Ionic liquid-caged nucleic acids enable active folding-based molecular recognition with hydrolysis resistance

Electrochemical pan-variant detection of SARS-CoV-2 through host cell receptor-mimicking molecular recognition

The persistent emergence of new SARS-CoV-2 variants has presented significant challenges to vaccines and antiviral therapeutics, highlighting the need for the development of methods that ensure variant-independent responses. This study introduces a unique sensor capable of electrochemically detecting SARS-CoV-2 across a wide range of variants. The comprehensive detection is achieved by using a peptide-DNA hybrid, R7-02, as the capture probe, mimicking the binding interface between a SARS-CoV-2 spike protein and a host cell receptor, hACE2. Since the first step of viral infection is the binding of the spike protein to hACE2 regardless of variant type, the hACE2-mimicking probe can naturally acquire the pan-variant recognition capability. In constructing the sensor, the R7-02 probes are positioned on electrodes via a tetrahedral DNA nanostructure for enhanced detection efficiency. Since R7-02 directly captures the externally-exposed spike protein, our approach does not require sample pretreatments, such as virus particle lysis, unlike conventional diagnostic methods. The R7-02-embedded sensor demonstrated high sensitivity towards Omicron and its major subvariants-commonly known as 'stealth Omicron' (BA.5, BA.2.75, BQ.1.1, and XBB.1.5)-with a detection limit as low as 811.9 pM, along with robust specificity for SARS-CoV-2 against influenza and other human coronaviruses. The sensor also successfully detected SARS-CoV-2 directly from non-treated saliva samples of COVID-19-positive patients. Given the comprehensive and sensitive detection capability, combined with its simple operation, our receptor-mimicking probe-based electrochemical sensor holds the potential to be a sustainable and effective point-of-care diagnostic tool, offering a promising solution to the constant challenges posed by the endemic presence of SARS-CoV-2.

Utilizing ionic liquids as eco-friendly and sustainable carriers for delivering nucleic acids: A review on the revolutionary advancement in nano delivery systems

Ionic liquids (ILs) are an extremely versatile class of chemicals. It has been shown that they can effectively pass through many biological barriers in the human body to deliver medications. ILs are solvents noted for their ecological friendliness; they contain equal amounts of cations and anions and remain liquid at temperatures below 100 °C. Hence, these are ideal for biomedical applications owing to their advantageous properties such as biocompatibility, solubility, and adaptability. ILs are widely reported to improve the solubility and stability of nucleic acids (DNA and RNA) in aqueous conditions, allowing for more effective delivery. Certain ILs have shown the ability to enhance the absorption of nucleic acids into cells. In addition, ILs can also be used to create vectors for gene delivery, such as liposomes and nanoparticles, thereby improving the transfection efficiency of plasmid DNA and siRNA. Subsequently, the application of ILs for nucleic acid delivery has increased significantly in recent years. In this context, we believe that using ILs to enhance the transport of nucleic acids will have a considerable effect as a novel and crucial therapeutic method in the upcoming decades. The use of ILs as solvents to preserve the natural structure of DNA and RNA shows promise for a variety of biotechnological and medical applications. Notably, ILs may be utilized for a variety of functions, including extracting, concentrating, stabilizing, and spreading nucleic acids inside cells. Our review emphasizes the key findings of research works published in this domain, wherein outstanding effectiveness of delivering RNA to the desired areas was achieved, and was made possible through the utilization of ILs.

Aptasensor-encapsulating semi-permeable proteinosomes for direct target detection in non-treated biofluids

Detecting biomarkers in biofluids directly without sample treatments makes molecular diagnostics faster and more efficient. Aptasensors, the nucleic acid-based molecular biosensors, can detect a wide range of target molecules, but their susceptibility to degradation and aggregation by nucleases and charged proteins, respectively, limits their direct use in clinical samples. In this work, we demonstrate that when aptasensors are encapsulated in proteinosomes, the protein-based liposome mimics, clinically important small molecules can be sensitively and selectively detected in non-treated specimens, such as 100 % unpurified serum. As serum albumin is used to form the membrane, the nanomeshed proteinosomes become semi-permeable and antifouling, which enables exclusive admission of small molecules while blocking unwanted large proteins. Consequently, the enclosed aptasensors can maintain close-to-optimal performance for target binding, and nucleolytic degradation and electrostatic aggregation are effectively suppressed. Three different structure-switching aptamers specific for estradiol, dopamine, and cocaine, respectively, are demonstrated to fully conserve their high affinities and specificities inside the microcapsules. The shielding effect of proteinosomes is indeed exceptional; the enclosed DNA aptasensors remain completely intact over 18 h in serum and even in an extremely concentrated DNase solution (1 mg/ml, ∼300,000× the serum level). Moreover, the proteinosome-mediated compartmentalization enables independent operation of multiple aptasensors in the same mixture. Hence, simultaneous real-time sensing of two different targets is demonstrated with different operation modes, 'recording' target appearance and 'reporting' target concentration changes. This work is the first demonstration of small-molecule-specific aptasensors operating with optimal performance in serum environments and will find promising applications in molecular diagnostics.