Gallium Protoporphyrin Liquid Crystalline Lipid Nanoparticles: A Third-Generation Photosensitizer against Pseudomonas aeruginosa Biofilms

Abstract

The looming antimicrobial resistance pandemic has encouraged the investigation of antimicrobial photodynamic therapy (aPDT) as a promising technology to combat recalcitrant bacterial infections caused by antibiotic resistant strains. Here, we report on the optimization and effective application of gallium protoporphyrin liquid crystalline lipid nanoparticles (GaPP-LCNP) as a photosensitizer for aPDT against the Gram-negative bacteria P. aeruginosa in both planktonic and biofilm modes of growth. LCNP significantly enhanced the performance of GaPP as photosensitizer by two-fold, which was correlated with higher antibacterial activity, reducing the viability of planktonic P. aeruginosa by 7 log10 using 0.8 µM GaPP-LCNP and a light dose of 17 J.cm–2. Importantly, GaPP-LCNP also reduced the viability of biofilms by 6 log10 at relatively low light dose of 34.2 J.cm-2 using only 3 µM GaPP-LCNP. The high antibiofilm activity of GaPP-LCNP at low GaPP-LCNP dose indicated the high efficiency and safety profile of GaPP-LCNP as a promising platform for photodynamic inactivation of recalcitrant infections.

Lipid Liquid Crystal Nanoparticles: Promising Photosensitizer Carriers for the Treatment of Infected Cutaneous Wounds

“…LCNPs are a unique class of nanomaterials that are prepared from the self-assembly of amphiphilic lipids in water to yield 3D crystalline nanoparticles [ 28 ]. In this study, glycerol monooleate was utilized as the amphiphilic lipid to fabricate LCNP using the hydrotrope dilution method as previously described [ 17 , 22 ]. This formulation approach produces uniformly dispersed LCNP with higher stability, due to uniform distribution of the stabilizer [ 28 ].…”

“…The average particle diameter (Z-average), zeta potential and polydispersity index (PDI) were determined using a Zetasizer Nano ZS (Malvern, Worcestershire, UK), as previously described [ 22 ].…”

“…The concentration of GaPP within LCNP was determined using the native fluorescent signal of GaPP at 585 nm after excitation at 405 nm [ 22 ] using a Fluostar ®® Omega microplate reader. To determine the loaded GaPP concentration, a GaPP-LCNP dispersion in water was centrifuged for 10 min at 31,120 g; the unloaded GaPP precipitated, while the supernatant containing GaPP loaded in LCNP was dissolved in methanol, and the concentration was quantified from the corresponding calibration curve.…”

“…The light source used for the photoactivation process is a mounted blue LED at 405 nm (M405L4) [ 22 ]. The light beam was collimated using an aspheric condenser lens attached to the mounted LED using an SM1 Lens Tube to illuminate an area of 1 cm.…”

“…Previously, we have demonstrated the potential of lipid liquid crystalline nanoparticles (LCNP) to promote the antimicrobial photodynamic activity of gallium protoporphyrin (GaPP) against the notorious antibiotic-resistant bacteria S. aureus and Pseudomonas aeruginosa [ 17 , 22 ]. LCNP-promoted singlet oxygen production from photoactivated GaPP eradicated S. aureus biofilms and increased the proliferation of human skin fibroblasts in vitro [ 17 ].…”