Prussian Blue: A Safe Pigment with Zeolitic-Like Activity.

Prussian blue (PB) and PB analogues (PBA) are coordination network materials that present important similarities with zeolites concretely with their ability of adsorbing cations. Depending on the conditions of preparation, which is cheap and easy, PB can be classified into soluble PB and insoluble PB. The zeolitic-like properties are mainly inherent to insoluble form. This form presents some defects in its cubic lattice resulting in an open structure. The vacancies make PB capable of taking up and trapping ions or molecules into the lattice. Important adsorption characteristics of PB are a high specific area (370 m2 g-1 determined according the BET theory), uniform pore diameter, and large pore width. PB has numerous applications in many scientific and technological fields. PB are assembled into nanoparticles that, due to their biosafety and biocompatibility, can be used for biomedical applications. PB and PBA have been shown to be excellent sorbents of radioactive cesium and radioactive and nonradioactive thallium. Other cations adsorbed by PB are K+, Na+, NH4+, and some divalent cations. PB can also capture gaseous molecules, hydrocarbons, and even luminescent molecules such as 2-aminoanthracene. As the main adsorptive application of PB is the selective removal of cations from the environment, it is important to easily separate the sorbent of the purified solution. To facilitate this, PB is encapsulated into a polymer or coats a support, sometimes magnetic particles. Finally, is remarkable to point out that PB can be recycled and the adsorbed material can be recovered.

Superparamagnetic Nanoparticles with Efficient Near-Infrared Photothermal Effect at the Second Biological Window.

Superparamagnetic nanoparticles (iron oxide nanoparticles-IONs) are suitable for hyperthermia after irradiating with radiofrequency radiation. Concerning the suitability for laser ablation, IONs present a low molar absorption coefficient in the near-infrared region close to 800 nm. For this reason, they are combined with other photothermal agents into a hybrid composite. Here, we show that IONs absorb and convert into heat the infrared radiation characteristic of the so-called second-biological window (1000-1350 nm) and, in consequence, they can be used for thermal ablation in such wavelengths. To the known excellent water solubility, colloidal stability and biocompatibility exhibited by IONs, an outstanding photothermal performance must be added. For instance, a temperature increase of 36 °C was obtained after irradiating at 8.7 W cm-2 for 10 min a suspension of IONs at iron concentration of 255 mg L-1. The photothermal conversion efficiency was ~72%. Furthermore, IONs showed high thermogenic stability during the whole process of heating/cooling. To sum up, while the use of IONs in the first bio-window (700-950 nm) presents some concerns, they appear to be good photothermal agents in the second biological window.

Facile Synthesis of Novel Prussian Blue-Lipid Nanocomplexes.

Prussian blue (PB) is known for its multiple applications ranging from fine arts to therapeutics. More recently, PB nanoparticles have been pointed to as appealing photothermal agents (PA) when irradiated with wavelengths corresponding to the biological windows, namely regions located in the near infrared (NIR) zone. In addition, the combination of PB with other components such as phospholipids boosts their therapeutical potential by facilitating, for instance, the incorporation of drugs becoming suitable drug delivery systems. The novelty of the research relies on the synthesis procedure and characterization of hybrid lipid-PB nanoparticles with a high yield in a friendly environment suitable for photothermal therapy. This goal was achieved by first obtaining insoluble PB coated with oleylamine (OA) to facilitate its combination with lipids. The resulting lipid-PB complex showed a monomodal distribution of sizes with an overall size of around 100 nm and a polydispersity index of about 0.200. It highlights one critical step in the synthesis procedure that is the shaking time of the mixture of PB-OA nanoparticles with the lipid, which was found to be 48 h. This time assured homogeneous preparation without the need of further separation stages. Samples were stable for more than three months under several storage conditions.

Iron Oxide Nanoparticles in Photothermal Therapy.

