Label-free and dynamic monitoring of cell evolutions using wavelength-multiplexing surface plasmon resonance holographic microscopy

Siqing Dai; Jingyu Mi; Jiazhen Dou; Wenpu Shi; Jiwei Zhang; Jiwei Zhang; Jianlin Zhao; Jianlin Zhao

doi:10.1364/BOE.486467

1. Introduction

Cell activities at the bio-interface including adhesion, movement, replication, apoptosis, etc. play an essential role in the development and maintenance of tissue, organs and biological bodies [1–4]. Therefore, measuring cell-substrate interactions and intracellular variations to environmental factors is of great importance in the biological field [5]. A technique that can quantitatively characterize cell evolutions in a dynamic manner is highly desired.

Surface plasmon resonance (SPR), also known as collective oscillations of free electrons on metal surface (i.e., surface plasmon polaritons, SPPs), can be excited by light wave at metal-dielectric interface [6]. The wavevector of the SPPs k_spp is calculated by

(1)$${k_{\textrm{SPP}}} = \frac{\omega }{c}\sqrt {\frac{{{\varepsilon _\textrm{m}}{\varepsilon _\textrm{d}}}}{{{\varepsilon _\textrm{m}} + {\varepsilon _\textrm{d}}}}} ,$$

where, ω and c represent the angular frequency and the light speed in free space, respectively, and ε_m and ε_d denote dielectric constants of metal and dielectric materials, respectively [7]. If a p-polarized light wave is incident onto a gold surface at SPR angle θ through a medium (e. g., prism) which has a higher refractive index (RI) compared with that of air and satisfies wavevector matching condition, SPR will happen. The wavevector of the light wave k_light can be calculated with

(2)$${k_{\textrm{light}}} = \frac{\omega }{c}n\sin \theta ,$$

where, n is RI of the medium. When SPR occurs, the intensity and phase of reflected light wave have drastic changes since the energy of light wave is coupled into the SPPs [8]. Surface plasmon wave (SPW) will then propagate along the gold surface and decay exponentially along the vertical direction of gold surface [9]. Owing to label-free characteristic and high sensitivity to the tiny changes of specimens located in the evanescent wave area, SPR has been demonstrated as a powerful technique to explore the cell behaviors at cell-substrate interface [10–14]. For example, cell apoptosis and electroporation activities were monitored by a plasmonic-based microscopy with high time resolution [10]. The response of a HEK-293 cell under the chemical stimulations was investigated via long range SPR [11]. Generally, SPR-based techniques can be divided into the amplitude(intensity)- and phase-interrogation methods. The amplitude-based method extracts sample information from SPR reflectivity curve. For example, the cleft gap distance of living cells was measured based on the SPR reflectivity spectra [15]. Compared to amplitude detection, phase detection features at least two orders of magnitude higher sensitivity due to the sharp changes of SPR phase curve [16]. Therefore, multiple techniques were developed to measure the SPR phase to detect the tiny variations of specimens. Kabashin et al. proposed an SPR interferometer for bio- and chemical-sensors with RI detection sensitivity of 4 × 10⁻⁸ RIU [17]. Argoul et al. used the V(Z) curve which is based on SPR image contrast to obtain phase information [18,19]. A single-beam phase sensitive imaging SPR sensor was reported using a liquid crystal modulator for phase retardation [20].

Taking advantages of high sensitivity from SPR-based techniques and complex amplitude measurement by digital holographic microscopy (DHM), surface plasmon resonance holographic microscopy (SPRHM) has become an emerging technique in the last decade which can reconstruct both the amplitude- and phase-based SPR images at the same time [21–28]. In the biological application field, SPRHM was used to map the cell adhesion gap and its evolution during cell activities [26]. Combined with optical tweezers (OT), OT-SPRHM system was proposed to characterize cell-substrate interactions when cell individuals were stimulated with optical force [27]. Recently, a dual-wavelength SPRHM was reported to simultaneously measure cell-substrate distance and cytoplasm RI of living cells [28]. However, in that work, incident angle of light beam at two wavelengths is adjusted sequentially to excite SPR, making dynamic monitoring of cell parameters hard to realize.

