Interfacing biology with nanomaterials

Incredible progress continues to be made in elucidating the structure/function of biomolecules to the point where de novo biologicals with designer properties such as peptide nucleic acids, for example, are now a reality. Likewise, similar progress is continually being made for many nanomaterials with unique physiochemical and optoelectronic properties including semiconductor quantum dots (QDs), metal or other nanoparticles (NPs) along with carbon-based nanotubes and fullerenes. Nanoscience suggests that these disparate almost orthogonal nanomaterials can be combined to create value-added functional devices that will be capable of far more than the individual parts. For example, hybrid photosynthetic protein-NP or carbon nanostructures for efficient solar energy harvesting or antibody/nucleic acid-NP devices for biosensing and targeted drug delivery. These and a myriad of other related concepts are commonly presented to program managers, outlined as the goal in proposals, or become the motivational slide at the start of a talk and indeed the number of researchers active in what is now described as ‘Bionanotechnology’ are beyond counting. What is hardly ever addressed in detail is how to construct these new biological-inorganic composites as desired; in other words how do we bring the pieces of the different puzzles together every time? As this most often becomes the rate-limiting step, it is an area of importance to the future progress of this nascent field.

This current Materials Today issue focuses on ‘Materials for Sensing/Diagnosis’. A common theme amongst this issue is that almost all the hybrid nanomaterials described within would greatly benefit from having the ability to controllably or systematically attach any biological to any nanomaterial or surface. But what does ‘controllably’ mean in this case? Five criteria provide a good framework and they are easily visualized by using the attachment of a biological (protein, peptide, DNA) to a NP as a descriptive example, see cover image. Successful implementation would allow: (i) any biological to be homogenously attached to any NP/surface, with intimate control over (ii) orientation, (iii) separation distance from the surface, (iv) valence or density and v-affinity to that surface. Analogous ideas have already been iterated in various forms, see for example the excellent monograph by Hamad-Schifferli [1] and [2]. Although easily stated, these goals are hard to achieve individually, let alone cumulatively. Currently utilized chemistries borrow heavily from established biolabeling/bioconjugation techniques [3] and are plagued by numerous issues including lack of unique or specific target sites, heterogeneity, crosslinking, loss of function and an overall lack of control when applied to nanomaterials.

So how do we get there? Similar to the examples set by Tsien, Haugland, Hermanson and innumerable others who have developed the current toolset for bioconjugating and modifying biologicals, we need a dedicated chemical discipline that focuses on nanomaterial-bioconjugation [3]. Current and next generation nanoscientists will benefit greatly from a working knowledge of what biological-inorganic composites can be achieved practically and what is not yet feasible. As Nanoscience will soon be established as both a classroom subject and a focused major at a growing number of institutions, it's appropriate that this specialty be both researched and taught at the university level. With a combination of materials science, physics, molecular biology, bioengineering and chemistry all needing emphasis, the subject itself is really emblematic of this cross-disciplinary field. Further, many scientists already unknowingly rely on these chemistries to biofunctionalize surfaces or other materials, so it should be firmly recognized for the potential that it can provide in the long-term.