2,4,5-Triaminopyrimidines as blue fluorescent probes for cell viability monitoring: synthesis, photophysical properties, and microscopy applications

Monitoring cell viability is critical in cell biology, pathology, and drug discovery. Most cell viability assays are cell-destructive, time-consuming, expensive, and/or hazardous. Herein, we present a series of newly synthesized 2,4,5-triaminopyrimidine derivatives able to discriminate between live and dead cells. To our knowledge, these compounds are the first fluorescent nucleobase analogues (FNAs) with cell viability monitoring potential. These new fluorescent molecules are synthesized using highly efficient and cost-effective methods and feature unprecedented photophysical properties (longer absorption and emission wavelengths, environment-sensitive emission, and unprecedented brightness within FNAs). Using a live-dead Saccharomyces cerevisiae cell and theoretical assays, the fluorescent 2,4,5-triaminopyrimidine derivatives were found to specifically accumulate inside dead cells by interacting with dsDNA grooves, thus paving the way for the emergence of novel and safe fluorescent cell viability markers emitting in the blue region. As the majority of commercially available viability dyes emit in the green to red region of the visible spectrum, these novel markers might be useful to meet the needs of blue markers for co-staining combinations.

Magnetoliposomes with Calcium-Doped Magnesium Ferrites Anchored in the Lipid Surface for Enhanced DOX Release

Nanotechnology has provided a new insight into cancer treatment by enabling the development of nanocarriers for the encapsulation, transport, and controlled release of antitumor drugs at the target site. Among these nanocarriers, magnetic nanosystems have gained prominence. This work presents the design, development, and characterization of magnetoliposomes (MLs), wherein superparamagnetic nanoparticles are coupled to the lipid surface. For this purpose, dimercaptosuccinic acid (DMSA)-functionalized Ca0.25Mg0.75Fe2O4 superparamagnetic nanoparticles were prepared for the first time. The magnetic nanoparticles demonstrated a cubic shape with an average size of 13.36 nm. Furthermore, their potential for photothermal hyperthermia was evaluated using 4 mg/mL, 2 mg/mL, and 1 mg/mL concentrations of NPs@DMSA, which demonstrated a maximum temperature variation of 20.4 °C, 11.4 °C, and 7.3 °C, respectively, during a 30 min NIR-laser irradiation. Subsequently, these nanoparticles were coupled to the lipid surface of DPPC/DSPC/CHEMS and DPPC/DSPC/CHEMS/DSPE-PEG-based MLs using a new synthesis methodology, exhibiting average sizes of 153 ± 8 nm and 136 ± 2 nm, respectively. Doxorubicin (DOX) was encapsulated with high efficiency, achieving 96% ± 2% encapsulation in non-PEGylated MLs and 98.0% ± 0.6% in stealth MLs. Finally, drug release assays of the DOX-loaded DPPC/DSPC/CHEMS MLs were performed under different conditions of temperature (37 °C and 42 °C) and pH (5.5 and 7.4), simulating physiological and therapeutic conditions. The results revealed a higher release rate at 42 °C and acidic pH. Release rates significantly increased when introducing the stimulus of laser-induced photothermal hyperthermia at 808 nm (1 W/cm2) for 5 min. After 48 h of testing, at pH 5.5, 67.5% ± 0.5% of DOX was released, while at pH 7.4, only a modest release of 27.0% ± 0.1% was achieved. The results demonstrate the potential of the MLs developed in this work to the controlled release of DOX under NIR-laser stimulation and acidic environments and to maintain a sustained and reduced release profile in physiological environments with pH 7.4.

Chitosan/Alginate Nanogels Containing Multicore Magnetic Nanoparticles for Delivery of Doxorubicin

In this study, multicore-like iron oxide (Fe3O4) and manganese ferrite (MnFe2O4) nanoparticles were synthesized and combined with nanogels based on chitosan and alginate to obtain a multimodal drug delivery system. The nanoparticles exhibited crystalline structures and displayed sizes of 20 ± 3 nm (Fe3O4) and 11 ± 2 nm (MnFe2O4). The Fe3O4 nanoparticles showed a higher saturation magnetization and heating efficiency compared with the MnFe2O4 nanoparticles. Functionalization with citrate and bovine serum albumin was found to improve the stability and modified surface properties. The nanoparticles were encapsulated in nanogels, and provided high drug encapsulation efficiencies (~70%) using doxorubicin as a model drug. The nanogels exhibited sustained drug release, with enhanced release under near-infrared (NIR) laser irradiation and acidic pH. The nanogels containing BSA-functionalized nanoparticles displayed improved sustained drug release at physiological pH, and the release kinetics followed a diffusion-controlled mechanism. These results demonstrate the potential of synthesized nanoparticles and nanogels for controlled drug delivery, offering opportunities for targeted and on-demand release in biomedical applications.

Bovine Lactoferrin-Loaded Plasmonic Magnetoliposomes for Antifungal Therapeutic Applications

Bovine lactoferrin (bLf) is a milk-derived protein that exhibits potent broad-spectrum antifungal activity against multiple fungi. bLf is susceptible to degradation, while some of its properties depend on the tertiary structure. So, the encapsulation of bLf in stimuli-responsive therapeutic formulations provides an added value to enhance its biological activities. Plasmonic magnetoliposomes (PMLs) arise as promising nanocarriers for dual hyperthermia (magneto-photothermia) and local chemotherapy, since the combination of magnetic and gold nanoparticles (NPs) in a single nanosystem (multifunctional liposomes) enables the targeting and controlled release of loaded drugs. In this work, plasmonic magnetoliposomes (PMLs) containing manganese ferrite nanoparticles (28 nm size) and gold nanoparticles (5-7.5 nm size), functionalized with 11-mercaptoundecanoic acid or octadecanethiol, were prepared and loaded with bLf. The NPs' optical, magnetic and structural properties were measured via UV/vis/NIR absorption spectroscopy, SQUID and TEM, respectively. The Specific Absorption Rate (SAR) was calculated to assess the capabilities for magnetic and photothermal hyperthermia. Finally, the antifungal potential of bLf-loaded PMLs and their mechanism of internalization were assessed in Saccharomyces cerevisiae by counting the colony forming units and using fluorescence microscopy. The results demonstrate that PMLs are mainly internalized through an energy- and temperature-dependent endocytic process, though the contribution of a diffusion component cannot be discarded. Most notably, only bLf-loaded plasmonic magnetoliposomes display cytotoxicity with an efficiency similar to free bLf, attesting their promising potential for bLf delivery in the context of antifungal therapeutic interventions.