Photothermal therapy is a kind of therapy based on increasing the temperature of tumoral cells above 42 °C. To this aim, cells must be illuminated with a laser, and the energy of the radiation is transformed in heat. Usually, the employed radiation belongs to the near-infrared radiation range. At this range, the absorption and scattering of the radiation by the body is minimal. Thus, tissues are almost transparent. To improve the efficacy and selectivity of the energy-to-heat transduction, a light-absorbing material, the photothermal agent, must be introduced into the tumor. At present, a vast array of compounds are available as photothermal agents. Among the substances used as photothermal agents, gold-based compounds are one of the most employed. However, the undefined toxicity of this metal hinders their clinical investigations in the long run. Magnetic nanoparticles are a good alternative for use as a photothermal agent in the treatment of tumors. Such nanoparticles, especially those formed by iron oxides, can be used in combination with other substances or used themselves as photothermal agents. The combination of magnetic nanoparticles with other photothermal agents adds more capabilities to the therapeutic system: the nanoparticles can be directed magnetically to the site of interest (the tumor) and their distribution in tumors and other organs can be imaged. When used alone, magnetic nanoparticles present, in theory, an important limitation: their molar absorption coefficient in the near infrared region is low. The controlled clustering of the nanoparticles can solve this drawback. In such conditions, the absorption of the indicated radiation is higher and the conversion of energy in heat is more efficient than in individual nanoparticles. On the other hand, it can be designed as a therapeutic system, in which the heat generated by magnetic nanoparticles after irradiation with infrared light can release a drug attached to the nanoparticles in a controlled manner. This form of targeted drug delivery seems to be a promising tool of chemo-phototherapy. Finally, the heating efficiency of iron oxide nanoparticles can be increased if the infrared radiation is combined with an alternating magnetic field.

Liposomes Loaded with Hydrophobic Iron Oxide Nanoparticles: Suitable T2 Contrast Agents for MRI.

There has been a recent surge of interest in the use of superparamagnetic iron oxide nanoparticles (SPIONs) as contrast agents (CAs) for magnetic resonance imaging (MRI), due to their tunable properties and their low toxicity compared with other CAs such as gadolinium. SPIONs exert a strong influence on spin-spin T2 relaxation times by decreasing the MR signal in the regions to which they are delivered, consequently yielding darker images or negative contrast. Given the potential of these nanoparticles to enhance detection of alterations in soft tissues, we studied the MRI response of hydrophobic or hydrophilic SPIONs loaded into liposomes (magnetoliposomes) of different lipid composition obtained by sonication. These hybrid nanostructures were characterized by measuring several parameters such as size and polydispersity, and number of SPIONs encapsulated or embedded into the lipid systems. We then studied the influence of acyl chain length as well as its unsaturation, charge, and presence of cholesterol in the lipid bilayer at high field strength (7 T) to mimic the conditions used in preclinical assays. Our results showed a high variability depending on the nature of the magnetic particles. Focusing on the hydrophobic SPIONs, the cholesterol-containing samples showed a slight reduction in r2, while unsaturation of the lipid acyl chain and inclusion of a negatively charged lipid into the bilayer appeared to yield a marked increase in negative contrast, thus rendering these magnetoliposomes suitable candidates as CAs, especially as a liver CA.

Iron oxide nanoparticles for magnetically-guided and magnetically-responsive drug delivery.

In this review, we discuss the recent advances in and problems with the use of magnetically-guided and magnetically-responsive nanoparticles in drug delivery and magnetofection. In magnetically-guided nanoparticles, a constant external magnetic field is used to transport magnetic nanoparticles loaded with drugs to a specific site within the body or to increase the transfection capacity. Magnetofection is the delivery of nucleic acids under the influence of a magnetic field acting on nucleic acid vectors that are associated with magnetic nanoparticles. In magnetically-responsive nanoparticles, magnetic nanoparticles are encapsulated or embedded in a larger colloidal structure that carries a drug. In this last case, an alternating magnetic field can modify the structure of the colloid, thereby providing spatial and temporal control over drug release.

Application of heparin as a dual agent with antimalarial and liposome targeting activities toward Plasmodium-infected red blood cells.

