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Hyperthermia can be used as a modality for increasing liposomal drug delivery to tumor by triggering release of drug from the liposome.at the temperature close to the thermal phase transition of liposome.The release of the drug depends on lipid pore size.Liposomes and planar black lipid membranes (pBLMs) are both demonstrate permeability increase at the phase transition of lipid (Antonov et al.,1980).Single pore conductance in the letter case allows to calculate the size of the pore.The main goal of the report is the discussion of calibration data obtained by testing single pore conductivity in pBLM from DPPC with a number of neutral polymer molecules.As a polymeric probe the range of PEGs has been used consisting of PEG200 (0.43nm), PEG300 (0.60nm), PEG400 (0.70nm), PEG600 (0.78nm), PEG1450 (1.05nm), PEG2000 (1.22mn), PEG3000 (1.44nm), PEG3350 (1.63nm), PEG4600 (2.10nm), PEG6000 (2.50nm),PEG20000 (3.2 lnm) (hydrodynamics radii of corresponding molecule are indicated).It was shown that symmetrical addition to membrane-bathing 1M LiC1 solution of 20% (w/w) of differently sized PEGs was followed by significant decrease of single pore conductance up to complete closing in solutions of PEG 1450, PEG2000 and PEG3350.However subsequent exposition of pBLM in solutions of larger PEG6000 and PEG20000 demonstrated a full restoration of pore conductance.Exclusion effect observed with PEG6000 and PEG20000 allows to calculate the pore radius with more high precision taking into account the effect of access resistance.The more precise estimation of average pore radius should be increased up to 2.4nm.The blocking effect of PEG1450, PEG2000 and PEG3350 mentioned above could be used for regulation of drug release velocity in thermosensitive liposomes in tumor treatment.