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Patent Law at M. Carvalho
An innovate application in drug delivery takes advantage of the superior ability of shock waves to produce transfected cells. Particularly, a recent patent application described the use of shock waves as a means to transfect biological cells with extraneous deoxyribonucleic acid (DNA) and other materials with minimal adverse effects.
June 1st, 2009
Shock Waves: Transfection of Biological Cells.
Shock waves occur in nature and its dynamic behaviors have been characterized. Shock waves are a type of propagating disturbance generated by a source moving faster than the speed of sound. Shock waves carry energy and can propagate through solid, liquid, gas or electromagnetic fields.
Already well known is the fact that shock waves are used in biological therapies and used to deliver large molecules into cells. Shock wave lithotripsy—particularly, with enhanced acoustic cavitation—is already widely used for treatment of stone disease. Mammalian cells have been successfully transfected with DNA by using ultrasound transmitted through the walls of cell culture flasks or plates (cavitation is a key component of ultrasound-mediated transfection).
The transfer of molecules into cells is a potential method of tumor therapy. The transfer of DNA plasmids subsequently leads to the expression of marker proteins inside of selected biological cells. Cell transfection is a widely used technique in both clinical and basic research. Transfection is a process whereby a predetermined amount of either nucleic acid sequences (DNA or RNA) or a chemical compound are introduced into cells by either biochemical or physical processes. It serves many applications since protein production to changing the protein expression profile of a cell and the addition of genetic markers to a cell line. To deliver molecules into biological cells, several techniques are employed (physicochemical or biological). Biochemical methods may include DEAE-dextran (endocytosis), calcium phosphate, and liposome (cationic lipids). Physical transfection methods routinely include direct micro-injection of materials, biolistic particle delivery system or gene gun (heavy metal coated with DNA) and electroporation (high-voltage electric shocks). Biological methods include virus-aided delivery. Among a varied range of problems related to the application of transfecting cells with extraneous material is death of a substantial number of cells. This is so because the increase of cell permeability (membrane leakage) may have adverse effect to the cell survival.
Patenting Application US 2009/0105738 —Transfecting biological cells.
The patent application US 2009/0105738 involves a miniature device that creates and directs shock waves into targets such as biological cells. The device uses the energy of combustion of explosive material (nanoenergetic) to produce shock waves suitable for delivering compounds to biological cell types with a high degree of cell permeabilization. Moreover, the miniature device may be used for various purposes in the biomedical field such as cell permeabilization, acceleration of microparticles or nanoparticles, and cavitation.
The novelty relies on the fact that the miniature device generates shock waves with high peak pressures, fast rise times, and high pressure impulses, resulting in the ability to transfect cells with relatively high efficiency compared to existing chemical and electrical transfection techniques. According to the application, the transfection efficiency is in the range of 99%.
According to the application, the device includes an energetic material and a transmissive barrier. The combustion material is made up of a mixture of fuel and oxidizer nanoparticles. The combustible compound produces a combustion front that has a propagation velocity greater than the speed of sound through the surrounding materials. The transmissive barrier is made up of a flexible material. It transmits the shock wave pressures generated by the combustion of the energetic material.
This application dealt with a critical aspect of the characteristics of the pressure waves in biological applications. The inventors had to fine-tune the characteristics of the shock waves to fall between the threshold of permeabilization and the threshold for cell damage. This is so because shock waves may cause cell death if the peak pressure or the pressure impulse exceeds a certain level. For example, shock waves possessing short rise times, high peak pressures, or high pressure impulses have been correlated with a high degree of cell permeabilization, but also cause cell injury. Since the thresholds for cell permeabilization and cell injury also vary among the different cell line and molecules being introduced to the cells, a need existed to match the characteristics of the shock waves to the varied cell lines and molecules being delivered.
These results are encouraging indications for the future development of simultaneous gene therapy.
Literature of interest:
Patent Application US 2009/0105738 assigned to The Curators of the University of Missouri for DEVICE FOR TRANSFECTING CELL USING SHOCK WAVES GENERATED BY THE IGNITION OF NANOENERGETIC MATERIALS. (Inventors: Steve Apperson, Shubhra Gangopadhyay, Luis Polo-Parada, Andrey Bezmelnitsyn and Keshab Gangopadhyay).
Ciaravino, et al., Pulsed Enhancement of acoustic cavitation: a postulated model. Ultrasound Med. Biol. 7:159-66 (1981).
Bao, S. et al., Ultrasound Induced Gene Transfection and its Implications in Cancer Gene Therapy. Conference Proceedings, vol. 43 (suppl2): S82; (1997).
Rubanyi GM. The future of human gene therapy. Molecular Aspects Medicine. 22(3):113-42; (Jun. 2001).
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