Recent Advances on Cell Culture Platforms for In Vitro Drug Screening and Cell Therapies: From Conventional to Microfluidic Strategies

The clinical translations of drugs and nanomedicines depend on coherent pharmaceutical research based on biologically accurate screening approaches. Since establishing the 2D in vitro cell culture method, the scientific community has improved cell-based drug screening assays and models. Those advances result in more informative biochemical assays and the development of 3D multicellular models to describe the biological complexity better and enhance the simulation of the in vivo microenvironment. Despite the overall dominance of conventional 2D and 3D cell macroscopic culture methods, they present physicochemical and operational challenges that impair the scale-up of drug screening by not allowing a high parallelization, multidrug combination, and high-throughput screening. Their combination and complementarity with microfluidic platforms enable the development of microfluidics-based cell culture platforms with unequivocal advantages in drug screening and cell therapies. Thus, this review presents an updated and consolidated view of cell culture miniaturization's physical, chemical, and operational considerations in the pharmaceutical research scenario. It clarifies advances in the field using gradient-based microfluidics, droplet-based microfluidics, printed-based microfluidics, digital-based microfluidics, SlipChip, and paper-based microfluidics. Finally, it presents a comparative analysis of the performance of cell-based methods in life research and development to achieve increased precision in the drug screening process.

Unveiling the Role of Capping Groups in Naphthalene N-Capped Dehydrodipeptide Hydrogels

Self-assembled peptide-based hydrogels are archetypical nanostructured materials with a plethora of foreseeable applications in nanomedicine and as biomaterials. N-protected di- and tri-peptides are effective minimalist (molecular) hydrogelators. Independent variation of the capping group, peptide sequence and side chain modifications allows a wide chemical space to be explored and hydrogel properties to be tuned. In this work, we report the synthesis of a focused library of dehydrodipeptides N-protected with 1-naphthoyl and 2-naphthylacetyl groups. The 2-naphthylacetyl group was extensively reported for preparation of peptide-based self-assembled hydrogels, whereas the 1-naphthaloyl group was largely overlooked, owing presumably to the lack of a methylene linker between the naphthalene aromatic ring and the peptide backbone. Interestingly, dehydrodipeptides N-capped with the 1-naphthyl moiety afford stronger gels, at lower concentrations, than the 2-naphthylacetyl-capped dehydrodipeptides. Fluorescence and circular dichroism spectroscopy showed that the self-assembly of the dehydrodipeptides is driven by intermolecular aromatic π-π stacking interactions. Molecular dynamics simulations revealed that the 1-naphthoyl group allows higher order aromatic π-π stacking of the peptide molecules than the 2-naphthylacetyl group, together with hydrogen bonding of the peptide scaffold. The nanostructure of the gel networks was studied by TEM and STEM microscopy and was found to correlate well with the elasticity of the gels. This study contributes to understanding the interplay between peptide and capping group structure on the formation of self-assembled low-molecular-weight peptide hydrogels. Moreover, the results presented here add the 1-naphthoyl group to the palette of capping groups available for the preparation of efficacious low-molecular-weight peptide-based hydrogels.

The Buzz on Insecticides: A Review of Uses, Molecular Structures, Targets, Adverse Effects, and Alternatives

Insecticides play a critical role in controlling the spread of insect-borne diseases and preserving crop health. These chemical substances are specifically formulated to kill or manage insect populations. Over the years, various types of insecticides have been developed, including organophosphates, carbamates, pyrethroids, and neonicotinoids, each with unique modes of action, physiological targets, and efficacy. Despite the advantages that insecticides offer, it is imperative to recognize the potential consequences on non-target species, the environment, and human health. It is therefore crucial to follow recommended label instructions and employ integrated pest management practices for the judicious use of insecticides. This review article provides an in-depth examination of the various types of insecticides, including their modes of action, physiological targets, environmental and human health impacts, and alternatives. The aim is to furnish a comprehensive overview of insecticides and to emphasize the significance of responsible and sustainable utilization.

Development of pH-Sensitive Magnetoliposomes Containing Shape Anisotropic Nanoparticles for Potential Application in Combined Cancer Therapy

Late diagnosis and systemic toxicity associated with conventional treatments make oncological therapy significantly difficult. In this context, nanomedicine emerges as a new approach in the prevention, diagnosis and treatment of cancer. In this work, pH-sensitive solid magnetoliposomes (SMLs) were developed for controlled release of the chemotherapeutic drug doxorubicin (DOX). Shape anisotropic magnetic nanoparticles of magnesium ferrite with partial substitution by calcium (Mg_0.75Ca_0.25Fe₂O₄) were synthesized, with and without calcination, and their structural, morphological and magnetic properties were investigated. Their superparamagnetic properties were evaluated and heating capabilities proven, either by exposure to an alternating magnetic field (AMF) (magnetic hyperthermia) or by irradiation with near-infrared (NIR) light (photothermia). The Mg_0.75Ca_0.25Fe₂O₄ calcined nanoparticles were selected to integrate the SMLs, surrounded by a lipid bilayer of DOPE:Ch:CHEMS (45:45:10). DOX was encapsulated in the nanosystems with an efficiency above 98%. DOX release assays showed a much more efficient release of the drug at pH = 5 compared to the release kinetics at physiological pH. By subjecting tumor cells to DOX-loaded SMLs, cell viability was significantly reduced, confirming that they can release the encapsulated drug. These results point to the development of efficient pH-sensitive nanocarriers, suitable for a synergistic action in cancer therapy with magnetic targeting, stimulus-controlled drug delivery and dual hyperthermia (magnetic and plasmonic) therapy.

Synthesis and Cytotoxicity Assessment of Citrate-Coated Calcium and Manganese Ferrite Nanoparticles for Magnetic Hyperthermia

Calcium-doped manganese ferrite nanoparticles (NPs) are gaining special interest in the biomedical field due to their lower cytotoxicity compared with other ferrites, and the fact that they have improved magnetic properties. Magnetic hyperthermia (MH) is an alternative cancer treatment, in which magnetic nanoparticles promote local heating that can lead to the apoptosis of cancer cells. In this work, manganese/calcium ferrite NPs coated with citrate (Ca_xMn_1-xFe₂O₄ (x = 0, 0.2, 1), were synthesized by the sol-gel method, followed by calcination, and then characterized regarding their crystalline structure (by X-ray diffraction, XRD), size and shape (by Transmission Electron Microscopy, TEM), hydrodynamic size and zeta potential (by Dynamic Light Scattering, DLS), and heating efficiency (measuring the Specific Absorption Rate, SAR, and Intrinsic Loss Power, ILP) under an alternating magnetic field. The obtained NPs showed a particle size within the range of 10 nm to 20 nm (by TEM) with a spherical or cubic shape. Ca_0.2Mn_0.8Fe₂O₄ NPs exhibited the highest SAR value of 36.3 W/g at the lowest field frequency tested, and achieved a temperature variation of ~7 °C in 120 s, meaning that these NPs are suitable magnetic hyperthermia agents. In vitro cellular internalization and cytotoxicity experiments, performed using the human cell line HEK 293T, confirmed cytocompatibility over 0-250 µg/mL range and successful internalization after 24 h. Based on these studies, our data suggest that these manganese-calcium ferrite NPs have potential for MH application and further use in in vivo systems.

