| Stability: physicochemical, optical,
and biological properties
|
Ability to resist changes in chemical, physical, and optical properties in biological and physiological conditions over time |
|
Determinable factor for solubility, aggregation, degradation, serum protein binding, and nonspecific uptake in vivo
|
|
Physicochemical stability (solubility) is governed by chemical composition, HD, hydrophilicity/lipophilicity, and surface charge |
|
Optical stability: photobleaching, photodegradation, and quenching |
| Sensitivity: detectability and optical properties
|
Ability to detect either the probe signal at the target (direct response) or change in a signal, depending on the quantity of probes at the target (indirect response) |
|
Maximum excitation and emission wavelength in the NIR range for deep tissue imaging |
|
Require high extinction coefficient and high quantum yield |
| Specificity: targeting properties (Organ vs. Cellular) |
Ability to distinguish the target from non-target processes or tissues (enhanced contrast) |
|
Require high concentration of contrast agents per unit volume of target tissue: targeting improves image resolution by enhancing the target signal and reducing background signals. |
|
Organ-specific targeting (mode of action): effective delivery to the target tissue (i.e., biodistribution, pharmacokinetics, and clearance) |
|
Cellular-specific targeting (mechanism of action): active and activatable targeting |
| Safety: physicochemical, biological, and physiological properties
|
Ability to resist innate immune defenses or undesirable consequences related to toxicity |
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Affecting factors are molecule’s size, surface chemistry, formulation, surface physics, dosage and route of administration, and ADME (absorption, distribution, metabolism, elimination). |
|
Require nontoxic, biocompatible, or biodegradable properties |
