Tissue Factor (natural or recombinant truncated) can be incorporated into stable, soluble nanoscale particles so that activity is maintained. These particles can be used as a reagent in prothrombin clotting time assays or they can be used in therapeutic compositions for use in humans or animals. Therapeutic settings can include supplementation in the case of a genetic deficiency, uncontrolled bleeding, surgical incisions or seepage, thrombocytopenia, soft tissue trauma or other trauma, to effect tumor regression or to inhibit tumor growth.