In this work, we propose a wavelength-multiplexing SPRHM to dynamically monitor cell-substrate distance and cytoplasm RI evolutions at the same time. Two beam splitters are employed to tune the incident angle of lasers at wavelengths of 632.8 nm and 690 nm to excite SPR. Then, phase-contrast SPR images of living cells are reconstructed by double-exposure DHM. The cell-substrate distance and cytoplasm RI are demodulated from reflection phase shift difference of the two wavelengths. Using the proposed technique, we carry out a series of measurements of cell parameters when osmotic pressure of extracellular environment is changed from isotonic, hypertonic to hypotonic conditions. The time traces of cell-substrate distance and cytoplasm RI in these processes clearly reveal cellular states under different external stimulations, which could provide useful information of cell properties for biological studies. Compared to previous work which also measured the cell-substrate distance and cytoplasm RI using scanning surface plasmon resonance microscopy [29], our method can realize higher temporal resolution, which is very useful for detections of ultrafast biological processes thanks to the wide-field detection capabilities. The proposed wavelength-multiplexing SPRHM is a promising tool to quantitatively detect living-cell with high throughput in a non-invasion fashion, and can be useful in various biological applications.

2. Materials and methods

2.1 Materials

The isotonic fluid is Dulbecco’s modified eagle medium (DMEM), which is supplemented with high glucose medium (gibco) contained 4.5 g/L D-Glucose, L-Glutamine and 110 mg/L Sodium Pyruvate. We prepared the hypertonic medium by adding a certain amount of sorbitol to DMEM. The hypotonic medium was made by diluting DMEM with deionized water.

2.2 Establishment of the SPR model

Based on the cell components, a six-layer SPR model consisting of the coverslip, Cr layer (adhesion layer), gold layer, culture medium, membrane and cytoplasm is built [26]. The phase interrogation of reflection light wave was employed to measure SPR signals. The reflection coefficient of reflection light wave in the six-layer SPR model r_1,6 can be calculated by the Fresnel formulas, which are expressed as

(3)$${r_{j,6}} = \frac{{{r_{j,j + 1}} + {r_{j + 1,6}}\exp [{2\textrm{i}{d_{j + 1}}{k_{z( j + 1) }}} ]}}{{1 + {r_{j,j + 1}}{r_{j + 1,6}}\exp [{2\textrm{i}{d_{j + 1}}{k_{z(j + 1) }}} ]}},\textrm{ }\left( {\textrm{i} = \sqrt { - 1} ,\textrm{ }j\textrm{ = 1, 2, 3, 4}} \right),$$

(4)$${r_{j,j + 1}} = \frac{{{\xi _{j + 1}} - {\xi _j}}}{{{\xi _{j + 1}} + {\xi _j}}},\textrm{ }({j = \textrm{1, 2, 3, 4, }5} ),$$

(5)$${\xi _j} = {\varepsilon _j}/{k_{zj}},\textrm{ }({j = \textrm{1, 2, 3, 4, 5, }6} ),$$

(6)$${k_{zj}} = 2\mathrm{\pi }\frac{{\sqrt {{\varepsilon _j} - {\varepsilon _1}{{\sin }^2}(\theta )} }}{\lambda },\textrm{ }({j = \textrm{1, 2, 3, 4, 5, }6} ),$$

where, r_j_{, j}_+ 1 denotes the reflection coefficient between the jth and j + 1th layers, d_j_+ 1 is the thickness of the j + 1th layer, k_zj and k_z_(j_+ 1) represent the wavevectors in z direction at the jth and j + 1th layers, respectively, ε_j is the dielectric constant of the jth layer (ε_j = n_j², n_j is the RI of jth layer), and λ represents the wavelength of light wave [25]. The reflection phase shift of reflected light wave φ can be calculated by

(7)$$\varphi = \arctan [{{\mathop{\rm Im}\nolimits} ({{r_{1,6}}} )/Re ({{r_{1,6}}} )} ].$$

To eliminate the environmental disturbances, a background hologram is recorded. Then, the reflection phase shift difference Δφ is calculated by subtracting the reflection phase shift with pure background from that with the cell specimen. Practically, we can obtain the reflection phase shift difference in SPR from phase difference of the object wave (i.e., the reflected light wave), which is reconstructed with the numerical reconstruction algorithm in DHM [24]. Four-layer SPR model (coverslip-Cr layer-gold layer-culture medium) is used when there is no cell specimen in order to record the background. The parameters of the six-layer SPR model are shown in Table 1. The dispersion is considered between the wavelengths of 632.8 nm and 690 nm [28].

Table 1. Parameters for the theoretical calculations^a

View Table

We determined the cell-substrate distance and cytoplasm RI using a demodulation method (Supplement 1). Briefly, given a specific phase value for one wavelength, one can obtain a monotonical curve of cell-substrate distance versus cytoplasm RI. Then, two curves can be obtained from two wavelengths (632.8 nm and 690 nm). Since the phase responses for two wavelengths are different, there will be an intersection point from the two curves. The cell-substrate distance and cytoplasm RI can then be extracted from this intersection point. It should be note that the penetration depths for 632.8 nm and 690 nm are ∼170 nm and ∼220 nm, respectively [19]. Considering the thickness of the cell cytoplasm layer is at the scale of several micrometers, the difference of the penetration depth between two wavelengths is quite small. Moreover, since the penetration depth of evanescent wave only covers a very thin slice of the cell near the cell bottom membrane, we assume that the cytoplasm RI is homogeneous along the z direction of the evanescent wave area (the direction perpendicular to gold surface). Thus, the difference in the penetration depth of the evanescent field between two wavelengths can be neglected in our measurement.

