Mitra Shojania Feizabadi

Droplet-based microfluidics has rapidly advanced applications in chemistry, biology, materials science, medicine, food science, and cosmetics. Using this technology, various oils have been employed for fluid encapsulation. This study is the first to investigate the use of an animal-based unsaturated fatty acid oil—emu oil—for microdroplet formation. We characterized droplet generation in the presence and absence of a non-fluorinated surfactant at a defined concentration and examined the influence of geometrical parameters using T-junction microchannels with two different central channel widths. The results were compared with those obtained from a plant-based oil (olive oil) under parallel experimental conditions. Given the growing concerns regarding the environmental and health risks of fluorocarbon oils combined with fluorinated surfactants, which are widely used in microfluidics, emu oil represents a potentially safer alternative for microdroplet-based technologies across multiple fields.

Overexpression of Tau protein in breast cancer cells is identified as an indicator for potential resistance to taxane-based therapy. As reported findings have been obtained mostly from clinical studies, the undetermined underlying mechanism of such drug resistance needs to be thoroughly explored through comprehensive in vitro evaluations. Tau and Taxol bind to the beta tubulin site in microtubules’ structure. This is of particular interest in breast cancer, as microtubules of these cancer cells are structurally distinct from some other microtubules, such as neuronal microtubules, due to their unique beta tubulin isotype distribution. The observed changes in the in vitro polymerization of breast cancer microtubules, and the different function of some molecular motors along them, leave open the possibility that the drug resistance mechanism can potentially be associated with different responses of these microtubules to Tau and Taxol. We carried out a series of parallel experiments to allow comparison of the in vitro dual effect of Tau and Taxol on the polymerization of MCF7 microtubules. We observed a concentration-dependent demotion-like alteration in the self-polymerization kinetics of Tau-induced MCF7 microtubules. In contrast, microtubules polymerized under the simultaneous effects of Tau and Taxol showed promoted assembly as compared with those observed in Tau-induced microtubules. The analysis of our data obtained from the length of MCF7 microtubules polymerized under the interaction with Tau and Taxol in vitro suggests that the phenomenon known as drug resistance in microtubule-targeted drugs such as Taxol may not be directly linked to the different responses of microtubules to the drug. The effect of the drug may be mitigated due to the simultaneous interactions with other microtubule-associated proteins such as Tau protein. The observed regulatory effect of Tau and Taxol on the polymerization of breast cancer microtubules in vitro points to additional evidence for the possible role of tubulin isotypes in microtubules’ functions.

Molecular motors are microtubule-based proteins which contribute to many cell functions, such as intracellular transportation and cell division. The details of the nature of the mutual interactions between motors and microtubules still needs to be extensively explored. However, electrostatic interaction is known as one of the key factors making motor-microtubule association possible. The association rate of molecular motors to microtubules is a way to observe and evaluate the charge of the bio-motors in vivo. Growing evidence indicates that microtubules with distinct structural compositions in terms of beta tubulin isotypes carry different charges. Therefore, the electrostatic-driven association rate of motors–microtubules, which is a base for identifying the charge of motors, can be more likely influenced. Here, we present a novel method to experimentally confirm the charge of molecular motors in vitro. The offered nanotechnology-based approach can validate the charge of motors in the absence of any cellular components through the observation and analysis of the changes that biomolecular motors can cause on the dynamic of charged microspheres inside a uniform electric field produced by a microscope slide-based nanocapacitor. This new in vitro experimental method is significant as it minimizes the intracellular factors that may interfere the electric charge that molecular motors carry.

Drug-induced resistance is one the major obstacles that may lead to therapeutic failure during cancer treatment. Different genetic alterations occur when tumor cells divide. Among new generations of tumor cells, some may express intrinsic resistance to a specific chemotherapeutic agent. Also, some tumor cells may carry a gene that can develop resistance induced by the therapeutic drug. The methods by which the therapeutic approaches need to be revised in the occurrence of drug induced resistance is still being explored. Previously, we introduced a model that expresses only intrinsic drug resistance in a conjoint normal-tumor cell setting. The focus of this work is to expand our previously reported model to include terms that can express both intrinsic drug resistance and drug-induced resistance. Additionally, we assess the response of the cell population as a function of time under different treatment strategies and discuss the outcomes. The model introduced is expressed in the format of coupled differential equations which describe the growth pattern of the cells. The dynamic of the cell populations is simulated under different treatment cases. All computational simulations were executed using Mathematica v7.0. The outcome of the simulations clearly demonstrates that while some therapeutic strategies can overcome or control the intrinsic drug resistance, they may not be effective, and are even to some extent damaging, if the administered drug creates resistance by itself. In the present study, the evolution of the cells in a conjoint setting, when the system expresses both intrinsic and induced resistance, is mathematically modeled. Followed by a set of computer simulations, the different growing patterns that can be created based on choices of therapy were examined. The model can still be improved by considering other factors including, but not limited to, the nature of the cancer growth, the level of toxicity that the body can tolerate, or the strength of the patient’s immune system.

The extent to which beta tubulin isotypes contribute to the function of microtubules and the microtubule-driven transport of molecular motors is poorly understood. The major differences in these isotypes are associated with the structure of their C-terminal tails. Recent studies have revealed a few aspects of the C-terminal tails’ regulatory role on the activities of some of the motor proteins on a single-molecule level. However, little attention is given to the degree to which the function of a team of motor proteins can be altered by the microtubule’s tail. In a set of parallel experiments, we investigated this open question by studying the force production of several kinesin-1 (kinesin) molecular motors along two groups of microtubules: regular ones and those microtubules whose C-terminals are cleaved by subtilisin digestion. The results indicate that the difference between the average of the force production of motors along two types of microtubules is statistically significant. The underlying mechanism of such production is substantially different as well. As compared to untreated microtubules, the magnitude of the binding time of several kinesin-1 is almost three times greater along subtilisin-treated microtubules. Also, the velocity of the group of kinesin molecules shows a higher sensitivity to external loads and reduces significantly under higher loads along subtilisin-treated microtubules. Together, this work shows the capacity of the tails in fine-tuning the force production characteristics of several kinesin molecules.

Control of intracellular transport is poorly understood, and functional ramifications of tubulin isoform differences between cell types are mostly unexplored. Motors' force production and detachment kinetics are critical for their group function, but how microtubule (MT) details affect these properties – if at all – is unknown. We investigated these questions using both a vesicular transport human kinesin, kinesin‐1, and also a mitotic kinesin likely optimized for group function, kinesin‐5, moving along either bovine brain or MCF7(breast cancer) MTs. We found that kinesin‐1 functioned similarly on the two sets of MTs – in particular, its mean force production was approximately the same, though due to its previously reported decreased processivity, the mean duration of kinesin‐1 force production was slightly decreased on MCF7 MTs. In contrast, kinesin‐5's function changed dramatically on MCF7 MTs: its average detachment force was reduced and its force–velocity curve was different. In spite of the reduced detachment force, the force–velocity alteration surprisingly improved high‐load group function for kinesin‐5 on the cancer‐cell MTs, potentially contributing to functions such as spindle‐mediated chromosome separation. Significant differences were previously reported for C‐terminal tubulin tails in MCF7 versus bovine brain tubulin. Consistent with this difference being functionally important, elimination of the tails made transport along the two sets of MTs similar.