Recent advances in porphyrin-based nanocomposites for effective targeted imaging and therapy

Abstract

Porphyrins are organic compounds that continue to attract much theoretical interest, and have been called the "pigments of life". They have a wide role in photodynamic and sonodynamic therapy, along with uses in magnetic resonance, fluorescence and photoacoustic imaging. There is a vast range of porphyrins that have been isolated or designed, but few of them have real clinical applications. Due to the hydrophobic properties of porphyrins, and their tendency to aggregate by stacking of the planar molecules they are difficult to work with in aqueous media. Therefore encapsulating them in nanoparticles (NPs) or attachment to various delivery vehicles have been used to improve delivery characteristics. Porphyrins can be used in a composite designed material with properties that allow specific targeting, immune tolerance, extended tissue lifetime and improved hydrophilicity. Drug delivery, healing and repairing of damaged organs, and cancer theranostics are some of the medical uses of porphyrin-based nanocomposites covered in this review.

Keywords: Drug delivery; Nanocomposite; Nanoparticle; Porphyrin; Theranostics.

Figure 1.

Basic chemical structure of porphyrins and the main family members

Figure 2.

PS1-EPMO and PS2-EPMO nanoparticles and their HRTEM micrographs, respectively (a and b). Images exhibit usual mesoporosities. Photosensitizer precursors and their visible UV-spectrum via their NPs in EtOH (c and d) [35].

Figure 3.

PS1, PS2 and their photosensitizer precursors Silylation (a and b). ethanephotosensitizer via PMO nanoparticles production by Sol-gel (c). Functions of PMO nanoparticles for drug delivery and photodynamic therapy (synergistic manner) (d) [35].

Figure 4.

PCN-224 construction Image. (a) a cluster of Zr6 with the open formula of (Zr6O4 (OH) 4(H2O) 6(OH) 6(COO) 6), tetratopic linker with the open formula of (tetrakis (4-carboxyphenyl) porphyrin with the open formula of (H2TCPP)), and image of PCN-224 as the 3D nanoporous framework. (b) A PCN-224 cubic unit and a schematic image of spherical PCN-224 NPs in cubic units structure form, potential to make various sizes [36].

Figure 5.

(a) A typical scheme for porphysome, containing porphyrin and long-chain lipid. The phospholipid headgroup (red) and porphyrin (blue) are highlighted in the subunit (left) and assembled nanovesicle (right). (b), Electron micrographs of negatively stained porphysomes (5% PEG-lipid, 95% pyropheophorbide-lipid). (c), Absorbance of the porphyrin-lipid subunits added in porphysomes formed from pyropheophorbide (blue), zinc-pyropheophorbide (orange) and bacteriochlorophyll (red) in PBS. (d), Resonance light scattering spectra ratio between gold nanorods and pyropheophorbide porphysomes. Nanorod and porphysome concentration was adjusted to have equal optical density at 680 nm. (e), Dynamic light scattering size profiles of indicated porphysomes recorded in PBS. [71]

Figure 6.

A different approach for surface modification of VLPs; (a) Primary amines (lysines, N-termini): NHS-ester conjugation (left, black) is most common. Thioimidate conjugation (green, right) has recently been described and is based on the reaction of imidoesters. (b) Thiols (cysteines): maleimides are mainly employed for covalent bonding. Thiols can also form disulfide bonds under mild oxidative conditions. (c) Carboxylic acids (glutamic acid, aspartic acid): carbodiimide activates the acid to react with primary amines. (d) Phenol (tyrosine): oxidation of the ligand moiety to diazonium permits for ortho-attachment to the phenol group. (e) Alkynes (uAA): alkynes react with azides in the presence of Cu(I). (f) P-aminophenylalalnine (uAA): the reaction is similar to that displayed with tyrosine (d), but remains completely orthogonal. (g) Azides (uAA): azides can undergo the Staudinger ligation (left, green), Cu(I)-catalyzed click chemistry (e) or Copper-free click chemistry (black, right). The Staudinger ligand has fallen out of favor becuase of kinetic limitations and has not recently been utilized for VNP functionalization. The reaction of the cyclooctyne or other copper-free click chemistry reagent has yet to be ascertained employing VNPs and is displayed only to conceptualize how click chemistry can become copper-free [116]

Figure 7.

Schematic demonstration of the PCTF and PCTF-Mn producing [146]

Figure 8.

(a) the MOF@POPs based on UiO-AM and polyaniline as MOF and porous organic polymer, respectively [179] and (b) Developing water-soluble MOF-templated porphyrin polymer thin film with high PDT effect against bacteria [180]