Liquid Cell Transmission Electron Microscopy Sheds Light on The Mechanism of Palladium Electrodeposition

Electrodeposition is widely used to fabricate tunable nanostructured materials in applications ranging from biosensing to energy conversion. A model based on 3D island growth is widely accepted in the explanation of the initial stages of nucleation and growth in electrodeposition. However, there are regions in the electrodeposition parameter space where this model becomes inapplicable. We use liquid cell transmission electron microscopy along with post situ scanning electron microscopy to investigate electrodeposition in this parameter space, focusing on the effect of the supporting electrolyte, and to shed light on the nucleation and growth of palladium. Using a collection of electron microscopy images and current time transients recorded during electrodeposition, we discover that electrochemical aggregative growth, rather than 3D island growth, best describes the electrodeposition process. We then use this model to explain the change in the morphology of palladium electrodeposits from spherical to open clusters with nonspherical morphology when HCl is added to the electrolyte solution. The enhanced understanding of the early stages of palladium nucleation and growth and the role of electrolyte in this process provides a systematic route toward the electrochemical fabrication of nanostructured materials

Ultra-sensitive Detection of Nucleic Acids using an Electronic Chip

The detection of particular genetic sequences aids in the early detection and diagnosis of disease; permits monitoring of the health and state of the natural environment; and informs forensic investigations. To date, gene detection has relied on enzymatic amplification followed by optical readout. Though these technologies have advanced dramatically, the instruments and assays are costly and lack portability. The work presented herein addresses an urgent challenge: molecular diagnostics at the point-of-need. This work reports the first electronic chip capable of analyzing - directly, without amplification, and with clinically-relevant sensitivity - multiple genes of interest present in a clinical sample. It reports a dramatic acceleration in sample-to-answer times, with clinically actionable findings in minutes where legacy techniques take hours or days. The key to the sensitivity and speed of the biosensors reported herein lies in their architecture and morphology on multiple lengthscales. It is proven that hybridization-based assays employing a nucleic probe attached to a solid surface can only achieve efficient performance when displayed on a nanotextured surface. It is also discovered that these same sensing elements must reach tens of micrometers into solution to achieve rapid, sensitive detection of nucleic acids in clinical samples. As a result, the materials integrated onto the sensing chip reported herein are engineered on multiple lengthscales - from the nanometers to the tens of micrometers. Engineering is done through a combination of low-cost, convenient top-down photolithographic patterning; combined with hierarchically-designed bottom-up growth of electrodeposited sensing elements. The capstone of this work is a chip that distinguishes among different types of bacteria in an unpurified sample. The chip gives accurate answers in under half an hour when detecting bacteria at a level of 1.5 colony-forming-unit (cfu) per microliter. These speeds and sensitivies enable the application of this technology in point-of-need assays for infectious disease detection. Ultimately, the work showcases the power of bringing together techniques and principles from materials chemistry, biochemistry, applied physics, and electrical engineering to the solution of an important problem relevant to human health.Ph

Integrated nanostructures for direct detection of DNA at attomolar concentrations

We report an integrated chip that senses nucleic acid biomarkers at exceptionally low concentrations. To achieve such sensitivities we exploit four concepts. (1) Nanostructured electrodes allow efficient display of probe sequences. (2) The use of uncharged probe sequences lowers the background signal in our read-out system. (3) Electrocatalysis provides built-in amplification of the electrical signal that reports hybridization events. (4) An optimal self-assembled monolayer of thiol-functionalized probe molecules is best achieved with the aid of a short spacer molecule to confer enhanced accessibility. We show herein that via joint optimization along these four axes we achieve attomolar sensitivity

Editors’ Choice—Challenges and Opportunities for Developing Electrochemical Biosensors with Commercialization Potential in the Point-of-Care Diagnostics Market

There is a plethora of electrochemical biosensors developed for ultrasensitive detection of clinically relevant biomarkers. However, many of these systems lose their performance in heterogeneous clinical samples and are too complex to be operated by end users at the point-of-care (POC), prohibiting their commercial success. Integration of biosensors with sample processing technology addresses both of these challenges; however, it adds to the manufacturing complexity and the overall cost of these systems. Herein, we review the different components of a biosensor and avenues for creating fully integrated systems. In the context of integration, we focus on discussing the trade-offs between sensing performance, cost, and scalable manufacturing to guide the readers toward designing new electrochemical biosensors with commercialization potential

