Photothermal Techniques Applied to the Thermal ... - Springer Link

Int J Thermophys (2013) 34:948–954 DOI 10.1007/s10765-012-1232-y

Photothermal Techniques Applied to the Thermal Characterization of l–Cysteine Nanofluids E. Maldonado Alvarado · E. Ramón-Gallegos · J. L. Jiménez Pérez · A. Cruz-Orea · J. Hernández Rosas

Received: 12 October 2011 / Accepted: 8 June 2012 / Published online: 28 June 2012 © Springer Science+Business Media, LLC 2012

Abstract Thermal-diffusivity (D) and thermal-effusivity (e) measurements were carried out in l-cysteine nanoliquids (l-cysteine in combination with Au nanoparticles and protoporphyrin IX (PpIX) nanofluid) by using thermal lens spectrometry (TLS) and photopyroelectric (PPE) techniques. The TLS technique was used in the two mismatched mode experimental configuration to obtain the thermal-diffusivity of the samples. On the other hand, the sample thermal effusivity (e) was obtained by using the PPE technique where the temperature variation of a sample, exposed to modulated radiation, is measured with a pyrolectric sensor. From the obtained thermal-diffusivity and thermal-effusivity values, the thermal conductivity and specific heat capacity of the sample were calculated. The obtained thermal parameters were compared with the thermal parameters of water. The results of this study could be applied to the detection of tumors by using the l-cysteine in combination with Au nanoparticles and PpIX nanofluid, called conjugated in this study.

E. M. Alvarado · E. Ramón-Gallegos Environment Citopathology Laboratory, Department of Morphology, Escuela Nacional de Ciencias Biológicas del IPN, Carpio y Plan de Ayala S/N, Col. Sto. Tomas, C.P. 11340, México, DF, México J. L. Jiménez Pérez · J. Hernández Rosas Unidad Profesional Interdisciplinaria en Ingeniería y Tecnologías Avanzadas del IPN, Avenida Instituto Politécnico Nacional No. 2580, Colonia Barrio la Laguna Ticomán Delegación Gustavo A. Madero, C.P. 07340 México, DF, México A. Cruz-Orea (B) Departamento de Física, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional 2508 Col. San Pedro Zacatenco, D.F. Apartado postal 14-740, C.P. 07360 México, DF, México e-mail: [email protected]

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Keywords Nanofluids · Photopyroelectric technique · Photothermal techniques · Thermal lens spectrometry 1 Introduction The biological application of nanoparticles is a rapidly developing area of nanotechnology that raises new possibilities in the diagnosis and treatment of cancers; for example, in diagnostic methods, fluorescent nanoparticles can be used for multiplex simultaneous profiles of tumor biomarkers and also for detection of multiple genes with fluorescence in situ [1]. Also, nanoparticles are used as biomarkers that can be detected and quantified into the tumor by using nanoparticles conjugated to antibodies. Also, the use of nanoparticles will allow simultaneous tumor targeting and drug delivery in a unique manner, in a particular way. The use of drug-loaded nanoparticles offers the promise of improved tumor penetration with a selective targeting of tumor, and a subsequent decrease of toxic effects. Gold nanoparticles in different modifications represent interesting candidates when their optical and thermal properties are well-characterized [2–4]; in addition, they are very efficient absorbers because the absorption cross-section of a gold nanoparticle is at least more than three- to four-orders of magnitude greater than that of any organic dye because of plasmon resonance (for specific geometric configurations, such as shells or rods, even five to six-orders of magnitude greater [5,6]). Recently, developments in Au nanoparticle synthesis showed that the use of l-cysteine-capped monodispersed gold (Au) nanoparticles change their optical properties [4]. The l-cysteine concentration has been optimized to achieve a strong ultraviolet absorption and consequently strong luminescence intensity. On the other hand, a laser technique, based on selective thermal heating of tumor cells or bacteria tagged with absorbing nanoparticles serving as photothermal sensitizers [6–8], is a promising alternative to photodynamic therapy with conventional organic photosensitizers. The affinity of gold nanoparticles towards cysteine (by its thiol group) can induce the formation of aggregates and changes in the interparticle distances with metals ions or others carboxyl groups that can lead to the development of new detection methods for analytical purposes, medical diagnostics, and biosensors and to potential controlled drug delivery applications [9,10]. These studies are also important due to the photothermal effects in photodynamic therapy. In this study, we report the thermal-diffusivity and effusivity of l-cysteine in combination with Au nanoparticles and protoporphyrin IX (PpIX) nanofluids (called conjugated in this study); these thermal parameters were obtained by using thermal lens (TL) and photopyroelectric (PPE) photothermal techniques, respectively. 2 Experimental 2.1 Photothermal Measurements 2.1.1 Thermal Lens We have used a variation of the TL dual-beam mode-mismatched method. The TL effect is caused by heat deposition, via nonradiative decay processes, after the laser

