Opportunities and challenges for antimicrobial nanostructured materials in the management of skin infections

The management of skin and soft-tissue infections represents a burden for healthcare systems worldwide, demanding additional scientific efforts. Despite combined advances in modern medicine from different disciplines, chronic non-healing topical wounds still represent an unresolved clinical challenge. Nanotechnology has contributed significantly to the development of advanced therapeutic and diagnostic approaches in wound care. From this perspective, recommendations on the design of nano-based approaches for the management of infected non-healing chronic wounds are suggested. Preclinical results have demonstrated that nanostructured antimicrobial-loaded dressings and hydrogels can reduce the pathogenic bioburden and can restore the wound’s physiological balance. Future clinical trials that ensure meaningful results are recommended

Microflow nanoprecipitation of positively charged gastroresistant polymer nanoparticles of Eudragit® RS100: A study of fluid dynamics and chemical parameters

The objective of the present work was to produce gastroresistant Eudragit® RS100 nanoparticles by a reproducible synthesis approach that ensured mono-disperse nanoparticles under the size of 100 nm. Batch and micromixing nanoprecipitation approaches were selected to produce the demanded nanoparticles, identifying the critical parameters affecting the synthesis process. To shed some light on the formulation of the targeted nanoparticles, the effects of particle size and homogeneity of fluid dynamics, and physicochemical parameters such as polymer concentration, type of solvent, ratio of solvent to antisolvent, and total flow rate were studied. The physicochemical characteristics of resulting nanoparticles were studied applying dynamic light scattering (DLS) particle size analysis and electron microscopy imaging. Nanoparticles produced using a micromixer demonstrated a narrower and more homogenous distribution than the ones obtained under similar conditions in conventional batch reactors. Besides, fluid dynamics ensured that the best mixing conditions were achieved at the highest flow rate. It was concluded that nucleation and growth events must also be considered to avoid uncontrolled nanoparticle growth and evolution at the collection vial. Further, rifampicin-encapsulated nanoparticles were prepared using both approaches, demonstrating that the micromixing-assisted approach provided an excellent control of the particle size and polydispersity index. Not only the micromixing-assisted nanoprecipitation promoted a remarkable control in the nanoparticle formulation, but also it enhanced drug encapsulation efficiency and loading, as well as productivity. To the best of our knowledge, this was the very first time that drug-loaded Eudragit® RS100 nanoparticles (NPs) were produced in a continuous fashion under 100 nm (16.5 ± 4.3 nm) using microreactor technology. Furthermore, we performed a detailed analysis of the influence of various fluid dynamics and physicochemical parameters on the size and uniformity of the resulting nanoparticles. According to these findings, the proposed methodology can be a useful approach to synthesize a myriad of nanoparticles of alternative polymers

Hybrid thermoresponsive nanoparticles containing drug nanocrystals for NIR-triggered remote release

The on-demand administration of anaesthetic drugs can be a promising alternative for chronic pain management. To further improve the efficacy of drug delivery vectors, high drug loadings combined with a spatiotemporal control on the release can not only relief the pain according to patient''s needs, but also improve the drawbacks of conventional burst release delivery systems. In this study, a hybrid nanomaterial was developed by loading bupivacaine nanocrystals (BNCs) into oligo(ethylene glycol) methyl ether methacrylate (OEGMA)-based thermoresponsive nanogels and coupling them to NIR-absorbing biodegradable copper sulphide nanoparticles (CuS NPs). Those CuS NPs were surface modified with polyelectrolytes using layer-by-layer techniques to be efficiently attached to the surface of nanogels by means of supramolecular interactions. The encapsulation of bupivacaine in the form of nanocrystals allowed to achieve CuS@BNC-nanogels having drug loadings as high as 65.5 wt%. The nanocrystals acted as longlasting drug reservoirs, leading to an elevated localized drug content, which was useful for their application in prolonged pain relief. The CuS@BNC-nanogels exhibited favorable photothermal transducing properties upon NIR-light irradiation. The photothermal effect granted by the CuS NPs triggered the nano-crystallized drug release to be boosted by the collapse of the thermoresponsive nanogels upon heating. Remote control was achieved for on-demand release at a specific time and place, indicating their potential use as an externally activated triggerable drug-delivery system. Furthermore, cell viability tests and flow cytometry analysis were performed showing satisfactory cytocompatibility in the dose-ranging study having a subcytotoxic concentration of 0.05 mg/mL for CuS@BNC-nanogels. This remotely activated nanoplatform is a promising strategy for long-lasting controlled analgesia and a potential alternative for clinical pain management. (c) 2021 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND licens

Ordered mesoporous silica monoliths: synthesis, preparation and potential applications