Heparin had been demonstrated to have antimalarial activity and specific binding affinity for Plasmodium-infected red blood cells (pRBCs) vs. non-infected erythrocytes. Here we have explored if both properties could be joined into a drug delivery strategy where heparin would have a dual role as antimalarial and as a targeting element of drug-loaded nanoparticles. Confocal fluorescence and transmission electron microscopy data show that after 30 min of being added to living pRBCs fluorescein-labeled heparin colocalizes with the intracellular parasites. Heparin electrostatically adsorbed onto positively charged liposomes containing the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane and loaded with the antimalarial drug primaquine was capable of increasing three-fold the activity of encapsulated drug in Plasmodium falciparum cultures. At concentrations below those inducing anticoagulation of mouse blood in vivo, parasiticidal activity was found to be the additive result of the separate activities of free heparin as antimalarial and of liposome-bound heparin as targeting element for encapsulated primaquine. FROM THE CLINICAL EDITOR: Malaria remains an enormous global public health concern. In this study, a novel functionalized heparin formulation used as drug delivery agent for primaquine was demonstrated to result in threefold increased drug activity in cell cultures, and in a murine model it was able to provide these benefits in concentrations below what would be required for anticoagulation. Further studies are needed determine if this approach is applicable in the human disease as well.

In Vivo Assays for Amyloid-Related Diseases.

Amyloid-related diseases, such as Alzheimer's and Parkinson's disease, are devastating conditions caused by the accumulation of abnormal protein aggregates known as amyloid fibrils. While assays involving animal models are essential for understanding the pathogenesis and developing therapies, a wide array of standard analytical techniques exists to enhance our understanding of these disorders. These techniques provide valuable information on the formation and propagation of amyloid fibrils, as well as the pharmacokinetics and pharmacodynamics of candidate drugs. Despite ethical concerns surrounding animal use, animal models remain vital tools in the search for treatments. Regardless of the specific animal model chosen, the analytical methods used are usually standardized. Therefore, the main objective of this review is to categorize and outline the primary analytical methods used in in vivo assays for amyloid-related diseases, highlighting their critical role in furthering our understanding of these disorders and developing effective therapies.

Proximity-Induced Pharmacology for Amyloid-Related Diseases.

Proximity-induced pharmacology (PIP) for amyloid-related diseases is a cutting-edge approach to treating conditions such as Alzheimer's disease and other forms of dementia. By bringing small molecules close to amyloid-related proteins, these molecules can induce a plethora of effects that can break down pathogenic proteins and reduce the buildup of plaques. One of the most promising aspects of this drug discovery modality is that it can be used to target specific types of amyloid proteins, such as the beta-amyloid protein that is commonly associated with Alzheimer's disease. This level of specificity could allow for more targeted and effective treatments. With ongoing research and development, it is hoped that these treatments can be refined and optimized to provide even greater benefits to patients. As our understanding of the underlying mechanisms of these diseases continues to grow, proximity-induced pharmacology treatments may become an increasingly important tool in the fight against dementia and other related conditions.

Trioleyl Pyridinium, a Cationic Transfection Agent for the Lipofection of Therapeutic Oligonucleotides into Mammalian Cells.

BACKGROUND: One of the most significant limitations that therapeutic oligonucleotides present is the development of specific and efficient delivery vectors for the internalization of nucleic acids into cells. Therefore, there is a need for the development of new transfection agents that ensure a proper and efficient delivery into mammalian cells. METHODS: We describe the synthesis of 1,3,5-tris[(4-oelyl-1-pyridinio)methyl]benzene tribromide (TROPY) and proceeded to the validation of its binding capacity toward oligonucleotides, the internalization of DNA into the cells, the effect on cell viability, apoptosis, and its capability to transfect plasmid DNA. RESULTS: The synthesis and chemical characterization of TROPY, which can bind DNA and transfect oligonucleotides into mammalian cells through clathrin and caveolin-mediated endocytosis, are described. Using a PPRH against the antiapoptotic survivin gene as a model, we validated that the complex TROPY-PPRH decreased cell viability in human cancer cells, increased apoptosis, and reduced survivin mRNA and protein levels. TROPY was also able to stably transfect plasmid DNA, as demonstrated by the formation of viable colonies upon the transfection of a dhfr minigene into dhfr-negative cells and the subsequent metabolic selection. CONCLUSIONS: TROPY is an efficient transfecting agent that allows the delivery of therapeutic oligonucleotides, such as PPRHs and plasmid DNA, inside mammalian cells.

Three to Tango: Inhibitory Effect of Quercetin and Apigenin on Acetylcholinesterase, Amyloid-ß Aggregation and Acetylcholinesterase-Amyloid Interaction.