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energy is absorbed by the sample. The TL effect can be theoretically treated by calculating the temporal evolution of the sample temperature profile ΔT . The propagation of a probe beam through this TL results in a variation of its on axis intensity, I (t). Shen et al. [11] has derived an expression for the TL signal using a diffraction approximation for Gaussian beams: 2 2mV θ −1 tc (1) I (t) = I (0) 1 − tan 2 (1 + 2m)2 + V 2 2t + 1 + 2m + V 2 In Eq. 1, I (0) is the initial value of I (t); θ is the thermally induced phase shift of the probe beam after passing through the sample; V = Z 1 /Z c , where Z c (12.89 cm) is the confocal distance of the probe beam and Z 1 (8.0 cm) is the distance from the probe beam waist to the sample. Also, m = (ω1p /ωe )2 , where ωe (ωp ) is the spot size of the excitation (probe) laser beam at the sample, ω1p (z) is the radius of beam at distance z relative to the beam waist, and tc is the characteristic thermal time (tc = ωe2 /4D) where D and k are the thermal-diffusivity and thermal-conductivity coefficients of the sample. The TL transient signal amplitude, θ is given by Pe Ae l0 dn (2) θ =− kλp dT p where λp is the wavelength of the probe beam, Pe is the total power of the pump beam, Ae is the absorption coefficient, l0 is the thickness of the sample, and n is the sample refractive index. All the details of the experimental setup can be found in Refs. [12] and [13]. 2.1.2 Photopyroelectric (PPE) Technique The thermal-effusivity parameter (e) was obtained using the PPE technique; in this technique the temperature variation of the sample, exposed to a modulated radiation, is measured with a pyroelectric sensor [14,15]. The experimental setup in the PPE measurements is shown in Ref. [15]. A He–Ne laser beam, modulated by an acoustooptical modulator, impinges on the pyroelectric transducer. On the other side of this transducer, the liquid sample has good thermal contact with the pyroelectric transducer. Using the theory proposed by Caerels et al. [15] the thermal effusivity was obtained by fitting the Eq. 3 from Ref. [15], for thermally thick samples, to the experimental data as a function of frequency ( f ). In this fitting, b = es /ep was used as a fitting parameter, where es and ep are the thermal effusivities of the sample and pyroelectric detector, respectively. 2.2 Sample Preparation 2.2.1 Chemical Synthesis of the Au Nanoparticles and Conjugate-PpIX To obtain the Au nanoparticles in aqueous solution, with a diameter of approximately 25 nm, the method of monodisperse colloids as proposed by Wagner [16]

