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. 2017 Dec 10;10(12):1411.
doi: 10.3390/ma10121411.

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Alessandra Zizzari  1   2 , Monica Bianco  3 , Luigi Carbone  4 , Elisabetta Perrone  5 , Francesco Amato  6 , Giuseppe Maruccio  7   8 , Filippo Rendina  9 , Valentina Arima  10
Affiliations

Continuous-Flow Production of Injectable Liposomes via a Microfluidic Approach

Alessandra Zizzari et al. Materials (Basel). .

Abstract

Injectable liposomes are characterized by a suitable size and unique lipid mixtures, which require time-consuming and nonstraightforward production processes. The complexity of the manufacturing methods may affect liposome solubility, the phase transition temperatures of the membranes, the average particle size, and the associated particle size distribution, with a possible impact on the drug encapsulation and release. By leveraging the precise steady-state control over the mixing of miscible liquids and a highly efficient heat transfer, microfluidic technology has proved to be an effective and direct methodology to produce liposomes. This approach results particularly efficient in reducing the number of the sizing steps, when compared to standard industrial methods. Here, Microfluidic Hydrodynamic Focusing chips were produced and used to form liposomes upon tuning experimental parameters such as lipids concentration and Flow-Rate-Ratios (FRRs). Although modelling evidenced the dependence of the laminar flow on the geometric constraints and the FRR conditions, for the specific formulation investigated in this study, the lipids concentration was identified as the primary factor influencing the size of the liposomes and their polydispersity index. This was attributed to a predominance of the bending elasticity modulus over the vesiculation index in the lipid mixture used. Eventually, liposomes of injectable size were produced using microfluidic one-pot synthesis in continuous flow.

Keywords: liposomes; microfluidics; microreactors.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Images of (a) 45° chips and (b) 90° chips with zoomed images in the focusing regions shown in the insets. The ethanol laminas formed at Flow-Rate-Ratios FRR = 10 and total volumetric flow rate Qt = 105 μL/min in the 45° chip, and FRR = 2, and Qt = 90 μL/min in the 90° chip.
Figure 2
Figure 2
The colour maps represent the distribution of ethanol (EtOH) in the hydrodynamic flow focusing region for (a) 45° chips and (c) 90° chips at a FRR = 5, and Qt of 30 µL/min and 150 µL/min. The red and blue colors refer to the EtOH and water domains, respectively. The maps reproduce the mixing of the two fluids occurring in the mixing channel. The red arrows indicate the mixing channel position where the ethanol distributions (shown in (b,d)) and the values of Re, Pe, and Ca (insets of Figure 2a,c) were calculated. The values of the peak areas estimated at three different FRRs are reported in Table 1.
Figure 3
Figure 3
(a) Dynamic light scattering (DLS) spectra of liposome solutions produced inside 45° and 90° chips at FRR = 5 and at a lipid concentration of 0.9 mg/mL; (b) plot of the Z-average mean hydrodynamic diameter (MHD) versus the FRR of liposomes produced at a lipid concentration of 0.9 mg/mL inside 45° and 90° chips. The black x axis is related to FRRs used in the 45° chips and the red one (upper side of graph) to FRRs used in the 90° chips.
Figure 4
Figure 4
(a) DLS spectra of liposome solutions produced inside 45° chips at FRR = 5, at three different lipids concentrations; (b) plot of the Z-average MHD versus the FRR at three different lipids concentrations inside 45° chips. Transmission electron microscopy (TEM) pictures of vesicles obtained through a 45° chip; (c) at FRR = 30 and lipids concentration of 90 mg/mL; and (d) at FRR = 70 and lipids concentration 0.9 mg/mL.
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