Fully integrated nanodevices that allow the complete functional implementation without an external accessory or equipment are deemed to be one of the most ideal and ultimate goals for modern nanodevice design and construction. In this work, we demonstrate the first example of a bendable biofuel cell (BFC)-based fully integrated biomedical nanodevice with simple, palm-sized, easy-to-carry, pump-free, cost-saving, and easy-to-use features for the point-of-care (POC) diagnosis of scurvy from a single drop of untreated human serum (down to 0.2 μL) by integrating a bendable and disposable vitamin C/air microfluidic BFC (micro-BFC) (named iezCard) for self-powered vitamin C biosensing with a custom mini digital LED voltmeter (named iezBox) for signal processing and transmission, along with a ″built-in″ biocomputing BUFFER gate for intelligent diagnosis. Under the simplicity- and practicability-oriented idea, a cost-effective strategy (e.g., biomass-derived hierarchical micro–mesoporous carbon aerogels, screen-printed technique, a single piece of Kimwipes paper, LED display, and universal components) was implemented for nanodevice design rather than any top-end or pricey method (e.g., photolithography/electron-beam evaporation, peristaltic pump, wireless system, and 3D printing technique), which enormously reduces the cost of feedstock down to ∼USD 2.55 per integrated kit including a disposal iezCard (∼USD 0.08 per test) and a reusable iezBox (∼USD 2.47 for large-scale tests). These distinctive and attractive features allow such a fully integrated biomedical nanodevice to fully satisfy the basic requirements for POC diagnosis of scurvy from a single drop of raw human serum and make it particularly appropriate for resource-poor settings, where there is a lack of medical facilities, funds, and qualified personnel.

Hydroxylatopillar[6]arene (HP6) has been used as a stable ligand for the synthesis of gold nanoparticles (AuNPs). HP6 with excellent molecular recognition capability will securely capture the electron transfer medium thionin (Thi). Compared with other electroactive molecular capture methods (physical adsorption, etc.), the formation of an HP6⊃Thi complex can effectively inhibit the leakage of Thi and significantly increase the loading of Thi. HP6@Au was prepared in an aqueous solution with OH − at room temperature through an oxidation−reduction reaction between HP6 and AuCl 4 − , without the need for conventional harsh reducing agents. X-ray photoelectron spectroscopy and Fourier transform infrared studies have shown that the −OH groups in HP6 are oxidized to −COOH groups, and Au 3+ in AuCl 4− is reduced to Au 0 , leading to nucleation and production of AuNPs. The formation of HP6@Au strengthens the electron transfer rate, increases surface area, and captures a large number of primary antibodies (Ab1). Besides, the surface of N-doped carbon quantum dots and cobalt oxide (N-CQDs@Co 3 O 4 ) can be used for the deposition of HP6@ Au by π−π interaction to form a green highly conductive nanocomposite. An electrochemical immunosensor with significant stability was constructed based on HP6@Au/N-CQDs@Co 3 O 4 , and it was used for the effective detection of human epididymis protein 4 (HE4). The detection limit of the proposed immunosensor platform is 1.5 pg mL −1 , and it provides a wide linear range from 0.002 to 20 ng mL −1 under optimal conditions. The analysis results of HE4 in human serum are satisfactory and have broad application prospects in clinical monitoring.