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Browsing by Author "Bhattacharjee, Abhishek, author"

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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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    Bacterial culture components activating colorimetric transition in polydiacetylene nanofiber composites
    (Colorado State University. Libraries, 2020) Bhattacharjee, Abhishek, author; Li, Yan Vivian, advisor; Gentry-Weeks, Claudia, committee member; Diddi, Sonali, committee member
    Polydiacetylene (PDA) demonstrates colorimetric transition behaviors due to conformational changes in π conjugated backbone of PDA macromolecules at external stimuli of bacteria, suggesting potential applications in biosensors. However, the bacterial culture components activating colorimetric transition in PDAs are still undetermined due to the complexity of the bacterial system. In this study, PU-PDA nanofiber composite was prepared via electrospinning and tested with components from Escherichia coli (E. coli) culture including supernatant fluid, cell pellet, and extracellular polymeric substances (EPS). When PU-PDA nanofiber was tested with supernatant fluid, it changed color from blue to red. In contrast, bacterial cell pellets could not induce a color change, suggesting the color-changing substances (CCS) are not cell-associated, rather can be found in the spent media (supernatant fluid) generated by E. coli during its growth phase. Intense color change in the nanofiber by the autoclaved supernatant fluid indicated that the CCS may not be a protein, DNA, or RNA since they denature in high heat and pressure from the autoclaving process. With an increase in storage time of the supernatant fluid, the color-changing rate was reduced significantly, suggesting a degradation in CCS with time. Free EPS from the supernatant fluid could induce a color change in the nanofibers, which confirmed that EPS contains the CCS. No significant changes were found in the morphology of PU-PDA nanofibers before and after the exposure of E. coli culture components. Critical bacterial concentration (CBC) was found approximately 9 × 108 CFU/ml, suggesting the efficiency of the PU-PDA nanofiber composite to be used as a biosensor. Additionally, solvatochromism of the nanofiber composite was investigated using organic solvents commonly used in extracting bacterial culture components. The results from this study provided a guideline for using PU-PDA nanofiber composite as a biosensor in point-of-care applications.