A Dual Optical Tweezer for Microrheology of Bacterial Suspensions

Yogesha,; Raghu, Appu Vengattoor; Nagesh, B.V.; Bhattacharya, Sarbari; Mohana, Devihalli Chikkaiah; Ananthamurthy, Sharath

doi:10.1142/s0219581x11007739

Cited by 8 publications

(6 citation statements)

References 8 publications

(9 reference statements)

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“…The corner frequency values of the PSD -frequency plots in figure 3 are obtained by fitting the PSD curve to an expression (Yogesha et al 2011) …”

Section: Resultsmentioning

confidence: 99%

“…The optical tweezer setup used by us has been described elsewhere (figure 2) (Yogesha et al 2011). Briefly, it consists of a trapping diode laser (980 nm) guided into an oil immersion objective (1·4 NA, EA100×) on a custom made inverted microscope.…”

Section: Optical Tweezersmentioning

confidence: 99%

“…The deviation in the PSD is taken into account. We have defined a term called activity factor (AF) which is a ratio of PSD of the bead in presence of active bacterial cells to that of the bead in the presence of inactive bacterial cells at the same cell count (Yogesha et al 2011). This is a parameter which has been defined for the first time to quantify collective bacterial activity.…”

Section: Bacterial Activitymentioning

confidence: 99%

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An optical tweezer-based study of antimicrobial activity of silver nanoparticles

et al. 2012

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Abstract. Understanding and characterizing microbial activity reduction in the presence of antimicrobial agents can help in the design and manufacture of antimicrobial drugs. We demonstrate the use of an optical tweezer setup in recording the changes in bacterial activity with time, induced by the presence of foreign bodies in a bacterial suspension. This is achieved by monitoring the fluctuations of an optically trapped polystyrene bead immersed in it. Examining the changes in the fluctuation pattern of the bead with time provides an accurate characterization of the reduction in the microbial activity. Here, we report on the effect of addition of silver nanoparticles on bacterial cultures of Pseudomonas aeroginosa, Escherichia coli and Bacillus subtilis. We observe a decrease in the bacterial activity with time for the investigated bacterial samples. This method in our opinion, enables one to track changes in bacterial activity levels as a function of time of contact with the antibacterial agent with greater efficacy than traditional cell counting methods.

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“…The corner frequency values of the PSD -frequency plots in figure 3 are obtained by fitting the PSD curve to an expression (Yogesha et al 2011) …”

Section: Resultsmentioning

confidence: 99%

Section: Optical Tweezersmentioning

confidence: 99%

Section: Bacterial Activitymentioning

confidence: 99%

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An optical tweezer-based study of antimicrobial activity of silver nanoparticles

et al. 2012

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“…20 We present here the method used in obtaining microrheological parameters. 20 We present here the method used in obtaining microrheological parameters.…”

Section: Measurement Techniquesmentioning

confidence: 99%

Investigations on rheological properties and gelation of tasar regenerated silk fibroin solution

Lakkegowda

Ammannappa

Ananthamurthy

2013

J of Applied Polymer Sci

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Tasar silk is a variety of non-mulberry silk indigenous to the Indian subcontinent. We present the measured frequencydependent viscoelastic moduli of Tasar regenerated silk fibroin (RSF) solution using optical tweezers at two concentrations (0.16% and 0.25% w/v) and extend these measurements to the low frequency regime using a video microscopy technique. We extend the investigation on the rheological behavior of Tasar RSF for four more RSF concentrations, viz., 0.50%, 1.00%, 2.50% and 5.00% using video microscopy. In all the RSF samples, both storage and loss moduli are found to increase with frequency. At lower frequencies the loss modulus is more than the storage modulus and exhibit similar behavior until a crossover frequency beyond which the storage modulus exceeds the loss modulus at all frequencies. The relaxation time which is inversely related to the crossover frequency is found to rise sharply at 5% w/v, indicating the onset of gelation in the sample. These results are examined in relation to the viscoelastic parameters of mulberry silk, wherein the larger crossover frequencies at the same higher concentrations indicate relaxation times that are an order of magnitude smaller than those measured for Tasar RSF.

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“…A tweezer based experiment was performed immediately following the culture growth for active cell studies after adding about 1-2 Pl of 3 micron polystyrene beads, to calculate the power spectral density (PSD) of the trapped bead in that medium [37]. To detect the activity of the bacterial medium the PSD data was compared with that of the inactive cells ( Figure 4).…”

Section: Microrheology In Active Mediamentioning

confidence: 99%

Optical tweezer for micro and nano scale rheology of biomaterials

2010

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Since the first proposal and demonstration of an optical trap to hold micron sized particles by Ashkin in 1986, optical tweezer-based techniques for control and manipulation of particles has seen tremendous progress and enabled the exploration of the structure and dynamics of materials at the nano length scale. In biophysical applications, these techniques have enabled a range of activities from measurements of very small forces (at sub-pN levels) at operation within cells thus assisting in the elucidation of intracellular transport mechanisms, to obtaining elastic parameters of biomolecules. The techniques have helped in gaining insights on the viscoelastic properties at micro and nano length scales of a range of soft materials such as colloids, polymer melts, bio membranes etc.The paper describes some of the studies carried out by us to understand polymer structure and elasticity of these materials in solution. The domains of "passive" and "active" rheology are explained with examples of studies undertaken to address these domains. The work using video microscopy to study silk fibroin solutions is used to exemplify the domain of passive rheology. We present recent work on bacterial solutions wherein live bacteria influence the optical trap region and thereby help us study the local viscoelasticity of such a medium.

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A Dual Optical Tweezer for Microrheology of Bacterial Suspensions

Cited by 8 publications

References 8 publications

An optical tweezer-based study of antimicrobial activity of silver nanoparticles

An optical tweezer-based study of antimicrobial activity of silver nanoparticles

Investigations on rheological properties and gelation of tasar regenerated silk fibroin solution

Optical tweezer for micro and nano scale rheology of biomaterials

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