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Browsing by Author "Wang, Zhijie, committee member"

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    Advanced nanostructured materials for enhancing bioactivity
    (Colorado State University. Libraries, 2024) Bhattacharjee, Abhishek, author; Popat, Ketul C., advisor; Sampath, Walajabad, committee member; Herrera-Alonso, Margarita, committee member; Wang, Zhijie, committee member
    Health hazards such as pathogenic infection, communicable diseases, and bone damage and injuries cause enormous human suffering and pain worldwide. Biomaterials such as orthopedic implants and biosensors are crucial tools to remedy these complications. Development of novel biomaterials and modifying existing materials can help enhance medical device efficacy. One of the key aspects of improving biomaterials is the utilization of nanotechnology. Nanoscale surface features can improve the interaction between materials and biological agents, thus improving their bioactivity. In this dissertation research, two different biomaterials were used for two distinct applications. Firstly, titanium, a common material for orthopedic implants, was used. Ti is a popular implant material because of its superior corrosion resistance, lightweight, and excellent biocompatibility. However, 10% of Ti implants fail each year due to pathogenic bacterial infection and poor osseointegration resulting in revision surgeries and immense suffering of the patients. Nanostructured surface modification approaches can potentially reduce the failure rate of Ti implants. In this study, TiO2 nanotube arrays (NT) were fabricated followed by zinc (Zn) and strontium (Sr) doping. These elements provide important signals to mesenchymal stem cells to differentiate into osteoblasts which helps in bone healing. Zn also reduces bacterial adhesion to the implant surface. Results showed that the modified surfaces could significantly reduce bacterial adhesion and improved osseointegration properties of the mesenchymal stem cells. Secondly, a polydiacetylene (PDA)-based electrospun nanofiber biosensor was prepared that is flexible in nature for monitoring bacterial or viral infection. The nanofiber biosensor could selectively detect Gram-negative bacteria via a vivid blue-to-red color transition. Since the color transition is visible to the naked eye, the biosensor offers immense potential to be used as a screening device for Gram-negative bacterial infection in various industries such as food packaging, medical, intelligence, and national security. During the COVID-19 pandemic, the PDA biosensing platform was utilized to detect the spike (S) protein of the SARS-CoV-2. For this, the surface chemistry of the PDA fibers was modified, and a receptor protein was conjugated at the end of the PDA polymer chain. When the modified PDA fibers were incubated with the S protein, the blue-to-red color transition happened, thus sensing the presence of S protein in the environment. This result indicated that PDA nanofiber biosensor is a flexible sensing platform for effectively detecting both bacteria and viruses. The two biomaterials investigated in this research indicated that the use of nanotechnology can help in enhancing their bioactivity.
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    Biomechanical analysis of hypoplastic left heart syndrome and calcific aortic stenosis: a statistical and computational study
    (Colorado State University. Libraries, 2021) Zebhi, Banafsheh, author; Bark, David, advisor; Gao, Xinfeng, committee member; Wang, Zhijie, committee member; Scansen, Brian, committee member
    Cardiovascular diseases are a leading cause of death in the United States. In this dissertation, a congenital heart disease (CHD) and a valvular disease are discussed. CHDs occur in ~5% of live births. Structural CHDs can be complex and difficult to treat, such as hypoplastic left heart syndrome (HLHS) in which the left ventricle is generally underdeveloped, representing ~9% of all congenital heart diseases. Calcific aortic stenosis is one of the most common valvular diseases in which valves thicken and stiffen, and in some cases nodular deposits form, limiting valve function that may result in flow regurgitation and outflow obstruction. The overarching hypothesis of this research is that patient-specific heart geometry and valve characteristics are linked to cardiovascular diseases and may play an important role in regulating hemodynamics within the heart. This hypothesis is studied through three specific aims. In specific aim 1, a computational fluid dynamics study was developed to quantify the hemodynamic characteristics within the right ventricles of healthy fetuses and fetuses with HLHS, using 4D patient-specific ultrasound scans. In these simulations, we find that the HLHS right ventricle exhibits a greater cardiac output than normal; yet, hemodynamics are relatively similar between normal and HLHS right ventricles. Overall, this study provides detailed quantitative flow patterns for HLHS, which has the potential to guide future prevention and therapeutic interventions, while more immediately providing additional functional detail to cardiologists to aid in decision making. The specific aim 2 is a comprehensive review in which we highlight underlying molecular mechanisms of acquired aortic stenosis calcification in relation to hemodynamics, complications related to the disease, diagnostic methods, and evolving treatment practices for calcific aortic stenosis and, bioprosthetic or native aortic scallop intentional laceration (BASILICA) procedure to free coronary arteries from obstruction. In specific aim 3, we use statistical trends and relationships to identify the role of patient-specific aortic valve characteristics in post-BASILICA coronary obstruction. The findings of this study shows that in addition to direct anatomical measurements of the aortic valve, the aspect ratios of the anatomical features are important in determining the cause of post-BASILICA coronary obstruction. The overall significance of this dissertation is that computational and statistical analysis of patient's specific flow hemodynamics and geometric characteristics can provide more insight into the cardiovascular disease and treatment approaches which can ultimately assist surgeons with procedural planning.
