The possibility of functional roles played by platelets in close alliance with cancer cells has inspired the design of new biomimetic systems that exploit platelet-cancer cell interactions. Here, the role of platelets in cancer diagnostics is leveraged to design a microfluidic platform capable of detecting cancer-derived extracellular vesicles (EVs) from ultrasmall volumes (1 µL) of human plasma samples. Further, the captured EVs are counted by direct optical coding of plasmonic nanoprobes modified with EV-specific antibodies. Owing to the inherent properties of platelets for multifaceted interaction with cancer cells, the microfluidic chip equipped with a biologically interfaced platelet membrane-cloaked surface (denoted "PLT-Chip") can capture a significantly higher number of EVs from multiple types of cancer cell lines (prostate, lung, bladder, and breast) than the normal cell-derived EVs. Furthermore, this chip allows the monitoring of the growth of tumor spheroids (100 µm-2.5 mm) and clearly distinguishes the plasma of cancer patients from that of normal healthy controls. This robust, multifaceted, and cancer-specific binding affinity, coupled with excellent biocompatibility, is a unique feature of platelet membrane-cloaked surfaces, which therefore represent promising alternatives to antibodies for application in EVs-based cancer theranostics.
Avoiding the growth of SiOx has been an enduring task for the use of silicon as an electrode material in dynamic electrochemistry. This is because electrochemical assays become unstable when the SiOx levels change during measurements. Moreover, the silicon electrode can be completely passivated for electron transfer if a thick layer of insulating SiOx grows on the surface. As such, the field of silicon electrochemistry was mainly developed by electron-transfer studies in nonaqueous electrolytes and by applications employing SiOx-passivated silicon-electrodes where no DC currents are required to cross the electrode/electrolyte interface. A solution to this challenge began by functionalizing Si–H electrodes with monolayers based on Si–O–Si linkages. These monolayers have proven very efficient to avoid SiOx formation but are not stable for a long-term operation in aqueous electrolytes due to hydrolysis. It was only with the development of self-assembled monolayers based on Si–C linkages that a reliable protection against SiOx formation was achieved, particularly with monolayers based on α,ω-dialkynes. This review discusses in detail how this surface chemistry achieves such protection, the electron-transfer behavior of these monolayer-modified silicon surfaces, and the new opportunities for electrochemical applications in aqueous solution.
Heterojunctions are typically used to generate large photovoltages and to influence the direction of flow of charge carriers on photovoltaic and photocatalytic devices. Herein, we propose how heterojunctions can be used as a pathway for tuning the peak position of redox active monolayers. This was possible by exploring the principle of contact between materials in heterojunctions leading to a common equilibrium Fermi level for both sides of the heterojunction. The phenomenon was demonstrated with thin layers of intrinsic amorphous silicon deposited on platinum, indium tin oxide and either ntype or p-type crystalline silicon electrodes. At fixed light-intensity conditions, the potential required for electron transfer of a model redox probe was modulated according to the substrate on which the amorphous silicon was deposited. This allowed us to alter peak position of a redox process occurring on the electrolyte side of the junction despite it being isolated from the underlying conducting material. We show how such an effect can be explored in a potential range that encompasses any of the redox monolayers electroactive in aqueous electrolytes.
The spatial resolution of silicon photoelectrochemistry is improved to 500 nm by using amorphous silicon, 60 times improvement as compared to crystalline silicon.
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