Polymethine dyes-loaded solid lipid nanoparticles (SLN) as promising photosensitizers for biomedical applications

Solid lipid nanoparticles and their application in the treatment of bacterial infectious diseases

Nano pharmacology is considered an effective, safe, and applicable approach for drug delivery applications. Solid lipid nanoparticle (SLNs) colloids contain biocompatible lipids which are capable of encapsulating and maintaining hydrophilic or hydrophobic drugs in the solid matrix followed by releasing the drug in a sustained manner in the target site. SLNs have more promising potential than other drug delivery systems for various purposes. Nowadays, the SLNs are used as a carrier for antibiotics, chemotherapeutic drugs, nucleic acids, herbal compounds, etc. The SLNs have been widely applied in biomedicine because of their non-toxicity, biocompatibility, and simple production procedures. In this review, the complications related to the optimization, preparation process, routes of transplantation, uptake and delivery system, and release of the loaded drug along with the advantages of SLNs as therapeutic agents were discussed.

A quality by design approach for the synthesis of palmitoyl-L-carnitine-loaded nanoemulsions as drug delivery systems

Nanoemulsions (NE) are lipid nanocarriers that can efficiently load hydrophobic active compounds, like palmitoyl-L-carnitine (pC), used here as model molecule. The use of design of experiments (DoE) approach is a useful tool to develop NEs with optimized properties, requiring less experiments compared to trial-and-error approach. In this work, NE were prepared by the solvent injection technique and DoE using a two-level fractional factorial design (FFD) as model was implemented for designing pC-loaded NE. NEs were fully characterized by a combination of techniques, studying its stability, scalability, pC entrapment and loading capacity and biodistribution, which was studied ex-vivo after injection of fluorescent NEs in mice. We selected the optimal composition for NE, named pC-NE_U, after analysis of four variables using DoE. pC-NE_U incorporated pC in a very efficient manner, with high entrapment efficiency (EE) and loading capacity. pC-NE_U did not change its initial colloidal properties stored at 4 °C in water during 120 days, nor in buffers with different pH values (5.3 and 7.4) during 30 days. Moreover, the scalability process did not affect NE properties and stability profile. Finally, biodistribution study showed that pC-NE_U formulation was predominantly concentrated in the liver, with minimal accumulation in spleen, stomach, and kidneys.

NIR squaraine dyes for dual colorimetric and fluorescent determination of Fe3+, Cu2+, and Hg2+ ions

Four benzoindolenine-based squaraine dyes (SQs), which have the advantages of intense visible and near-infrared (NIR) absorption and emission (λ_abs/max 663-695 nm, λ_em/max 686-730 nm) were synthesized and characterized by UV-vis absorption, fluorescent emission spectrophotometry, FTIR, NMR and HRMS analysis. Among them, BBSQ showed excellent performance, which exhibited high selectivity to Fe³⁺, Cu²⁺, and Hg²⁺ in acetonitrile solution even in the presence of other competitive metal ions, accompanied by obvious color change easily detected by the naked eye. The detection limit was 14.17 μM for Fe³⁺ and 6.06 μM for Cu²⁺. Most importantly, the response mechanism of BBSQ to Fe³⁺, Cu²⁺, and Hg²⁺ involves the coordination of BBSQ and metal ions through the O atom on the central squarate ring, N atom, and olefin π bond of BBSQ and has been demonstrated by Job's plot, FTIR, and ¹H NMR titration analyses. Furthermore, BBSQ was applied successfully to detect Fe³⁺, Cu²⁺, and Hg²⁺ in thin-layer chromatography (TLC) plates with good precision and is quite promising for the quantitative detection of Fe³⁺ and Cu²⁺ ions in water samples.

Quatsomes Loaded with Squaraine Dye as an Effective Photosensitizer for Photodynamic Therapy

Photodynamic therapy is a non-invasive therapeutic strategy that combines external light with a photosensitizer (PS) to destroy abnormal cells. Despite the great progress in the development of new photosensitizers with improved efficacy, the PS’s photosensitivity, high hydrophobicity, and tumor target avidity still represent the main challenges. Herein, newly synthesized brominated squaraine, exhibiting intense absorption in the red/near-infrared region, has been successfully incorporated into Quatsome (QS) nanovesicles at different loadings. The formulations under study have been characterized and interrogated in vitro for cytotoxicity, cellular uptake, and PDT efficiency in a breast cancer cell line. The nanoencapsulation of brominated squaraine into QS overcomes the non-water solubility limitation of the brominated squaraine without compromising its ability to generate ROS rapidly. In addition, PDT effectiveness is maximized due to the highly localized PS loadings in the QS. This strategy allows using a therapeutic squaraine concentration that is 100 times lower than the concentration of free squaraine usually employed in PDT. Taken together, our results reveal the benefits of the incorporation of brominated squaraine into QS to optimize their photoactive properties and support their applicability as photosensitizer agents for PDT.