Plasmonic lipogels: driving co-assembly of composites with peptide-based gels for controlled drug release

Supramolecular short peptide-based gels are promising materials for the controlled release of drugs (e.g. chemotherapeutic drugs) owing to the biocompatibility and similarity to cell matrix. However, the drug encapsulation and control over its release, mainly the hydrophilic drugs, can be a cumbersome task. This can be overcome through encapsulation/compartmentalization of drugs in liposomes, which can also enable spatiotemporal control and enhanced drug release through a trigger, such as photothermia. Having this in mind, we explored the assembly of silica-coated gold nanoparticles and liposomes (storage units) with dehydropeptide-based hydrogels as a proof-of-concept to afford peptide-based NIR light-responsive lipogels. Several liposomes compositions were assessed that displayed influence on the final assembly properties by combining with silica-coated gold nanorods (∼106 nm). Gold nanospheres (∼11 nm) were used to study the preparation method, which revealed the importance of initially combine liposomes with nanoparticles and then the gelator solution to achieve a closer proximity of the nanoparticles to the liposomes. The control over a hydrophilic model drug, 5(6)-carboxyfluorescein, was only achieved by its encapsulation in liposomes, in which the presence of silica-coated nanorods further enabled the use of photothermia to induce the liposomes phase transition and stimulate the drug release. Further, both composites, the liposomes and silica-coated gold nanorods, induced a lower elastic modulus, but also provided an enhanced gelation kinetics. Hereby, this work advances fabrication strategies for the development of short peptide-based hydrogels towards on-demand, sustained and controlled release of hydrophilic drugs through photothermia under NIR light irradiation.

Liposomal Formulations Loaded with a Eugenol Derivative for Application as Insecticides: Encapsulation Studies and In Silico Identification of Protein Targets

A recently synthesized new eugenol derivative, ethyl 4-(2-methoxy-4-(oxiran-2-ylmethyl)phenoxy)butanoate, with a high insecticidal activity against Sf9 (Spodoptera frugiperda) insect cells, was encapsulated in the liposomal formulations of egg-phosphatidylcholine/cholesterol (Egg-PC:Ch) 70:30 and 100% dioleoylphosphatidylglycerol (DOPG), aiming at the future application as insecticides. Compound-loaded DOPG liposomes have sizes of 274 ± 12 nm, while Egg-PC:Ch liposomes exhibit smaller hydrodynamic diameters (69.5 ± 7 nm), high encapsulation efficiency (88.8 ± 2.7%), higher stability, and a more efficient compound release, thus, they were chosen for assays in Sf9 insect cells. The compound elicited a loss of cell viability up to 80% after 72 h of incubation. Relevantly, nanoencapsulation maintained the toxicity of the compound toward insect cells while lowering the toxicity toward human cells, thus showing the selectivity of the system. Structure-based inverted virtual screening was used to predict the most likely targets and molecular dynamics simulations and free energy calculations were used to demonstrate that this molecule can form a stable complex with insect odorant binding proteins and/or acetylcholinesterase. The results are promising for the future application of compound-loaded nanoliposome formulations as crop insecticides.

Magnetoliposomes Containing Multicore Nanoparticles and a New Antitumor Thienopyridine Compound with Potential Application in Chemo/Thermotherapy

Multicore magnetic nanoparticles of manganese ferrite were prepared using carboxymethyl dextran as an agglutinating compound or by an innovative method using melamine as a cross-coupling agent. The nanoparticles prepared using melamine exhibited a flower-shape structure, a saturation magnetization of 6.16 emu/g and good capabilities for magnetic hyperthermia, with a specific absorption rate (SAR) of 0.14 W/g. Magnetoliposome-like structures containing the multicore nanoparticles were prepared, and their bilayer structure was confirmed by FRET (Förster Resonance Energy Transfer) assays. The nanosystems exhibited sizes in the range of 250–400 nm and a low polydispersity index. A new antitumor thienopyridine derivative, 7-[4-(pyridin-2-yl)-1H-1,2,3-triazol-1-yl]thieno[3,2-b]pyridine, active against HeLa (cervical carcinoma), MCF-7 (breast adenocarcinoma), NCI-H460 (non-small-cell lung carcinoma) and HepG2 (hepatocellular carcinoma) cell lines, was loaded in these nanocarriers, obtaining a high encapsulation efficiency of 98 ± 2.6%. The results indicate that the new magnetoliposomes can be suitable for dual cancer therapy (combined magnetic hyperthermia and chemotherapy).

An injectable, naproxen-conjugated, supramolecular hydrogel with ultra-low critical gelation concentration-prepared from a known folate receptor ligand

Short peptides capped on the N-terminus with aromatic groups are often able to form supramolecular hydrogels-self-assembled networks of fibrils able to trap water molecules. Typically, these hydrogelators can form stiff gels at concentrations of 0.1 to 1.0 wt%-i.e. they consist of mainly water. The properties of these soft materials mimic those of the extracellular matrix (ECM) of biological tissue and therefore they have found many biomedical uses in tissue engineering, wound healing, drug delivery, biosensing and bioprinting applications. In drug delivery strategies related to cancer therapy, injectable hydrogels can serve as a depot formulation, where a sustained release of the chemotherapeutic from near the tumour site allows reduced doses and, therefore, decreased side effects. To further target cancer cells, folic acid-conjugated hydrogels and nanostructures are often sought, to exploit the overexpression of folate receptors on cancer cells-an approach which can allow the selective cellular uptake of an encapsulated drug. In this present study, two known dipeptide folate receptor ligands (1 and 2) recently identified from a screen of a DNA-encoded compound library, were synthesised and investigated for their hydrogelation ability and cytotoxicity. Compound 1, containing a naproxen capping group, rapidly forms hydrogels at concentrations as low as 0.03 wt%-one of the lowest critical gelation concentrations (CGCs) known for a supramolecular hydrogelator. In contrast, compound 2, which contains a 3-indolepropionic acid capping group, was unable to form hydrogels under a range of conditions and concentrations, instead forming nanospheres with diameters of 0.5 μm. Hydrogels of 1 were characterised by STEM microscopy, rheology, fluorescence spectroscopy and circular dichroism. Both compounds 1 and 2 had no impact on the proliferation of kerotinocytes (HaCaT cells) at concentrations up to 100 μM. Compound 1, containing the NSAID, was tested for anti-inflammatory activity in a human cyclooxygenase-1/2 model. The rate of the release of model drug compounds from within hydrogels of 1 was also investigated.

