Microwave irradiation enhances gene and oligonucleotide delivery and induces effective exon skipping in myoblasts

Infrared Laser-Based Single Cell Permeabilization by Plasma Membrane Temperature Gradients

Single cell microinjection provides precise tuning of the volume and timing of delivery into the treated cells; however, it also introduces workflow complexity that requires highly skilled operators and specialized equipment. Laser-based microinjection provides an alternative method for targeting a single cell using a common laser and a workflow that may be readily standardized. This paper presents experiments using a 1550 nm, 100 fs pulse duration laser with a repetition rate of 20 ns for laser-based microinjection and calculations of the hypothesized physical mechanism responsible for the experimentally observed permeabilization. Chinese Hamster Ovarian (CHO) cells exposed to this laser underwent propidium iodide uptake, demonstrating the potential for selective cell permeabilization. The agreement between the experimental conditions and the electropermeabilization threshold based on estimated changes in the transmembrane potential induced by a laser-induced plasma membrane temperature gradient, even without accounting for enhancement due to traditional electroporation, strengthens the hypothesis of this mechanism for the experimental observations. Compared to standard 800 nm lasers, 1550 nm fs lasers may ultimately provide a lower cost microinjection method that readily interfaces with a microscope and is agnostic to operator skill, while inducing fewer deleterious effects (e.g., temperature rise, shockwaves, and cavitation bubbles).

Microwave-assisted delivery of an anticancer drug to cancer cells

Exposure of MCF-7 breast and PC-3 prostate cancer cells to 10 W microwaves at 2.45 GHz increased their uptake of the cancer drug doxorubicin from media by almost 100%, concomitantly increasing cell death, while microwave exposure alone had no cellular toxicity. Addition of inhibitors of endocytosis during the treatment of MCF-7 cells with doxorubicin and microwaves showed no impact on the uptake of the anticancer drug. Furthermore, the uptake of oligonucleotides by MCF-7 cells is not affected by the treatment with microwaves. These observations suggest that endocytosis is not involved in the uptake of doxorubicin while cells are exposed to microwave irradiation. Thus, targeted low power microwave irradiation could be a safe and effective means of promoting chemotoxin delivery to cancer cells, potentially reducing the dosages and side effects of anti-cancer drugs.

Exposure of MCF-7 breast and PC-3 prostate cancer cells to 10 W microwaves at 2.45 GHz increased their uptake of doxorubicin from media by almost 100%, concomitantly increasing cell death, while microwave exposure alone had no cellular toxicity.

Plasma membrane temperature gradients and multiple cell permeabilization induced by low peak power density femtosecond lasers

Calculations indicate that selectively heating the extracellular media induces membrane temperature gradients that combine with electric fields and a temperature-induced reduction in the electropermeabilization threshold to potentially facilitate exogenous molecular delivery. Experiments by a wide-field, pulsed femtosecond laser with peak power density far below typical single cell optical delivery systems confirmed this hypothesis. Operating this laser in continuous wave mode at the same average power permeabilized many fewer cells, suggesting that bulk heating alone is insufficient and temperature gradients are crucial for permeabilization. This work suggests promising opportunities for a high throughput, low cost, contactless method for laser mediated exogenous molecule delivery without the complex optics of typical single cell optoinjection, for potential integration into microscope imaging and microfluidic systems.

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Femtosecond lasers can transfect a single cell through optoporation.

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Multiple cells are transfected with much lower power densities at 1550 nm.

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Calculations show that temperature gradients contribute to the mechanism.

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These mechanisms resemble those also involved in microwave biological interactions.

A new extensively characterised conditionally immortal muscle cell-line for investigating therapeutic strategies in muscular dystrophies

A new conditionally immortal satellite cell-derived cell-line, H2K 2B4, was generated from the H2K^b-tsA58 immortomouse. Under permissive conditions H2K 2B4 cells terminally differentiate in vitro to form uniform myotubes with a myogenic protein profile comparable with freshly isolated satellite cells. Following engraftment into immunodeficient dystrophin-deficient mice, H2K 2B4 cells regenerated host muscle with donor derived myofibres that persisted for at least 24 weeks, without forming tumours. These cells were readily transfectable using both retrovirus and the non-viral transfection methods and importantly upon transplantation, were able to reconstitute the satellite cell niche with functional donor derived satellite cells. Finally using the Class II DNA transposon, Sleeping Beauty, we successfully integrated a reporter plasmid into the genome of H2K 2B4 cells without hindering the myogenic differentiation. Overall, these data suggest that H2K 2B4 cells represent a readily transfectable stable cell-line in which to investigate future stem cell based therapies for muscle disease.

Therapy for neuromuscular disorders

Research into therapeutic approaches for both recessive and dominant neuromuscular disorders has made great progress over the past few years. In the field of gene therapy, antisense-mediated exon skipping is being applied to bypass deleterious mutations in the dystrophin gene and restore dystrophin expression in animal models of muscular dystrophy. Approaches for the dominant genetic muscle diseases have turned toward elimination of the mutant gene product with anti-sense oligonucleotide therapy and RNA interference techniques. Refinements of adeno-associated viral vectors and strategies for their delivery are also leading towards future clinical trials. The discovery of new, multipotent cell lineages, some of which possess the ability to successfully engraft muscle following vascular delivery, presents exciting prospects for the field of stem cell therapy. These discoveries represent steady progress towards the development of effective therapies for a wide range of neuromuscular disorders.