One of the pathological hallmarks of Alzheimer's disease (AD) is the formation of amyloid-ß plaques. Since acetylcholinesterase (AChE) promotes the formation of such plaques, the inhibition of this enzyme could slow down the progression of amyloid-ß aggregation, hence being complementary to the palliative treatment of cholinergic decline. Antiaggregation assays performed for apigenin and quercetin, which are polyphenolic compounds that exhibit inhibitory properties against the formation of amyloid plaques, reveal distinct inhibitory effects of these compounds on Aß40 aggregation in the presence and absence of AChE. Furthermore, the analysis of the amyloid fibers formed in the presence of these flavonoids suggests that the Aß40 aggregates present different quaternary structures, viz., smaller molecular assemblies are generated. In agreement with a noncompetitive inhibition of AChE, molecular modeling studies indicate that these effects may be due to the binding of apigenin and quercetin at the peripheral binding site of AChE. Since apigenin and quercetin can also reduce the generation of reactive oxygen species, the data achieved suggest that multitarget catechol-type compounds may be used for the simultaneous treatment of various biological hallmarks of AD.

Activity of Antibiotics and Potential Antibiofilm Agents against Biofilm-Producing Mycobacterium avium-intracellulare Complex Causing Chronic Pulmonary Infections.

Nontuberculous mycobacteria (NTM) cause lung infections in patients with underlying pulmonary diseases (PD). The Mycobacteriumavium-intracellulare complex (MAC) is the most frequently involved NTM. The MAC-PD treatment is based on the administration of several antibiotics for long periods of time. Nonetheless, treatment outcomes remain very poor. Among the factors involved is the ability of MAC isolates to form biofilm. The aim of the study was to assess the in vitro activity of different antibiotics and potential antibiofilm agents (PAAs) against MAC biofilm. Four antibiotics and six PAAs, alone and/or in combination, were tested against planktonic forms of 11 MAC clinical isolates. Biofilm was produced after 4 weeks of incubation and analyzed with the crystal violet assay. The antibiotics and PAAs were tested by measuring the absorbance (minimum biofilm inhibition concentrations, MBICs) and by performing subcultures (minimum biofilm eradication concentrations, MBECs). The clarithromycin/amikacin and clarithromycin/ethambutol combinations were synergistic, decreasing the MBECs values compared to the individual antibiotics. The amikacin/moxifloxacin combination showed indifference. The MBIC values decreased significantly when PAAs were added to the antibiotic combinations. These results suggest that antibiotic combinations should be further studied to establish their antibiofilm activity. Moreover, PAAs could act against the biofilm matrix, facilitating the activity of antibiotics.

Synthesis and validation of DOPY: A new gemini dioleylbispyridinium based amphiphile for nucleic acid transfection.

Nucleic acids therapeutics provide a selective and promising alternative to traditional treatments for multiple genetic diseases. A major obstacle is the development of safe and efficient delivery systems. Here, we report the synthesis of the new cationic gemini amphiphile 1,3-bis[(4-oleyl-1-pyridinio)methyl]benzene dibromide (DOPY). Its transfection efficiency was evaluated using PolyPurine Reverse Hoogsteen hairpins (PPRHs), a nucleic acid tool for gene silencing and gene repair developed in our laboratory. The interaction of DOPY with PPRHs was confirmed by gel retardation assays, and it forms complexes of 155 nm. We also demonstrated the prominent internalization of PPRHs using DOPY compared to other chemical vehicles in SH-SY5Y, PC-3 and DF42 cells. Regarding gene silencing, a specific PPRH against the survivin gene delivered with DOPY decreased survivin protein levels and cell viability more effectively than with N-[1-(2,3-Dioleoyloxy)propyl]-N,N,N-trimethylammonium methylsulfate (DOTAP) in both SH-SY5Y and PC-3 cells. We also validated the applicability of DOPY in gene repair approaches by correcting a point mutation in the endogenous locus of the dhfr gene in DF42 cells using repair-PPRHs. All these results indicate both an efficient entry and release of PPRHs at the intracellular level. Therefore, DOPY can be considered as a new lipid-based vehicle for the delivery of therapeutic oligonucleotides.

Targeting transthyretin in Alzheimer's disease: Drug discovery of small-molecule chaperones as disease-modifying drug candidates for Alzheimer's disease.

