TABLE 1.

Representative theranostic nanomaterials utilized in drug delivery system.

Type		Size (nm)	Pros	Cons
Liposomes		80–150	◆ Biocompatibility and biodegradability ◆ Ability to deliver both the hydrophilic and hydrophobic payloads ◆ Controlled pharmacokinetics and reduced toxicity ◆ Diverse surface modification	◆ Limited loading efficiency ◆ Limited stability in vivo ◆ Rapid clearance from the blood
Polymers	◆ Polymer conjugate complexes ◆ Polymer nanospheres ◆ Polymer micelles ◆ Dendrimers	1–20 10–200 20–200 3–50	◆ Tunable physiochemical properties ◆ Controllable size and composition ◆ Diverse surface modification ◆ High loading efficiency and sustained release ◆ Good circulation stability	◆ Limited storage stability ◆ Potential toxicity ◆ Limited capability for hydrophilic drugs ◆ Limited chemical synthesis
Iron oxide nanoparticles		varies	◆ Clinical used MRI contrast agent ◆ Magnetic hyperthermia and PAI ◆ Easy surface modification	◆ Limited stability under aqueous conditions
Quantum dots		2–10	◆ Unique optical properties ◆ Utilization for PDT	◆ Limited biodegradability and potential toxicity
Carbon nanotubes		0.8-exceed 100 nm (diameter) less than 100 nm-several cm (length)	◆ Strong optical absorbance and utilization for PTT, PAI ◆ Unique electrical property ◆ Easy surface modification	◆ Potential toxicity ◆ Limited biodegradability
Gold nanoparticles	◆ Gold nanosphere ◆ Gold nanorod ◆ Gold nanoshell ◆ Gold nanocage	5–150 20 nm-several μm 10–400 20–200	◆ Utilization for PTT, PAI, SERS ◆ Controllable size and structure and easy surface modification ◆ Optical quenching ability	◆ Limited stability under aqueous conditions
Upconversion nanoparticles		<100	◆ Unique optical property and utilization for luminescence imaging ◆ Utilization for PDT, PTT ◆ Easy surface modification and functionalization	◆ Potential toxicity ◆ Limited biodegradability

MRI, magnetic resonance imaging; PTT, photothermal therapy; PAI, photoacoustic imaging; SERS, surface-enhanced Raman spectroscopy.