Bacteriophages (phages for short) are viruses, which have bacteria as hosts. The single phage body virion, is a colloidal particle, often possessing a dipole moment. As such, phages were used as perfectly monodisperse systems to study various physicochemical phenomena (e.g., transport or sedimentation in complex fluids), or in the material science (e.g., as scaffolds). Nevertheless, phages also execute the life cycle to multiply and produce progeny virions. Upon completion of the life cycle of phages, the host cells are usually destroyed. Natural abilities to bind to and kill bacteria were a starting point for utilizing phages in phage therapies (i.e., medical treatments that use phages to fight bacterial infections) and for bacteria detection. Numerous applications of phages became possible thanks to phage display—a method connecting the phenotype and genotype, which allows for selecting specific peptides or proteins with affinity to a given target. Here, we review the application of bacteriophages in nanoscience, emphasizing bio-related applications, material science, soft matter research, and physical chemistry.

Although DNA hybridization/melting is one of the most important biochemical reactions, the non-trivial kinetics of the process is not yet fully understood.

Anthracyclines are one of the most studied anticancer drugs approved for medical treatment. The equilibrium constant (K) of reaction between those drugs with DNA in both in-vitro and in-vivo experiments is a lack of consensus. The K values vary from 10⁴ up to 10⁸ M^-1, which suggests a 1000-fold error in determining the effective concentration needed to form the drug-DNA complex. Until 2014, only one study by Pérez-Arnaiz [Journal of Physical Chemistry B, 118, 1288–1295 (2014)] showed that the binding of anthracycline representative-doxorubicin occurs in two reactions. We support this result by brightness analysis at single molecular level for the four most common anthracyclines: doxorubicin, daunorubicin, epirubicin, and idarubicin.

Intrinsic molecular brightness (MB) is a number of emitted photons per second per molecule. When a substrate labeled by a fluorophore and a second unlabeled substrate form a complex in solution, the MB of the fluorophore changes. Here we use this change to determine the equilibrium constant (K) for the formation of the complex at pM concentrations. To illustrate this method, we used a reaction of DNA hybridization, where only one of the strands was fluorescently labeled. We determined K at the substrate concentrations from 80 pM to 30 nM. We validated this method against Förster resonance energy transfer (FRET). This method is much simpler than FRET as it requires only one fluorophore in the complex with a very small (a f̃ew percent) change in MB.