Transthyretin (TTR) has a well-established role in neuroprotection in Alzheimer's Disease (AD). We have setup a drug discovery program of small-molecule compounds that act as chaperones enhancing TTR/Amyloid-beta peptide (Aß) interactions. A combination of computational drug repurposing approaches and in vitro biological assays have resulted in a set of molecules which were then screened with our in-house validated high-throughput screening ternary test. A prioritized list of chaperones was obtained and corroborated with ITC studies. Small-molecule chaperones have been discovered, among them our lead compound Iododiflunisal (IDIF), a molecule in the discovery phase; one investigational drug (luteolin); and 3 marketed drugs (sulindac, olsalazine and flufenamic), which could be directly repurposed or repositioned for clinical use. Not all TTR tetramer stabilizers behave as chaperones in vitro. These chemically diverse chaperones will be used for validating TTR as a target in vivo, and to select one repurposed drug as a candidate to enter clinical trials as AD disease-modifying drug.

Prussian blue nanoparticles: synthesis, surface modification, and biomedical applications.

Prussian blue nanoparticles (PBNPs) are a nanomaterial that presents unique properties and an excellent biocompatibility. They can be synthesized in mild conditions and can be derivatized with polymers and/or biomolecules. PBNPs are used in biomedicine as therapy and diagnostic agents. In biomedical imaging, PBNPs constitute contrast agents in photoacoustic and magnetic resonance imaging (MRI). They are a good adsorbent to be used as antidotes for poisoning with cesium and/or thallium ions. Moreover, the ability to convert energy into heat makes them useful photothermal agents (PAs) in photothermal therapy (PTT) or as nonantibiotic substances with antibacterial properties. Finally, PBNPs can be both reduced to Prussian white and oxidized to Prussian green. A large window of redox potential exists between reduction and oxidation, which result in the enzyme-like characteristics of these NPs.

Flash tooth whitening: A friendly formulation based on a nanoencapsulated reductant.

Tooth whitening materials have not undergone relevant advances in the last years. Current materials base their action on the oxidant activity of peroxides, which present the disadvantage of requiring long application times, along with unpleasant side effects of dental hypersensitivity (e.g. sharp pain). In this work, a novel tooth whitening formulation based on the encapsulation of a reducing agent (sodium metabisulfite) in liposomes is developed. An experimental design was applied to optimize the formulation in terms of whitening action and safety, using bovine teeth as in vitro model. Results were obtained by colorimetry, profilometry and nanoindentation techniques. The comparison with standard whitening treatments showed a similar whitening action of the optimized formulation but in remarkable shorter application times. Moreover, teeth roughness values obtained with the presented formulation conformed with ISO 28399. As mechanism of action, results obtained from fluorescent confocal microscopy showed the liposomal formulation to form a layer surrounding the enamel surface, enhancing the treatment efficacy in terms of diffusion of the protected reductant towards the enamel. The better efficiency of this formulation encourages its use as an alternative to current oxidative treatments.

Bacterial Inclusion Bodies for Anti-Amyloid Drug Discovery: Current and Future Screening Methods.

Amyloid aggregation is linked to an increasing number of human disorders from nonneurological pathologies such as type-2 diabetes to neurodegenerative ones such as Alzheimer or Parkinson's diseases. Thirty-six human proteins have shown the capacity to aggregate into pathological amyloid structures. To date, it is widely accepted that amyloid folding/aggregation is a universal process present in eukaryotic and prokaryotic cells. In the last decade, several studies have unequivocally demonstrated that bacterial inclusion bodies - insoluble protein aggregates usually formed during heterologous protein overexpression in bacteria - are mainly composed of overexpressed proteins in amyloid conformation. This fact shows that amyloid-prone proteins display a similar aggregation propensity in humans and bacteria, opening the possibility to use bacteria as simple models to study amyloid aggregation process and the potential effect of both anti-amyloid drugs and pro-aggregative compounds. Under these considerations, several in vitro and in cellulo methods, which exploit the amyloid properties of bacterial inclusion bodies, have been proposed in the last few years. Since these new methods are fast, simple, inexpensive, highly reproducible, and tunable, they have aroused great interest as preliminary screening tools in the search for anti-amyloid (beta-blocker) drugs for conformational diseases. The aim of this mini-review is to compile recently developed methods aimed at tracking amyloid aggregation in bacteria, discussing their advantages and limitations, and the future potential applications of inclusion bodies in anti-amyloid drug discovery.