2.3 Experiment setup

Figure 1 shows the optical setup of the proposed wavelength-multiplexing SPRHM. Laser beams with the wavelengths of 632.8 nm and 690 nm pass through the collimating lenses CL_{1, 2} and halfwave plates HP_{1, 2} to be shaped as collimated light beams with the polarization direction of 45°, respectively. Then, the two light beams go through the focal lenses FL_{1, 2} (f₁ = 150 mm, f₂ = 250 mm) and are focused at the back focal plane BFP of the microscope objective (MO, APON100×HOTIRF, NA = 1.70, Olympus, Japan). The light beams are further incident onto the gold layer after passing the MO. The cell chip is coupled with MO via the matching oil. Here, the incident angle of the light beams at the wavelengths of 632.8 nm and 690 nm are adjusted by horizontally moving the beam splitters BS_{1, 2}, respectively. The incident angles are set as 55.4° @632.8 nm and 53.7° @690 nm. In this way, SPR can be excited by the two wavelengths simultaneously. The light beams reflected from the gold layer go through the imaging lens IL, Wollaston prism WP and polarizer P to realize the off-axis hologram recording. As show in the inset on the right side, a linearly-polarized light wave will be split into the p- and s-polarized light waves by WP. Since only the p-polarized light wave can excite SPR and carry the specimen information, it acts as the object light wave in DHM. And the s-polarized light wave has no SPR response and acts as the reference wave. After the modulation by the linear polarizer P, the two light waves have the same polarization direction and interfere with each other. Finally, the light beams of 632.8 nm and 690 nm are separated by the dichroic mirror DM and recorded by the CCD₁ and CCD₂, respectively. The right bottom inset shows the recorded light beam area at the CCD targets. The reason of using two CCDs for hologram recording is to maintain the sample information in frequency filtering (Supplement 1).

Fig. 1. Optical setup of wavelength-multiplexing SPRHM. CL_{1, 2}: collimating lenses; HP_{1, 2}: half-wave plates; FL_1,2: focal lenses; MO: microscope objective; BS_{1, 2}: beam splitters; IL: imaging lens; WP: Wollaston prism; P: polarizer; DM: dichroic mirror. Insets on the right side show the details of the dashed rectangle areas, d: displacement of BS, θ: SPR angle.

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2.4 Sample preparation

RAW264.7 cells were cultured in a humidified atmosphere at 37 °C with 5% CO₂. Cells were fed in the DMEM supplemented with high glucose medium (gibco), 10000 U/ml penicillin, 10 mg/ml streptomycin (BI) and 10% fetal bovine serum (BI). The RAW264.7 cell seeding density on the gold surface is 1 × 10⁵ cells/cm².

3. Results and discussions

3.1 Wide-field mapping of cell parameters under different environmental mediums

Using wavelength-multiplexing SPRHM, we firstly measured cell-substrate distance and cytoplasm RI when the cell is in an isotonic fluid. Initially, background holograms of two wavelengths were captured to extract image background. Then, digital holograms containing cell specimen were recorded successively for 169 s at 1 frame per second (fps). High-quality phase-contrast SPR images of the cell at wavelengths of 632.8 nm and 690 nm were reconstructed from digital holograms using numerical reconstruction algorithm in DHM. Figures 2(a₁–a3) and 2(b₁–b₃) present the reconstructed phase-contrast SPR images at the timepoints of 0, 84 and 169 s at the wavelengths of 632.8 nm and 690 nm, respectively. The SPR phase value varies from location to location over cellular area. The phase response presents differences between two wavelengths, revealing that the SPR signal is sensitive to the wavelength. It is worthy to mention that the wavelengths of 632.8 nm and 690 nm are sufficient to measure the cell and background separately in our system. Since the bulk solution may also lead to the SPR phase changes and influence the measurement accuracy [36], we averaged the phase of the background and subtracted it from the whole region of interest (ROI) to remove the noises from the cell culture medium in every frame. Moreover, our method does not require a designed pattern on the sensor surface as the plasmonic-based impedance microspectroscopy [37], so the local RI variation of sensor material is circumvented in our system. Since the SPR phase is inhomogeneous in the cellular area, the cell-substrate distance and cytoplasm RI also distribute unevenly in lateral direction. Figures 2(c₁–c₃) and 2(d₁–d₃) present the wide-field distributions of cell-substrate distance and cytoplasm RI at t = 0, 84 and 169 s when the cell is in the isotonic medium, respectively. Note that the signal difference at the cell edges in Fig. 2(c₁–c₃) and 2(d₁–d₃) results from the SPW propagation [38]. Additionally, at some sites within the cell, the cell-substrate distance approaches to zero. It is because of the focal contacts where cell adhesion proteins bind to integrins [39].

