c) Home-made sensing platform developed for VSOMs vapor detection[63] (color online).…”

Giant magnetoresistive biosensors for real-time quantitative detection of protease activity

“…Peptides used in SPR sensors must have uncharged amino acids to minimize background signal due to their sensitivity to surface charge 31 . Fluorescent and colorimetric protease assays have been developed to detect protease activity in biofluids such as urine 57,58 , cyst fluid 13 , serum 59,60 , semen 61 , and sputum 62 as well as used to discover protease inhibitors that have subsequently been developed into drugs [63][64][65][66][67] . However, many of these detection modalities require laboratory equipment, and thus are not suitable for POC and POU applications.…”

Giant magnetoresistive biosensors for real-time quantitative detection of protease activity

“…Peptides used in SPR sensors must have uncharged amino acids to minimize background signal due to their sensitivity to surface charge 26 . Fluorescent and colorimetric protease assays have been developed to detect protease activity in biofluids such as urine 49,50 , cyst fluid 13 , serum 51,52 , semen 53 , and sputum 54 as well as used to discover protease inhibitors that have subsequently been developed into drugs 55,56,57,58,59 . However, many of these detection modalities require laboratory equipment, and thus are not suitable for POC and POU applications.…”