Tuning the drug multimodal release through a co-assembly strategy based on magnetic gels

Self-assembled short peptide-based gels are highly promising drug delivery systems. However, implementing a stimulus often requires screening different structures to obtain gels with suitable properties, and drugs might not be well encapsulated and/or cause undesirable effects on the gel's properties. To overcome this challenge, a new design approach is presented to modulate the release of doxorubicin as a model chemotherapeutic drug through the interplay of (di)phenylalanine-coated magnetic nanoparticles, PEGylated liposomes and doxorubicin co-assembly in dehydropeptide-based gels. The composites enable an enhancement of the gelation kinetics in a concentration-dependent manner, mainly through the use of PEGylated liposomes. The effect of the co-assembly of phenylalanine-coated nanoparticles with the hydrogel displays a concentration and size dependence. Finally, the integration of liposomes as doxorubicin storage units and of nanoparticles as composites that co-assemble with the gel matrix enables the tuneability of both passive and active doxorubicin release through a thermal, and a low-frequency alternating magnetic field-based trigger. In addition to the modulation of the gel properties, the functionalization with (di)phenylalanine improves the cytocompatibility of the nanoparticles. Hereby, this work paves a way for the development of peptide-based supramolecular systems for on-demand and controlled release of drugs.

Chitosan Nano/Microformulations for Antimicrobial Protection of Leather with a Potential Impact in Tanning Industry

Tanned leather can be attacked by microorganisms. To ensure resistance to bacteria on leather surfaces, protection solutions need to be developed, addressing both environmental issues and economic viability. In this work, chitosan nano/microparticles (CNP) and chitosan/silver nano/microstructures (CSNP), containing silver nanoparticles around 17 nm size, were incorporated into leather, obtained from the industrial process. Low loads of chitosan-based nano/microformulations, 0.1% mass ratio, resulted in total bacteria reduction (100%) after 2 h towards Gram-positive Staphylococcus aureus, both with CNP and CSNP coatings. Otherwise, comparable tests with the Gram-negative bacteria, Klebsiella pneumoniae, Escherichia coli, showed no significant improvement under the coating acidic conditions. The antimicrobial activity was evaluated by standard test methods: (1) inhibition halo and (2) dynamic contact conditions. The developed protection of leather either with CNP or CSNP is much higher than the one obtained with a simple chitosan solution.

Properties and Applications of PDMS for Biomedical Engineering: A Review

Polydimethylsiloxane (PDMS) is an elastomer with excellent optical, electrical and mechanical properties, which makes it well-suited for several engineering applications. Due to its biocompatibility, PDMS is widely used for biomedical purposes. This widespread use has also led to the massification of the soft-lithography technique, introduced for facilitating the rapid prototyping of micro and nanostructures using elastomeric materials, most notably PDMS. This technique has allowed advances in microfluidic, electronic and biomedical fields. In this review, an overview of the properties of PDMS and some of its commonly used treatments, aiming at the suitability to those fields' needs, are presented. Applications such as microchips in the biomedical field, replication of cardiovascular flow and medical implants are also reviewed.

Amino Alcohols from Eugenol as Potential Semisynthetic Insecticides: Chemical, Biological, and Computational Insights

A series of β-amino alcohols were prepared by the reaction of eugenol epoxide with aliphatic and aromatic amine nucleophiles. The synthesized compounds were fully characterized and evaluated as potential insecticides through the assessment of their biological activity against Sf9 insect cells, compared with a commercial synthetic pesticide (chlorpyrifos, CHPY). Three derivatives bearing a terminal benzene ring, either substituted or unsubstituted, were identified as the most potent molecules, two of them displaying higher toxicity to insect cells than CHPY. In addition, the most promising molecules were able to increase the activity of serine proteases (caspases) pivotal to apoptosis and were more toxic to insect cells than human cells. Structure-based inverted virtual screening and molecular dynamics simulations demonstrate that these molecules likely target acetylcholinesterase and/or the insect odorant-binding proteins and are able to form stable complexes with these proteins. Encapsulation assays in liposomes of DMPG and DPPC/DMPG (1:1) were performed for the most active compound, and high encapsulation efficiencies were obtained. A thermosensitive formulation was achieved with the compound release being more efficient at higher temperatures.

New carvacrol and thymol derivatives as potential insecticides: synthesis, biological activity, computational studies and nanoencapsulation

New compounds with potential insecticide activity were synthesized by structural modifications performed in the monoterpenoid phenolic moieties of carvacrol and thymol, resulting in a set of derivatives with the ether function containing the propyl, chloropropyl or hydroxypropyl chains, as well as a bicyclic ether with an unsaturated chain containing a carboxylic acid terminal. In addition, an analogue of carvacrol and thymol isomers bearing methoxyl, 1-hydroxyethyl and (3-chlorobenzoyl)oxy, instead of the three original methyl groups, was also synthesized. Several structural changes that resulted in diminished insecticide activity have been identified, but two significantly active molecules have been synthesized, one of them being less toxic to human cells than the naturally-derived starting materials. Structure-based inverted virtual screening and molecular dynamics simulations demonstrate that these active molecules likely target the insect odorant binding proteins and/or acetylcholinesterase and are able to form stable complexes. For the most promising compounds, nanoencapsulation assays were carried out in liposomes of egg phosphatidylcholine/cholesterol (7 : 3) prepared by both thin film hydration and ethanolic injection methods. The compound-loaded liposomes were generally monodisperse and with sizes smaller than or around 200 nm. The thin film hydration method allowed high encapsulation efficiencies (above 85%) for both compounds and a delayed release, while for the systems prepared by ethanolic injection the encapsulation efficiency is lower than 50%, but the release is almost complete in two days.

Magnetoliposomes: recent advances in the field of controlled drug delivery

INTRODUCTION

Magnetoliposomes have gained increasing attention as delivery systems, as they surpass many limitations associated with liposomes. The combination with magnetic nanoparticles provides a means for development of multimodal and multifunctional theranostic agents that enable on-demand drug release and real-time monitoring of therapy.

AREAS COVERED

Recently, several magnetoliposome structures have been reported to ensure efficient transport and delivery of therapeutics, while improving magnetic properties. Besides, novel techniques have been introduced to improve on-demand release, as well as to achieve sequential release of different therapeutic agents. This review presents the major types and methods of preparation of magnetoliposomes, and discusses recent strategies in the trigger of drug release, development of theranostic formulations, and delivery of drugs and biological entities.

