Mohammad Robiul Hossan

This paper reports a non-braided, bioresorbable polycaprolactone (PCL) flow diverter (FD) for the endovascular treatment of aneurysms. Bioresorbable FDs can reduce the risk associated with the permanent metallic FDs as they are resorbed by the body after curing of aneurysms. PCL FDs were designed and fabricated using an in-house hybrid electromelt spinning-fused deposition fabrication unit. Flow diveter's properties, surface qualities, and mechanical characteristics of PCL FDs of 50%, 60% and 70% porosities were studied using SEM, AFM and high-precision UTM. The deployability through a clinically relevant catheter system was demonstrated. The angiographic visibility of PCL FDs was evaluated using BaSO₄ and Bi₂O₃ coatings. The average strut thicknesses were 74.12 ± 6.63 μm, 63.07 ± 1.26 μm and 56.82 ± 2.09 μm for PCL FDs with 50%, 60% and 70% porosities respectively. They average pore areas for the 50%, 60% and 70% porosities FDs were 0.055 ± 0.0056 mm², 0. 0605 ± 0.0065 mm², and 0.0712 ± 0.012 mm² respectively. The surface quality was good with a RMS roughness value of 14.45 nm. The tensile and radial strength and flexibility were comparable to the non-braided coronary stents. The visibility under X-ray increases with the increasing concentration of coating materials BaSO₄ and Bi₂O₃. The visibility intensity was slightly higher with Bi₂O₃ coating of PCL FDs. The overall results of the engineering analysis of the developed non-braided PCL FDs are promising.

Blood serum is arguably the most analyzed biofluid for disease prediction and diagnosis. Herein, we benchmarked five different serum abundant protein depletion (SAPD) kits with regard to the identification of disease‐specific biomarkers in human serum using bottom‐up proteomics. As expected, the IgG removal efficiency among the SAPD kits is highly variable, ranging from 70% to 93%. A pairwise comparison of database search results showed a 10%–19% variation in protein identification among the kits. Immunocapturing‐based SAPD kits against IgG and albumin outperformed the others in the removal of these two abundant proteins. Conversely, non‐antibody‐based methods (i.e., kits using ion exchange resins) and kits leveraging a multi‐antibody approach were proven to be less efficient in depleting IgG/albumin from samples but led to the highest number of identified peptides. Notably, our results indicate that different cancer biomarkers could be enriched up to 10% depending on the utilized SAPD kit compared with the undepleted sample. Additionally, functional analysis of the bottom‐up proteomic results revealed that different SAPD kits enrich distinct disease‐ and pathway‐specific protein sets. Overall, our study emphasizes that a careful selection of the appropriate commercial SAPD kit is crucial for the analysis of disease biomarkers in serum by shotgun proteomics.

The flow diverting stent (FDS) has become a promising endovascular device for the treatment of aneurysms. This research presents a novel biodegradable and non-braided Polycaprolactone (PCL) FDS. The PCL FDS was designed and developed using an in-house fabrication unit and coated on two ends with BaSO₄ for angiographic visibility. The mechanical flexibility and quality of FDS surfaces were examined with the UniVert testing machine, scanning electron microscope (SEM), and 3D profilometer. Human umbilical vein endothelial cell (HUVEC) adhesion, proliferation, and cell morphology studies on PCL FDS were performed. The cytotoxicity and NO production by HUVECs with PCL FDS were also conducted. The longitudinal tensile, radial, and bending flexibility were found to be 1.20 ± 0.19 N/mm, 0.56 ± 0.11 N/mm, and 0.34 ± 0.03 N/mm, respectively. The FDS was returned to the original shape and diameter after repeated compression and bending without compromising mechanical integrity. Results also showed that the proliferation and adhesion of HUVECs on the FDS surface increased over time compared to control without FDS. Lactate dehydrogenase (LDH) release and NO production showed that PCL FDS were non-toxic and satisfactory. Cell morphology studies showed that HUVECs were elongated to cover the FD surface and developed an endothelial monolayer. This study is a step forward toward the development and clinical use of biodegradable flow diverting stents for endovascular treatment of the aneurysm.

