Oligolysine‐Conjugated Zinc(II) Phthalocyanines as Efficient Photosensitizers for Antimicrobial Photodynamic Therapy

A series of zinc(II) phthalocyanines conjugated with an oligolysine chain (n=2, 4, and 8) were synthesized and characterized by using various spectroscopic methods. As shown by using UV/Vis and fluorescence spectroscopic methods, these compounds were nonaggregated in N,N‐dimethylformamide, and gave a weak fluorescence emission and high singlet oxygen quantum yield (Φ_Δ=0.86–0.89) as a result of their di‐α‐substitution. They became slightly aggregated in water with 0.05 % Cremophor EL, but they could still generate singlet oxygen effectively. The antimicrobial photodynamic activities of these compounds were then examined against various bacterial strains, including the Gram‐positive methicillin‐sensitive Staphylococcus aureus ATCC 25923 and methicillin‐resistant Staphylococcus aureus ATCC BAA‐43, and the Gram‐negative Escherichia coli ATCC 35218 and Pseudomonas aeruginosa ATCC 27853. Generally, the dyes were much more potent toward the Gram‐positive bacteria. Only 15 to 90 nM of these photosensitizers was required to induce a 4 log reduction in the cell viability of the strains. For Escherichia coli, the photocytotoxicity increased with the length of the oligolysine chain. The octalysine derivative showed the highest potency with a 4 log reduction concentration of 0.8 μM . Pseudomonas aeruginosa was most resistant to the photodynamic treatment. The potency of the tetralysine derivative toward a series of clinical strains of Staphylococcus aureus was also examined and found to be comparable with that toward the nonclinical counterparts. Moreover, the efficacy of these compounds in photodynamic inactivation of viruses was also examined. They were highly photocytotoxic against the enveloped viruses influenza A virus (H1N1) and herpes simplex virus type 1 (HSV1), but exhibited no significant cytotoxicity against the nonenveloped viruses adenovirus type 3 (Ad3) or coxsackievirus (Cox B1). The octalysine derivative also showed the highest potency with an IC₅₀ value of 0.05 nM for the two enveloped viruses.     

Virus‐Based Chemical and Biological Sensing

Viruses have recently proven useful for the detection of target analytes such as explosives, proteins, bacteria, viruses, spores, and toxins with high selectivity and sensitivity. Bacteriophages (often shortened to phages), viruses that specifically infect bacteria, are currently the most studied viruses, mainly because target‐specific nonlytic phages (and the peptides and proteins carried by them) can be identified by using the well‐established phage display technique, and lytic phages can specifically break bacteria to release cell‐specific marker molecules such as enzymes that can be assayed. In addition, phages have good chemical and thermal stability, and can be conjugated with nanomaterials and immobilized on a transducer surface in an analytical device. This Review focuses on progress made in the use of phages in chemical and biological sensors in combination with traditional analytical techniques. Recent progress in the use of virus–nanomaterial composites and other viruses in sensing applications is also highlighted.     

N‐Linked Glycans of Chloroviruses Sharing a Core Architecture without Precedent

N‐glycosylation is a fundamental modification of proteins and exists in the three domains of life and in some viruses, including the chloroviruses, for which a new type of core N‐glycan is herein described. This N‐glycan core structure, common to all chloroviruses, is a pentasaccharide with a β‐glucose linked to an asparagine residue which is not located in the typical sequon N‐X‐T/S. The glucose is linked to a terminal xylose unit and a hyperbranched fucose, which is in turn substituted with a terminal galactose and a second xylose residue. The third position of the fucose unit is always linked to a rhamnose, which is a semiconserved element because its absolute configuration is virus‐dependent. Additional decorations occur on this core N‐glycan and represent a molecular signature for each chlorovirus.     

Label‐Free Analysis of Single Viruses with a Resolution Comparable to That of Electron Microscopy and the Throughput of Flow Cytometry

Viruses are by far the most abundant biological entities on our planet, yet existing characterization methods are limited by either their speed or lack of resolution. By applying a laboratory‐built high‐sensitivity flow cytometer (HSFCM) to precisely quantify the extremely weak elastically scattered light from single viral particles, we herein report the label‐free analysis of viruses with a resolution comparable to that of electron microscopy and the throughput of flow cytometry. The detection of single viruses with diameters down to 27 nm is described. T7 and lambda bacteriophages, which differ in size by as little as 4 nm, could be baseline‐resolved. Moreover, subtle structural differences of the same viral particles can be discriminated. Using monodisperse silica nanoparticles as the size reference standards, the virus sizes measured by the HSFCM are in agreement with the equivalent particle diameters derived from their structural dimensions. The HSFCM opens a new avenue for virus characterization.