Targeted Drug-Carrying Bacteriophages as Antibacterial Nanomedicines

Abstract

While the resistance of bacteria to traditional antibiotics is a major public health concern, the use of extremely potent antibacterial agents is limited by their lack of selectivity. As in cancer therapy, antibacterial targeted therapy could provide an opportunity to reintroduce toxic substances to the antibacterial arsenal. A desirable targeted antibacterial agent should combine binding specificity, a large drug payload per binding event, and a programmed drug release mechanism. Recently, we presented a novel application of filamentous bacteriophages as targeted drug carriers that could partially inhibit the growth of Staphylococcus aureus bacteria. This partial success was due to limitations of drug-loading capacity that resulted from the hydrophobicity of the drug. Here we present a novel drug conjugation chemistry which is based on connecting hydrophobic drugs to the phage via aminoglycoside antibiotics that serve as solubility-enhancing branched linkers. This new formulation allowed a significantly larger drugcarrying capacity of the phages, resulting in a drastic improvement in their performance as targeted drug-carrying nanoparticles. As an example for a potential systemic use for potent agents that are limited for topical use, we present antibody-targeted phage nanoparticles that carry a large payload of the hemolytic antibiotic chloramphenicol connected through the aminoglycoside neomycin. We demonstrate complete growth inhibition toward the pathogens Staphylococcus aureus, Streptococcus pyogenes, and Escherichia coli with an improvement in potency by a factor of ϳ20,000 compared to the free drug.The increasing development of bacterial resistance to traditional antibiotics has reached alarming levels (2, 3), spurring a strong need to develop new antimicrobial agents. Classical short-term approaches include chemical modification of existing agents to improve potency or spectrum. Long-term approaches rely on bacterial and phage genomics to discover new antibiotics that attack new protein targets which are essential to bacterial survival and therefore with no known resistance (1, 8). In both traditional and newly developed antibiotics, the target selectivity lies in the drug itself, in its ability to affect a mechanism that is unique to the target microorganism and absent in its host. As a result, a vast number of potent drugs have been excluded from use as therapeutics due to low selectivity. This brings to mind the limited selectivity of anticancer drugs and recent efforts to overcome it by developing targeted therapeutic strategies. Antibody-based targeted drug delivery approaches have been developed since the advent of monoclonal antibodies (6). Since then, monoclonal antibodies and derived single-chain antibodies were used to deliver potent cytotoxic components to cancer cells that, once bound, internalize and kill the target cell (7, 12). A similar immunotargeting of bacteria is not feasible due to the lack of a bacterial internalization process, making the use of an extracellular release mechanism ...

Nanoscale bacteriophage biosensors beyond phage display

“…9 In essence, bacteriophages have transcended their mere use in phage display technology to play an expanded role in the development of various applications such as biosensing, cellular imaging, vaccine development, and drug and gene delivery. [10][11][12][13][14][15] Herein, we categorize bacteriophages by their morphology into M13-based filamentous phages and T4-or T7-based …”

Applications of Nanomedicine in Antibacterial Medical Therapeutics and Diagnostics~!2009-08-26~!2009-11-25~!2010-02-24~!

“…In this experiment they tested the drug-carrying phage nanoparticles against three pathogenic bacteria, which included staphylococcus aureus, streptococcus pyogenes and E.coli. Through this they were able to achieve complete growth inhibition towards all three bacterium and are comparable to using the free drug itself, resulting in an improvement factor of 20,000 compared with the free drug alone [21].…”

“…A way to overcome this shortcoming is to increase the selectivity of the agent by targeted therapy which is indeed what a group of researchers have accomplished. Yacoby [21] has devised an efficient targeted drug platform to address the requirements of targeted drug delivery, in that it is able to selectively bind to its target, provide large drug delivery payload and timely drug release. Their approach to such criteria was in the development of a drug-carrying phage nanoparticle that was successfully able to inhibit the growth of both gram-negative and gram-positive bacteria [20].…”

“…Specific lytic mixture of bacteriophages was prepared using the induced, modified and laboratory variants of phages in the past [21][22][23][24][25][26]. There are currently many highly antibacterial agents that have been developed but due to the lack of selectivity they are too potent to be used clinically.…”

Phage engineering: how advances in molecular biology and synthetic biology are being utilized to enhance the therapeutic potential of bacteriophages

“…A number of different approaches have been considered regarding how phages can best be utilised as part of combination therapies (Figure 3). Yacoby et al have chemically modified filamentous phages to specifically deliver antibiotic drugs to Staphylococcus, Streptococcus and E. coli bacteria [73]. Although strictly speaking this is a chemical rather than a genetic engineering approach to the problem, by combining anti-bacterial polyclonal IgG antibodies bound to the minor phage coat protein p3 with chloramphenicol chemically attached to the major coat protein p8 it was possible to increase the potency of the antibiotic 10,000-fold compared to treatment with chloramphenicol alone.…”