Fig. 2. Measurement results of cell-substrate distance and cytoplasm RI when the cell is surrounded by an isotonic fluid at three time points. Reconstructed phase-contrast SPR images under wavelengths of (a₁–a₃) 632.8 nm and (b₁–b₃) 690 nm. Wide-field distributions of (c₁–c₃) cell-substrate distance and (d₁–d₃) cytoplasm RI. Scale bars: 5 µm.

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Then, we explored the cell response to a high osmotic pressure condition by replacing the isotonic culture medium with hypertonic fluid. The cell-substrate interactions under the high osmotic pressure stimulations were monitored by recording digital holograms of two wavelengths with a period of 169 s. We reconstructed the phase-contrast SPR images of two wavelengths and obtained the distributions of cell-substrate distance and cytoplasm RI (Supplementary Fig. S3). Finally, we removed the hypertonic solution and added hypotonic fluid in the cell culture chamber to follow the cell behaviors at the cell-substrate interface. On the contrary to the hypertonic fluid, the hypotonic medium has a low osmotic pressure. The cell was monitored with the same period of 169 s with the above experiments. The phase-contrast SPR images, cell-substrate distance and cytoplasm RI distributions in this process can be found in Supplementary Fig. S4.

3.2 Dual parameter evolutions of a living cell under different environmental mediums

In addition to wide-field characterization of cell-substrate distance and cytoplasm RI, the dynamic evolutions of cell parameters under different external environments were also studied. Specifically, four cellular regions (70 × 70 pixels) were randomly selected, as shown in the inset of Fig. 3(a₁). Then, the average values of cell parameters in these ROIs are calculated and the time traces are plotted. The measurement results of cell parameters in the isotonic fluid are depicted in Figs. 3 (a₁) and 3(a₂). When the cell is in the isotonic medium, the cell keeps normal morphology, as shown in the inset of first row in Fig. 3. The values of cell-substrate distance and cytoplasm RI in the four ROIs vary in the range of 55–105 nm and 1.35–1.37 RIU, respectively. The cell-substrate distance quantitatively reveals the cell-substrate interactions of the measured cell. There exist close contacts and extracellular matrix contacts in the bottom membrane of the cell [39]. Furthermore, one can note that the values of cell parameters remain steady with small fluctuations over time, indicating a stable intracellular environment.

Fig. 3. Dynamic evolutions of average cell-substrate distance and cytoplasm RI in four selected regions of interest (inset in (a₁)) under the (a₁), (a₂) isotonic, (b₁), (b₂) hypertonic and (c₁), (c₂) hypotonic conditions. (a₁), (b₁) and (c₁): temporal traces of average cell-substrate distance during the monitor time of 169 s. (a₂), (b₂) and (c₂): temporal traces of average cytoplasm RI during the monitor time of 169 s.

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Furthermore, Figs. 3(b₁) and 3(b₂) plot the temporal evolutions of cell-substrate distance and cytoplasm RI in the same ROIs after the hypertonic fluid was pumped in the cell chamber, respectively. Clearly, all the ROIs exhibit an increasing trend in cell parameters during the monitoring period. Larger fluctuations of the signals are observed, which indicates a dynamically-changing intracellular environment induced by the external stimulations. Moreover, the temporal changes of cell parameters are not homogeneous across the cell area. The cell-substrate distance increasing from initial to final moments in ROIs 1–4 (marked by grey, red, blue and green colors, respectively in Fig. 3(a₁)) are 3.3, 9.6, 13.3, and 26.2 nm, respectively. As for cytoplasm RI, it displays an increase of 0.002, 0.004, 0.006, 0.012 RIU in ROIs 1–4, respectively. Actually, the signal changes are in good agreement of cell response in the high osmotic pressure condition. As illustrated in the inset of the second row in Fig. 3, when the cell is surrounded by hypertonic medium, cell morphology shrinks because of the higher osmotic pressure in extracellular environment. The cell bottom membrane moves upward, leading to a larger cell-substrate distance. Meanwhile, since the water flows out of the cell, the intracellular concentration will be higher, which results in an increased cytoplasm RI [40].

