Highly fluorescent quantum dots (QDs)-loaded nanocapsules, intended for fluorescent cell imaging, were prepared via an emulsification/solvent-evaporation method. CdSe/ZnS core/shell quantum dots were applied as cargo; Poloxamer 403 as the polymer component; Cremophor EL as the nonionic surfactant; and mineral oil, oleic acid, or silicone oil were applied as the oil phases. Transmission electron microscopy, atomic force microscopy, dynamic light scattering, and zeta potential measurements were used to characterize the novel QDs-labeled nanoparticles by particle size, distribution, and morphology, as well as by ζ-potential and physical stability. The fabricated long-lasting nanocapsules exhibit good luminescence properties upon both one-photon and two-photon excitation. The potential of the encapsulated QDs for fluorescent imaging was evaluated in cytotoxicity studies as well as in imaging of intracellular localization, accumulation, and distribution of QDs delivered to well-characterized human cancer cell lines--doxorubicin-sensitive breast (MCF-7/WT) and alveolar basal epithelial (A549)--as well as on normal human umbilical vein endothelial (HUVEC) cells, as investigated by confocal laser scanning microscopy (CLSM). The colloidal CdSe/ZnS-loaded nanocapsules are shown to exhibit strong two-photon-induced luminescence upon excitation in the NIR optical transmission window spectral range, making them ideal markers for bioimaging application. The total two-photon cross section of a single nanocapsule was determined to be about 4.1 × 10(6) GM at 800 nm.

We report activation of a photodynamic therapy photosensitizer, zinc phthalocyanine, by Förster resonant energy transfer (FRET) from two-photon absorption excited CdSe x S 1-x /ZnS quantum dots coencapsulated in multifunctional biocompatible polymer nanocapsules.Polymer nanocapsules (100 nm size) were prepared via solvent/evaporation method using Poloxamer 403 as the polymer component, Cremophor EL ® as the surfactant and mixture of silicone oil with hydrogenated caprylyl olive oil esters as the oil phase. UV-VIS-NIR absorption and multiphoton fluorescence studies confirmed successful coencapsulation of both components of the FRET system. The energy transfer between the quantum dots as donors and Zn phthalocyanine molecules as acceptors was studied using steady-state photoluminescence and time-correlated single photon counting techniques. The changes in the lifetime of the QDs emission indicate that the excitation of ZnPc occurs not only through reabsorption but also through FRET. The generation of the reactive oxygen species was confirmed by formation of non-fluorescent endoperoxide -derivative of fluorescent 9,10-anthracenediyl-bis(methylene)dimalonic acid sodium salt under irradiation of the nanocapsules co-loaded with both QDs and ZnPc.

The present work is focused on the long-term stability and in vitro cellular internalization of newly designed biocompatible polyester nanocapsules prepared via nanoprecipitation approach with mean diameter <165 nm and narrow size distribution, dedicated to theranostic applications. We monitored the optical, morphological, and biological properties of the nanocarriers loaded by multifunctional cargo, i.e., paclitaxel (PTX) and a fluorescent marker: coumarin-6 (CR-6) or Nile Red (NR), by fluorescence and UV–vis spectroscopy (encapsulation efficiency), dynamic light scattering (average size expressed as hydrodynamic diameter, DH), zeta potential (ζ, colloidal stability), atomic force microscopy (AFM, imaging), and confocal laser scanning microscopy (CLSM, nanocapsule visualization, and cellular internalization in vitro by human breast cancer MCF-7/WT cells). The fabricated nanocapsules with optimal composition of oleic phase, i.e., coconut oil, palm oil, and Capmul MCM, as well as polymeric shell, i.e., polylactic acid (PLA), poly (ε-caprolactone) (PCL), and poly (lactide-co-glycolide) (PLGA), showed high loading capacity, long-term stability, and improved localization of the active cargo in studied tumor cells. Therefore, our results prove that the studied polyester oil core nanocapsules provide lifelong and biocompatible nanocarriers suitable for in vivo administration and for diagnostic applications.

An antimicrobial peptide, nisin Z, was embedded within polyelectrolyte multilayers (PEMs) composed of natural polysaccharides in order to explore the potential of forming a multilayer with antimicrobial properties. Using attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR), the formation of carrageenan/chitosan multilayers and the inclusion of nisin Z in two different configurations was investigated. Approximately 0.89 µg cm−2 nisin Z was contained within a 4.5 bilayer film. The antimicrobial properties of these films were also investigated. The peptide containing films were able to kill over 90% and 99% of planktonic and biofilm cells, respectively, against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) strains compared to control films. Additionally, surface topography and wettability studies using atomic force microscopy (AFM) and the captive bubble technique revealed that surface roughness and hydrophobicity was similar for both nisin containing multilayers. This suggests that the antimicrobial efficacy of the peptide is unaffected by its location within the multilayer. Overall, these results demonstrate the potential to embed and protect natural antimicrobials within a multilayer to create functionalised coatings that may be desired by industry, such as in the food, biomaterials, and pharmaceutical industry sectors.