Laser micromachining technique offers a promising alternative method for rapid production of microfluidic devices. However, the effect of process parameters on the channel geometry and quality of channels on common microfluidic substrates has not been fully understood yet. In this research, we studied the effect of laser system parameters on the microchannel characteristics of Polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), and microscope glass substrate—three most widely used materials for microchannels. We also conducted a cell adhesion experiment using normal human dermal fibroblasts on laser-machined microchannels on these substrates. A commercial CO₂ laser system consisting of a 45W laser tube, circulating water loop within the laser tube and air cooling of the substrate was used for machining microchannels in PDMS, PMMA and glass. Four laser system parameters—speed, power, focal distance, and number of passes were varied to fabricate straight microchannels. The channel characteristics such as depth, width, and shape were measured using a scanning electron microscope (SEM) and a 3D profilometer. The results show that higher speed produces lower depth while higher laser power produces deeper channels regardless of the substrate materials. Unfocused laser machining produces wider but shallower channels. For the same speed and power, PDMS channels were the widest while PMMA channels were the deepest. Results also showed that the profiles of microchannels can be controlled by increasing the number of passes. With an increased number of passes, both glass and PDMS produced uniform, wider, and more circular channels; in contrast, PMMA channels were sharper at the bottom and skewed. In rapid cell adhesion experiments, PDMS and glass microchannels performed better than PMMA microchannels. This study can serve as a quick reference in material-specific laser-based microchannel fabrications.

Class performance and classroom environment have a direct impact on students’ learning and long-term retention of key engineering concepts. In addition, class performance is critical for preserving students’ interest and continuous engagement. However, engineering classes are widely rated as boring and monotonous by students due to one-way lectures and lack of application of active learning techniques. In this study, we employed mock tests as an active learning technique to empower students on their own learning through identification of conceptual weakness, reinforcement of understanding and hence, to improve their overall learning and class performance in two different engineering classes at two different universities. Mock tests were conducted on the exam materials before the occurrence of the actual exams. The mock test key with grading rubric was provided to the students. Students were required to grade their mock test based on the rubric. The impact of this technique is evaluated using questionnaires where students were asked to provide their feedback on the enhancement of their understanding of the material, understanding of grading criteria, improvement on their study habits, and identifying conceptual weakness about a topic. The assessment and student feedback shows that the use of the mock test improves the understanding of basic concepts and topics through perspective transformation. It also shows that it improves the average grade of the class, motivates students to study hard, promotes peer discussion, reduces exam related stresses, and strengthens fellowship among students. Thus, mock tests can be used in other disciplines and classes with similar positive effect.

Laser micromachining has emerged as a promising technique for mass production of microfluidic devices. However, control and optimization of process parameters, and design of substrate materials are still ongoing challenges for the widespread application of laser micromachining. This article reports a systematic study on the effect of laser system parameters and thermo-physical properties of substrate materials on laser micromachining. Three dimensional transient heat conduction equation with a Gaussian laser heat source was solved using finite element based Multiphysics software COMSOL 5.2a. Large heat convection coefficients were used to consider the rapid phase transition of the material during the laser treatment. The depth of the laser cut was measured by removing material at a pre-set temperature. The grid independent analysis was performed for ensuring the accuracy of the model. The results show that laser power and scanning speed have a strong effect on the channel depth, while the level of focus of the laser beam contributes in determining both the depth and width of the channel. Higher thermal conductivity results deeper in cuts, in contrast the higher specific heat produces shallower channels for a given condition. These findings can help in designing and optimizing process parameters for laser micromachining of microfluidic devices.

Application of electric field has become one of the most promising actuation tools in bio-microfluidics for cell deformation, poration and manipulation. However, electric field guided cell deformation process is still not well understood due to its complex multiphysics nature. In this paper, we present an electric field induced cell deformation study using hybrid immersed interface-immersed boundary method where both electric and hydrodynamic forces are evaluated with interface-resolved approach. Immersed interface method is employed to evaluate electric field in fluids with submerged cells while immersed boundary method is used to study hydrodynamics with flexible immersed boundaries. Electric field induced force is calculated using Maxwell’s stress tensor approach. The results show that the deformation process depends on the electrical properties of fluid as well as cells, the direction of applied electric field and nature of electric field induced forces. When electrical conductivity of cell is less than that of fluid medium, cell experiences compressive force and deformation rate is faster. The response of fluids to the deformation process is also depend on the relative electrical properties of cell and fluid medium. This study provides critical insight of the transient cell deformation mechanism and better understanding which can help in designing experimental studies and exploring new applications of electric field guided cell deformation.