Applicator and electrode design for in vivo DNA delivery by electroporation

Electrochemotherapy - possible benefits and limitations to its use in the head and neck region

CONCLUSION

Electrochemotherapy (ECT) is an efficacious treatment. It should, however, be used with some caution in the treatment of head and neck cancer.

OBJECTIVES

To assess local tumor control, safety, survival, and functional outcome after treatment of cancer in the head and neck region with ECT.

METHODS

Four patients with primary T2 cancer of the oral cavity or oropharynx and one patient with a metastasis of renal cancer in the masseter muscle were treated with ECT with intratumorally administered bleomycin. Control biopsies were carried out 2 months after treatment. Postoperative radiotherapy was performed based on tumor T-stage and the depth of tumor infiltration. Serious adverse events and treatment malfunctions were recorded. The follow-up time was 24 months for the surviving patients and 20 months overall. The PSS-HN scale was used to assess the functional outcome.

RESULTS

No local recurrence was recorded in any patient during the follow-up. However, only one patient was treated with ECT alone. There were four serious adverse events: one nearly lethal bleeding, two cases of osteoradionecrosis, and a fistula. One patient died from distant metastasis. The other patients were tumor-free both locally and overall at 24 months. The median functional outcome in all parameters was worse 1 year after treatment.

Contactless magneto-permeabilization for intracellular plasmid DNA delivery in-vivo

Electroporation, an attractive process for delivering DNA and other molecules into target cells in vivo and in vitro is limited by the necessity of electrodes that need to be in contact with the subject or object to be electroporated. We have used magnetic fields, which do not require material contact with the subject, to temporarily permeabilize cells in guinea pig skin in vivo to enhance uptake and expression of GFP plasmid DNA. The results show for the first time that magnetic fields can trigger a process likely similar to electroporation. In designing the magnetic pulses, our most important criterion was a high rate of change of the magnetic field, based on the principle described by Michael Faraday which is expressed by the formula: E = -dB/dt, (E, electric field, B, magnetic field, t, time). Magnetic fields were generated by a flat electromagnet in a hand-held applicator positioned above the target tissue. The magnetic pulses had a peak magnetic flux density of 4 tesla; 50 pulses were applied in 5 sec. Biphasic magnetic pulses were twice as effective as monophasic pulses and about equally effective as traditional electroporation pulses . Advantages of magnetopermeabilization over electoporation include: No contact between applicator and subject ("contact-less"); no need for invasive, disposable, sterile electrodes ("needle-less"); no pain from needles and reduced overall pain; no known side effects; easier and faster to administer than electroporation; less expensive due to absence of disposables; and, importantly, greater tissue penetration of the magnetic field allowing treatment of anatomical areas inaccessible by electroporation.

Adjustment of ultrasound exposure duration to microbubble sonodestruction kinetics for optimal cell sonoporation in vitro

Cell sonoporation enables the delivery of various exogenous molecules into the cells. To maximize the percentage of reversibly sonoporated cells and to increase cell viability we propose a model for implicit dosimetry for adjustment of ultrasound (US) exposure duration. The Chinese hamster ovary cell suspension was supplemented with microbubbles (MB) and exposed to US, operating at the frequency of 880kHz, with a 100% duty cycle and with an output peak negative pressure (PNP) of 500kPa for durations ranging from 0.5 to 30s. Using diagnostic B-scan imaging we showed that the majority of the MB at 500kPa US peak negative pressure undergo sonodestruction in less than a second. During this time maximal number of reversibly sonoporated cells was achieved. Increase of US exposure duration did not increase sonoporated cell number, however it induced additional cell viability decrease. Therefore aiming to achieve the highest level of reversibly sonoporated cells and also to preserve the highest level of cell viability, the duration of US exposure should not exceed the duration needed for complete MB sonodestruction.

Optimized in vivo transfer of small interfering RNA targeting dermal tissue using in vivo surface electroporation

Electroporation (EP) of mammalian tissue is a technique that has been used successfully in the clinic for the delivery of genetic-based vaccines in the form of DNA plasmids. There is great interest in platforms which efficiently deliver RNA molecules such as messenger RNA and small interfering RNA (siRNA) to mammalian tissue. However, the in vivo delivery of RNA enhanced by EP has not been extensively characterized. This paper details the optimization of electrical parameters for a novel low-voltage EP method to deliver oligonucleotides (both DNA and RNA) to dermal tissue in vivo. Initially, the electrical parameters were optimized for dermal delivery of plasmid DNA encoding green fluorescent protein (GFP) using this novel surface dermal EP device. While all investigated parameters resulted in visible transfection, voltage parameters in the 10 V range elicited the most robust signal. The parameters optimized for DNA, were then assessed for translation of successful electrotransfer of siRNA into dermal tissue. Robust tagged-siRNA transfection in skin was detected. We then assessed whether these parameters translated to successful transfer of siRNA resulting in gene knockdown in vivo. Using a reporter gene construct encoding GFP and tagged siRNA targeting the GFP message, we show simultaneous transfection of the siRNA to the skin via EP and the concomitant knockdown of the reporter gene signal. The siRNA delivery was accomplished with no evidence of injection site inflammation or local tissue damage. The minimally invasive low-voltage EP method is thus capable of efficiently delivering both DNA and RNA molecules to dermal tissue in a tolerable manner.

