Table 4. Design Parameters for Nanoparticle vehicles for Photosensitizer Delivery to Solid Tumors.

Criteria	Rationale
Size and Shape	Facilitate vascular margination and extravasation into tumor
Plasma Half-Life	Increase circulation time for tumor-selective passive accumulation
Drug Encapsulation Efficiency	Limit partitioning of drug in plasma and reduce nonspecific uptake Ensure that drug is not in a highly aggregated form
Surface Charge (zeta potential)	Minimize aggregation of nanoparticle vehicles in suspension
Controlled Release Kinetics	Maintain desirable therapeutic action specifically at the target site
Active Cell-Targeting Ability	Facilitate receptor- or membrane-mediated intracellular uptake
Ease of Formulation and Scale Up	Facilitate translation into large-scale clinical use
Possible Imaging Component	Enable image-guided therapy and image-assisted evaluation