A New Methodology to Create Polymeric Nanocarriers Containing Hydrophilic Low Molecular-Weight Drugs: A Green Strategy Providing a Very High Drug Loading.

To date, a large number of active molecules are hydrophilic and aromatic low molecular-weight drugs (HALMD). Unfortunately, the low capacity of these molecules to interact with excipients and the fast release when a formulation containing them is exposed to biological media jeopardize the elaboration of drug delivery systems by using noncovalent interactions. In this work, a new, green, and highly efficient methodology to noncovalently attach HALMD to hydrophilic aromatic polymers to create nanocarriers is presented. The proposed method is simple and consists in mixing an aqueous solution containing HALMD (model drugs: imipramine, amitriptyline, or cyclobenzaprine) with another aqueous solution containing the aromatic polymer [model polymer: poly(sodium 4-styrenesulfonate) (PSS)]. NMR experiments demonstrate strong chemical shifting of HALMD aromatic rings when interacting with PSS, evidencing aromatic-aromatic interactions. Ion pair formation and aggregation produce the collapse of the system in the form of nanoparticles. The obtained nanocarriers are spheroidal, their size ranging between 120 and 170 nm, and possess low polydispersity (≤0.2) and negative zeta potential (from -60 to -80 mV); conversely, the absence of the aromatic group in the polymer does not allow the formation of nanostructures. Importantly, in addition to high drug association efficiencies (≥90%), the formed nanocarriers show drug loading values never evidenced for other systems comprising HALMD, reaching ≈50%. Diafiltration and stopped flow experiments evidenced kinetic drug entrapment governed by molecular rearrangements. Importantly, the nanocarriers are stable in suspension for at least 18 days and are also stable when exposed to different high ionic strength, pH, and temperature values. Finally, they are transformable to a reconstitutable dry powder without losing their original characteristics. Considering the large quantity of HALMD with importance in therapeutics and the simplicity of the presented strategy, we envisage these results as the basis to elaborate a number of drug delivery systems with applications in different pathologies.

Therapeutic potential of a low-cost device for wound healing: a study of three cases of healing after lower-extremity amputation in patients with diabetes.

Diabetic foot ulcers constitute a tremendous challenge for patients, caregivers, and health care systems. The high incidence and high financial costs associated with their treatment have transformed them in a health and economic worldwide problem. The increase in population life expectancy and lifestyle changes have facilitated the spreading of diabetes, rising diabetic foot ulcer incidence. Only 60%-80% of the patients achieve healing of ulcers, and the incidence of a second ulcer, in the same or different site of the foot that has had a previous ulcer, is approximately 50% in 2-5 years. In addition, ulcers with duration longer than 4 weeks are commonly associated with bad results in healing and an increased risk of amputation. Three patients with type 2 diabetes mellitus have been subjected to treatment with NL.1.2, a low-cost, biocompatible solid device that presented pro-angiogenic properties. The selected patients had undergone amputation, and their wounds, classified as Wagner II, did not show a significant progress in healing after a period of 2-5 months before treatment with NL.1.2. Complete closure of their wounds was achieved in 42-60 days.

The key role of the drug self-aggregation ability to obtain optimal nanocarriers based on aromatic-aromatic drug-polymer interactions.

The efficient association and controlled release of hydrophilic and aromatic low molecular-weight drugs (HALMD) still remains a challenge due to their relatively weak interactions with excipients and strong affinity to water. Considering that a wide variety of drugs to treat chronic diseases are HALMD, their inclusion in polymeric nanoparticles (NPs) constitutes an attractive possibility by providing to these drugs with controllable physiochemical properties, preventing crisis episodes, decreasing dose-dependent side effects and promoting therapeutic adhesiveness. However, the strong interaction of HALMD with the aqueous medium jeopardizes their encapsulation and controlled release. In this work, the role of the self-assembly tendency of HALMD on their association with the aromatic excipient poly(sodium 4-styrensulfonate) (PSS) to form NPs is studied. For this aim, the widely used drugs amitriptyline (AMT), promethazine (PMZ), and chlorpheniramine (CPM) are selected due to their well described critical aggregation concentration (cac) (36 mM for AMT, 36 mM for PMZ, and 69.5 mM for CPM). These drugs undergo aromatic-aromatic interactions with the polymer, which stabilize their mutual binding, as seen by NMR. The simple mixing of solutions of opposite charged molecules (drug + PSS) allowed obtaining NPs. Importantly, comparing the three drugs, the formation of NPs occurred at significantly lower absolute concentration and significantly lower drug/polymer ratio as the cac takes lower values, indicating a stronger binding to the polymer, as also deduced from the respective drug/polymer dissociation constant values. In addition, the number of formed NPs is similar for all formulations, even though a much lower concentration of the drug and polymer is present in systems comprising lower cac. The obtained NPs are spheroidal and present size between 100 and 160 nm, low polydispersity (≤0.3) and negative zeta potential (from -30 to -60 mV). The association efficiency reaches values ≥ 83% and drug loading could achieve values up to 68% (never evidenced before for systems comprising HALMD). In addition, drug release studies are also significantly influenced by cac, providing more prolonged release for AMT and PMZ (lower cac), whose delivery profiles adjust to the Korsmeyer-Peppas equation. As a novelty of this work, a synergic contribution of drug self-association tendency and aromatic-aromatic interaction between the drug and polymers is highlighted, a fact that could be crucial for the rational design and development of efficient drug delivery systems.

Ionic Nanocomplexes of Hyaluronic Acid and Polyarginine to Form Solid Materials: A Green Methodology to Obtain Sponges with Biomedical Potential.