Peptide-conjugated PAMAM dendrimer as a universal DNA vaccine platform to target antigen-presenting cells

DNA-based vaccines hold promise to outperform conventional antigen-based vaccines by virtue of many unique features. However, DNA vaccines have thus far fallen short of expectations, due in part to poor targeting of professional antigen-presenting cells (APC) and low immunogenicity. In this study, we describe a new platform for effective and selective delivery of DNA to APCs in vivo that offers intrinsic immune-enhancing characteristics. This platform is based on conjugation of fifth generation polyamidoamine (G5-PAMAM) dendrimers, a DNA-loading surface, with MHC class II-targeting peptides that can selectively deliver these dendrimers to APCs under conditions that enhance their immune stimulatory potency. DNA conjugated with this platform efficiently transfected murine and human APCs in vitro. Subcutaneous administration of DNA-peptide-dendrimer complexes in vivo preferentially transfected dendritic cells (DC) in the draining lymph nodes, promoted generation of high affinity T cells, and elicited rejection of established tumors. Taken together, our findings show how PAMAM dendrimer complexes can be used for high transfection efficiency and effective targeting of APCs in vivo, conferring properties essential to generate effective DNA vaccines.

Electroporation therapy for T1 and T2 oral tongue cancer

CONCLUSION

Electroporation therapy appears to be a safe treatment achieving excellent local tumor control and very good functional results in our study and it should be further clinically evaluated.

OBJECTIVES

The objectives of this study were to assess local tumor control, survival, and effects on speech and eating after treatment of tongue cancer with electroporation therapy, a new local therapeutic modality. In this approach intracellular accumulation of a chemotherapeutic agent is achieved by using a locally applied electrical field.

METHODS

Fifteen patients with primary T1 and T2 oral tongue cancer were treated with electroporation therapy with intratumorally administered bleomycin. Postoperative radiotherapy was performed when the tumor infiltration was 5 mm or more. The follow-up time was 24 months for the surviving patients and 20.4 months overall. The effects on eating and speech were assessed using the PSS-HN scale and voice recordings.

RESULTS

No local recurrence was recorded in any patient during the follow-up. Three patients died, two from progressive regional disease. Of the 12 surviving patients, 2 patients had regional recurrence and 10 patients including the 5 patients treated with EPT alone were tumor-free both locally and regionally at the last follow-up. The functional outcome for speech and eating were very good.

Electro-gene transfer to skin using a noninvasive multielectrode array

Because of its large surface area and easy access for both delivery and monitoring, the skin is an attractive target for gene therapy for cutaneous diseases, vaccinations and several metabolic disorders. The critical factors for DNA delivery to the skin by electroporation (EP) are effective expression levels and minimal or no tissue damage. Here, we evaluated the non-invasive multielectrode array (MEA) for gene electrotransfer. For these studies we utilized a guinea pig model, which has been shown to have a similar thickness and structure to human skin. Our results demonstrate significantly increased gene expression 2 to 3 logs above injection of plasmid DNA alone over 15 days. Furthermore, gene expression could be enhanced by increasing the size of the treatment area. Transgene-expressing cells were observed exclusively in the epidermal layer of the skin. In contrast to caliper or plate electrodes, skin EP with the MEA greatly reduced muscle twitching and resulted in minimal and completely recoverable skin damage. These results suggest that EP with MEA can be an efficient and non-invasive skin delivery method with less adverse side effects than other EP delivery systems and promising clinical applications.

Down-modulation of cancer targets using locked nucleic acid (LNA)-based antisense oligonucleotides without transfection

Usually, small interfering RNAs and most antisense molecules need mechanical or chemical delivery methods to down-modulate the targeted mRNA. However, these delivery approaches complicate the interpretations of biological consequences. We show that locked nucleic acid (LNA)-based antisense oligonucleotides (LNA-ONs) readily down-modulate genes of interest in multiple cell lines without any delivery means. The down-modulation of genes was quick, robust, long-lasting and specific followed by potent down-modulation of protein. The efficiency of the effect varied among the 30 tumor cell lines investigated. The most robust effects were found in those cells where nuclear localization of the LNA-ON was clearly observed. Importantly, without using any delivery agent, we demonstrated that HER3 mRNA and protein could be efficiently down-modulated in cells and a tumor xenograft model. These data provide a simple and efficient approach to identify potential drug targets and animal models. Further elucidation of the mechanism of cellular uptake and trafficking of LNA-ONs may enhance not only the therapeutic values of this platform but also antisense molecules in general.

