Bacteriophages and phage-inspired nanocarriers for targeted delivery of therapeutic cargos

Abstract

The main goal of drug delivery systems is to target therapeutic cargoes to desired cells and to ensure their efficient uptake. Recently a number of studies have focused on designing bio-inspired nanocarriers, such as bacteriophages, and synthetic carriers based on the bacteriophage structure. Bacteriophages are viruses that specifically recognize their bacterial hosts. They can replicate only inside their host cell and can act as natural gene carriers. Each type of phage has a particular shape, a different capacity for loading cargo, a specific production time, and their own mechanisms of supramolecular assembly, that have enabled them to act as tunable carriers. New phage-based technologies have led to the construction of different peptide libraries, and recognition abilities provided by novel targeting ligands. Phage hybridization with non-organic compounds introduces new properties to phages and could be a suitable strategy for construction of bio-inorganic carriers. In this review we try to cover the major phage species that have been used in drug and gene delivery systems, and the biological application of phages as novel targeting ligands and targeted therapeutics.

Keywords: Bacteriophage; Bioinspired drug delivery; Display; Nanocarriers; Phage; Targeting; Virus-like particles.

Figure 1

Phage display and phage-based targeted delivery technology; A: Insertion of ligand-encoding hybrid oligonucleotides into a gene encoding a capsid (e.g. gene III) and consequent display of the ligand on the surface of phage and B: targeted delivery of the loaded genes or therapeutic compounds into the desired cells.

Figure 2

Genetic manipulation of M13 bacteriophage for prostate tumor targeting; A) the phage is genetically manipulated to express prostate-specific penetrating peptide on PIII protein and biotin acceptor protein (BAP) on PIX protein. B) Further modification of BAP by biotin-streptavidin provides a binding site for conjugation of exogenous cargo to be transferred into the targeted cells. Reprinted with permission from[55]. Copyright (2016) American Chemical Society.

Figure 3

Basic structure of MS2 nanocarriers: A) the external surface of the MS2 coat displays the modified aminoacid p-aminophenyllalamine(paF19) and the protein on the internal phage surface displays cysteine residues (Cys 87). B) After removing the phage genome, the Cys 87 is modified with a maleimide-conjugated porphyrin, and a Jurkat leukemia T cell-specific DNA aptamer is attached to the paF19. After the carrier enters into the targeted cell and is illuminated, reactive oxygen species are produced and the cancerous cells are disrupted. (Reprinted from ref.[72] Copyright (2016) American Chemical Society).

Figure 4

Mechanism of gene delivery by T4 capsid-based nanoparticles. A) Initiation of DNA packaging by aggregation of gp17; B) DNA encapsulation into the head by ATP utilization; C) Adding the Soc proteins; D) Fusing the Hoc- targeting peptide; E) Nonspecific binding of the nanoparticle to the cell surface; F) Receptor mediated binding to the cell surface; G) As a result of cell binding internalization takes place; (H and I) Either the transferred gene produces the displayed peptide such as beta-galactosidase; (K, L,M) Or DNA is transformed in the nucleus and encodes the desired protein such as luciferase (Reprinted from ref.[113] with permission from PNAS).

Figure 5

Basic properties of M13-SWCNT fluorescent-labeled nanocarrier; A) basic structure of the imaging vector: SWCNT is embedded in the pVIII structure and pIII is engineered to bind to prostate cancer; B) UV-absorption spectra at different wavelengths; C) comparison of PL excitation of M13-SWNTs in sodium cholate (SC) and phosphate-buffer saline (PBS); D) stability test of SWNTs in serum(Reprinted from ref.[54] Copyright (2016) American Chemical Society).

Figure 6

Efficient activity of MCF-7-targeted “Phage-Doxil”. A) Fluorescence images of tumor accumulation of DOX (Red fluorescence). (Blue fluorescence: DAPI-stained nuclei). B) Antitumor activity of Doxil with MR images of tumors in different groups (Doxil, non-targeted Phage-Doxil and MCF-7 targeted Phage-Doxil). C) Antitumor activity images of tumor sections with H & E staining. Necrotic cells (N) and viable cells (V) showing eosinophilic cytosol (pink) accompanied by hematoxylin stained nuclei (blue) (Reproduced from ref. [168] with permission from ELSEVIER).

Figure 7

A) Delivery of horseradish peroxidase (HRP) to prostate cancer cells. 1) no treatment; 2) 50 × 10⁹; 3) 10 × 10⁹; 4) 5 × 10⁹; 5) 1 × 10⁹ Ypep2(p3)/SAVHRP(p9) or SPARC binding peptide (SBP)(p3)/SAV-HRP(p9) pfu/mL phage; 6) ~1.6nM recombinant SAV-HRP. (B) Quantitative demonstration of image (A) results (SAV-HRP: streptavidin- horseradish peroxidase) (Reprinted from ref. [55] with permission from American Chemical Society).