EXPERT OPINION

Despite significant advances in efficient drug delivery, current literature lacks an assessment of formulations as theranostic agents and complementary techniques to optimize thermotherapy efficiency. Plasmonic magnetoliposomes are highly promising multimodal and multifunctional systems, providing the required design versatility to optimize theranostic capabilities. Further, photodynamic therapy and delivery of proteins/genes can be improved with a deeper research on the employed magnetic material and associated toxicity. A scale-up procedure is also lacking in recent research, which is limiting their translation to clinical use.

Interactions between contact lenses and lens care solutions: Influence in optical properties

PURPOSE

Investigate changes in optical properties of contact lenses materials (transmittance and reflectance) and lens care solutions (absorption and fluorescence) resulting from its interaction.

METHODS

From an experimental study, triplicate measurements of transmittance and reflectance of five contact lenses (Senofilcon A, Lotrafilcon B, Balafilcon A, Comfilcon A, and Omafilcon A), as well as UV-vis absorption and fluorescence of four lens care solutions (LCS) (ReNu MultiPlus, Biotrue, OPTI-FREE PureMoist, and AOSept Plus), were evaluated before and after 8 h, one day and one week in storage. The outcomes were provided by Shimadzu UV3101-PC UV-vis-NIR spectrophotometer equipped with an integrating sphere, between 200-700 nm, and SPEX-Fluorolog 2 FL3-22 spectrofluorometer.

RESULTS

All variables exhibited statistically significant differences over time. Comfilcon A showed the lowest ultraviolet radiation (UVR) A & B attenuation. Balafilcon A and Lotrafilcon B displayed a slight suppression of UVR. Senofilcon A was effective in UVR protection and showed less effect on the fluorescence of lens care solutions. Overall, the reflectance decreased after storage (p < 0.05). AOSept Plus absorbance and fluorescence demonstrated lower interactions than multipurpose solutions (MPS), and Lotrafilcon B induced more remarkable changes in optical properties of LCS than the other materials.

CONCLUSION

The findings suggest that optical variables of lens care solutions and contact lenses changed mutually after storage, probably associated with biochemical and biophysical interactions between components and the release of some polymer compounds. These findings can provide additional information about the interaction of CL materials and LCS in clinical behavior.

Supramolecular ultra-short carboxybenzyl-protected dehydropeptide-based hydrogels for drug delivery

Self-assembled peptide-based hydrogels are promising materials for biomedical research owing to biocompatibility and similarity to the extracellular matrix, amenable synthesis and functionalization and structural tailoring of the rheological properties. Wider developments of self-assembled peptide-based hydrogels in biomedical research and clinical translation are hampered by limited commercial availability allied to prohibitive costs. In this work a focused library of Cbz-protected dehydrodipeptides Cbz-L-Xaa-Z-ΔPhe-OH (Xaa= Met, Phe, Tyr, Ala, Gly) was synthesised and evaluated as minimalist hydrogels. The Cbz-L-Met-Z-ΔPhe-OH and Cbz-L-Phe-Z-ΔPhe-OH hydrogelators were comprehensively evaluated regarding molecular aggregation and self-assembly, gelation, biocompatibility and as drug carriers for delivery of the natural compound curcumin and the clinically important antitumor drug doxorubicin. Drug release profiles and FRET studies of drug transport into small unilamellar vesicles (as biomembrane models) demonstrated that the Cbz-protected dehydropeptide hydrogels are effective nanocarriers for drug delivery. The expedite and scalable synthesis (in 3 steps), using commercially available reagents and amenable reaction conditions, makes Cbz-protected dehydrodipeptide hydrogels, widely available at affordable cost to the research community.

Impact of Citrate and Lipid-Functionalized Magnetic Nanoparticles in Dehydropeptide Supramolecular Magnetogels: Properties, Design and Drug Release

Currently, the nanoparticle functionalization effect on supramolecular peptide-based hydrogels remains undescribed, but is expected to affect the hydrogels' self-assembly and final magnetic gel properties. Herein, two different functionalized nanoparticles: citrate-stabilized (14.4 ± 2.6 nm) and lipid-coated (8.9 ± 2.1 nm) magnetic nanoparticles, were used for the formation of dehydropeptide-based supramolecular magnetogels consisting of the ultra-short hydrogelator Cbz-L-Met-Z-ΔPhe-OH, with an assessment of their effect over gel properties. The lipid-coated nanoparticles were distributed along the hydrogel fibers, while citrate-stabilized nanoparticles were aggregated upon gelation, which resulted into a heating efficiency improvement and decrease, respectively. Further, the lipid-coated nanoparticles did not affect drug encapsulation and displayed improved drug release reproducibility compared to citrate-stabilized nanoparticles, despite the latter attaining a stronger AMF-trigger. This report points out that adsorption of nanoparticles to hydrogel fibers, which display domains that improve or do not affect drug encapsulation, can be explored as a means to optimize the development of supramolecular magnetogels to advance theranostic applications.

Cytotoxic Plant Extracts towards Insect Cells: Bioactivity and Nanoencapsulation Studies for Application as Biopesticides

The potential of plant extracts as bioinsecticides has been described as a promising field of agricultural development. In this work, the extracts of Punica granatum (pomegranate), Phytolacca americana (American pokeweed), Glandora prostrata (shrubby gromwell), Ulex europaeus (gorce), Tagetes patula (French marigold), Camellia japonica red (camellia), Ruta graveolens (rue or herb-of-grace) were obtained, purified, and their activity against Spodoptera frugiperda (Sf9) insect cells was investigated. From the pool of over twenty extracts obtained, comprising different polarities and vegetable materials, less polar samples were shown to be more toxic towards the insect cell line Sf9. Among these, a dichloromethane extract of R. graveolens was capable of causing a loss of viability of over 50%, exceeding the effect of the commercial insecticide chlorpyrifos. This extract elicited chromatin condensation and the fragmentation in treated cells. Nanoencapsulation assays of the cytotoxic plant extracts in soybean liposomes and chitosan nanostructures were carried out. The nanosystems exhibited sizes lower or around 200 nm, low polydispersity, and generally high encapsulation efficiencies. Release assays showed that chitosan nanoemulsions provide a fast and total extract release, while liposome-based systems are suitable for a more delayed release. These results represent a proof-of-concept for the future development of bioinsecticide nanoformulations based on the cytotoxic plant extracts.

Magnetoliposomes Incorporated in Peptide-Based Hydrogels: Towards Development of Magnetolipogels

A major problem with magnetogels is the encapsulation of hydrophobic drugs. Magnetoliposomes not only provide these domains but also improve drug stability and avert the aggregation of the magnetic nanoparticles. In this work, two magnetoliposome architectures, solid and aqueous, were combined with supramolecular peptide-based hydrogels, which are of biomedical interest owing to their biocompatibility, easy tunability, and wide array of applications. This proof-of-concept was carried out through combination of magnetoliposomes (loaded with the model drug curcumin and the lipid probe Nile Red) with the hydrogels prior to pH triggered gelation, and fluorescence spectroscopy was used to assess the dynamics of the encapsulated molecules. These systems allow for the encapsulation of a wider array of drugs. Further, the local environment of the encapsulated molecules after gelation is unaffected by the used magnetoliposome architecture. This system design is promising for future developments on drug delivery as it provides a means to independently modify the components and adapt and optimize the design according to the required conditions.

