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. 2010 Aug 6;7 Suppl 4(Suppl 4):S393-402.
doi: 10.1098/rsif.2010.0099.focus. Epub 2010 Jun 2.

Size mapping of electric field-assisted production of polycaprolactone particles

Affiliations

Size mapping of electric field-assisted production of polycaprolactone particles

M Enayati et al. J R Soc Interface. .

Abstract

In this investigation, biodegradable polycaprolactone polymeric particles (300-4500 nm in diameter) were prepared by jetting a solution in an electric field. An extensive study has been carried out to determine how the size and size distribution of the particles generated can be controlled by systematically varying the polymer concentration in solution (and thereby its viscosity and electrical conductivity), and also the selected flow rate (2-50 microl min(-1)) and applied voltage (0-15 kV) during particle generation. Change in these parameters affects the mode of jetting, and within the stable cone-jet mode window, an increase in the applied voltage (approx. 15 kV) resulted in a reduction in particle size and this was more pronounced at high flow rates (such as; 30, 40 and 50 microl min(-1)) in the same region. The carrier particles were more polydisperse at the peripheral regions of the stable cone-jet mode, as defined in the applied voltage-flow rate parametric map. The effect of loading a drug on the particle size, size distribution and encapsulation efficiency was also studied. Release from drug-loaded particles was investigated using UV spectrophotometry over 45 days. This work demonstrates a powerful method of generating drug-loaded polymeric particles, with the ability to control size and polydispersivity, which has great potential in several categories of biotechnology requiring carrier particles, such as drug delivery and gene therapy.

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Figures

Figure 1.
Figure 1.
Schematic of the experimental apparatus used for PCL particle production.
Figure 2.
Figure 2.
Flow of 5 wt% PCL solution under an electric field showing, with flow rate set at 10 µl min−1, (a) no flow, (b) dripping mode, (c) microdripping mode, (d) rapid dripping mode, (e) unstable cone-jet mode, (f) stable cone-jet mode, (g) multi-jet mode, and (h) irregular instabilies mode. Scale bars, 600 µm.
Figure 3.
Figure 3.
Operating ranges used to obtain different spraying modes (a) PCL : DMAC 2∶98 (wt%), (b) PCL : DMAC 5∶95 (wt%), (c) PCL : DMAC 10∶90 (wt%). (d) Comparison of the cone-jet mode region of different solutions. (d) Triangles, PCL 10 wt%; circles, PCL 5 wt%; diamonds, PCL 2 wt%.
Figure 4.
Figure 4.
Variation of mean size of the particles obtained as (a) a function of applied voltage and flow rate and (b) highlighting the cone-jet region for PCL : DMAC 5∶95 wt% solution. (a) Blue diamond line, F.R. = 50 µl min−1; pink square line, F.R. = 40 µl min−1; yellow line, F.R. = 30 µl min−1; dark blue line, F.R. = 20 µl min−1; pink cross line, 10 µl min−1; red diamond line, 5 µl min−1; green line, 2 µl min−1; (b) blue bar, 50 µl min−1; pink bar, 40 µl min−1; green bar, 30 µl min−1; purple bar, 20 µl min−1; brown bar, 10 µl min−1; dark blue bar, 5 µl min−1; red bar, 2 µl min−1.
Figure 5.
Figure 5.
Relationship between mean particle size generated and the electrical conductivity and the viscosity of the PCL solutions used (flow rate: 10 µl min−1, applied voltage: 10 kV). Square with solid line, mean size; circle with dotted line, conductivity.
Figure 6.
Figure 6.
Size distribution of PCL particles produced using different concentrations of PCL solution (a) PCL 2 wt%, (b) PCL 5 wt%, (c) PCL 10 wt%, (flow rate: 10 µl min−1, applied voltage: 10 kV), (d) polydispersivity index of particles produced in the cone-jet region as a function of flow rate (applied voltage: 10 kV). (d) Square line, PCL 2 wt% (viscosity: 2.6 mPa s); triangle line, PCL 5 wt% (viscosity: 4.6 mPa s); diamond line, PCL 10 wt% (viscosity: 11.1 mPa s).
Figure 7.
Figure 7.
(ac) Optical micrographs and (df) SEM images of particles prepared at different polymer concentrations. ((a) 2 wt% PCL, (b) 5 wt% PCL, and (c) 10 wt% PCL), flow rate = 10 µl min−1, collecting distance = 150 mm, voltage approximately 10 kV. Scale bars, (a,b) 3 µm; (c) 20 µm.
Figure 8.
Figure 8.
Scanning electron micrographs of PCL particles incorporating β-oestradiol. (a) 10 wt% PCL, (b) 5 wt% PCL, and (c) 2 wt% PCL with each contains 15 wt% β-oestradiol, flow rate = 10 µl min−1, collecting distance = 150 mm, voltage approximately 10 kV.
Figure 9.
Figure 9.
β-oestradiol release profile of PCL particles prepared from different PCL solutions loaded with 15 wt% β-oestradiol. Diamond line, PCL 10 wt%; square line, PCL 5 wt%; triangle line, PCL 2 wt%.

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