Nanobiotechnology today: focus on nanoparticles

Some of the most promising applications of biologically inspired nanoparticles have so far been in nanobiotechnology and in tissue- and cell-specific drug delivery in particular. Unlike liposomes, dendrimers, metal and semiconductor nanoparticles, the nanoparticles made of biopolymers, such as bacterial spores, viruses and alike are naturally uniform in size and offer precise control for the surface-displayed targeting groups and their components. Furthermore, such biological nanoparticles may be produced recombinantly relatively easy and at low cost, and their assembly may be easily followed using a plethora of molecular and cellular approaches and instrumental techniques. The stability of nanoparticles made of biopolymers is one of the limiting factors which will determine the range of their applications. In their most recent paper Caldeira and Peabody [1] investigated in vitro assembly and stability of virus-like icosahedral capsid of the RNA bacteriophage PP7 particles. Contrary to expectations, recombinant fusion of the subunits have not stabilized PP7 virus-like particles against thermal denaturation, whilst disulphide bonds between coat protein dimers greatly increased the viral particles' stability.A loading capacity of nanoparticles made of biopolymers is another important criterion in the use of such nanoparticles as nano-containers for specific targeting applications. A comprehensive study of the assembly and stability of canine parvovirus-like particles (CPV) was conducted by Gilbert et al [2] who employed a novel strategy, based on Fluorescence Correlation Spectroscopy analysis, to monitor the assembly of a series of truncated monomeric canine parvovirus VP2 structural proteins and their GFP fusions. The trancations ranged from 0 (native protein) to 40 amino acids. Intriguingly, only one truncated variant (-14 amino acids) failed to assemble into a CPV-like particle, which was confirmed independently using more traditional confocal and electron microsco