Proceedings: IMAPS/ACerS 11th International CICMT Conference and Exhibition | April 20-23, 2015 | Dresden, Germany
3D FOCALIZATION MICROFLUIDIC DEVICE BUILT WITH LTCC TECHNOLOGY FOR NANOPARTICLE GENERATION USING NANOPRECIPITATION ROUTE
Houari Cobas Gomez1, Mario Ricardo Gongora-Rubio2, Bianca Oliveira Agio2, Vanessa Tiemi Kimura2, Adriano Marim de Oliveira2, Luciana Wasnievski da Silva de Luca Ramos2, Antonio Carlos Seabra1 1
Escola Politécnica da Universidade de São Paulo (USP), Laboratório de Sistemas Integráveis, Av. Prof. Luciano Gualberto, 158, 05508-900, São Paulo, Brasil,
[email protected] 2 Instituto de Pesquisas Tecnológicas do Estado de São Paulo (IPT), Núcleo de Bionanomanufatura, Av. Prof. Almeida Prado, 532, 05508-901, São Paulo, Brasil,
[email protected]
Abstract Nanoprecipitation is a nanonization technique used for nanoparticle generation. Several fields, like pharmacology and fine chemistry, make use of such technique. Typically are used a bulky batch mechanical processes rendering high polydispersity index of generated nanoparticles, poorly particle size reproducibility and energy wasting. LTCC-based microsystem technologies allow the implementation of different unitary operations for chemical process, making it an enabling technology for the miniaturization of chemical processes. In fact, recently LTCC microfluidic reactors have been used to produce micro and nanoparticles with excellent control of size distribution and morphology. The present work provides a report on the performance of a 3D LTCC flow focusing Microfluidic device designed to fabricate polymeric nanocapsules for Hydrocortisone drug encapsulation, using nanoprecipitation route. Monodisperse Hydrocortisone nanocapsules were obtained with sizes (Tp) from 188.9 nm to 459.1 nm with polydispersity index (PDI) from 0.102 to 0.235. Key words: Nanoprecipitation, Fluid Flow Focusing, LTCC, Nanoparticle. improve the total diffusion process and hence the nanoprecipitation process. For this work T-junction shapes are named as 2D flow focalization due to all contact interfaces, formed between the solvent and antisolvent flows, are planar. Diffusion process can also be improved having the solvent stream surrounded by the antisolvent stream. This technique is named as 3D flow focalization [14, 15, 17, 18, 23]. In this approach, the dissolved material streams do not wet the channels walls. This can also be useful in order to prevent channel clogging when working with hydrophobic materials using water as antisolvent [14]. This work shows a 3D microfluidic flow focalization device manufactured with LTCC technology intended to be used in a nanoprecipitation process. The proposed geometry aims to improve the solvent diffusion process by surrounding the organic phase with antisolvent fluid flow. This is a research in progress, at this time is presented initial results of a nanoprecipitation device used for Hydrocortisone drug polymeric nanoencapsulation.
1. Introduction Nanoprecipitation is a nanonization technique used for nanoparticle generation in fields like drug formulation and chemistry, among others [1-6]. In this strategy, the organic solution is made up by dissolved materials (polymers and pharmaceutical actives) is placed in contact with an antisolvent flow. High material concentration regions are created due to the solvent diffusion from organic phase to the antisolvent flow. At these regions spontaneous nucleation takes place, generating nanoparticles. Several works have reported the use of microfluidics devices in nanoprecipitation. They mainly make use of topologies with Y-junction shape [7-11] or T-junction shape with central channel for the organic dissolved material, and two antisolvent input channels with 180° angle [12-18] or lower [1922]. The Y-junction shape bases it functioning principle in a solvent diffusion through a single solvent-antisolvent fluid interface. In turn, T-junction has two solvent-antisolvent fluid interfaces because of the antisolvent streams focalization effect, which
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Proceedings: IMAPS/ACerS 11th International CICMT Conference and Exhibition | April 20-23, 2015 | Dresden, Germany
Sample Preparation
2. Device Layout
Organic phase fluid dissolved material was prepared from 1 g of a homemade block copolymer and 100 mg of Hydrocortisone and mixed in 20 ml Acetone (Sigma Aldrich) until completely dissolve. As Antisolvent fluid material we used 100 ml of purified DI water. A Milli-Q system (Millipore Corporation, USA) was employed to obtain the purified water.