Effect of Respiratory Rehabilitation before Open Cardiac Surgery on Respiratory Function: A Randomized Clinical Trial

Introduction: Prevention of pulmonary complications after coronary artery bypass graft is attended as a very important issue. The aim of this study was to evaluate the role of pulmonary rehabilitation before surgery for reducing the risk of pulmonary complications after surgery. Methods: In a randomized clinical trial, 60 patients undergoing heart surgery were randomly divided into two groups A and B. Chest physiotherapy was performed before and after surgery on group A patients however it was done on group B’s, only after surgery. Effects of preoperative pulmonary rehabilitation were compared between two groups, using spirometry and arterial blood gas (ABG). Results: Thirty nine males (65%) and 21 females (35%) with mean age of 8.10 ± 9.56 were analyzed.The mean differences were statistically significant for predicted forced vital capacity (FVC) (CI95%:1.3 to 8.7) and Predicted Peak Flow indices (PEF) (CI 95%: 1.9 to 9.4) of spirometry indicator,PCO2 index (of ABG parameter) (CI 95%: 1.4 to 8.9) and mean oxygen saturation (mean Spo2) (CI 95%: 0.6 to 1.7) of ABG index in two groups. Conclusion: The performance of pulmonary rehabilitation program before surgery is recommended, as it may result in the reduction of complications of heart surgery

In Liquid Observation and Quantification of Nucleation and Growth of Gold Nanostructures Using in Situ Transmission Electron Microscopy

In situ liquid transmission electron microscopy (TEM) is a powerful technique for observing nanoscale processes in their native liquid environment and in real time. However, the imaging electron beam can have major interferences with the processes under study, altering the experimental outcome. Here, we use in situ liquid TEM to understand the differences between beam-induced and electrodeposition processes that result in nucleation and growth of gold crystallites. Through this study, we find that beam-induced and electrodeposition processes result in crystallites that deposit at different locations within the liquid cell and differ significantly in morphology. Furthermore, we develop a strategy based on increasing the liquid layer thickness for reducing the amount of beam-induced crystallites to negligible levels. Through this optimized system, we study the electrodeposition of gold on carbon electrodes by correlating current time transients and their corresponding time-resolved scanning TEM images. This analysis demonstrates that even when the electron-beam plays a negligible role in gold deposition under optimal conditions, there is a large discrepancy between the amount of deposits observed and the amount measured using the current time transients. This finding sheds light on the heterogeneity of the deposition process and provides insights into designing a new class of in situ liquid TEM systems

Producing Fluorine- and Lubricant-Free Flexible Pathogen- and Blood-Repellent Surfaces Using Polysiloxane-Based Hierarchical Structures

High-touch surfaces are known to be a major route for the spread of pathogens in healthcare and public settings. Antimicrobial coatings have, therefore, garnered significant attention to help mitigate the transmission of infectious diseases via the surface route. Among antimicrobial coatings, pathogen-repellent surfaces provide unique advantages in terms of safety in public settings such as instant repellency, affordability, biocompatibility, and long-term stability. While there have been many advances in the fabrication of biorepellent surfaces in the past two decades, this area of research continues to suffer challenges in scalability, cost, compatibility with high-touch applications, and performance for pathogen repellency. These features are critical for high-touch surfaces to be used in public settings. Additionally, the environmental impact of manufacturing repellent surfaces remains a challenge, mainly due to the use of fluorinated coatings. Here, we present a flexible hierarchical coating with straightforward and cost-effective manufacturing without the use of fluorine or a lubricant. Hierarchical surfaces were prepared through the growth of polysiloxane nanostructures using n-propyltrichlorosilane (n-PTCS) on activated polyolefin (PO), followed by heat shrinking to induce microscale wrinkles. The developed coatings demonstrated repellency, with contact angles over 153 degrees and sliding angles <1 degrees. In assays mimicking touch, these hierarchical surfaces demonstrated a 97.5% reduction in transmission of Escherichia coli (E.coli), demonstrating their potential as antimicrobial coatings to mitigate the spread of infectious diseases. Additionally, the developed surfaces displayed a 93% reduction in blood staining after incubation with human whole blood, confirming repellent properties that reduce bacterial deposition.NSERC Discovery grant; Ontario Early Researcher Award (ERA) grant; McMaster start-up fundsThis work was supported by the NSERC Discovery grant, Ontario Early Researcher Award (ERA) grant, and McMaster start-up funds to T.F.D. T.F.D and L.S are Tier II Canada Research Chairs