DNA vaccines for targeting bacterial infections

DNA vaccination has been of great interest since its discovery in the 1990s due to its ability to elicit both humoral and cellular immune responses. DNA vaccines consist of a DNA plasmid containing a transgene that encodes the sequence of a target protein from a pathogen under the control of a eukaryotic promoter. This revolutionary technology has proven to be effective in animal models and four DNA vaccine products have recently been approved for veterinary use. Although few DNA vaccines against bacterial infections have been tested, the results are encouraging. Because of their versatility, safety and simplicity a wider range of organisms can be targeted by these vaccines, which shows their potential advantages to public health. This article describes the mechanism of action of DNA vaccines and their potential use for targeting bacterial infections. In addition, it provides an updated summary of the methods used to enhance immunogenicity from codon optimization and adjuvants to delivery techniques including electroporation and use of nanoparticles.

Electrodes for in vivo localised subcutaneous electropulsation and associated drug and nucleic acid delivery

BACKGROUND

Drug and nucleic acids can be delivered in vivo by an injection of the product followed by the application of a train of electric pulses.

OBJECTIVE

The success of the method is linked to the proper distribution of the electric field in the target tissue. This is under the control of the design of the electrodes.

METHODS

The field distribution can be obtained by computer simulation mainly by using numerical methods and simplifying hypothesis. The conclusions are validated by comparing the computed current and its experimental values on phantoms. A good agreement is obtained.

RESULTS/CONCLUSION

Targeting the delivery to the skin can be obtained by using an array of very short needle electrodes, by pinching the skin between two parallel plate electrodes, or by using contact wire electrodes.

DNA vaccines and intradermal vaccination by DNA tattooing

Over the past two decades, DNA vaccination has been developed as a method for the induction of immune responses. However, in spite of high expectations based on their efficacy in preclinical models, immunogenicity of first generation DNA vaccines in clinical trials was shown to be poor, and no DNA vaccines have yet been licensed for human use. In recent years significant progress has been made in the development of second generation DNA vaccines and DNA vaccine delivery methods. Here we review the key characteristics of DNA vaccines as compared to other vaccine platforms, and recent insights into the prerequisites for induction of immune responses by DNA vaccines will be discussed. We illustrate the development of second generation DNA vaccines with the description of DNA tattooing as a novel DNA delivery method. This technique has shown great promise both in a small animal model and in non-human primates and is currently under clinical evaluation.

Electroporation and ultrasound enhanced non-viral gene delivery in vitro and in vivo

Non-viral vectors are less efficient than the use of viral vectors for delivery of genetic material to cells in vitro and especially in vivo. However, viral vectors involve the use of foreign proteins that can stimulate both the innate and acquired immune response. In contrast, plasmid DNA can be delivered without carrier proteins and is non-immunogenic. Plasmid gene delivery can be enhanced by the use of physical methods that aid the passage of the plasmid through the cell membrane. Electroporation and microbubble-enhanced ultrasound are two of the most effective physical delivery methods and these can be applied to a range of different cell types in vitro and a broad range of tissues in vivo. Both techniques also have the advantage that, unlike viral vectors, they can be used to target specific tissues with systemic delivery. Although electroporation is often the more efficient of the two, microbubble-enhanced ultrasound causes less damage and is less invasive. This review provides an introduction to the methodology and summarises the range of cells and tissues that have been genetically modified using these techniques.

Tolerability of two sequential electroporation treatments using MedPulser DNA delivery system (DDS) in healthy adults

Immunotherapy against infectious agents and malignant tumors requires efficient priming of effector cells through direct expression and/or efficient cross-presentation of antigens by antigen-presenting cells. Electroporation is a new procedure aimed at transiently increasing cell membrane permeability and direct delivery of antigen or antigen-encoding nucleic acids inside targeted cells. We evaluated the tolerability including compliance with repeated electroporation treatments using MedPulser DDS in 24 healthy adults. Pain severity was evaluated at time of electroporation treatment, and at 1, 5, 10, and 20 minutes, and 24 hours thereafter, using two clinically validated questionnaires: McGill Pain Questionnaire (MPQ) (Present Pain Intensity) and Brief Pain Inventory (BPI). Electroporation treatments were generally well tolerated. Twenty-two out of 24 subjects returned for the second electroporation treatment 14 days after first treatment. Only two subjects reported a treatment-related systemic adverse experience following either electroporation application. For both pain assessment tools, maximum pain and/or discomfort were mostly reported immediately (within 5 minutes) after electroporation; Furthermore, no difference was observed when comparing peak-pain scores after first and second electroporation treatments. This study supports the clinical application of MedPulser DDS for the improvement of antigen-induced immune responses for prophylactic or therapeutic vaccines, especially in gene-based therapies for cancer.