The work carried out was focused on the preparation of rigid porous silica monoliths, in order to investigate applications as controlled drug release matrices. All work was based on the hexagonally-ordered mesoporous SBA-15 materials, and monoliths were obtained by gel-casting procedures. SBA-15 powder was successfully synthesized and characterized using SEM and TEM imaging, nitrogen adsorption and small-angle X-ray diffraction. Synthesis yielded fibrous SBA-15 particles with diameters between 4,5 and 7,5µm and lengths between 75 and 105µm, and highly ordered cylindrical pores arranged in a hexagonal fashion with a diameter between 5,6 and 6,9 nm. Functionalization of SBA-15 powder was carried out using (3-Aminopropyl)triethoxysilane as a functionalizing agent, in order to test functionalization effects on drug release, and to prepare more stable monoliths. Monoliths were prepared using gel-casting procedures; a suspension of polyacrylamide precursors and powder SBA-15 was centrifuged in a glass mold, and polymer hardening and further removal of the polymer template yielded stable monoliths exhibiting a bimodal pore structure confirmed by intrusion characterization. Macroscopic dimensions of the monoliths were 3mm in diameter and approximately 6 mm in length, with macropores around 3 µm and the characteristic mesopores of SBA-15. Monoliths were also functionalized using (3-Aminopropyl)triethoxysilane. Drug loading for drug delivery experiments was carried out by placing as-synthesized and functionalized SBA-15 powders and monoliths in direct contact with a solution of a model antibiotic, namely cefuroxime sodium salt. Functionalized powders yielded the highest loads, followed by unmodified powders, modified monoliths and with as-synthesized monoliths exhibiting the lowest loads. Drug release experiments were focused on release of cefuroxime from as-synthesized and amino-functionalized SBA-15 powders and monoliths. Monoliths exhibit an initial burst release that was attributed to antibiotic loaded in the macroporous reservoirs, while a more controlled release was obtained from the powder counterparts

A bone-on-a-chip collagen hydrogel-based model using pre-differentiated adipose-derived stem cells for personalized bone tissue engineering

Mesenchymal stem cells have contributed to the continuous progress of tissue engineering and regenerative medicine. Adipose-derived stem cells (ADSC) possess many advantages compared to other origins including easy tissue harvesting, self-renewal potential, and fast population doubling time. As multipotent cells, they can differentiate into osteoblastic cell linages. In vitro bone models are needed to carry out an initial safety assessment in the study of novel bone regeneration therapies. We hypothesized that 3D bone-on-a-chip models containing ADSC could closely recreate the physiological bone microenvironment and promote differentiation. They represent an intermedium step between traditional 2D–in vitro and in vivo experiments facilitating the screening of therapeutic molecules while saving resources. Herein, we have differentiated ADSC for 7 and 14 days and used them to fabricate in vitro bone models by embedding the pre-differentiated cells in a 3D collagen matrix placed in a microfluidic chip. Osteogenic markers such as alkaline phosphatase activity, calcium mineralization, changes on cell morphology, and expression of specific proteins (bone sialoprotein 2, dentin matrix acidic phosphoprotein-1, and osteocalcin) were evaluated to determine cell differentiation potential and evolution. This is the first miniaturized 3D-in vitro bone model created from pre-differentiated ADSC embedded in a hydrogel collagen matrix which could be used for personalized bone tissue engineering

Encapsulation of iron-saturated lactoferrin for proteolysis protection with preserving iron coordination and sustained release

Lactoferrin (Lf) is a globular glycoprotein found mainly in milk. It has a very high affinity for iron(III) ions, and its fully saturated form is called holoLf. The antimicrobial, antiviral, anticancer, and immunomodulatory properties of Lf have been studied extensively for the past two decades. However, to demonstrate therapeutic benefits, Lf has to be efficiently delivered to the intestinal tract in its structurally intact form. This work aimed to optimize the encapsulation of holoLf in a system based on the versatile Eudragit® RS polymer to protect Lf against the proteolytic environment of the stomach. Microparticles (MPs) with entrapped holoLf were obtained with satisfactory entrapment efficiency (90–95%), high loading capacity (9.7%), and suitable morphology (spherical without cracks or pores). Detailed studies of the Lf release from the MPs under conditions that included simulated gastric or intestinal fluids, prepared according to the 10th edition of the European Pharmacopeia, showed that MPs partially protected holoLf against enzymatic digestion and ionic iron release. The preincubation of MPs loaded with holoLf under conditions simulating the stomach environment resulted in the release of 40% of Lf from the MPs. The protein released was saturated with iron ions at 33%, was structurally intact, and its iron scavenging properties were preserved

On the synthesis of polymeric, inorganic and hybrid nanoparticles for controlled drug delivery applications. From a molecular level to a whole-body distribution

