Precise mass determination of single cell with cantilever-based microbiosensor system

Having determined the mass of a single cell of brewer yeast Saccharomyces cerevisiae by means of a microcantilever-based biosensor Cantisens CSR-801 (Concentris, Basel, Switzerland), it was found that its dry mass is 47,65 $\pm$ 1,05 pg. Found to be crucial in this mass determination was the cell position along the length of the cantilever. Moreover, calculations including cells positions on the cantilever provide a threefold better degree of accuracy than those which assume uniform mass distribution. We have also examined the influence of storage time on the single cell mass. Our results show that after 6 months there is an increase in the average mass of a single yeast cell

Conductivity percolation in water network on silica surface A380

W pracy badano zjawisko przejścia perkolacyjnego w sieci 2D wody przy niskim stopniu uwodnienia na powierzchni krzemionki Aerosil 380. Pomiary przeprowadzono metodą spektroskopii dielektrycznej, z wykorzystaniem mostka impedancyjnego. Wykonano 3 serie pomiarowe podczas swobodnej dehydratacji próbki do otoczenia (RH ok. 30%) oraz jedną serię pomiarową przy włączonym nawilżaczu powietrza utrzymującym wilgotność RH=50% w pomieszczeniu. Wyznaczone widma dielektryczne (składowa rzeczywista i urojona) są charakterystyczne dla nawodnionych układów biologicznych. Nie dostrzeżono wyraźnej różnicy w poszczególnych widmach pochodzących z badań przeprowadzonych w różnych warunkach atmosfery otoczenia. Zaobserwowano przejścia perkolacyjne dla wszystkich wyżej wymienionych serii. Otrzymano średnie parametry w progu perkolacji: stopień uwodnienia h*= 0,256(2), oraz wykładnik krytyczny t*=1,092(4) charakterystyczny dla procesu perkolacji przewodnictwa w sieci 2D.The work concerns the 2D conductivity percolation in water network on low hydrated surface of silica Aerosil 380. Measurements were carried out using the method of dielectric spectroscopy (impedance bridge). 3 series of measurements of the free-dehydration samples to the environment (30% RH) and one course of measurements in the presence of the air humidifier turned on persistent humidity RH = 50% were performed. Recorded dielectric spectrum (real and imaginary components) are characteristic of hydrated biological systems. No significant difference was noticed in the individual spectra from the experiment carried out under different conditions of ambient atmosphere. Percolation transition was observed for all of the above series. The average parameters of percolation obtained: hydration level h* = 0.256 (2), and the critical exponent t* = 1.092 (4), the latter being characteristic of the process of conductivity percolation in the 2D water network

Microcantilever sensors in the analysis of fundamental biophysical parameters of biological systems

W tej pracy wyznaczono średnią masę pojedynczej komórki drożdży Saccharomyces cerevisiae. W pomiarach wykorzystano sensor mikrobeleczkowy Cantisens® CSR-801 pracujący w trybie dynamicznym na zestawie ośmiobeleczkowym CLA500-070-08V (Concentris). Na beleczki nanoszono komórki drożdży w postaci zawiesiny w wodzie destylowanej 5 minut po sporządzeniu zawiesiny. Mierzono częstotliwość rezonansową beleczki dla pierwszego modu drgań w środowisku gazowym przed i po nałożeniu drożdży. Wykonano 4 serie pomiarowe, po 5-7 beleczek pokrytych drożdżami w każdej serii. W każdym pomiarze zaobserwowano spadek wartości częstotliwości rezonansowej związany z dodaniem masy na beleczce. Liczbę i położenie drożdży wyznaczono metodą mikroskopii optycznej oraz mikroskopii konfokalnej. W tym celu opracowano nowatorską metodę analizy obrazów. Wyznaczono średnią masę komórki drożdży m_d=(45,1±4,7) pg.In this work we determined average single cell mass of yeast Saccharomyces cerevisiae. Cantilever sensor Cantisens® CSR-801 in dynamic work mode with 8-Cantilever Arrays CLA500-070-08V (Concentris) was employed in this experiment. The yeast cells were loaded on the cantilevers as a suspension in distilled water (five minutes after suspending). Fundamental mode of resonant frequency of the cantilever was measured before and after loading of the yeast cells in gas. 4 measurements series were performed with 5-7 loaded cantilevers in each series. Decreasing in the value of the resonant frequency related to increasing cantilever’s weight in each measurement was observed. The optical and confocal microscopy were used to determine the number and position of the each yeast cell on cantilever. In this purpose the new image analysis method was created. The average mass of yeast cells is equal: m_d=(45,1±4,7) pg

Comparison of results with and without taking into account an individual cell position along the cantilever.

<p>Box charts for an average single cell mass determination. (I)—cells positions are taken into account and (II)—assuming uniform cell distribution. 25-50-75 percent of results are marked by boxes, the minimum and maximum values are marked by whiskers. The small squares show the average value of each series.</p

Comparison of results with and without taking into account an individual cell position along the cantilever.

<p>Box charts for an average single cell mass determination. (I)—cells positions are taken into account and (II)—assuming uniform cell distribution. 25-50-75 percent of results are marked by boxes, the minimum and maximum values are marked by whiskers. The small squares show the average value of each series.</p

Cantilever dimensions were obtained by analyzing the line profiles on the cantilever images.

<p>A) Image of the cantilever with a superimposed line used to make the profile. B) Obtained intensity profile along a marked line. C) Derivative of intensity profile curve from Graph B. The Gauss function was fitted to the obtained peaks (line). The distance between the peak positions was interpreted as being the cantilever width. To estimate cantilever length the same procedure was performed.</p

Change in the lyophilized yeast cell mass after a 6-month period of refrigerated storage.

<p>A) Initial yeast cell mass value and B) after 6 months of storage.</p

The normalized frequency response of the cantilever as a function of cantilever length.

<p>A) assuming uniform cell distribution (or the whole deposited mass on the tip of the cantilever). B) position of every deposited cell taken into consideration. In part A, every average frequency shift per deposited cell was normalized to the maximum value obtained in all experiments. In part B, the contribution of each cell to the frequency shift was taken into account by function U(z).</p

Yeast cells located on the cantilever surface.

<p>Left panel–a cluster of 5 yeast cell near the free end of the cantilever. Right panel–magnification of the square from the left panel showing the graphical determination of a cell distance from the edge of the cantilever.</p

Working principle of the cantilever-based optomechanical sensor.

<p>The cantilever bending amplitude or oscillation frequency is detected by a laser-based optical system. The light from laser (A) on being deflected from the oscillating cantilever (B) falls on PSD (C) where the signal is transformed into the electronic form. Subsequently signal is sent to the computer where its magnitude is displayed on the screen.</p