Pulsatile Controlled Release and Stability Evaluation of Polymeric Particles Containing Piper nigrum Essential Oil and Preservatives

Abstract

Considerable efforts have been spent on environmentally friendly particles for the encapsulation of essential oils. Polymeric particles were developed to encapsulate the essential oil from Piper nigrum based on gelatin and poly-ε-caprolactone (PCL) carriers. Gas Chromatography ((Flame Ionization Detection (GC/FID) and Mass Spectrometry (GC/MS)), Atomic Force Microscopy (AFM), Nanoparticle Tracking Analysis (NTA), Confocal Laser Scanning Microscopy (CLSM), Attenuated Total Reflectance-Fourier-transform Infrared Spectroscopy (ATR-FTIR), and Ultraviolet-Visible (UV-VIS) spectroscopy were used for the full colloidal system characterization. The essential oil was mainly composed of β-caryophyllene (~35%). The stability of the encapsulated systems was evaluated by Encapsulation Efficiency (EE%), electrical conductivity, turbidity, pH, and organoleptic properties (color and odor) after adding different preservatives. The mixture of phenoxyethanol/isotialzoni-3-one (PNE system) resulted in enhanced stability of approximately 120 and 210 days under constant handling and shelf-life tests, respectively. The developed polymeric system presented a similar controlled release in acidic, neutral, or basic pH, and the release curves suggested a pulsatile release mechanism due to a complexation of essential oil in the PCL matrix. Our results showed that the developed system has potential as an alternative stable product and as a controlling agent, due to the pronounced bioactivity of the encapsulated essential oil.

Keywords: Piper nigrum; controlled release; polymeric particles; pulsatile mechanism; stability evaluation.

Figure 1

NTA particle size distribution analysis of unloaded and loaded systems. Representative histograms of the average size distribution (black line) from three measurements of a single sample. Red areas specify the standard deviation (SD) between measurements, and blue numbers indicate the maxima of individual peaks.

Figure 2

Two-dimensional and three-dimensional AFM micrographs: (a) unloaded particles, (b) loaded particles, (c) size distribution of unloaded and loaded particles.

Figure 3

(a) Encapsulation Efficiency (EE%), (b) electrical conductivity, (c) turbidity and (d) pH of the loaded systems containing preservatives as a function of time (days).

Figure 4

Two-dimensional and three-dimensional AFM micrographs: (a) PNE system destabilized, and (b) topographic map.

Figure 5

Color evaluation of the systems maintained under constant handling at (25 ± 2) °C: (a) control system, and (b) systems after evaluation.

Figure 6

Confocal microscopy images of the particles from the (a) unloaded system and (b) loaded PNE system.

Figure 7

Fluorescence measurements of the loaded particle (part 1 and 2), essential oil in natura and unloaded particle.

Figure 8

ATR-FTIR spectra of the in natura essential oil, PCL, span 60, TACC, and solution II (a) from 4000–650 cm⁻¹, (b) from 2000–650 cm⁻¹ and (c) from 4000–2400 cm⁻¹.

Figure 9

(a) Controlled release of essential oil at pH 4, 7, and 10, and (b) derived curve from the controlled release.

Figure 10

Schematic diagram of the speculative proposal for the interpretation of the controlled release associated with particle design as a function of time: (a) particle consisting mainly of gelatin, PCL, and essential oil, (b) hydration/solubilization process of the gelatin layer, allowing the release of some amount of essential oil, (c) starting of the degradation of PCL, (d,e) increasing of the released essential oil.