Benzoate Group Attachment to Tempo Provides Enhanced Discrimination of Liposomes Fabricated Using Human Lung Normal and Carcinoma Cells

Abstract

It is widely accepted that the lipid compositions of the plasma membranes of healthy and cancer cells significantly differ from each other. During the cancer progression, cancer cells change the lipid constituent of the membranes resulting in the loss of lipid asymmetry between the membrane leaflets. Consequently, physicochemical properties of the cell membranes are also changed in response to altered lipid organization. Partitioning of the spin probe 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) into the membranes of the cells has broadly been applied to characterize membrane properties of various cells in health and disease conditions. In this work, we used liposomes fabricated using lipids extracted from normal and carcinoma cells. This system permits the determination of the properties of the healthy and cancer cell membranes provided exclusively by its lipid components. Application of TEMPO-benzoate, in which the benzoate group is attached to the TEMPO, indicates significantly enhanced discrimination of liposomes between cancer and normal cells. Partitioning experiments with TEMPO-benzoate revealed relatively enhanced incorporation efficiency for liposomes of cancer cells. On the contrary, TEMPO incorporation efficiency in the same liposomes of cancer cells was not much different compared to healthy cells. Data indicate that TEMPO-benzoate as a probe is more suitable than TEMPO to discriminate cancer cells from healthy cells. Free energy gain observed for TEMPO-benzoate resulted mainly from the hydrophobic effect of the benzoate group.

Membrane Partitioning of TEMPO Discriminates Human Lung Cancer from Neighboring Normal Cells

“…The study revealed differences in parameters (polarity, micro-viscosity, and the energy required to transfer TEMPO from the aqueous to the membrane environment) between the membranes of cancer and healthy cells. Compared with previous works on liposomes [ 26 , 27 ], the results obtained in this study indicate that pro teins embedded in the cell membranes significantly alter the dynamics of the lipid fraction, making them more dynamic and permeable to small molecules. The determined temperature and pH sensitivities of the cell membranes may help to choose or create the appropriate conditions for cancer therapy.…”

“…Therefore, the use of TEMPO in membrane research allows for a selective characterization of the lipid phase. Unlike the findings obtained in liposomes [26,27], in this case, lipid phase properties are modified by the membrane proteins of the corresponding cells. Below, we provide experiments of TEMPO partitioning into the membranes of the cells at the temperature of 283-317 K interval and pH values of 7.3 and 6.2, conditions that are relevant for cancer therapeutics.…”

“…Therefore, the EPR spectra of TEMPO assigned to the lipophilic phase displays the characteristics of the lipid fraction of the cell membranes. The partition coefficients for the cell membranes are significantly higher compared to those obtained in liposomes fabricated from the corresponding cells [ 26 , 27 ]. Thus, the proteins embedded into the membranes modify lipid phase properties, resulting in augmented partitioning of TEMPO.…”

“…TEMPO and its derivatives show significant anti-cancer effects when applied to various types of cancer, including lung cancer [42][43][44][45][46][47]. It is highly anticipated that TEMPO-benzoate, which shows significantly enhanced partitioning in liposome studies [26,27], will also be very effective in the membranes of the corresponding cells. A FTIR study of the lipids extracted from the normal and cancer cells supports this finding.…”

“…The sensitivity of cancer cell membranes to relevant environmental conditions is an important attribute in developing a method for preferential drug delivery to cancer cells using the differences in the properties of the lipid domains. Previously, to segregate the contribution of only lipid components of the cell membranes, we investigated the properties of liposomes fabricated using lipids extracted from human lung cancer and normal cells [ 26 , 27 ]. The liposomes composed of the cancer cell lipids showed significantly enhanced partitioning of spin probe 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) compared to those fabricated using normal cell lipids.…”