  Currently, gold nanorods can be synthesized in a wide range of sizes.
However, for intended biological applications gold nanorods with approximate
dimensions 50 nm x 15 nm are used. We investigate by computer simulation the
effect of particle dimensions on the optical and thermal properties in the
context of the specific applications of photoacoustic imaging. In addition we
discuss the influence of particle size in overcoming the following biophysical
barriers when administrated in vivo: extravasation, avoidance of uptake by
organs of the reticuloendothelial system, penetration through the interstitium,
binding capability and uptake by the target cells. Although more complex
biological influences can be introduced in future analysis, the present work
illustrates that larger gold nanorods, designated by us as "nanobig rods", may
perform relatively better at meeting the requirements for successful in vivo
applications compared to their smaller counterparts which are conventionally
used.
