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Varier, G. K.

Publications and source records attributed to Varier, G. K..

2 recordsLinked to original sources
bioRxiv2023

Enhanced uptake and retention of graphene quantum dots in HeLa cell nuclei

The nuclear pore complexes on the nuclear membrane function as the sole gateway of molecular communication between the nucleus and the cytoplasm regulating the transport of molecules, including nucleic acids and proteins. The present study seeks to undertake a comprehensive investigation of the kinetics of transport of negatively charged graphene quantum dots through nuclear membranes and quantify their nuclear transport characteristics and translocation rates. Experiments are carried out in permeabilized HeLa cells using time-lapse confocal fluorescence microscopy. Introducing negative charge onto biomolecular probes leads to electrostatic interaction with the nuclear pore complexes resulting in significant changes in their nuclear translocation rates. We find that the negatively charged graphene quantum dots are transported to the nuclei at a fast rate and two distinct transport pathways are involved in the translocation. Furthermore, complementary experiments on the nuclear import and export of these graphene quantum dots confirm the bidirectionality of transport with similar translocation rates. Our studies also show that negatively charged graphene quantum dots exhibit good retention properties revealing their potential as excellent drug carriers. Statement of significanceThe nuclear pore complexes control the bidirectional transport of biomolecules between the nucleus and cytoplasm. The noteworthy behaviors exhibited by negatively charged graphene quantum dots with respect to the nuclear uptake show their potential utility not only as drug carriers but also as facilitators for the retention of drugs within the nucleus. The fast import of carriers helps to achieve faster drug delivery, and the retention ensures the passing of the drug to daughter nuclei. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/559706v2_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@104d497org.highwire.dtl.DTLVardef@21091aorg.highwire.dtl.DTLVardef@dcb208org.highwire.dtl.DTLVardef@12c59d2_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗
bioRxiv2023

Size dependent steady-state saturation limit in biomolecular transport through nuclear membranes

The nucleus preserves the genomic DNA of eukaryotic organisms and maintains the integrity of the cell by regulating the transport of molecules across the nuclear membrane. It is hitherto assumed that small molecules having a size below the passive permeability limit are allowed to diffuse freely to the nucleus while the transport of larger molecules are regulated via an active mechanism involving energy. Here we report on the kinetics of nuclear import and export of a model system of dextran molecules having a size below the passive permeability limit. The studies carried out using time-lapse confocal fluorescence microscopy show a clear deviation from the passive diffusion model. In particular, it is observed that the steady-state concentration of dextran molecules inside the nucleus is consistently less than the concentration outside, in contradiction to the predictions of the passive diffusion model. Detailed analysis and modeling of the transport show that the nuclear export rates significantly differ from the import rates and the difference in rates is dependent on the size of the molecules. The nuclear export rates are further confirmed by an independent experimental study where we observe the diffusion of dextran molecules from the nucleus directly. Our experiments and transport model would suggest that the nucleus actively rejects exogenous macromolecules even below the passive permeability limit. This result can have significant impact on biomedical research especially in areas related to targeted drug delivery and gene therapy.

biophysics↗