Construction Of Paper Chip Based On 3D Printed Microneedle Array And Application Of Histamine Detection In Food

Food safety has become the fourth "hot" topic followed population,resources,and environment.Timely determination and analysis of pathogenic substances in food is one of the effective ways to curb food poisoning.Traditional detection methods require the complex sample preparation and high cost,and it is difficult to achieve on-site instant detection of food safety.Therefore,the establishment of simple,efficient,low-cost,and portable detection methods is expected to be the key to ensuring a healthy diet for humans.Microneedle(MNs)is generally studied as a painless subcutaneous drug delivery tool and minimally invasive biosensor widely,in which porous hydrogel hollow micro-needle penetrates human skin painlessly,and extracts biofluids by capillarity action and provides a new research idea for the food safety detection.However,the direct use of the microneedle one-step colorimetric detection method is not yet mature and needs to be integrated with portable detection technology to build a new real-time detection and monitoring mechanism.A conceptual two-layer microneedle paper chip sensor was constructed for colorimetric detection of food freshness by using 3D printing technology and molding method to fabricate a vitrification silk protein hollow microneedles(SF-HMNs)patch integrated with a patterned paper-based chip.The micro-needle layer of the sensor can be directly pierced into the spoiled food,using the porous adsorption property of silk protein(SF)and the hollow structure of MNs,The detected substances in the food are extracted and enriched by capillary force and directly transferred to the paper-based sensing layer for colorimetric detection.This strategy not only simplifies the tedious steps of food safety detection but also provides a new method to purify the source of the food market.The details of the study and the results are shown as follows:1.Preparation and characterization of vitrified silk fibroin hollow microneedles.Two 3D printing technologies,fused deposition molding(FDM)and liquid crystal display(LCD)were used to print microneedle array molds,respectively,and vitrified SF-HMNs patches with good mechanical strength and insolubility were successfully prepared by the molding method.The structural characterization and mechanical tests of SF-HMNs before and after modification were carried out to investigate their porosity and mechanical strength by exploring the extraction conditions of SF concentration,and it was found that the surface of the LCD-3D printed microneedle mold is smooth.When the salt solution ratio of dry silk fibroin and LiBr was 1:3 and the concentration-time was 12 hours,the formation and peeling of the silk-based microneedles were easy;when the diameter of 0.99 mm,and the height of 1.5 mm and the water annealing modification time of 8 hours for the silk-based microneedles are performed,and the prepared vitrified SF-HMNs have a complete and uniform structure and excellent mechanical properties,which can meet the puncture detection of various foods.2.Design and fabrication of micro-needle paper-based chip sensor.Four kinds of paper with good water absorption and color rendering on the market were selected as the paper-based sensing layer of the sensor.Through the contact angle,color strength,and color uniformity test of hydrophobized paper.a rice paper with a contact angle of 120.6°,a relative color intensity of 0.31,and uniform and stable color was finally selected as the patterned paperbased sensing layer.and assembled with vitrified SF-HMNs into a conceptual sensor of microneedles paper chip.The transmission effect and rate of the sensor were investigated,and the results imply that the sensor was able to achieve rapid extraction and transmission of liquid in solid gels within 9 minutes.3.Microneedle paper chip sensor is used for the colorimetric detection of histamine in food.Cu NCs were prepared as fluorescent probes for the detection of histamine by a classical synthetic method and loaded into the hydrophilic patterned region of a microneedle paper chip for the colorimetric semi-quantitative detection of histamine in food,The practicality of this conceptual microneedle paper chip sensor can be verified.The color-developing area was captured by the camera and the colorimetric analysis was carried out.The quantitative analysis standard curves between the red channel values and the histamine concentrations were constructed in the range of 0?20 ?moL·L-1 and concentration of 20?60 ?moL·L-1,While the correlation coefficients were 0.9827 and 0.9901,respectively.The minimum limit for nakedeye detection is 2 ?moL·L-1.The continuous monitoring of histamine produced during the storage of fresh pork and fresh shrimp and the color comparison with the standard colorimetric card for histamine detection enables the semi-quantitative visualization of histamine in actual samples.This study provides a new way of thinking for the food freshness assessment.