Browsing by Subject "Nanobiotechnology"

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    Peptide-mediated constructs of quantum dot nanocomposites for enzymatic control of nonradiative energy transfer
    (American Chemical Society, 2011) Seker U.O.S.; Ozel, T.; Demir, Hilmi Volkan
    A bottom-up approach for constructing colloidal semiconductor quantum dot (QDot) nanocomposites that facilitate nonradiative Förster-type resonance energy transfer (FRET) using polyelectrolyte peptides was proposed and realized. The electrostatic interaction of these polypeptides with altering chain lengths was probed for thermodynamic, structural, and morphological aspects. The resulting nanocomposite film was successfully cut with the protease by digesting the biomimetic peptide layer upon which the QDot assembly was constructed. The ability to control photoluminescence decay lifetime was demonstrated by proteolytic enzyme activity, opening up new possibilities for biosensor applications.
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    ItemOpen Access
    Portable microfluidic integrated plasmonic platform for pathogen detection
    (Nature Publishing Group, 2015) Tokel, O.; Yildiz, U. H.; Inci, F.; Durmus, N. G.; Ekiz, O. O.; Turker, B.; Cetin, C.; Rao, S.; Sridhar, K.; Natarajan, N.; Shafiee, H.; Dana, A.; Demirci, U.
    Timely detection of infectious agents is critical in early diagnosis and treatment of infectious diseases. Conventional pathogen detection methods, such as enzyme linked immunosorbent assay (ELISA), culturing or polymerase chain reaction (PCR) require long assay times, and complex and expensive instruments, which are not adaptable to point-of-care (POC) needs at resource-constrained as well as primary care settings. Therefore, there is an unmet need to develop simple, rapid, and accurate methods for detection of pathogens at the POC. Here, we present a portable, multiplex, inexpensive microfluidic-integrated surface plasmon resonance (SPR) platform that detects and quantifies bacteria, i.e., Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) rapidly. The platform presented reliable capture and detection of E. coli at concentrations ranging from ∼105 to 3.2 × 107 CFUs/mL in phosphate buffered saline (PBS) and peritoneal dialysis (PD) fluid. The multiplexing and specificity capability of the platform was also tested with S. aureus samples. The presented platform technology could potentially be applicable to capture and detect other pathogens at the POC and primary care settings. © 2015, Nature Publishing Group. All rights reserved.
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    Synthesis and characterization of nanosized calcium phosphates by flame spray pyrolysis, and their effect on osteogenic differentiation of stem cells
    (Springer, 2015) Ataol, S.; Tezcaner, A.; Duygulu, O.; Keskin, D.; Machin, N. E.
    The present study evaluates the synthesis of biocompatible osteoconductive and osteoinductive nano calcium phosphate (CaP) particles by industrially applied, aerosol-derived flame spray pyrolysis method for biomedical field. Calcium phosphate nanoparticles were produced in a range of calcium-to-phosphorus ratio, (1.20–2.19) in order to analyze the morphology and crystallinity changes, and to test the bioactivity of particles. The characterization results confirmed that nanometer-sized, spherical calcium phosphate particles were produced. The average primary particle size was determined as 23 nm by counting more than 500 particles in TEM pictures. XRD patterns, HRTEM, SAED, and SEM analyses revealed the amorphous nature of the as-prepared nano calcium phosphate particles at low Ca/P ratios. Increases in the specific surface area and crystallinity were observed with the increasing Ca/P ratio. TGA–DTA analysis showed that the thermally stable crystal phases formed after 700 °C. Cell culture studies were conducted with urine-derived stem cells that possess the characteristics of mesenchymal stem cells. Synthesized amorphous nanoparticles did not have cytotoxic effect at 5–50 μg/ml concentration range. Cells treated with the as-prepared nanoparticles had higher alkaline phosphatase (ALP) enzyme activity than control cells, indicating osteogenic differentiation of cells. A slight decrease in ALP activity of cells treated with two highest Ca:P ratios at 50 μg/ml concentration was observed at day 7. The findings suggest that calcium phosphate nanoparticles produced in this work have a potential to be used as biomaterials in biomedical applications. © 2015, Springer Science+Business Media Dordrecht.