Dynamics of intracellular clusters of nanoparticles

Model for random internalization of nanoparticles by cells

We propose a stochastic model for the internalization of nanoparticles by cells formulating cellular uptake as a compound Poisson process with a random probability of success. This is an alternative approach to the one presented by Rees et al. [Nat. Commun. 10, 2341 (2019)2041-172310.1038/s41467-018-07882-8] who explained overdispersion in nanoparticle uptake and associated negative binomial distribution by considering a Poisson distribution for particle arrival and a gamma-distributed cell area. In our stochastic model, the formation of new pits is represented by the Poisson process, whereas the capturing process and the population heterogeneity are described by a random Bernoulli process with a beta-distributed probability of success. The random probability of success generates ensemble-averaged conditional transition probabilities that increase with the number of newly formed pits (self-reinforcement). As a result, an ensemble-averaged nanoparticle uptake can be represented as a Polya process. We derive an explicit formula for the distribution of the random number of pits containing nanoparticles. In the limit of the fast nucleation and low probability of nanoparticle capture, we find the negative binomial distribution.

Heterogeneous anomalous transport in cellular and molecular biology

It is well established that a wide variety of phenomena in cellular and molecular biology involve anomalous transport e.g. the statistics for the motility of cells and molecules are fractional and do not conform to the archetypes of simple diffusion or ballistic transport. Recent research demonstrates that anomalous transport is in many cases heterogeneous in both time and space. Thus single anomalous exponents and single generalised diffusion coefficients are unable to satisfactorily describe many crucial phenomena in cellular and molecular biology. We consider advances in the field ofheterogeneous anomalous transport(HAT) highlighting: experimental techniques (single molecule methods, microscopy, image analysis, fluorescence correlation spectroscopy, inelastic neutron scattering, and nuclear magnetic resonance), theoretical tools for data analysis (robust statistical methods such as first passage probabilities, survival analysis, different varieties of mean square displacements, etc), analytic theory and generative theoretical models based on simulations. Special emphasis is made on high throughput analysis techniques based on machine learning and neural networks. Furthermore, we consider anomalous transport in the context of microrheology and the heterogeneous viscoelasticity of complex fluids. HAT in the wavefronts of reaction-diffusion systems is also considered since it plays an important role in morphogenesis and signalling. In addition, we present specific examples from cellular biology including embryonic cells, leucocytes, cancer cells, bacterial cells, bacterial biofilms, and eukaryotic microorganisms. Case studies from molecular biology include DNA, membranes, endosomal transport, endoplasmic reticula, mucins, globular proteins, and amyloids.

Dose-enhancement of MCF 7 cell line radiotherapy using silica-iron oxide nanocomposite

Cancer radiotherapy is one of the most effective regimens of cancer treatments, but cancer cell radioresistance remains a concern. Radiosensitizers can selectively improve the efficacy of radiotherapy and reduce inherent damage. The purpose of this work is to evaluate the effect of silica-coated iron oxide magnetic nanoparticles (SIONPs) as a radiosensitizer and compare their therapeutic effect with that of Iron oxide magnetic nanoparticles (IONPs). IONPs and SIONPs were characterized using several physical techniques such as a transmission electron microscope (TEM) and Vibrating sample magnetometer (VSM). MTT and DNA double-strand breaks (Comet) assays have been used to detect the cytotoxicity, cell viability, and DNA damage of MCF-7 cells, which were treated with different concentrations of prepared nanoparticles and exposed to an X-ray beam. In this study, an efficient radiosensitizer, SIONPs, was successfully prepared and characterized. With 0.5 Gy dose, dose enhancement factor (DEF) values of cells treated with 5 and 10 μg/ml of IONPs were 1 and 1.09, respectively, while those treated with SIONPs at these concentrations had DEF of 1.21 and 1.32, respectively. Results demonstrated that SIONPs provide a potential for improving the radiosensitivity of breast cancer.

A Stable Mode of Dendritic Growth in Cases of Conductive and Convective Heat and Mass Transfer

In this paper, we develop a theory of stable dendritic growth in undercooled melts in the presence of conductive and convective heat and mass transfer boundary conditions at the solid/liquid interface of a dendrite. To simplify the matter and construct the analytical theory, conductive and convective mechanisms are considered separately. Namely, the laws for total undercooling and selection criterion defining the stable growth mode (dendrite tip velocity and diameter) are derived for conductive and convective boundary conditions. To describe the case of simultaneous occurrence of these heat and mass transfer mechanisms, we sew together conductive and convective laws using power stitching functions. The generalised selection theory is compared with experimental data for Al24Ge76 and Ti45Al55 undercooled melts.