Moreover, the time traces of cell-substrate distance and cytoplasm RI under the low osmotic pressure stimulus are plotted in Figs. 3(c₁) and 3(c₂), respectively. This time we observe a decreasing trend in the cell parameters under the hypotonic environment. The changing amplitude of cell-substrate distance and cytoplasm RI is not spatially homogeneous. Specifically, ROI4 (marked in green color) has the most prominent variations with cell-substrate distance descending of 13.7 nm and cytoplasm RI dropping of 0.006 RIU. The most moderate changes of cell parameters are identified in ROI1 (marked in grey color) with cell-substrate distance decreasing from 98 nm to 95 nm and cytoplasm RI descending from 1.369 RIU to 1.368 RIU. The measurement results of cell dual parameters can also be interpreted by the cell behavior in the hypotonic condition, as shown in the inset of the third row in Fig. 3. With the decreased osmotic pressure in extracellular environment, the cell will swell with water flowing into the cell. This leads to an increased cell volume. The cell bottom membrane is pushed to the substrate with a decreased cell-substrate distance. Meanwhile, the medium flowing into the cell dilutes intracellular fluids with lower concentration, leading to a reduced cytoplasm RI.

In order to further compare the cell-substrate distance and cytoplasm RI changes under the isotonic, hypertonic and hypotonic mediums, we performed statistical analysis by obtaining histograms of cell parameters in three conditions. The results are shown in Fig. 4. Specifically, Figs. 4(a₁), 4(a₂) and Figs. 4(a₃), 4(a₄) present the histograms of cell-substrate distance and cytoplasm RI when the cell was exposed to an isotonic fluid at the initial and final moments, respectively. The Gaussian fitting was employed and Gaussian average values of cell dual parameters were determined. It can be seen that the average values of cell-substrate distance and cytoplasm RI remain stable in the normal environment. Moreover, Figs. 4(b₁–b₄) and 4(c₁–c₄) exhibit the results after the hypertonic and hypotonic solutions were injected, respectively. When the cell is in a hypertonic medium, the average values of cell dual parameters increase and the histograms move rightward to a higher value. The contrary behaviors of these two parameters are observed when the cell is stimulated by low osmotic pressure environment. Therefore, the statistical analysis here is consistent with the results in Fig. 3. Compared to the work which only reveals either cytoplasm RI or cell bottom membrane displacement under osmotic pressure stimulations [40,41], our approach realizes simultaneous measurement of cell dual parameters, providing more insights of cell behavior to biological studies. Moreover, one can notice that the cytoplasm RI before hypertonic medium is below that under the isotonic and hypotonic mediums. This is because of the cell variations during the transitional period of three treatments. In our experiment, after the old medium was gently replaced by a new one and fluidic environment was stabilized, the measurement was resumed. Therefore, time interval exists between measurements of three conditions, leading to a discontinuous RI change in Fig. 4. The cell parameter measurement results under hypertonic and hypotonic conditions from another cell were also provided, showing the similar changes to the results in Fig. 4 (Supplement 1).

Fig. 4. Statistical analysis of cell-substrate distance and cytoplasm RI in (a₁–a₄) normal, (b₁–b₄) high- and (c₁–c₄) low-osmotic pressure conditions at the initial and last moments of the monitoring period. (a₁), (a₂), (b₁), (b₂), (c₁) and (c₂): histograms and Gaussian fitting of cell-substrate distance; (a₃), (a₄), (b₃), (b₄), (c₃) and (c₄): histograms and Gaussian fitting of cytoplasm RI.

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3.3 Discussions

Since the cell dual parameters in our work are determined from the reflection phase shift difference of SPR, we characterized the system stability by monitoring the phase fluctuations of the system. The temporal fluctuations of the SPR phase could originate from several possible factors including the temperature variations, mechanical vibrations and electronic noise from the CCD camera in the system. In the experiment, we successively recorded the digital holograms without cell specimens for 500 s at the rate of 1 fps. Using the double-exposure DHM and numerical reconstruction algorithm, the reflection phase shift difference of each frame was obtained at the wavelengths of 632.8 nm and 690 nm. Then, an area containing 100 × 100 pixels was chosen at random and the standard deviation of the reflection phase shift difference in each pixel was calculated. The histograms of the standard deviation of the phase values at the wavelengths of 632.8 nm and 690 nm were further obtained, as shown in Figs. 5(a) and 5(b), respectively. The average value of the standard deviation of the reflection phase shift difference is 2.7° and 3.8° in 500 s at the wavelengths of 632.8 nm and 690 nm, respectively, reflecting a high temporal stability of the setup. The phase fluctuations in our setup at both wavelengths are very small and consistent with our previous work [30]. As a matter of fact, the high temporal stability is due to the holographic recording structure in our setup, in which the object and reference waves transmit in the common optical path to resist environmental disturbances [42]. The measurement uncertainties of cell-substrate distance and cytoplasm RI caused by the phase fluctuations of two wavelengths were analyzed in Supplement 1. Additionally, in order to assess the contributions of experiment noise to the inhomogeneous distribution of cell parameter, we simplified the SPR model with a fixed cytoplasm RI to study the cell-substrate distance. It shows that the measurement error of cell-substrate distance is small and the error at the cell edge is larger than that in the central area (Supplement 1). We also analyzed the measurement uncertainty of cell parameters caused by the possible deviations of parameter values in SPR model (Supplement 1).