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was followed. The nanoparticles were purified by dialysis using a membrane with a cutoff size of 10 kDa. Once the Au nanoparticles were obtained and purified, they were reacted with cysteine at 60 ◦ C for 48 h according to the suggestion by Hermanson [17]. Cysteine reaction is not removed by dialysis membranes, cutoff size of 10 kDa. Subsequently, to promote the reaction of the carbonyl groups of PpIX, the reaction was catalyzed in a 2:1 ratio with 1-(3-dimethylaminopropyl)-3-etilcarbodiimina and N-hydroxysuccinimide, with respect to the concentration of protoporphyrin IX, after 15 min were added together to Au nanoparticle-cysteine and the reaction was carried out in aqueous solution at 25 ◦ C for 2 h. PpIX unreacted was retrieved by dialysis as mentioned above. 2.2.2 Characterization of Au Nanoparticle-PpIX-Cysteine By using transmission electron microscopy, the size and shape of the PpIX-Au nanoparticle-conjugate was determined. A 0.1 mL sample of the conjugate was placed on copper grids of 200 mesh and was left to adsorb for 24 h and then observed by transmission electron microscopy. Afterwards, all thermo-optical measurements were carried out with the solutions in a 1 cm quartz cuvette. 3 Results and Discussion From the TEM image the size of the Au nanoparticles (shown in Fig. 1 ) was obtained. The diameter average size was found around 25 nm. Afterwards, it was found (shown in Fig. 2) that PpIX has a sharp main peak at 409 nm and a secondary one at 550 nm, while the “conjugated” solution has a broad main peak at the same 409 nm location and a secondary one shifted to 539 nm.

Fig. 1 Transmission electron microscopy image of Au nanoparticles with its size distribution

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Fig. 2 Optical absorption spectrum of PpIX and conjugate solution

Fig. 3 TL signal evolution for conjugated solution

Figure 3 shows the normalized time resolved thermal-lens signal of the conjugate (Au + PpIX + cysteine + water, where their concentrations are gold 2.9 %, cysteine 4.7 %, PpIX 0.58 %, and water 91.82 %) solution; symbols (◦) represent the experimental points and the solid line corresponds to the best fit of Eq. 1 to the experimental data, taking θ and tc as adjustable parameters. From the tc value the thermal diffusivity was obtained (D = (14 ± 0.2) × 10−8 m2 · s−1 ). The experimental setup was calibrated by measuring the thermal-diffusivity of deionized water (14.08 × 10−8 m2 · s−1 ). A trace amount (approximately 10−5 M) of rhodamine 6G dye was added to de-ionized water for the thermal-diffusivity measurements. Since water has a thermal diffusivity similar in magnitude compared to common organic solvents, it shows poor thermal blooming effects. A small amount of dye helps in improving the light absorption; also, it is reported that a very small amount of dye will not affect the thermal diffusivity of the medium [7,8].

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Normalized PPE signal amplitude, a.u.

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(a)

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(b)

1.1 1.0 0.9 0.8 0.7

80 100 120 140 160 180 200 220 240 260

Frequency, Hz

Fig. 4 Normalized PPE signal (a) amplitude and (b) phase for conjugate solution as a function of light modulation frequency. Solid dots represent the experimental data and the solid line is the best fit of the theoretical expression to the experimental data as mentioned in the text