Magnetic Nanoemulsions: Comparison between Nanoemulsions Formed by Ultrasonication and by Spontaneous Emulsification.

Nanoemulsions are particularly suitable as a platform in the development of delivery systems. The type of nanoemulsion with a higher stability will offer an advantage in the preparation of a delivery system for lipophilic drugs. Nanoemulsions can be fabricated by different processing methods, which are usually categorized as either high- or low-energy methods. In this study, a comparison between two methods of preparing magnetic oil-in-water (O/W) nanoemulsions is described. The nanoemulsions were formed by sonication (the high-energy method) or by spontaneous emulsification (the low-energy method). In both cases, the oil phase was olive oil, and a phospholipid and a pegylated phospholipid were used as emulsifiers. To favor the comparison, the amounts of the components were the same in both kinds of nanoemulsions. Moreover, nanoemulsions were loaded with hydrophobic superparamagnetic nanoparticles and indomethacin. In vitro, releases studies indicated a short drug burst period followed by a prolonged phase of dissolutive drug release. The Korsmeyer-Peppas model can fit the associated kinetics. The results showed that such nanoemulsions are suitable as a platform in the development of delivering systems for lipophilic drugs. The long-term stability was also examined at different temperatures, as well as the interaction with plasma proteins. Nanoemulsion obtained by the low-energy method showed a great stability at 4 °C and at ambient temperature. Its size and polydispersity did not change over more than two months. The spontaneous emulsification method therefore has great potential for forming nanoemulsion-based delivery systems.

Effect of PEGylation on Ligand-Targeted Magnetoliposomes: A Missed Goal.

We tested the targeting efficiency of magnetoliposomes (MLPs) labeled with tripeptide arginine-glycine-aspartic acid (RGD) on two types of cells: HeLa cells expressing RGD receptors and 3T3 cells lacking RGD receptors. The targeting ability of RGD-MLPs was compared to that of bare MLPs and MLPs stabilized with poly(ethylene glycol) (PEG). Cellular internalization of these liposomes was determined by flow cytometry and confocal microscopy, which showed that both types of cells took up more nontargeting MLPs than targeting RGD-MLPs or PEG-MLPs, with PEG-MLPs showing the lowest degree of internalization. The presence of specific receptors on HeLa cells did not facilitate the binding of RGD-MLPs, probably due to the presence of PEG chains on the liposomal surface. The polymer increases the circulation time of the liposomes in the organism but reduces their interactions with cells. Despite the localization of the RGD peptide on the tip of PEG in RGD-MLPs, the interaction between the liposome and cell was still limited. To avoid this drawback, targeting drug delivery systems can be prepared with two types of PEG: one of a short length to enable biocompatibility and the other of a longer chain to carry the ligand.

Evidence of Protein Adsorption in Pegylated Liposomes: Influence of Liposomal Decoration.

In order to contribute to a better knowledge of the events involved in the formation of the protein corona when nanoparticles (NPs) come in contact with proteins, we report a study about the changes on the physicochemical properties of pristine, PEGylated and Cyclic Arginine-Glycine-Aspartate peptide (RGD)-functionalized large unilamelar liposomes (LUVs) or magnetoliposomes (MLs) upon incubation with Bovine Serum Albumin (BSA). The main phospholipid component of both LUVs and MLs was l-α-phosphatydylcholine (PC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) with 20% of cholesterol. The most obvious indication of the interaction of BSA-nanosystems is given by changes in the hydrodynamic diameter of the particles but other evidence is needed to corroborate the process. Our findings indicate that size modification is a process that is accomplished in few hours and that is strongly dependent not only on the surface decoration but also of the lipid composition of both LUVs and MLs. Fluorescence quenching experiments as well as cryogenic transmission electron microscopy (Cryo-TEM) images assessed these changes and confirmed that although each system has to be studied in a particular way, we can establish three distinctive features that turn into more reactive systems: (a) compositions containing PC compared with their DMPC counterparts; (b) the presence of PEG and/or RGD compared to the pristine counterparts; and (c) the presence of SPIONs: MLs show higher interaction than LUVs of the same lipid composition. Consequently, PEGylation (that is supposed to make stealth NPs) actually fails in preventing complete protein binding.