Fig. 5. Statistical histograms of the standard deviation of reflection phase shift difference in a randomly-selected area (100 × 100 pixels) at the wavelengths of (a) 632.8 nm and (b) 690 nm. σ: standard deviation of reflection phase shift difference.

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4. Conclusions

In conclusion, a wavelength-multiplexing SPRHM was demonstrated to dynamically measure the cell-substrate distance and cytoplasm RI at the same time. By independently adjusting the incident angle of 632.8 nm and 690 nm with two separated BS, SPR can be excited at two wavelengths simultaneously. Therefore, compared to the previously-reported setup in Ref. 28 which requires sequential excitation of SPR for two wavelengths, the proposed setup possesses the advanced functionality of real-time tracking of cell parameters. Experimentally, we revealed the cell responses at the cell-substrate interface to external stimuli including high- and low-osmotic pressure conditions by tracking the dynamic changes of cell parameters. The cell shrinkage and swelling under hypertonic and hypotonic solutions were detected from the evolutions of cell-substate distance and cytoplasm RI thanks to the high sensitivity of SPR. We believe the proposed optical sensing tool opens up new perspectives for interfacial phenomenon detection of living cells.

Funding

National Natural Science Foundation of China (61927810, 62005219); Fundamental Research Funds for the Central Universities (310202011qd004).

Disclosures

The authors declare no conflicts of interest regarding this article.

Data availability

Data underlying the results presented in this paper are not publicly available at this time but may be obtained from the authors upon reasonable request.

Supplemental document

See Supplement 1 for supporting content.

References

1. A. A. Khalili and M. R. Ahmad, “A review of cell adhesion studies for biomedical and biological applications,” Int. J. Mol. Sci. 16(8), 18149–18184 (2015). [CrossRef]

2. V. Sanz-Moreno, G. Gadea, J. Ahn, H. Paterson, P. Marra, S. Pinner, E. Sahai, and C. J. Marshall, “Rac activation and inactivation control plasticity of tumor cell movement,” Cell 135(3), 510–523 (2008). [CrossRef]

3. V. Dileep and D. M. Gilbert, “Single-cell replication profiling to measure stochastic variation in mammalian replication timing,” Nat. Commun. 9(1), 1–8 (2018). [CrossRef]

4. V. Duronio, “The life of a cell: apoptosis regulation by the PI3K/PKB pathway,” Biochem. J. 415(3), 333–344 (2008). [CrossRef]

5. M. Bocková, J. Slabý, T. Špringer, and J. Homola, “Advances in surface plasmon resonance imaging and microscopy and their biological applications,” Annu. Rev. Anal. Chem. 12(1), 151–176 (2019). [CrossRef]

6. X. Wang, S. Zhan, Z. Huang, and X. Hong, “Advances and applications of surface plasmon resonance biosensing instrumentation,” Instrum. Sci. Technol. 41(6), 574–607 (2013). [CrossRef]

7. H. Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings (Springer-Verlag, 1988), p. 111.

8. X. L. Zhou, Y. Yang, S. Wang, and X. W. Liu, “Surface plasmon resonance microscopy: From single-molecule sensing to single-cell imaging,” Angew. Chem., Int. Ed. 59(5), 1776–1785 (2020). [CrossRef]

9. P. Pattnaik, “Surface plasmon resonance,” Appl. Biochem. Biotechnol. 126(2), 79–92 (2005). [CrossRef]

10. W. Wang, K. Foley, X. Shan, S. Wang, S. Eaton, V. J. Nagaraj, P. Wiktor, U. Patel, and N. Tao, “Single cells and intracellular processes studied by a plasmonic-based electrochemical impedance microscopy,” Nat. Chem. 3(3), 249–255 (2011). [CrossRef]

11. V. Chabot, Y. Miron, M. Grandbois, and P. G. Charette, “Long range surface plasmon resonance for increased sensitivity in living cell biosensing through greater probing depth,” Sens. Actuators, B 174, 94–101 (2012). [CrossRef]

12. F. Liu, J. Zhang, Y. Deng, D. Wang, Y. Lu, and X. Yu, “Detection of EGFR on living human gastric cancer BGC823 cells using surface plasmon resonance phase sensing,” Sens. Actuators, B 153(2), 398–403 (2011). [CrossRef]