Natural Pigments of Anthocyanin and Betalain for Coloring Soy-Based Yogurt Alternative

The aim of this work was to evaluate the color stability of betalain- and anthocyanin-rich extracts in yogurt-like fermented soy, in order to develop a preliminary understanding of how these pigments behave in this type of food system during storage for 21 days at 4 °C. Thus, the extracts of red beetroot, opuntia, hibiscus and red radish were integrated into the yogurt-like fermented soy in two different ways-directly after lyophilization, and encapsulated in nanosystems based in soybean lecithin-as this approach has never been used to further increase the value and potential of the dairy-free alternatives of yogurt-like fermented soy. The results showed that non-encapsulated betalain-rich extracts from red radish are the most promising for coloring yogurt-like fermented soy. However, encapsulated opuntia extracts can also be an alternative to supplement the soy fermented beverages with betalains, without changing significantly the color of the system but giving all its health benefits, due to the protection of the pigments by nanoencapsulation.

Stealth Magnetoliposomes Based on Calcium-Substituted Magnesium Ferrite Nanoparticles for Curcumin Transport and Release

Despite the promising pharmacological properties of curcumin, the transport and effective release of curcumin is still a challenge. The advances in functionalized nanocarriers for curcumin have also been motivated by the anticancer activity of this natural compound, aiming at targeted therapies. Here, stealth (aqueous and solid) magnetoliposomes containing calcium-substituted magnesium ferrite nanoparticles, Ca_xMg_1−xFe₂O₄ (with x = 0.25, 0.50, 0.75) were developed as nanocarriers for curcumin. The magnetic nanoparticles exhibit superparamagnetic properties and crystalline structure, with sizes below 10 nm. The magnetoliposomes based on these nanoparticles have hydrodynamic diameters around or below 150 nm and a low polydispersity. The influence of an alternating magnetic field (AMF) on drug release over time was evaluated and compared with curcumin release by diffusion. The results suggest the potential of drug-loaded magnetoliposomes as nanocarriers that can be magnetically guided to the tumor sites and act as agents for a synergistic effect combining magnetic hyperthermia and controlled drug release.

Application of Natural Pigments in Ordinary Cooked Ham

The possibility of obtaining a carmine or pink color on ordinary cooked ham by applying natural dyes from three plant species, namely red radish (Raphanus sativus L.), hibiscus (Roselle sabdariffa L.) and red beetroot (Beta vulgaris L.), was investigated. The extracts were evaluated for the stability at physical-chemical parameters and subjected to cytotoxicity assays in the gastric cell line AGS Encapsulation of the extracts in soybean lecithin liposomes and maltodextrin microcapsules was performed. Lyophilized extracts before and after encapsulation in maltodextrin were applied in the formulation of ordinary cooked ham and used in a pilot scale of production. The color of cooked ham samples from different assays was evaluated visually and by colorimetry. The results suggest that the coloration of ordinary cooked ham obtained with extracts of red beetroot is very promising for future applications in this type of meat product.

Shape Anisotropic Iron Oxide-Based Magnetic Nanoparticles: Synthesis and Biomedical Applications

Research on iron oxide-based magnetic nanoparticles and their clinical use has been, so far, mainly focused on the spherical shape. However, efforts have been made to develop synthetic routes that produce different anisotropic shapes not only in magnetite nanoparticles, but also in other ferrites, as their magnetic behavior and biological activity can be improved by controlling the shape. Ferrite nanoparticles show several properties that arise from finite-size and surface effects, like high magnetization and superparamagnetism, which make them interesting for use in nanomedicine. Herein, we show recent developments on the synthesis of anisotropic ferrite nanoparticles and the importance of shape-dependent properties for biomedical applications, such as magnetic drug delivery, magnetic hyperthermia and magnetic resonance imaging. A brief discussion on toxicity of iron oxide nanoparticles is also included.

Dehydropeptide-based plasmonic magnetogels: a supramolecular composite nanosystem for multimodal cancer therapy

Supramolecular hydrogels are highly promising candidates as biomedical materials owing to their wide array of properties, which can be tailored and modulated. Additionally, their combination with plasmonic/magnetic nanoparticles to form plasmonic magnetogels further improves their potential in biomedical applications through the combination of complementary strategies, such as photothermia, magnetic hyperthermia, photodynamic therapy and magnetic-guided drug delivery. Here, a new dehydropeptide hydrogelator, Npx-l-Met-Z-ΔPhe-OH, was developed and combined with two different plasmonic/magnetic nanoparticle architectures, i.e., core/shell manganese ferrite/gold nanoparticles and gold-decorated manganese ferrite nanoparticles with ca. 55 nm and 45 nm sizes, respectively. The magnetogels were characterized via HR-TEM, FTIR spectroscopy, circular dichroism and rheological assays. The gels were tested as nanocarriers for a model antitumor drug, the natural compound curcumin. The incorporation of the drug in the magnetogel matrices was confirmed through fluorescence-based techniques (FRET, fluorescence anisotropy and quenching). The curcumin release profiles were studied with and without the excitation of the gold plasmon band. The transport of curcumin from the magnetogels towards biomembrane models (small unilamellar vesicles) was assessed via FRET between the fluorescent drug and the lipid probe Nile Red. The developed magnetogels showed promising results for photothermia and photo-triggered drug release. The magnetogels bearing gold-decorated nanoparticles showed the best photothermia properties, while the ones containing core/shell nanoparticles had the best photoinduced curcumin release.

Novel dehydropeptide-based magnetogels containing manganese ferrite nanoparticles as antitumor drug nanocarriers

Novel peptide-based magnetogels, containing MnFe₂O₄ nanoparticles of 20 nm size, were developed and successfully tested as nanocarriers for antitumor drugs.

