Abstract
Developing nanomaterials that are effective, safe, and selective for gene transfer applications is challenging. Bacteriophages (phage), viruses that infect bacteria only, have shown promise for targeted gene transfer applications. Unfortunately, limited progress has been achieved in improving their potential to overcome mammalian cellular barriers. We hypothesized that chemical modification of the bacteriophage capsid could be applied to improve targeted gene delivery by phage vectors into mammalian cells. Here, we introduce a novel hybrid system consisting of two classes of nanomaterial systems, cationic polymers and M13 bacteriophage virus particles genetically engineered to display a tumor-targeting ligand and carry a transgene cassette. We demonstrate that the phage complex with cationic polymers generates positively charged phage and large aggregates that show enhanced cell surface attachment, buffering capacity, and improved transgene expression while retaining cell type specificity. Moreover, phage/polymer complexes carrying a therapeutic gene achieve greater cancer cell killing than phage alone. This new class of hybrid nanomaterial platform can advance targeted gene delivery applications by bacteriophage.
Highlights
Successful delivery of gene expression to desired sites in vivo following systemic administration will have a major impact on the practice of medicine,[1] in particular on the advance of gene therapy, genetic imaging, and DNA vaccine applications
Displaying the RGD4C-targeting ligand and containing a eukaryotic transgene cassette, coupled with a synthetic cationic polymer material (Figure 1). We have investigated their physical and chemical properties, and their biological activity
To determine whether the decreased transgene expression at high amounts of cationic polymers was associated with PDL and DEAE.DEX cytotoxicity, we performed cell viability assays and showed that this range of polymer concentrations was not associated with any toxic effects (Figure 2b)
Summary
Successful delivery of gene expression to desired sites in vivo following systemic administration will have a major impact on the practice of medicine,[1] in particular on the advance of gene therapy, genetic imaging, and DNA vaccine applications. The high tolerance for phage coat protein mutations allows insertions of foreign peptides to achieve ligand-directed targeting to the desired cell types and unlike eukaryotic viral vectors, targeting bacteriophage vectors does not require elimination of native tropism.[10] They are safe, having long been used for both prophylaxis and treatment of bacterial infections, both in adults and children, with no safety concerns being identified.[11] They have been approved by the US Food and Drug Administration for use as safe antibacterial food additives.[12] Large-scale production and purification of phage vectors are simple and economical They have a large cloning capacity for insertion of foreign DNA.[13] We previously introduced an M13 phage-based vector displaying the double cyclic RGD (CDCRGDCFC, RGD4C) ligand to target overexpressed αv integrin receptors in tumors, and incorporating a mammalian transgene cassette flanked by inverted terminal repeats from AAV2. They have no intrinsic strategies for delivering genes to mammalian cells.[19,20] As a result, phage-derived vectors undoubtedly have great promise, due to this inherent limitation, they need to be improved if they are going to find wide clinical applications
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