A Comparison of Osteoblast and Bacteria Functions on Micro Fibrous Nanorough Scaffolds Produced by Electrospinning, Rotary-Jet Spinning and Airbrush Processes
Paria Ghannadian, Thomas Webster
Department of Chemical Engineering, Northeastern University
Recently, scientists have been investigating novel materials and techniques for growing orthopedic tissue engineering needs. Due to problems (such as infection and long healing time) that titanium based implants can cause in vivo, new polymeric materials have been introduced. In this study, poly(ε-caprolactone) (PCL) micron fibrous scaffolds with nanorough surface features were fabricated using 3 different concentrations (8%, 12%, and 17%) of PCL dissolved in 1,1,1,3,3,3-Hexafluoro-2-propanol via several fabrication methods specifically electrospinning, rotary-jet spinning, and airbrush. Mechanical, biological, and morphological properties were determined. Most importantly, results showed that without the use of any antibiotics, by changing the fabrication method alone and the size of the fibers, antimicrobial properties were improved without sacrificing mechanical properties and osteoblast functions. Specifically, it was found that the antimicrobial properties were improved when using airbrushing compared to electrospun and rotary-jet spun scaffolds where up to a 50% decrease in bacterial density was observed. Moreover, between 8% all of the PCL concentrations tested, 12% PCL scaffolds possessed the least bacterial density. It was found that osteoblast adhesion and proliferation were similar for all fabrication methods; however, osteoblast differentiation was higher on the electrospun PCL scaffolds. 12% PCL possessed the best mechanical properties for orthopedic applications. Thus, based on the results, 12% PCL airbrushed scaffolds show the highest Young’s modulus and the optimum antimicrobial properties. Although the cell proliferation, calcium deposition and cell viability results are close to each other, it is observed that the cell adhesion in airbrushed samples are poorer than those in electrospun and rotary-jet spun scaffolds. In general, 12% airbrushed PCL scaffolds are recommended since they cause the least probability of infection in body and can support the tissue in regard of strength.
Peptide-Enriched Nanocarriers for the Growth Inhibition of Antibiotic-Resistant Bacteria
Nicole J. Bassous, Thomas J. Webster
Department of Chemical Engineering, Northeastern University
Statement of Purpose: Clinically applied antibiotic treatments are losing their efficacy due to resistant bacterial strains, and the development of clinical alternatives is of primary importance. Prevalent research is currently directed towards the fabrication of highly refined nano-vesicles that are functionalized to combat antibiotic-resistant bacterial infections, especially those caused by methicillin-resistant Staphylococcus aureus (MRSA), and that aid with wound healing or immunomodulation1,2. Such a drug delivery approach is especially significant for patients who are susceptible to S. aureus infections post-operatively. Technical challenges associated with the aim of preventing these infections can be approached through the evaluation of the chemical properties of drug delivery synthesis materials and methods. The purpose of this research is to (1) propose an alternative to antibiotics to which bacteria are non-resistant, (2) to describe the design of a suitable drug delivery vehicle, and (3) to contribute to a general knowledge about the mechanisms involved in the inhibition of bacterial growth through the use of antimicrobial peptides (AMPs) and metallic nanoparticles. Here, formulations of metallic nanoparticles and AMPs were incorporated into polymersomes (PS), which are polymeric, biocompatible vesicles that self-assemble via hydrophobicity interactions of admixed aqueous and organic substances. In vitro assays were designed to determine the efficacy of variable Ag/AMP PS treatment concentrations at prohibiting MRSA proliferation. Moreover, the cytotoxicity of the PS composites towards human dermal fibroblasts was measured in order to gauge their potential for future clinical use.
Methodologies for Life Cycle Inventory Generation of Chemicals and their Implication on the Life Cycle Impact Assessment Results*
Department of Chemical Engineering, 360 Huntington Avenue, Boston, MA 02115
The use of industrial chemicals is prevalent in the modern society as raw materials and intermediates, making them an integral part of the life cycle of several products we use every day. Growing concerns over climate change, regulations and consumer awareness have necessitated a declaration of environmental impacts of these products. Life Cycle Assessment (LCA), the most popular tool to calculate these environmental impacts require a detailed analysis of input and output flows to the various stages of production of these chemicals. However, due to the vast universe of chemicals and hurdles such as restricted access to primary data from plants, LCA practitioners are faced with a challenging task of generating life cycle inventories for chemicals based on limited data availability in the open literature. This study comprehensively examines eight different approaches used by LCA practitioners to incorporate chemical LCIs in their analysis based on varying data availability and the uncertainties associated with them. The implications of overestimating or underestimating the chemical LCI on the overall life cycle assessment of a product has been explored using a case study of styrene. The study suggests that, while approaches such as, using stoichiometry to determine the inputs and outputs in a chemical process can grossly underestimate the environmental impacts such as global warming potential (GWP) and cumulative energy demand (CED), using basic process calculations without appropriately accounting for heat integration etc. can lead to overestimation of these impacts. Approaches which do not consider auxiliary operations and uses indeterminate estimations for electricity consumption could lead to misleading estimates for impact categories such as Eco-toxicity and such studies should avoid reporting these impacts. Acknowledgment: this project is supported by National Science Foundation (NSF) (*) This project is supervised by Prof. Matthew Eckelman.