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    Development of novel mechanical diagnostic techniques for early prediction of bone fracture healing outcome
    (Colorado State University. Libraries, 2021) Wolynski, Jakob G., author; McGilvray, Kirk, advisor; Puttlitz, Christian, advisor; Heyliger, Paul, committee member; James, Susan, committee member; Wang, Zhijie, committee member
    To view the abstract, please see the full text of the document.
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    Development of surface modifications on titanium for biomedical applications
    (Colorado State University. Libraries, 2021) Maia Sabino, Roberta, author; Popat, Ketul C., advisor; Martins, Alessandro F, advisor; Herrera-Alonso, Margarita, committee member; Li, Yan Vivian, committee member; Wang, Zhijie, committee member
    For decades, titanium-based implants have been largely employed for different medical applications due to their excellent mechanical properties, corrosion resistance, and remarkable biocompatibility with many body tissues. However, even titanium-based materials can cause adverse effects which ultimately lead to implant failure and a need for revision surgeries. The major causes for implant failure are thrombus formation, bacterial infection, and poor osseointegration. Therefore, it is essential to develop multifunctional surfaces that can prevent clot formation and microbial infections, as well as better integrate into the body tissue. To address these challenges, two different surface modifications on titanium were investigated in this dissertation. The first one was the fabrication of superhemophobic titania nanotube (NT) surfaces. The second approach was the development of tanfloc-based polyelectrolyte multilayers (PEMs) on NT. The hemocompatibility and the ability of these surfaces to promote cell growth and to prevent bacterial infection were investigated. The results indicate that both surface modifications on titanium enhance blood compatibility, and that tanfloc-based PEMs on NT improve cell proliferation and differentiation, and antibacterial properties, thus being a promising approach for designing biomedical devices.
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    Hemocompatibility of titania nanotube arrays under static and dynamic conditions
    (Colorado State University. Libraries, 2020) Ghosh, Sayudh, author; Popat, Ketul C., advisor; Wang, Zhijie, committee member; Li, Yan, committee member
    Titanium and titanium alloys have been extensively used to make blood contacting medical devices such as vascular stents, mechanical heart valves, etc. However, the material is not always hemocompatible, often resulting in thrombosis and eventual rejection of the medical device. To overcome this, medical practitioners have used anti coagulating methods which have had other detrimental effects on patients. Researchers have tried to overcome this problem by developing different surfaces for materials and evaluating hemocompatibility in static conditions, however it is important to evaluate hemocompatibility under dynamic conditions to get a realistic biological response. Recent studies have shown that nanotextured surfaces show better hemocompatibility than non-nanotextured surfaces. In this study, we have developed a dynamic chamber to evaluate hemocompatibility of titania nanotube arrays. The nanotube arrays were fabricated using anodization technique and modified to make the surface either supherhydrophobic or superhydrophillic. The stability of these surfaces and their interaction with blood and its components (protein adsorption, cell adhesion, platelet adhesion and activation) was investigated under dynamic flow conditions and compared to that from static conditions. The results indicate that the Titania nanotube arrays that were superhydrophobic show significantly enhanced hemocompatibility than other surfaces.
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    Hydrothermal surface modifications on titanium for biomedical applications
    (Colorado State University. Libraries, 2023) Manivasagam, Vignesh K., author; Popat, Ketul C., advisor; Cox-York, Kimberly, committee member; Walajabad, Sampath, committee member; Wang, Zhijie, committee member
    Titanium and its alloys are widely used in different biomaterial applications due to their remarkable mechanical properties and bio-inertness. However, titanium-based materials still face some challenges, with an emphasis on hemocompatibility. Blood-contacting devices such as stents, heart valves, and circulatory devices are prone to thrombus formation, restenosis, and inflammation due to inappropriate blood–implant surface interactions. After implantation, when blood encounters these implant surfaces, a series of reactions takes place, such as protein adsorption, platelet adhesion and activation, and white blood cell complex formation as a defense mechanism. Currently, patients are prescribed anticoagulant drugs to prevent blood clotting, but these drugs can weaken their immune system and cause profound bleeding during injury. Extensive research has been done to modify the surface properties of titanium to enhance its hemocompatibility. Results have shown that the modification of surface morphology, roughness, and chemistry has been effective in reducing thrombus formation. A simple hydrothermal treatments with different acidic/basic medium were investigated in this dissertation. The first treatment with sodium hydroxide and the second treatment with sulfuric acid. Hemocompatability, cytocompatibility and antibacterial properties of these surfaces were investigated. The results indicated that sodium hydroxide surface is suitable for orthopedic application and sulfuric acid surface with silane coating is highly suitable for blood contacting implant surface.
