Surface polyethylene glycol enhances substrate-mediated gene delivery by nonspecifically immobilized complexes

Abstract

Substrate-mediated gene delivery describes the immobilization of gene therapy vectors to a biomaterial, which enhances gene transfer by exposing adhered cells to elevated DNA concentrations within the local microenvironment. Surface chemistry has been shown to affect transfection by nonspecifically immobilized complexes using self-assembled monolayers (SAMs) of alkanethiols on gold. In this report, SAMs were again used to provide a controlled surface to investigate whether the presence of oligo(ethylene glycol) (EG) groups in a SAM could affect complex morphology and enhance transfection. EG groups were included at percentages that did not affect cell adhesion. Nonspecific complex immobilization to SAMs containing combinations of EG-and carboxylic acidterminated alkanethiols resulted in substantially greater transfection than surfaces containing no EG groups or SAMs composed of EG groups combined with other functional groups. Enhancement in transfection levels could not be attributed to complex binding densities or release profiles. Atomic force microscopy imaging of immobilized complexes revealed that EG groups within SAMs affected complex size and appearance and could indicate the ability of these surfaces to preserve complex morphology upon binding. The ability to control the morphology of the immobilized complexes and influence transfection levels through surface chemistry could be translated to scaffolds for gene delivery in tissue engineering and diagnostic applications.

Dynamic analysis of DNA nanoparticle immobilization to model biomaterial substrates using combinatorial spectroscopic ellipsometry and quartz crystal microbalance with dissipation

“…There have been many efforts to increase the efficiency of nonviral complex delivery, including alternative delivery strategies like substrate-mediated gene delivery (SMD). SMD is a technique where DNA-NPs are immobilized to substrates, and cells are then seeded onto these DNA-NPs [7][8][9][10]. SMD is often compared and contrasted to bolus gene delivery, amore traditional gene delivery technique where DNA-NP complexes are simply pipetted into cell culture media and allowed to diffuse to the seeded cell layer.…”

“…In comparison to bolus methods, SMD is a particularly advantageous gene delivery technique, as immobilization of DNA to surfaces places it directly within the cell's microenvironment, therefore overcoming diffusion and mass transport limitations associated with trafficking of nonviral complexes to cells [9]. In addition, the immobilization of DNA complexes to a substrate enhances gene transfer, since surface immobilization of DNA-NPs has the ability to preserve NP size observed in solution and inhibit complex aggregation, while cytotoxicity is reduced because less DNA is required to achieve gene transfer [7][8][9][11][12][13]. Finally, SMD offers the ability to pattern the immobilization of nonviral complexes on surfaces, which can lead to patterned transgene expression, which is particularly pertinent to tissue engineering applications [7].…”

“…For example, previous work has investigated surface chemistry as a variable to improve SMD, employing self assembled monolayers (SAMs) of alkanethiols on gold to influence electrostatic interactions between the surface and DNA-NP complex [7,8]. In addition, the roles of nonspecific interactions in DNA-NP adsorption and enhanced transfection have been investigated on surfaces coated with extracellular matrix and serum proteins, such as fetal bovine serum (FBS) [9,11].…”

Surface- and Hydrogel-Mediated Delivery of Nucleic Acid Nanoparticles

“…Incorporation of poly(ethylene glycol) groups into carboxylic acid-terminated SAMs may increase transfection (10) 13. Typically we use gold substrates of ~0.5 cm 2 cut from a gold-coated microscope slide, as described above.…”

“…This method of delivery was first described in 2002 using a specific avidin-biotin bond to tether nanoparticles to surfaces (2,3) and was later extended to nonspecific absorption of the nanoparticles to a variety of biomaterial surfaces (1,(4)(5)(6)(7)(8)(9)(10). Nonspecific adsorption of nanoparticles is accomplished through noncovalent mechanisms (1,(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), including hydrophobic, electrostatic, and van der Waals interactions. Nonspecific binding depends upon the molecular composition of the vector (e.g., lipid versus polymer) and the relative quantity of each (e.g., nitrogen-to-phosphate ratio or N/P), as well as properties of the surface (e.g., hydrophilicity, charge, presence of serum proteins).…”