The device layout is presented in Fig. 1. It is formed by three fundamental blocks. These are the Organic phase dissolved material (DM) input, the anti solvent (AS) inputs and the nanoprecipitation channel output (NPC). The DM input is centered in the NPC and has an input hydraulic diameter (DH) of 214.6 µm. In turn, the NPC has a DH of 772 µm and a length of 6.5 mm. The four AS inputs have an input angle of 45º to the NPC direction. In the vertical direction this angle is assured with stairs like channels (fabrication constraint). AS channels configuration will force the DM to be focalized in the NPC center along the device. This is due to the AS flow force action on a central DM flow inducing a cylindrical flow stream.
Size Measurement For measuring nanoparticles diameter size, the Zetasizer Nano-ZS (Mo.: ZEN3600, Malvern Instruments Limited) was used. Pumping System Two syringe pumps (PHD 4400, Harvard Apparatus) [24] were used to pump the DM and AS into the microfluidic device. Simulation and Processing Software COMSOL® Multiphysics software was used for Acetone diffusion profile and diffusion length qualitative evaluation. For simulations, Laminar Flow and Transport of Diluted Species models were used. Statistica12® software was used for analyzing simulation and experimental results. Experimental Design
Fig. 1 – 3D focalization microfluidic device.
A factorial experimental planning approach (without central point) was used to validate the device performance [25]. Two process variables (Flow rate ratio and total flow rate), as shown in Table I, were analyzed, totalizing four experiments (for conditions -1 and 1). An additional experiment was executed for testing device functioning in an intermediate process variable value.
3. Materials and Method Manufacturing Process Microfluidic device fabrication employed the typical LTCC process. Dupont green LTCC ceramic tapes 951P2 and 951PX were used. Layers were fabricated using a prototyping machine equipped with an ultraviolet laser (355 nm wavelength), model LPKF Protolaser U3 (LPKF Laser & Electronics AG). One step thermocompression lamination process was performed by means of a uniaxial laminator with pressure of 11.8 MPa at 70 ºC (hydraulic press machine, model MA098/A30, Marconi). Previous to the lamination process, aligned sheet were baked at 60 ºC for 20 min. For sintering we used a muffle furnace (EDG Equipment, model EDG10P-S), in a two stage profile: first, heating the device at 450 ºC per 30 min. and in sequence, sintering at 850 ºC per 30 min. The input and output brass fluidic interconnection tubes were glued to the ceramics using a high temperature epoxy (EPO-TEK 353ND). The gluing process was performed by means of a hot plate at 150 ºC for 2 min.
TABLE I.
EXPERIMENT CONFIGURATION Experiment Conditions -1
1
Intermediate value
RQ - Flow Rate Ratioa
1.3
10
6.26
QT - Total Flow Rate (ml/min)b
1
7.5
Process Variables
4.64 a. b.
RQ = QAS / QDM
QT = QAS + QDM
The experimental plan was also simulated using COMSOL® software in order to estimate the average concentration evolution and diffusion profile in perpendicular planes to the NPC length and spaced every 0.5 mm from the NPC start point. For each simulation the QAS (antisolvent flow rate) and QDM (Organic phase flow rate) values were calculated and defined as input values. For the AS inlets, the flow at
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Proceedings: IMAPS/ACerS 11th International CICMT Conference and Exhibition | April 20-23, 2015 | Dresden, Germany
every input was defined as QAS/4. At the solvent input channel, Acetone concentration was fixed to be: 13.619.35 mol/m3. 4. Results and Discussions Simulations Results Fig. 2 shows the focalized organic phase dissolved material stream in the NPC center. As expected, Antisolvent flow force action on the organic phase dissolved material, due to the inlet topology, assured a focalized stream. As RQ value increases, the stream diameter decreases as well as stream concentration. This effect can be helpful in the solvent diffusion and could help in the super saturation regions formation and hence the nanoparticles generation.
