Table 1.
Merits and defects of various in vivo imaging agents
| Merits | Applications | Defects | References | ||
|---|---|---|---|---|---|
| Fluorescent proteins | 1. High sensitivity 2. Non-toxic |
1. Detection and tracking | 1. Prone to transduction failure 2. Darker color |
48,49 | |
| Fluorescent dyes | Coumarins | 1. High QY 2. Large Stokes shift 3. Good light stability 4. Easy modification |
1. Detection of various ions and active substances 2. Fluorescent labeling of nucleic acid and protein molecules |
1. Short emission wave 2. Easy to be interfered with background fluorescence |
50,51 |
| Rhodamines | 1. High QY and molar extinction coefficient 2. Excellent Water solubility |
1. Single particle tracking 2. Super-resolution imaging 3. Detection |
Absorption and emission wavelengths are only in the visible region | 52,53 | |
| Anthocyanins | 1. NIR fluorescence 2. Good biocompatibility 3. Low toxicity |
1. Tumor targeting 2. Imaging in vivo 3. Biosensing |
1. Poor light stability 2. Prone to photobleaching 3. Low fluorescence QY 4. Low solubility in water |
54,55 | |
| Bioluminescence | Luciferase | 1. Strong specificity 2. High sensitivity 3. Accurate quantification 4. Non-toxic 5. Easy to penetrate membranes barrier |
1. Markers of multiple enzyme genes 2. Tracer stem cells |
1. Requires an external source to give the substrate to emit light 2. Only two-dimensional images |
56 |
| Nanomaterials | Long afterglow NPs | 1. No excitation 2. Avoid background interference 4. Strong tissue penetration ability 3. No toxic |
1. Biosensing detection 2. Imaging in vivo 3. Drug delivery and treatment |
1. Difficult to prepare for NIR materials 2. Difficult to modify 3. Poorly water-soluble |
57 |
| Semiconductor quantum dots | 1. Adjustable size 2. High yield 3. Good light stability 4. Easy modification |
1. Imaging 2. Sensor photovoltaic |
1. Metal ions 2. Toxic 3. Insoluble in water |
58 | |
| Upconversion NPs | 1. High chemical stability 2. Light bleaching resistance 3. Good water solubility, Low toxicity 4. Long fluorescence lifetime |
1. Bioimaging 2. Biodetection, 3. PDT 4. Drug delivery |
1. Low luminous efficiency 2. Large size |
59 | |
| Magnetic NPs | 1. Unique magnetic properties 2. Good biocompatibility 3. Large specific surface area 4. Easy to modify |
1. Magnetic resonance imaging 2. Hyperthermia 3. Targeted drug delivery |
1. Prone to reunion 2. Low use efficiency |
60 | |
| RNA aptamer | 1. No background interference 2. Simple preparation |
1. Cell RNA imaging | 1. Highly dependent on non-physiological ion concentration 2. Low light stability |
61,62 | |
| Isotopes | Radionuclide | 1. Real-time non-invasive tracing 2. Targeting various biological molecules in vivo |
1. Stem cell therapy 2. Tumor cell labeling and therapy 3. Cellular immunity research |
1. Low spatial resolution 2. Radiation generation 3. Expensive detection equipment |
63,64 |