Liquid crystalline lipid nanoparticle promotes the photodynamic activity of gallium protoporphyrin against S. aureus biofilms

Trifluoromethyl-pyrrolidone phthalocyanine nanoparticles for targeted lipid droplet imaging and in vitro photodynamic therapy in breast cancer cells

Lipid droplets (LDs) serve as vital subcellular organelles, crucial for the maintenance of lipid and energy homeostasis within cells. Their visualization is of significant value for elucidating the intricate interactions between LDs and other cellular organelles. Despite the importance of LDs, the literature on the utilization of phthalocyanine-based photosensitizers for targeted LD imaging and two-photon imaging-guided photodynamic therapy (PDT) remains sparse. In this study, we have designed and synthesized trifluoromethyl-pyrrolidone silicon phthalocyanine (PyCF3SiPc). To enhance the water solubility of PyCF3SiPc and improve its tumor cells accumulation, we employed 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(poly(ethylene glycol))-2000] (DSPE-mPEG2000) as a nanocarrier, thereby formulating DSPE@PyCF3SiPc nanoparticles. Our in vitro experiments in MCF-7 cells demonstrated that DSPE@PyCF3SiPc selectively targets and visualizes LDs, offering a reliable tool for tracking their dynamic movement. Moreover, DSPE@PyCF3SiPc demonstrates considerable phototoxicity against MCF-7 cells subjected to PDT underscoring its potential as an effective therapeutic agent. In conclusion, DSPE@PyCF3SiPc presents itself as a promising novel probe for the dual purpose of monitoring the dynamic movement of LDs and guiding imaging-assisted PDT. The development of this nanoparticle system not only advances our understanding of LD biology but also paves the way for innovative therapeutic strategies in oncology.

Preparation of MPN@Zein-PpIX Membrane and Its Antibacterial Properties

For antibacterial purposes, a photothermal and photodynamic antibacterial membrane was prepared through electrospinning. We used zein as the substrate and introduced Protoporphyrin IX (PpIX) into the protein structure. Then, we used electrospinning technology to weave the modified zein into a fiber structure. We finally introduced a metallic polyphenol network (MPN) coating on the fiber surface to form the final membrane: MPN@Zein-PpIX. Then, we investigated the photothermal and photodynamic properties of the membrane and assessed its antibacterial activity with in vitro agar plate counting methods. The MPN@Zein-PpIX membrane exhibited good singlet oxygen generation and excellent photothermal conversion. Additionally, it showed good antibacterial capacity in vitro, owing to the combination of photothermal and photodynamic properties. Our research provides a simple approach to prepare a multifunctional membrane with excellent antibacterial ability. We used the electrospinning technique to anchor PpIX onto zein to produce a fiber membrane (Zein-PpIX) that can be adhered in situ to improve the biocompatibility of PpIX, and the MPN makes the membrane surface more hydrophilic and more accessible to adhere to biological tissues. The MPN@Zein-PpIX membrane provided new ideas for combining PDT and PTT, and it had great potential for use in the antibacterial application field.

Lyophilized Lipid Liquid Crystalline Nanoparticles as an Antimicrobial Delivery System

Lipid liquid crystalline nanoparticles (LCNPs) are unique nanocarriers that efficiently deliver antimicrobials through biological barriers. Yet, their wide application as an antimicrobial delivery system is hindered by their poor stability in aqueous dispersions. The production of dried LCNP powder via lyophilization is a promising approach to promote the stability of LCNPs. However, the impact of the process on the functionality of the loaded hydrophobic cargoes has not been reported yet. Herein, we investigated the potential of lyophilization to produce dispersible dry LCNPs loaded with a hydrophobic antimicrobial compound, gallium protoporphyrin (GaPP). The effect of lyophilization on the physicochemical characteristics and the antimicrobial activity of rehydrated GaPP-LCNPs was studied. The rehydrated GaPP-LCNPs retained the liquid crystalline structure and were monodisperse (PDI: 0.27 ± 0.02), with no significant change in nanoparticle concentration despite the minor increase in hydrodynamic diameter (193 ± 6.5 compared to 173 ± 4.2 prior to freeze-drying). Most importantly, the efficacy of the loaded GaPP as an antimicrobial agent and a photosensitizer was not affected as similar MIC values were obtained against S. aureus (0.125 µg/mL), with a singlet oxygen quantum yield of 0.72. These findings indicate the suitability of lyophilization to produce a dry form of LCNPs and pave the way for future studies to promote the application of LCNPs as an antimicrobial delivery system.

Improved anticancer efficacy of methyl pyropheophorbide-a-incorporated solid lipid nanoparticles in photodynamic therapy

Photodynamic therapy (PDT) is a promising anticancer treatment because it is patient-friendly and non-invasive. Methyl pyropheophorbide-a (MPPa), one of the chlorin class photosensitizers, is a drug with poor aqueous solubility. The purpose of this study was to synthesize MPPa and develop MPPa-loaded solid lipid nanoparticles (SLNs) with improved solubility and PDT efficacy. The synthesized MPPa was confirmed ¹H nuclear magnetic resonance (¹H-NMR) spectroscopy and UV-Vis spectroscopy. MPPa was encapsulated in SLN via a hot homogenization with sonication. Particle characterization was performed using particle size and zeta potential measurements. The pharmacological effect of MPPa was evaluated using the 1,3-diphenylisobenzofuran (DPBF) assay and anti-cancer effect against HeLa and A549 cell lines. The particle size and zeta potential ranged from 231.37 to 424.07 nm and - 17.37 to - 24.20 mV, respectively. MPPa showed sustained release from MPPa-loaded SLNs. All formulations improved the photostability of MPPa. The DPBF assay showed that SLNs enhanced the ¹O₂ generation from MPPa. In the photocytotoxicity analysis, MPPa-loaded SLNs demonstrated cytotoxicity upon photoirradiation but not in the dark. The PDT efficacy of MPPa improved following its entrapment in SLNs. This observation suggests that MPPa-loaded SLNs are suitable for the enhanced permeability and retention effect. Together, these results demonstrate that the developed MPPa-loaded SLNs are promising candidates for cancer treatment using PDT.

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

Cutaneous chronic wounds impose a silent pandemic that affects the lives of millions worldwide. The delayed healing process is usually complicated by opportunistic bacteria that infect wounds. Staphylococcus aureus is one of the most prevalent bacteria in infected cutaneous wounds, with the ability to form antibiotic-resistant biofilms. Recently, we have demonstrated the potential of gallium protoporphyrin lipid liquid crystalline nanoparticles (GaPP-LCNP) as a photosensitizer against S. aureus biofilms in vitro. Herein, we investigate the potential of GaPP-LCNP using a pre-clinical model of infected cutaneous wounds. GaPP-LCNP showed superior antibacterial activity compared to unformulated GaPP, reducing biofilm bacterial viability by 5.5 log₁₀ compared to 2.5 log₁₀ in an ex vivo model, and reducing bacterial viability by 1 log₁₀ in vivo, while unformulated GaPP failed to reduce bacterial burden. Furthermore, GaPP-LCNP significantly promoted wound healing through reduction in the bacterial burden and improved early collagen deposition. These findings pave the way for future pre-clinical investigation and treatment optimizations to translate GaPP-LCNP towards clinical application.

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

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.