Increased Incorporation of Photosensitive Dyes into Yeast Cells by Electroporation

Synergistic electrochemotherapy on cancer cells by photodynamically active cytostatic agents

Two reliable methods have been combined: i) the electroporation of the cell membranes for facilitating the sensitizer incorporation into hystiocytic human lymphoma cells U-937 and (ii) the photodynamics applied by excitation of natural and synthetic sensitizers for cancer therapy. In the case of cytostatic sensitizers as daunomycin or actinomycin their photooxidation of guanine in DNA was added to their known dark medical efficacy for the first time. Several applications of single d.c. pulses and continuous visible light irradiations were performed, which resulted in about five times higher efficacy by 14 min of irradiation after the electroporation than the ordinary photodynamic effect itself on intact cell membranes. Yielding about 90% killing rate by a combination of electroporation and photooxidation this synergism will be the basis of an extended electrochemotherapy by light irradiation according to the photodynamic mechanism type 1 for the treatment of malignant cells and tissues. Analogous results--including the first synergistic treatment of tumor mice according to photodynamic mechanism type 2--were discussed, too.

Electroporation and alternating current cause membrane permeation of photodynamic cytotoxins yielding necrosis and apoptosis of cancer cells

In order to increase the permeability of cell membranes for low doses of cytostatic drugs, two bioelectrochemical methods have been compared: (a) electric pore formation in the plasma membranes by single electric impulses (electroporation), and (b) reordering of membrane structure by alternating currents (capacitively coupled). These treatments were applied to human leukemic K-562 cells and human lymphoma U-937 cells, yielding apoptotic and necrotic effects, determined by flow cytometry. Additional cell death occurs after exposure to light irradiation at wavelengths lambda > 600 nm, of cells which were electroporated and had incorporated actinomycin-C or daunomycin (daunorubicin). It is observed that drug uptake after an exponentially decaying electroporation pulse of the initial field strength Eo=1.4 kV/cm and pulse time constants in the time range 0.5-3 ms is faster than during PEMF-treatment, i.e., application of an alternating current of 16 kHz, voltage U<100 V, I=55 mA, and exposure time 20 min. However, at the low a.c. voltage of this treatment, more apoptotic and necrotic cells are produced as compared to the electroporation treatment with one exponentially decaying voltage pulse. Thus, additional photodynamic action appears to be more effective than solely drugs and electroporation as applied in clinical electrochemotherapy, and more effective than the noninvasive pulsed electromagnetic fields (PEMFs), for cancer cells in general and animals bearing tumors in particular.

Electroporation of cell membranes supporting penetration of photodynamic active macromolecular chromophore dextrans

The aim is to demonstrate that macromolecular chromophore dextrans (Cibacron-dextran) acting as photosensitizers can be transported easily into cancer cells by electroporation of their membranes (short electric pulses on cell suspension between electrodes). There are two possibilities, either:(A)irradiation starts with the electropulse-showed with easily penetrating thiopyronin-yielding nearly 100% dead cells;(B)irradiation starts after a resealing time of membrane pores during which macromolecular photosensitizers can penetrate into cells. In this way, fractions of Cibacron-dextran with molecular weights (Mw) 3300, 10,900 and 500,000 are now able to kill. This combination of bioelectrochemistry and photobiology will be suitable also for other biopolymers, connected with photodynamic active chromophores (e.g. chromopeptides) to transport them through cell walls and membranes into cells and tissues. The human cancer cells U-935 and K-562 (pulsed by 1.15 kV/cm field strength) additionally or synergistically reach high rates of necrotic cells (colored by trypan blue) by this combination.