13. H. Chen, Y. Hou, Z. Ye, H. Wang, K. Koh, Z. Shen, and Y. Shu, “Label-free surface plasmon resonance cytosensor for breast cancer cell detection based on nano-conjugation of monodisperse magnetic nanoparticle and folic acid,” Sens. Actuators, B 201, 433–438 (2018). [CrossRef]

14. L. Berguiga, L. Streppa, E. Boyer-Provera, C. Martinez-Torres, L. Schaeffer, J. Elezgaray, A. Arneodo, and F. Argoul, “Time-lapse scanning surface plasmon microscopy of living adherent cells with a radially polarized beam,” Appl. Opt. 55(6), 1216–1227 (2016). [CrossRef]

15. K. Toma, H. Kano, and A. Offenhäusser, “Label-free measurement of cell–electrode cleft gap distance with high spatial resolution surface plasmon microscopy,” ACS Nano 8(12), 12612–12619 (2014). [CrossRef]

16. A. V. Kabashin, S. Patskovsky, and A. N. Grigorenko, “Phase and amplitude sensitivities in surface plasmon resonance bio and chemical sensing,” Opt. Express 17(23), 21191–21204 (2009). [CrossRef]

17. A. V. Kabashin and P. I. Nikitin, “Surface plasmon resonance interferometer for bio-and chemical-sensors,” Opt. Commun. 150(1-6), 5–8 (1998). [CrossRef]

18. L. Berguiga, T. Roland, K. Monier, J. Elezgaray, and F. Argoul, “Amplitude and phase images of cellular structures with a scanning surface plasmon microscope,” Opt. Express 19(7), 6571–6586 (2011). [CrossRef]

19. F. Argoul, T. Roland, A. Fahys, L. Berguiga, and J. Elezgaray, “Uncovering phase maps from surface plasmon resonance images: Towards a sub-wavelength resolution,” C. R. Physique 13(8), 800–814 (2012). [CrossRef]

20. Y. Shao, Y. Li, D. Gu, K. Zhang, J. Qu, J. He, X. Li, S. Wu, H. Ho, M. G. Somekh, and H. Niu, “Wavelength-multiplexing phase-sensitive surface plasmon imaging sensor,” Opt. Lett. 38(9), 1370–1372 (2013). [CrossRef]

21. C. Hu, J. Zhong, and J. Weng, “Digital holographic microscopy by use of surface plasmon resonance for imaging of cell membranes,” J. Biomed. Opt. 15(5), 056015 (2010). [CrossRef]

22. S. Li and J. Zhong, “Simultaneous amplitude-contrast and phase-contrast surface plasmon resonance imaging by use of digital holography,” Biomed. Opt. Express 3(12), 3190–3202 (2012). [CrossRef]

23. B. Mandracchia, V. Pagliarulo, M. Paturzo, and P. Ferraro, “Surface plasmon resonance imaging by holographic enhanced mapping,” Anal. Chem. 87(8), 4124–4128 (2015). [CrossRef]

24. J. Zhang, S. Dai, C. Ma, J. Di, and J. Zhao, “Common-path digital holographic microscopy for near-field phase imaging based on surface plasmon resonance,” Appl. Opt. 56(11), 3223–3228 (2017). [CrossRef]

25. J. Zhang, S. Dai, J. Zhong, T. Xi, C. Ma, Y. Li, J. Di, and J. Zhao, “Wavelength-multiplexing surface plasmon holographic microscopy,” Opt. Express 26(10), 13549–13560 (2018). [CrossRef]

26. S. Dai, T. Yu, J. Zhang, H. Lu, J. Dou, M. Zhang, C. Dong, J. Di, and J. Zhao, “Real-time and wide-field mapping of cell-substrate adhesion gap and its evolution via surface plasmon resonance holographic microscopy,” Biosens. Bioelectron. 174, 112826 (2021). [CrossRef]

27. S. Dai, J. Mi, J. Dou, H. Lu, C. Dong, L. Ren, R. Zhao, W. Shi, N. Zhang, Y. Zhou, J. Zhang, J. Di, and J. Zhao, “Optical tweezers integrated surface plasmon resonance holographic microscopy for characterizing cell-substrate interactions under noninvasive optical force stimuli,” Biosens. Bioelectron. 206, 114131 (2022). [CrossRef]

28. S. Dai, J. Mi, J. Dou, T. Yu, M. Zhang, J. Di, J. Zhang, and J. Zhao, “Dual-wavelength surface plasmon resonance holographic microscopy for simultaneous measurements of cell-substrate distance and cytoplasm refractive index,” Opt. Lett. 47(9), 2306–2309 (2022). [CrossRef]

29. E. Kreysing, H. Hassani, N. Hampe, and A. Offenhäusser, “Nanometer-resolved mapping of cell–substrate distances of contracting cardiomyocytes using surface plasmon resonance microscopy,” ACS Nano 12(9), 8934–8942 (2018). [CrossRef]

30. I. H. Malitson and M. J. Dodge, “Refractive index and birefringence of synthetic sapphire,” J. Opt. Soc. Am. 62(11), 1405 (1972).

