Physical mechanisms and methods employed in drug delivery to tumors

Magnetoporation: New Method for Permeabilization of Cancerous Cells to Hydrophilic Drugs

BACKGROUND

In the present study, we investigated the application of pulsed magnetic field (MF) (3.5 T, 1 Hz, 8 square-wave/160 µs) permeabilization on murine breast adenocarcinoma cells when administering bleomycin (BLM) in vivo.

OBJECTIVE

This cross-over study aims to find a noninvasive method to facilitate penetration of hydrophilic anti-cancer drugs through the cancerous cells membrane into the cytosoll in order to minimize the side effects of the chemotherapy treatments of tumors.

MATERIAL AND METHODS

In this cross-over study, a total of 50 female Balb/c mice were tumorized via homograft. After about 2 weeks, magnetic pulses (3.5 T, 1 Hz, 8 square-wave/160 µs) were applied to tumor-bearing mice 3 min after intratumoral BLM solution injection. Tumor volume was measured every 48 h during 22 days.

RESULTS

The results showed that the difference between the BLM plus 3.5 T MF group versus the sham control or sham MF groups was significant. Uptake of BLM molecules by tumoral cells in the BLM plus 3.5 T MF group versus the BLM control group was 7- folds higher that this result was statistically insignificant (P<0.05, SEM=266.8676, analysis of variance).

CONCLUSION

Significant cell permeabilization to BLM requires greater MF strength or exposure time. Further investigation is necessary.

Ultrasound response of viscoelastic changes of cellulose hydrogels triggered with Sono-deviced rheometer

Sono-deviced rheometer,which enabled viscoelastic properties under ultrasound operation, was used to investigate for cellulosic hydrogels. The viscoelastic behavior was compared in cellulosic hydrogels prepared at 0.5, 1 and 2 wt% concentration in the DMAc/LiCl solution. The sono-deviced equipment could measure the effect of changes in storage modulus G' and loss modulus G" under 43 kHz ultrasound exposure. It was noted that the 43 kHz ultrasound significantly changed the values of the G', meaning that the hydrogel was soften under the exposure within few seconds. When the ultrasound exposed 50 W of the out-put power at 1% strain, the G' value of 4.2x10⁴ Pa was reduced to 4.0x10³ Pa during 5 min of the US interval. The declined lowering value of G' then returned to the original moduli value when ultrasound was stopped. The values of both G' and G" values were measured at applied strain % during viscoelastic measurements of the cellulosic hydrogels without and with ultrasound exposure. The comparison indicated that the ultrasoundhas reinforced the effect of the mechanical deformationof the hydrogel structureat the smaller mechanical strain values appliedduring the ultrasound operation. The ultrasound soften effect onthe viscoelastic change efficiently occurred in the 0.5 wt% sample and easily induced the structural deformation probably due to the breakage of hydrogen bonds in the cellulose hydrogels.

On the chemotherapeutic agents localization in tissue by means of snake venoms

The efficiency of anti-tumour drug strongly depends on its dose. Higher drug doses and exposure times usually result in better treatment. It is why the implementation of high-dose treatment is always attractive. However, most of the drug delivery techniques meet essential limitations. In isolated regional perfusion a tumour can be exposed to high-dose therapeutic influence but the target organ may be isolated from the rest of circulatory system only for a relatively short period of time. During systemic injection of anti-tumour agents dose limitations are dictated by side toxicity danger. Viperidae venoms are known to cause local stagnation of blood flow and blood-tissue exchange processes in the place of snakebite. In present paper we suggest to use Viperidae snake venoms in addition to anti-tumour drugs for regional anti-cancer therapy. We suppose that Viperidae venoms will assist in drug localization. We state that their usage will help in high-dosage therapy implementation.