Fig. 3 – Average concentration evolution from the NPC inlet start point a) Average concentration versus channel length; b) Relative difference to the average concentration at 6 mm from the NPC inlet start point. Experimental Results Proposed factorial experimental planning results are summarized in Table II. The last row shows the intermediate value experiment result. TABLE II.
EXPERIMENTAL RESULTS
RQ
QT (ml/min)
Tp (nm)
PDI
1.3
1
459.1
0.235
10
1
287.8
0.228
1.3
7.5
355.5
0.206
10
7.5
188.9
0.102
6.26
4.64
233.4
0.188
Results showed Hydrocortisone nanocapsules with sizes ranging from 459.1 nm to 188.9 nm. The polydispersity index remains lower than 0.235 which implies a narrow particle size distribution. Fig. 4 shows Zetasizer Nano-ZS measurement for RQ = 10 and QT = 7.5 ml/min. Obtained data was analyzed with Statistica12 software in order to obtain a better representation of process variables influence on particle size (TP) and polydispersity index (PDI). Fig. 5a and 5b shows the Pareto Chart for T P and pdi respectively. Both process variables showed an inversely proportional relation with Tp and PDI. Particle size showed a stronger dependence with Rq process variable, Fig. 5a. In turn, polydispersity index showed a stronger dependence with the QT process variable, Fig. 5b.
Fig. 2 – 3D focalization inside the device. Color bar is Organic phase (DM) concentration in mol/m3. a) RQ = 1.3 and QT = 1 ml/min; b) RQ = 10 and QT = 1 ml/min; c) RQ = 1.3 and QT = 7.5 ml/min; d) RQ = 10 and QT = 7.5 ml/min; e) RQ = 6.26 and QT = 4.64 ml/min. Fig. 3 shows the average concentration evolution in the NPC length. Simulation results show that from 3 mm and up, the variations are lower than 5%. We estimate the diffusion length in this device, to be 3 mm. Fig. 3 also shows that when flow rate ratio (Rq) increases, average concentration at the NPC outlet decreases. As expected, an increase in the total flow rate (QT) value will not affect the average concentration for the same Rq value.
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Proceedings: IMAPS/ACerS 11th International CICMT Conference and Exhibition | April 20-23, 2015 | Dresden, Germany
Fig. 4 – Zetasizer Nano-ZS measurement for RQ = 10 and QT = 7.5 ml/min. Experimental data in Table II were rearranged from the lowest Rq value to the highest. For the same Rq value, the data were organized from the lowest QT value to the highest. The arranged data were plotted using a 3D trajectory graph. Results are depicted in Fig. 6a and 6b for Tp and PDI respectively. As depicted by Pareto Chart (Fig.5), it can be seen that increase in Rq implies a decrease in Tp and PDI. The same applies for an increase in QT. These dependences show the system ability to tune the nanocapsules sizes. Variables Rq and QT could be used too for coarse and fine tuning, respectively.
Fig. 6 – 3D Trajectory Graph. a) Tp versus Rq and QT; b) PDI versus Rq and QT.
5. Conclusions A 3D flow focalization microfluidic device manufactured with LTCC technology for nanocapsule fabrication was presented. The device working principle is the nanoprecipitation process. Full 3D flow focalization was assured selecting inlet channels topology with suitable 45º inclination in the vertical and horizontal directions. Monodisperse Hydrocortisone nanopcasules were obtained with sizes from 188.9 nm to 459.1 nm with polydispersity index from 0.102 to 0.235. It was also showed the possibility to use the process variables Rq and QT for nanocapsules sizes coarse and fine tuning.
Fig. 5 – Pareto Chart. a) Influence of process variables on particle size; b) Influence of process variables on polydispersity index.
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Proceedings: IMAPS/ACerS 11th International CICMT Conference and Exhibition | April 20-23, 2015 | Dresden, Germany
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