31. P. B. Johnson and R. W. Christy, “Optical constants of transition metals: Ti, V, Cr, Mn, Fe, Co, Ni, and Pd,” Phys. Rev. B 9(12), 5056–5070 (1974). [CrossRef]

32. P. B. Johnson and R. W. Christy, “Optical constants of the noble metals,” Phys. Rev. B 6(12), 4370–4379 (1972). [CrossRef]

33. N. Lue, J. W. Kang, T. R. Hillman, R. R. Dasari, and Z. Yaqoob, “Single-shot quantitative dispersion phase microscopy,” Appl. Phys. Lett. 101(8), 084101 (2012). [CrossRef]

34. W. M. bin Mat Yunus and A. bin Abdul Rahman, “Refractive index of solutions at high concentrations,” Appl. Opt. 27(16), 3341–3343 (1988). [CrossRef]

35. R. A. Meyer, “Light scattering from biological cells: dependence of backscatter radiation on membrane thickness and refractive index,” Appl. Opt. 18(5), 585–588 (1979). [CrossRef]

36. S. Nizamov, V. Scherbahn, and V. M. Mirsky, “Self-referencing SPR-sensor based on integral measurements of light intensity reflected by arbitrarily distributed sensing and referencing spots,” Sens. Actuators, B 207, 740–747 (2015). [CrossRef]

37. S. A. Abayzeed, “Plasmonic-based impedance microspectroscopy of optically heterogeneous samples,” Biomed. Opt. Express 11(11), 6168–6180 (2020). [CrossRef]

38. K. Syal, W. Wang, X. Shan, S. Wang, H. Y. Chen, and N. Tao, “Plasmonic imaging of protein interactions with single bacterial cells,” Biosens. Bioelectron. 63, 131–137 (2015). [CrossRef]

39. J. S. Burmeister, L. A. Olivier, W. M. Reichert, and G. A. Truskey, “Application of total internal reflection fluorescence microscopy to study cell adhesion to biomaterials,” Biomaterials 19(4-5), 307–325 (1998). [CrossRef]

40. S. Przibilla, S. Dartmann, A. Vollmer, S. Ketelhut, G von Bally, B. Kemper, and B. Greve, “Sensing dynamic cytoplasm refractive index changes of adherent cells with quantitative phase microscopy using incorporated microspheres as optical probes,” J. Biomed. Opt. 17(9), 097001 (2012). [CrossRef]

41. W. Wang, S. Wang, Q. Liu, J. Wu, and N. Tao, “Mapping single-cell–substrate interactions by surface plasmon resonance microscopy,” Langmuir 28(37), 13373–13379 (2012). [CrossRef]

42. J. Zhang, S. Dai, C. Ma, T. Xi, J. Di, and J. Zhao, “A review of common-path off-axis digital holography: towards high stable optical instrument manufacturing,” Light: Advanced Manufacturing 2(3), 333–349 (2021). [CrossRef]

j	d_j(nm)	n_j(RIU, λ=632.8 nm)	n_j(RIU, λ=690 nm)
1	∞	1.7880 [29]	1.7860 [30]
2	1.5	3.0624 + 3.3744i [31]	3.1399 + 3.3150i [31]
3	45	0.1838 + 3.4313i [32]	0.1332 + 3.9722i [32]
		1.3354^a [29]	1.3338^a [33]
4	0–200	1.3358^b [34]	1.3342^b [33]
		1.3347^c [34]	1.3332^c [33]
5	7.5 [35]	1.5000 [35]	1.4985 [33]
6	∞	1.3400-1.4300	1.3385-1.4185 [33]

Label-free and dynamic monitoring of cell evolutions using wavelength-multiplexing surface plasmon resonance holographic microscopy

Abstract

1. Introduction

2. Materials and methods

2.1 Materials

2.2 Establishment of the SPR model

2.3 Experiment setup

2.4 Sample preparation

3. Results and discussions

3.1 Wide-field mapping of cell parameters under different environmental mediums

3.2 Dual parameter evolutions of a living cell under different environmental mediums

3.3 Discussions

4. Conclusions

Funding

Disclosures

Data availability

Supplemental document

References

Supplementary Material (1)

Data availability

Cited By

Figures (5)

Tables (1)

Equations (7)

Biomedical Optics Express