Development of Multifunctional Liposomes Containing Magnetic/Plasmonic MnFe₂O₄/Au Core/Shell Nanoparticles

Multifunctional liposomes containing manganese ferrite/gold core/shell nanoparticles were developed. These magnetic/plasmonic nanoparticles were covered by a lipid bilayer or entrapped in liposomes, which form solid or aqueous magnetoliposomes as nanocarriers for simultaneous chemotherapy and phototherapy. The core/shell nanoparticles were characterized by UV/Visible absorption, X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Superconducting Quantum Interference Device (SQUID). The magnetoliposomes were characterized by Dynamic Light Scattering (DLS) and TEM. Fluorescence-based techniques (FRET, steady-state emission, and anisotropy) investigated the incorporation of a potential anti-tumor drug (a thienopyridine derivative) in these nanosystems. The core/shell nanoparticles exhibit sizes of 25 ± 2 nm (from TEM), a plasmonic absorption band (λ_max = 550 nm), and keep magnetic character. XRD measurements allowed for the estimation of 13.3 nm diameter for manganese ferrite core and 11.7 nm due to the gold shell. Aqueous magnetoliposomes, with hydrodynamic diameters of 152 ± 18 nm, interact with model membranes by fusion and are able to transport the anti-tumor compound in the lipid membrane, with a high encapsulation efficiency (EE(%) = 98.4 ± 0.8). Solid magnetoliposomes exhibit hydrodynamic diameters around 140 nm and also carry successfully the anticancer drug (with EE (%) = 91.2 ± 5.2), while also being promising as agents for phototherapy. The developed multifunctional liposomes can be promising as therapeutic agents for combined chemo/phototherapy.

Magnetoliposomes containing magnesium ferrite nanoparticles as nanocarriers for the model drug curcumin

Magnesium ferrite nanoparticles, with diameters around 25 nm, were synthesized by coprecipitation method. The magnetic properties indicate a superparamagnetic behaviour, with a maximum magnetization of 16.2 emu g-1, a coercive field of 22.1 Oe and a blocking temperature of 183.2 K. These MgFe2O4 nanoparticles were used to produce aqueous and solid magnetoliposomes, with sizes below 130 nm. The potential drug curcumin was successfully incorporated in these nanosystems, with high encapsulation efficiencies (above 89%). Interaction by fusion between both types of drug-loaded magnetoliposomes (with or without PEGylation) and models of biological membranes was demonstrated, using FRET or fluorescence quenching assays. These results point to future applications of magnetoliposomes containing MgFe2O4 nanoparticles in cancer therapy, allowing combined magnetic hyperthermia and chemotherapy.

Magnetogels: Prospects and Main Challenges in Biomedical Applications

Drug delivery nanosystems have been thriving in recent years as a promising application in therapeutics, seeking to solve the lack of specificity of conventional chemotherapy targeting and add further features such as enhanced magnetic resonance imaging, biosensing and hyperthermia. The combination of magnetic nanoparticles and hydrogels introduces a new generation of nanosystems, the magnetogels, which combine the advantages of both nanomaterials, apart from showing interesting properties unobtainable when both systems are separated. The presence of magnetic nanoparticles allows the control and targeting of the nanosystem to a specific location by an externally applied magnetic field gradient. Moreover, the application of an alternating magnetic field (AMF) not only allows therapy through hyperthermia, but also enhances drug delivery and chemotherapeutic desired effects, which combined with the hydrogel specificity, confer a high therapeutic efficiency. Therefore, the present review summarizes the magnetogels properties and critically discusses their current and recent biomedical applications, apart from an outlook on future goals and perspectives.

Self-assembled RGD dehydropeptide hydrogels for drug delivery applications

Peptide-based self-assembled hydrogels have triggered remarkable research interest in recent years owing to their biocompatibility and biomimetic properties and responsiveness, which warrant many technological and biomedical applications. Dehydrodipeptides N-capped with naproxen emerged from our research as effective hydrogelators endowed with resistance to proteolysis. Dehydrodipeptide-based hydrogels are promising nanocarriers for drug delivery applications. In this work, we demonstrate that dehydrodipetide Npx-l-Ala-Z-ΔPhe-OH can be deployed as a minimalist hydrogelator module for synthesizing a gelating construct Npx-l-Ala-Z-ΔPhe-G-R-G-D-G-OH bearing a GRGDG adhesion motif. The self-assembly of the peptide construct and the drug delivery properties of the hydrogel were studied in this work. The peptide construct showed no toxicity towards a fibroblast cell line expressing the α_vβ₃ integrin. Docking studies suggest that the hydrogelator block does not interfere with the recognition of the RGD motif by the integrin receptor. The self-assembly seems to be directed by intermolecular naphthalene π-π stacking interactions, with the peptide backbone assuming a random coil conformation both in solution and in the gel phase. TEM and STEM imaging revealed that the hydrogel is made of entangled bundles of long thin fibres (width circa 23 nm). The hydrogel exhibits viscoelastic properties, thermo-reversibility and recovery after mechanical fluidization. FRET studies showed that curcumin incorporated into the hydrogel interacts non-covalently with the hydrogel fibrils. Delivery of curcumin from the hydrogel into Nile red loaded model membranes (SUVs) was demonstrated by FRET. Naproxen N-capped dehydrodipeptides are efficacious minimalist hydrogelator modules for obtaining hydrogels functionalized with peptide ligands for cell receptors. These hydrogels are potential nanocarriers for drug delivery.

Magnetoliposomes as carriers for promising antitumor thieno[3,2-b]pyridin-7-arylamines: photophysical and biological studies

Magnetoliposomes containing MnFe₂O₄ nanoparticles were used as nanocarriers for new potent antitumor thieno[3,2-b]pyridin-7-arylamines, inhibiting the growth of human tumor cells.

Magnetoliposomes based on manganese ferrite nanoparticles as nanocarriers for antitumor drugs

Aqueous and solid magnetoliposomes containing MnFe₂O₄ nanoparticles were prepared and evaluated as nanocarriers for a new antitumor drug.

Interaction of fluorescent quinolin-2-one and coumarin derivatives including dipeptides with lipid bilayers

The interaction with lipid bilayers of a quinolin-2-one and a coumarin including dipeptides was investigated through fluorescence and DLS measurements.

Dehydrodipeptide Hydrogelators Containing Naproxen N-Capped Tryptophan: Self-Assembly, Hydrogel Characterization, and Evaluation as Potential Drug Nanocarriers

In this work, we introduce dipeptides containing tryptophan N-capped with the nonsteroidal anti-inflammatory drug naproxen and C-terminal dehydroamino acids, dehydrophenylalanine (ΔPhe), dehydroaminobutyric acid (ΔAbu), and dehydroalanine (ΔAla) as efficacious protease resistant hydrogelators. Optimized conditions for gel formation are reported. Transmission electron microscopy experiments revealed that the hydrogels consist of networks of micro/nanosized fibers formed by peptide self-assembly. Fluorescence and circular dichroism spectroscopy indicate that the self-assembly process is driven by stacking interactions of the aromatic groups. The naphthalene groups of the naproxen moieties are highly organized in the fibers through chiral stacking. Rheological experiments demonstrated that the most hydrophobic peptide (containing C-terminal ΔPhe) formed more elastic gels at lower critical gelation concentrations. This gel revealed irreversible breakup, while the C-terminal ΔAbu and ΔAla gels, although less elastic, exhibited structural recovery and partial healing of the elastic properties. A potential antitumor thieno[3,2-b]pyridine derivative was incorporated (noncovalently) into the gel formed by the hydrogelator containing C-terminal ΔPhe residue. Fluorescence and Förster resonance energy transfer measurements indicate that the drug is located in a hydrophobic environment, near/associated with the peptide fibers, establishing this type of hydrogel as a good drug-nanocarrier candidate.