On the other hand, the sample thermal effusivity was obtained by using the theory proposed by Caerels et al. for thermally thick samples. This thermal parameter was obtained by fitting Eq. 3 from Ref. [15] to the experimental normalized PPE signal amplitude and phase data, as a function of frequency ( f ). In these fittings, b = es /ep was used as an adjustable parameter, where es and ep are the thermal effusivities of the sample and pyroelectric detector, respectively. In the case of the pryroelectric detector (polyvinylidene difluoride, PVDF), ep = 559 W · s1/2 · m−2 · K−1 . Previous to the determination of the sample thermal effusivity, the thermal effusivity of pure water was obtained to calibrate the PPE system, in this case the obtained value for water thermal effusivity was (1619 ± 50) W · s1/2 · m−2 · K−1 . Figure 4 shows the experimental PPE data (solid symbols) and the best fit of the Eq. 3 of Ref. [15] to the experimental data (solid line) in the case of the conjugated solution. The obtained thermal effusivity for this sample was (1470 ± 87) W · s1/2 · m−2 · K−1 . The thermal conductivity and the specific heat capacity of the conjugated solution were calculated from the obtained thermal-diffusivity and thermal-effusivity values. The calculated thermal conductivity was (0.59 ± 0.04) W · m−1 · K−1 , and the specific heat capacity was (4 ± 0.24) × 106 J · m−3 · K−1 . 4 Conclusions From TL and PPE techniques, the thermal diffusivity and thermal effusivity of l-cysteine in combination with Au nanoparticles and PpIX nanofluids were obtained. The results show that the thermal diffusivity and thermal effusivity of PpIX mixed with gold nanoparticles and l-cysteine are near the water thermal diffusivity and thermal effusivity due to the low concentration of the nanoparticles, cysteine and PpIX in the solution. The determination of this thermal parameter is very important in photodynamic therapy (PDT) in order to know the heat transfer between photosensitizers (such as porphyrins) and nanoparticles that are being studied in cancerous tumor treatments.

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Acknowledgments We would like to thank Conacyt, ICyTDF, COFAA, CLAF, and CGPI-IPN agencies for their partial financial support. One of the authors (A. Cruz-Orea) is grateful for partial financial support from CONACYT Project No. 103632. We also want to thank Ing. D. Jacinto Méndez, Ing. E. Ayala, Ing. M. Guerrero, and Ing. A. B. Soto for their technical support at the Physics Department, CINVESTAV-IPN.

References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17.

P.N. Prasad, Bionanophotonics, in Introduction to Biophotonics (Wiley, Hoboken, NJ, 2003) M.C. Daniel, D. Astruc, Chem. Rev. 104, 293 (2004) G. Hultman, R. Birngruber, IEEE J. Sel. Top. Quant. Electron. 5, 954 (1999) S.N. Sarangi, A.M.P. Hussain, S.N. Sahu, Appl. Phys. Lett. 95, 073109-1 (2009) J.L. West, N.J. Halas, Annu. Rev. Biomed. Eng. 5, 285 (2003) C.M. Pitsillides, E.K. Joe, X. Wei, R.R. Anderson, C.P. Lin, Biophys. J. 84, 4023 (2003) V.P. Zharov, K.E. Mercer, E.N. Galitovskaya, M.S. Smeltzer, Biophys. J. 90, 619 (2006) V.P. Zharov, D.O. Lapotko, IEEE J. Sel. Top. Quant. Electron. 11, 733 (2005) K. Berg, P.K. Selbo, A. Weyergang, A. Dietze, L. Prasmikaite, A. Bonsted, B.O. Engesaeter, E. Angell Petersen, T. Warloe, N. Frandsen, A. Hogeset, J. Microsc. 218, 47 (2005) G. Jori, J.D. Spikes, J. Photochem. Photobiol. B 6, 93 (1990) J. Chen, R.D. Lowe, R.D. Snook, Chem. Phys. 165, 385 (1992) J.L. Jiménez Pérez, J.F. Sánchez Ramírez, R. Gutiérrez Fuentes, A. Cruz Orea, J.L. Herrera Pérez, Braz. J. Phys. 36, 1025 (2006) R. Gutiérrez Fuentes, J.F. Sánchez Ramírez, J.L. Jiménez Pérez, J.A. Pescador Rojas, E. Ramón Gallegos, A. Cruz Orea, Int. J. Thermophys. 28, 1048 (2007) D. Dadarlat, C. Neamtu, E. Surducan, A. Hadj Sahraoui, S. Longuemart, D. Bicanic, Instrum. Sci. Technol. 30, 387 (2002) J. Caerels, C. Glorieux, J. Thoen, Rev. Sci. Instrum. 69, 2452 (1998) J. Wagner, J.M. Köhler, Nano Lett. 5, 685 (2005) G.T. Hermanson, Bioconjugate Techniques (Academic Press Inc., San Diego, 1996)

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