Bright molecules for sensing, computing and imaging: a tale of two once-troubled cities

Molecular Probes, Chemosensors, and Nanosensors for Optical Detection of Biorelevant Molecules and Ions in Aqueous Media and Biofluids

Synthetic molecular probes, chemosensors, and nanosensors used in combination with innovative assay protocols hold great potential for the development of robust, low-cost, and fast-responding sensors that are applicable in biofluids (urine, blood, and saliva). Particularly, the development of sensors for metabolites, neurotransmitters, drugs, and inorganic ions is highly desirable due to a lack of suitable biosensors. In addition, the monitoring and analysis of metabolic and signaling networks in cells and organisms by optical probes and chemosensors is becoming increasingly important in molecular biology and medicine. Thus, new perspectives for personalized diagnostics, theranostics, and biochemical/medical research will be unlocked when standing limitations of artificial binders and receptors are overcome. In this review, we survey synthetic sensing systems that have promising (future) application potential for the detection of small molecules, cations, and anions in aqueous media and biofluids. Special attention was given to sensing systems that provide a readily measurable optical signal through dynamic covalent chemistry, supramolecular host-guest interactions, or nanoparticles featuring plasmonic effects. This review shall also enable the reader to evaluate the current performance of molecular probes, chemosensors, and nanosensors in terms of sensitivity and selectivity with respect to practical requirement, and thereby inspiring new ideas for the development of further advanced systems.

Fluorescent Nanozeolite Receptors for the Highly Selective and Sensitive Detection of Neurotransmitters in Water and Biofluids

The design and preparation of synthetic binders (SBs) applicable for small biomolecule sensing in aqueous media remains very challenging. SBs designed by the lock-and-key principle can be selective for their target analyte but usually show an insufficient binding strength in water. In contrast, SBs based on symmetric macrocycles with a hydrophobic cavity can display high binding affinities but generally suffer from indiscriminate binding of many analytes. Herein, a completely new and modular receptor design strategy based on microporous hybrid materials is presented yielding zeolite-based artificial receptors (ZARs) which reversibly bind the neurotransmitters serotonin and dopamine with unprecedented affinity and selectivity even in saline biofluids. ZARs are thought to uniquely exploit both the non-classical hydrophobic effect and direct non-covalent recognition motifs, which is supported by in-depth photophysical, and calorimetric experiments combined with full atomistic modeling. ZARs are thermally and chemically robust and can be readily prepared at gram scales. Their applicability for the label-free monitoring of important enzymatic reactions, for (two-photon) fluorescence imaging, and for high-throughput diagnostics in biofluids is demonstrated. This study showcases that artificial receptor based on microporous hybrid materials can overcome standing limitations of synthetic chemosensors, paving the way towards personalized diagnostics and metabolomics.

Symmetric-Key Encryption Based on Bioaffinity Interactions

The research presented here shows a bridge between biochemistry and cryptography. Enzyme-based assays were used in a new methodology linked to ciphers and cipher systems. Three separate enzyme assays, alkaline phosphatase (ALP) (E.C. 3.1.3.1), lysozyme (E.C. 3.2.1.17), and horseradish peroxidase (HRP) (E.C. 1.11.1.7), were used to create a cipher key in order to encrypt a message. By choosing certain parameters for one's experiment that are performed in the same way as a person receiving the message, correct encryption and decryption keys would be produced, resulting in a correct encryption and decryption of a message. It is imperative that both parties perform the same experiment under the same conditions in order to correctly interpret the message. Bioaffinity-based assays, in particular enzymatic assays, provide a specific, yet flexible mechanism to use for the encryption of messages. Because of the nature of this process there are a multitude of sets of parameters that may be chosen, each of which would result in a different key being produced, heightening the security and the robustness of the method. This paper shows that by using this concept of forming encryption keys using a bioaffinity-based approach, one is able to properly encrypt and decrypt a message, which could be viable for other biochemically based techniques.

"Dynamic" molecular recognition and chirality segregation utilizing concepts of molecular machines and molecular assemblies

The need to measure the concentration of selected ions and small organic molecules in both in vivo and in vitro processes is continuously increasing beyond the borders of various research fields. This need has been fulfilled using "host-guest chemistry", or in general, by the use of "molecular recognition". The basic idea in these research fields was derived from the 1 : 1 host-guest interaction based on the "key-and-lock" concept. However, we have experienced that only with this classical concept, more precise, higher-order recognition faces serious difficulty. In this review article, I wish to explain that the introduction of two new concepts, i.e., the dynamic action of molecular systems and the amplification effect of molecular assemblies, overcame the limitation of the "key-and-lock" concept. In fact, we have found that even "complete" chirality segregation can be achieved under optimal conditions.