Naked-eye point-of-care testing platform based on a pH-responsive superwetting surface: toward the non-invasive detection of glucose

Abstract

Herein, we demonstrate a contact angle (CA)-based naked-eye point-of-care testing platform with rapid pH-responsive superwettability that can switch between superhydrophilic and superhydrophobic properties for quantitative biosensing. The CA of the droplet on the pH-responsive surface approached~0°at pH 1 and conversely reached 161.4°± 6.2°at pH 13. We realized the sensitive detection of the pH, urea, and glucose by monitoring the changes in the CA. The traditional invasive diagnosis of diabetes causes pain and brings the risk of infections, such as acquired immune deficiency syndrome (AIDS), hepatitis B, hepatitis C, and syphilis, to the user. To address this issue, we implemented a method for the non-invasive diagnosis of diabetes in human saliva and urine, which avoided the significant drawbacks mentioned above. The accuracy of this method was demonstrated by comparing the results with those from commercial glucometers and theoretical calculations. Interestingly, we successfully monitored glucose levels in sweat before, during, and after cycling. The sensing performance was barely influenced by the temperature, elevation, and droplet color, illustrating promise for expansion to hundreds of millions of potential customers, especially those with color blindness or color weakness. Given its low cost, lack of instruments, and rapid response (within 1 s), this strategy might overcome the limitations of the mechanical stability and durability of superwettable materials and thus might extend the industrial-scale application of bioinspired superwettable systems.

Rapid preparation of polydopamine coating as a multifunctional hair dye

“…4 However, organic compounds with molecular masses of less than 500 Da, such as PPD, have been shown to easily cross the skin barrier and are regarded as human allergens and carcinogens. 5 To address this issue, some nontoxic nanomaterials, which are versatile in biomedical, [6][7][8] nano-engineering, 9,10 and clean energy 11,12 applications, have also been developed as safe dyeing agents. For example, Huang and coworkers found that graphene-based hair dyes could greatly shorten the dyeing time and improve antistatic performance.…”

Bioinspired superwetting surfaces for biosensing

“…Subsequently, in 2017, their group reported another electrochemical biosensor based on a novel stimuli‐responsive copolymer, 137 which was applied for selectively and sensitively detecting sialic acid (SA) in mouse brain. Our group reported an effective point‐of‐care testing (POCT) device based on pH‐responsive superwettable surfaces (Figure 10A), 138 which were prepared by modifying silica nanoparticles with the organosilanes (3‐[2‐(2‐amino ethylamino) ethylamino] propyl trimethoxy silane (AEPTMS) and octyl trimethoxy silane (OTMS)). Because of the switch between superhydrophobicity and superhydrophilicity, pH, urea, and glucose were specifically detected just by naked‐eye.…”

“…(D) Non‐invasive detection of saliva and urine obtained from nine patients with diabetes and six normal people illustrating that the CA can be employed to distinguish between samples of people with diabetes and normal people. Reproduced with permission 138 . Copyright 2018, Nature Publishing Group…”

Bio-responsive smart polymers and biomedical applications

“…An acidic environment results in the protonation of the amino groups, which makes the surfaces very hydrophilic, while an alkali condition changes the surfaces into a very hydrophobic state. With this surface, the level of glucose in the saliva and urine can be accurately measured in one second by recording the contact angle of the liquid sample, based on the produced gluconic acid after the addition of glucose oxidase in the sample [83]. This non-invasive, low-cost, rapid glucose detection method is beneficial to overcome the limitations of the traditional invasive diagnosis of diabetes such as pain and infection risk.…”