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    Non-ionizing tomographic imaging modalities for bedside lung monitoring
    (Colorado State University. Libraries, 2023) Vieira Pigatto, Andre, author; Mueller, Jennifer L., advisor; Wilson, Jesse, committee member; Rezende, Marlis, committee member; Wang, Zhijie, committee member
    The need for an accurate and non-ionizing imaging modality for pulmonary assessment of patients undergoing mechanical ventilation due to respiratory failure has increased due to COVID. The ability to quickly detect the development of pathologies at an early stage is highly desirable and could help reduce the incidence of complications. It is also clear that mechanical ventilation can cause ventilator-induced lung injuries, which can be avoided by adequately optimizing the positive end-expiratory pressure to induce alveolar recruitment while preventing hyperinflation. Here, I will explore two non-ionizing pulmonary imaging systems that could be used as monitoring systems in the intensive care unit: Ultrasound Computed Tomography (USCT) and Electrical Impedance Tomography (EIT). The most comprehensive part of this research is the development of a Low-Frequency USCT system, which was motivated by recent studies demonstrating that acoustic waves transmitted at frequencies between 10 kHz and 750 kHz penetrate the lungs and may be useful for thoracic imaging. A novel transducer based on Tonpilz was designed, characterized, and calibrated through vibrational, electrical, and acoustic measurements, and a flexible belt that holds up to 32 transducers was constructed. A Verasonics Vantage 64 Low-frequency Research Ultrasound system was programmed to collect data by transmitting and receiving signals at frequencies of 125 and 156 kHz. The data collection and processing algorithms were developed in MATLAB, and the system was tested on phantom and vertebrate animal experiments; image reconstructions were conducted using a Time-Of-Flight algorithm. As a secondary study, SMA-1, COVID, and regular patients were imaged and analyzed using EIT technology; these results are shown through journal and conference articles presented in the Appendix A and C of this document.
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    Preparation and characterization of poly lactic-co-glycolic nanoparticles encapsulated with gentamicin for drug delivery applications
    (Colorado State University. Libraries, 2019) Sun, Yu, author; Li, Yan Vivian, advisor; Bailey, Travis, committee member; Wang, Zhijie, committee member
    Wound treatment has always been a popular topic around the world. Since the emergence of nanotechnology, the development and design of novel wound dressing materials have been dramatically improved. The ues of nanoparticles encapsulated with antibiotics to deliver drugs has been shown to be a potentially effective approach to control bacterial infections at a wound position. Recently, biodegradable and biocompatible polymers have drawn lots of attention for the manufacture of drug-loaded nanoparticles in the pharmaceutical industry. In this work, poly-lactic-co-glycolic acid (PLGA) was used in nanoparticle synthesis due to its biodegradability, biocompatibility, and nontoxicity. For this work, gentamicin was loaded into the PLGA nanoparticles as an antibiotic because it is a broad-spectrum antibiotic effective in wound treatments. PLGA nanoparticles were prepared while gentamicin was loaded in the nanoparticles via a double emulsion evaporation method. Poly vinyl alcohol (PVA) was a surfactant that was an important factor in determining the most probable nanoparticle size and morphology. When the PVA concentrations were 9% and 12%, the nanoparticles demonstrated a spherical structure with a porous surface. The porous surface of a nanoparticle was promising for the purpose of releasing encapsulated antibiotics. Another important factor in determining the formation of nanoparticles was the PLGA concentration. Poly lactic-co-glycolic acid (PLGA) was the main material affecting PLGA nanoparticles' properties. PLGA nanoparticles would have various release profiles, morphology, and size distribution with different PLGA concentrations. The results suggested that different PLGA concentrations can endow PLGA nanoparticles with various properties which can lead to different applications of PLGA nanoparticles.
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    The selective de-identification of ECGs
    (Colorado State University. Libraries, 2022) Akhtar, Musamma, author; Simske, Steven, advisor; Wang, Zhijie, committee member; Vans, Marie, committee member
    Biometrics are often used for immigration control, business applications, civil identity, and healthcare. Biometrics can also be used for authentication, monitoring (e.g., subtle changes in biometrics may have health implications), and personalized medical concerns. Increased use of biometrics creates identity vulnerability through the exposure of personal identifiable information (PII). Hence an increasing need to not only validate but secure a patient's biometric data and identity. The latter is achieved by anonymization, or de-identification, of the PII. Using Python in collaboration with the PTB-XL ECG database from Physionet, the goal of this thesis is to create "selective de-identification." When dealing with data and de-identification, clusters, or groupings, of data with similarity of content and location in feature space are created. Classes are groupings of data with content matching that of a class definition within a given tolerance and are assigned metadata. Clusters start without derived information, i.e., metadata, that is created by intelligent algorithms, and are thus considered unstructured. Clusters are then assigned to pre-defined classes based on the features they exhibit. The goal is to focus on features that identify pathology without compromising PII. Methods to classify different pathologies are explored, and the effect on PII classification is measured. The classification scheme with the highest "gain," or (improvement in pathology classification)/ (improvement in PII classification), is deemed the preferred approach. Importantly, the process outlined can be used in many other systems involving patient recordings and diagnostic-relevant data collection.