We report on the design, development, characterization, and a preliminary cellular evaluation of a novel solid material. This material is composed of low-molecular-weight hyaluronic acid (LMWHA) and polyarginine (PArg), which generate aqueous ionic nanocomplexes (INC) that are then freeze-dried to create the final product. Different ratios of LMWHA/PArg were selected to elaborate INC, the size and zeta potential of which ranged from 100 to 200 nm and +25 to -43 mV, respectively. Turbidimetry and nanoparticle concentration analyses demonstrated the high capacity of the INC to interact with increasing concentrations of LMWHA, improving the yield of production of the nanostructures. Interestingly, once the selected formulations of INC were freeze-dried, only those comprising a larger excess of LMWHA could form reproducible sponge formulations, as seen with the naked eye. This optical behavior was consistent with the scanning transmission electron microscopy (STEM) images, which showed a tendency of the particles to agglomerate when an excess of LMWHA was present. Mechanical characterization evidenced low stiffness in the materials, attributed to the low density and high porosity. A preliminary cellular evaluation in a fibroblast cell line (RMF-EG) evidenced the concentration range where swollen formulations did not affect cell proliferation (93-464 µM) at 24, 48, or 72 h. Considering that the reproducible sponge formulations were elaborated following inexpensive and non-contaminant methods and comprised bioactive components, we postulate them with potential for biomedical purposes. Additionally, this systematic study provides important information to design reproducible porous solid materials using ionic nanocomplexes.

Aerogels made of chitosan and chondroitin sulfate at high degree of neutralization: Biological properties toward wound healing.

In this study, highly neutralized, highly porous, and ultralight polymeric aerogels prepared from aqueous colloidal suspensions of chitosan (CS) and chondroitin sulfate (ChS) nanocomplexes, formulated as quasi-equimolar amounts of both, are described. These aerogels were designed as healing agents under the inspiration of minimizing the amount of matter applied to wounds, reducing the electrostatic potential of the material and avoiding covalent cross-linkers in order to decrease metabolic stress over wounds. Aerogels synthesized under these criteria are biocompatible and provide specific properties for the induction of wound healing. They do not affect neither the metabolic activity of cultured 3T3 fibroblasts nor the biochemical parameters of experimental animals, open wounds close significantly faster and, unlike control wounds, complete reepithelialization and scarring can be attained 14 days after surgery. Because of its hydration abilities, rapid adaptation to the wound bed and the early accelerator effect of wound closure, the CS/ChS aerogels appear to be functional inducers of the healing. Previous information show that CS/ChS aerogels improve wound bed quality, increase granulation tissue and have pain suppressive effect. CS/ChS aerogels are useful as safe, inexpensive and easy to handle materials for topical applications, such as skin chronic wounds. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2464-2471, 2018.

Hyaluronan nanocapsules as a new vehicle for intracellular drug delivery.

Here we report the development of new drug nanocarriers - named hyaluronan nanocapsules - for the intracellular delivery of hydrophobic anticancer drugs. These nanocapsules are composed of a lipid core and a shell of hyaluronic acid (HA). Nanocapsules were produced by a modified solvent displacement technique, which allows the formation of the polymer shell around the oily core using a cationic surfactant as an interphase bridge. The resulting nanocapsules have a size of ∼200 nm, a negative zeta potential and a spherical shape. The model drug docetaxel could be efficiently encapsulated within their core. The in vitro cell culture studies (NCI-H460 cancer cell line) showed that the cytotoxicity of docetaxel could be significantly enhanced due to its encapsulation within the nanocapsules. Interestingly, the nanocapsules were stable during storage and they could also be transformed into a powder by freeze-drying. These novel nanostructures hold promise as intracellular drug delivery systems.

A potential nanomedicine consisting of heparin-loaded polysaccharide nanocarriers for the treatment of asthma.

A new nanomedicine consisting of chitosan/carboxymethyl-ß-cyclodextrin loaded with unfractioned or low-molecular-weight heparin is described and its potential in asthma treatment is evaluated. The nanoparticles are prepared by ionotropic gelation showing a size that between 221 and 729 nm with a positive zeta potential. The drug association efficiency is higher than 70%. Developed nanosystems are stable in Hank's balanced salt solution at pH = 6.4, releasing the drug slowly. Ex vivo assays show that nanocarriers lead to an improvement of heparin preventing mast cell degranulation. These results agree with the effective cellular internalization of the fluorescently labeled nanocarriers, and suggest these nanomedicines as promising formulations for asthma treatment.

A new drug nanocarrier consisting of polyarginine and hyaluronic acid.

The purpose of this study was to produce and characterize a variety of nanostructures comprised of the polyaminoacid polyarginine (PArg) and the polysaccharide hyaluronic acid (HA) as a preliminary stage before evaluating their potential application in drug delivery. PArg was combined with high- or low-molecular-weight HA (HMWHA or LMWHA, respectively) to form nanoparticles by simply mixing polymeric aqueous solutions at room temperature. The average size of the resulting nanocarriers was between 116 and 155 nm, and their zeta potential value ranged from +31.3 to -35.9 mV, indicating that the surface composition of the particle could be conveniently modified according to the mass ratio of the polymers. Importantly, the systems prepared with HMWHA remained stable after isolation by centrifugation and in conditions that mimic the physiological medium, whereas particles that incorporated LMWHA were unstable. Transmission electron microscopy showed that the nanostructures made with HMWHA were spherical. Finally, the systems were stable for at least three months at storage conditions (4°C).