New self-assembled supramolecular hydrogels based on dehydropeptides

Supramolecular hydrogels rely on small molecules that self-assemble in water as a result of the cooperative effect of several relatively weak intermolecular interactions. Peptide-based low molecular weight hydrogelators have attracted enormous interest owing to the simplicity of small molecules combined with the versatility and biocompatibility of peptides. In this work, naproxen, a well known non-steroidal anti-inflammatory drug, was N-conjugated with various dehydrodipeptides to give aromatic peptide amphiphiles that resist proteolysis. Molecular dynamics simulations were used to obtain insight into the underlying molecular mechanism of self-assembly and to rationalize the design of this type of hydrogelators. The results obtained were in excellent agreement with the experimental observations. Only dehydrodipeptides having at least one aromatic amino acid gave hydrogels. The characterization of the hydrogels was carried out using transmission electron microscopy (TEM), circular dichroism (CD), fluorescence spectroscopy and also rheological assays.

Magnetic liposomes based on nickel ferrite nanoparticles for biomedical applications

Aqueous and dry magnetoliposomes containing NiFe₂O₄ nanoparticles were prepared using a new method and fusion with model membranes was demonstrated.

A new antitumoral Heteroarylaminothieno[3,2-b]pyridine derivative: its incorporation into liposomes and interaction with proteins monitored by fluorescence

The fluorescence properties of the new potent antitumoral methyl 3-amino-6-(benzo[d]thiazol-2-ylamino)thieno[3,2-b]pyridine-2-carboxylate in solution and when encapsulated in several different nanoliposome formulations were investigated. The compound exhibits very reasonable fluorescence quantum yields and a solvent sensitive emission in several polar and non-polar media, despite not being fluorescent in protic solvents. Fluorescence anisotropy measurements of the compound incorporated into liposomes revealed that this thienopyridine derivative can be carried in the hydrophobic region of the lipid membrane. Liposome formulations including this antitumor compound are nanometric in size, with a diameter lower than 130 nm and generally low polydispersity, and are promising for future drug delivery developments. The interaction of the compound with bovine serum albumin (BSA) and the multidrug resistance protein MDR1 was monitored by FRET, the compound acting as an energy acceptor. It was observed that the drug had a lower interaction with the MDR1 protein than with the native form of BSA, which is an important result regarding applications of this antitumoral drug.

Comparison of IgA, TNF-α and surface tension of the tear film in two different times of the day

PURPOSE

The main goal was to study the biochemical composition of the tear film in two different times of the day.

METHODS

Tear samples were collected from 10 individuals, non contact lenses wearers, from the university population without pathologies. To assess daily variations in the tear film, samples were collected twice in the day, one early in the morning and another in the evening using capillary tubes. Tear protein profile was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), tumor necrosis factor α (TNF-α) and immunoglobulin A (IgA) were quantified by Enzyme-Linked ImmunoSorbent Assay (ELISA). Tear film stability was obtained through measurements of Non-Invasive Break Up Time and tear surface tension was measured by obtaining the Langmuir isotherms.

RESULTS

The stability of the tear film was higher in the morning than in the afternoon; corresponding to a higher value of surface tension in the afternoon. Protein electrophoresis tear profile is variable during the day as IgA concentration decreased from morning to afternoon (p<0.05). TNF-α concentration also decreased, but there were not significant statistical differences (p=0.089).

CONCLUSION

We concluded that there are daily variations in the composition and properties of the tear film, indicating that changes occur without being caused by contact lenses wear or by the presence of ocular and systemic pathologies. Presence of TNF-α is not a direct indication of inflammatory pathology, since this cytokine was identified in relatively high amounts in subjects without inflammatory pathology.

Aggregation behavior of aqueous dioctadecyldimethylammonium bromide/monoolein mixtures: a multitechnique investigation on the influence of composition and temperature

A recently described non-viral gene delivery system [dioctadecyldimethylammonium bromide (DODAB)/monoolein (MO)] has been studied in detail to improve knowledge on the interactions between lamellar (DODAB) and non-lamellar-forming (MO) lipids, as a means to enhance their final cell transfection efficiency. Indeed, the morphology, fluidity, and size of these cationic surfactant/neutral lipid mixtures play an important role in the ability of these systems to complex nucleic acids. The different techniques used in this work, namely dynamic light scattering (DLS), fluorescence spectroscopy, differential scanning calorimetry (DSC), cryogenic transmission electron microscopy (cryo-TEM), light microscopy (LM), and surface pressure-area isotherms, allowed fully characterization of the phase behavior and aggregate morphology of DODAB/MO mixtures at different molar ratios. Overall, the results indicate that the final morphology of DODAB/MO aggregates depends on the balance between the tendency of DODAB to form zero-curvature bilayer structures and the propensity of MO to form non-bilayer structures with negative curvature. These results also show that in the MO-rich region, an increase in temperature has a similar effect on aggregate morphology as an increase in MO concentration.

Study of the release of a microencapsulated acid dye in polyamide dyeing using mixed cationic liposomes

The main objective of this work was to increase the retarding effect of the acid dye Telon(®) Blue RR (C.I. Acid Blue 62; DyStar, Frankfurt, Germany) release on polyamide fibres dyeing by encapsulation of the dye in liposomes as an alternative to synthetic auxiliaries, in order to reduce effluent pollution. The retarding effect achieved with the use of mixed cationic liposomes of dioctadecyldimethylammonium bromide (DODAB)/soybean lecithin (containing a 10% molar fraction of DODAB) was better in comparison with either pure soybean lecithin liposomes or synthetic auxiliaries. The retarding effect of liposomes on the dye release was analysed through changes in the absorption and fluorescence spectra of the acid dye at different conditions. The effect of temperature (in the range of 25 °C - 70 °C) on the spectroscopic behaviour of the dye in the absence and in presence of polyamide was also studied, in order to simulate the dyeing conditions. Exhaustion curves obtained in dyeing experiments showed that, below 45 °C, the retarding effect of the mixed liposomes (lecithin/DODAB (9:1)) was similar to that of the auxiliaries, but better than the one of pure lecithin liposomes. At higher temperatures (above 45 °C), the system lecithin/DODAB presents a better performance, achieving a higher final exhaustion level when compared with the commercial leveling agent without losing the smoothing effect of lecithin.