Sonodynamic therapy (SDT): a novel treatment of cancer based on sonosensitizer liposome as a new drug carrier

Cancer is a major cause of morbidity and mortality. Chemotherapy is one of the main means of cancer treatment. Conventional chemotherapy agents kill rapidly proliferating cells, resulting in some of the most common side effects of chemotherapy. Liposome-encapsulated drugs offer the possibility to increase target efficacy as well as reducing toxic side effects of chemotherapeutic drugs. However, the target specificity of liposome is dissatisfied. We urgently need to develop new approaches to improving drug target efficacy. Recently, sonodynamic therapy (SDT) of cancer, which is based on preferential uptake and retention of a sonosensitizer in tumor tissues and subsequent activation of drug by ultrasound radiation, is a developing field. In this article, we propose the use of sonosensitizers in combination with liposome to target chemotherapy drugs directly to tumor cells. SDT with low-intensity ultrasound combined with a sonosensitizer may be a promising approach to cancer therapy.

Tumor growth inhibition by sonodynamic therapy using a novel sonosensitizer

Sonodynamic therapy (SDT) with low-intensity ultrasound combined with a sonosensitizer may be a promising approach to cancer therapy. Use of ultrasound has the advantage of being noninvasive, with deep-penetration properties, and convenient because of the low or no sensitivity of sonosensitizers to light. In this study, SDT with a novel sonosensitizer (a porphyrin derivative) was evaluated in vitro and in vivo. Ultrasound irradiation with a sonosensitizer elicited potent sonotoxicity in vitro without the danger of phototoxicity. The sonotoxic effect was mediated by reactive oxygen species (ROS) and was reduced by ROS scavengers. Cell membrane lipid peroxidation increased significantly just after ultrasound irradiation with a sonosensitizer, but there was no increase in apoptosis. In an in vivo mouse xenograft model, SDT with a sonosensitizer markedly inhibited tumor cell growth. The skin hypersensitivity after light exposure was not observed in a sonosensitizer-treatment group, consistent with the in vitro findings. These results suggest that ROS generated by SDT with a sensitizer can damage tumor cells, resulting in necrosis and prevention of tumor growth. This noninvasive treatment with no adverse effects such as skin sensitivity is therefore promising for therapy of cancers located deep within patients.

Selective destabilization of tumor cells with pulsed electric and magnetic sequences: a preliminary report

BACKGROUND

Various studies in vitro suggest that low electric and magnetic fields may modify cancer cell growth and recent studies in vivo have revealed anti-tumoral effects. After screening different tumor cell lines, we identified specific sequences of localized magnetic and electric fields (MESQ) that reduce cancer cell survival in vitro. This finding led us to design an experiment to determine the actual efficacy of above sequences in selectively destabilizing tumor cells and their effect on healthy cells.

MATERIALS AND METHODS

We exposed the MCF7 cancer cell line and normal fibroblasts to MESQ for 1, 2, 3 and 6 hours, evaluating cell survival and induction of apoptosis.

RESULTS

Exposure to MESQ reduced MCF7 survival, inducing apoptosis in a timedependent way, whereas fibroblasts were completely unaffected.

CONCLUSION

These results have promising implications for the treatment of cancer and warrant further research.

Use of liposomes as drug delivery vehicles for treatment of melanoma

Melanoma is a progressive disease that claims many lives each year due to lack of therapeutics effective for the long-term treatment of patients. Currently, the best treatment option is early detection followed by surgical removal. Better melanoma therapies that are effectively delivered to tumors with minimal toxicity for patients are urgently needed. Nanotechnologies provide one approach to encapsulate therapeutic agents leading to improvements in circulation time, enhanced tumor uptake, avoidance of the reticulo-endothelial system, and minimization of toxicity. Liposomes in particular are a promising nanotechnology that can be used for more effective delivery of therapeutic agents to treat melanoma. Liposomes delivering chemotherapies, siRNA, asODNs, DNA, and radioactive particles are just some of the promising new nanotechnology based therapies under development for the treatment of melanoma that are discussed in this review.