En esta tesis doctoral, se han desarrollado vectores de liberación de fármacos basados en materiales híbridos para demostrar que es posible una liberación pulsada de fármacos mediante activación externa, haciéndolas potencialmente atractivas para aquellas patologías que necesitan la liberación puntual de una cantidad determinada de fármaco (como por ejemplo tratamientos contra el dolor o desajustes hormonales). Se ha tomado como punto de partida polímeros termosensibles ya conocidos y bien estudiados combinándolos con nanopartículas plasmónicas sensibles a la radiación en el rango del infrarrojo cercano (NIR). Además, se ha considerado la Bupivacaina como fármaco modelo debido a su uso habitual para el tratamiento del dolor crónico asociado a enfermedades del nervio ciático actuando como bloqueo del nervio. En el desarrollo de este trabajo, se han seguido numerosos pasos: desde la síntesis y la caracterización de las nanopartículas plasmónicas y poliméricas hasta el desarrollo de nano y micropartículas híbridas cargadas de fármaco con la habilidad de liberar el fármaco a demanda de manera reversible cuando son activadas externamente con luz. Para conseguir este objetivo, se ha aprovechado la combinación de nuevos métodos de síntesis, como el uso de plataformas de microfluídica, junto con métodos convencionales de síntesis en discontinuo.Por otro lado, se han tenido en cuenta diferentes puntos de vista en el desarrollo de estos vectores de liberación de fármacos. Se han llevado a cabo simulaciones basadas en dinámica molecular para entender las interacciones fármaco-polímero a escala molecular y con ello conseguir mejores y optimizadas cargas de fármaco. Para ello, se ha realizado el análisis de sistemas sencillos formados por cadenas poliméricas basadas en los polímeros termosensibles usados experimentalmente y la bupivacaina como fármaco modelo. Finalmente, el estudio de la persistencia in vivo de algunos de estos vectores de liberación de fármacos ha acercado el estudio de los mismos a su aplicación final para evaluar su comportamiento y destino final en modelos animales.Drug delivery vectors based on hybrid materials were developed to demonstrate that an externally activated pulsatile drug release is possible, making it potentially attractive for those pathologies that need the release of a specific drug amount at a specific time point (i.e., pain, hormonal disorders, etc.). The starting point were well-known thermoresponsive polymers combined with Near Infrared (NIR) sensitive plasmonic nanoparticles and a selected model drug (i.e., Bupivacaine), normally used for the treatment of chronic pain associated to sciatic nerve disease acting as a peripherial nerve blocker. Different steps were needed to follow to fulfill the aim of the research: from the synthesis and characterization of those polymeric and plasmonic inorganic nanoparticles, to the development of drug-loaded hybrid nano- and micro- drug delivery vectors with reversible ability to release a drug on-demand when externally activated with light. In order to achieve this aim, it was considered the combination of new synthesis methodologies such as the use of microfluidic continuous platforms together with conventional batch approaches. On the other hand, different points of view in the development of those drug delivery vectors were taken into account. Molecular dynamics simulations were carried out to understand drug-polymer interactions at molecular level and achieve large drug loadings. These analysis involved simple systems containing polymeric chains, based on those thermoresponsive materials, and the model drug chosen, bupivacaine. Additionally, in vivo persistence study brought some of these drug delivery vectors close to their final purpose in order to evaluate their in vivo persistence and fate.<br /

Desarrollo de recubrimientos antimicrobianos sobre dispositivos médicos

Se conocen numerosos casos en los que una amplia variedad de dispositivos médicos como catéteres, stents, prótesis, reservorios de acceso venoso, etc, se infectan tras su implantación en el cuerpo del paciente. Esto se debe a que durante este proceso, los microorganismos que habitan de forma habitual en el interior del cuerpo del paciente o en su epidermis o en la del personal médico sin las debidas medidas de prevención o que proceden de otras fuentes como material quirúrgico y equipos o líquidos de infusión contaminados, colonizan el tejido interno alrededor del dispositivo. Esta colonización puede provocar una infección localizada que en muchas ocasiones deriva en problemas más graves como bacteriemia en la que la infección se transloca al torrente sanguíneo, generando así complicaciones más severas que en la mayoría de los casos conllevan a la retirada del dispositivo médico infectado y a la reimplantación de un nuevo dispositivo con el consiguiente perjuicio para el paciente tras el sometimiento a una nueva cirugía y el consecuente elevado coste terapéutico. Como posible solución a este extendido problema, se plantea el desarrollo de una película polimérica que recubra el dispositivo en cuestión y que presente la capacidad de almacenar un antibiótico que será liberado localmente tras la implantación. De esta manera, junto con el tratamiento vía oral que se administra al paciente, se conseguiría reducir o evitar el riesgo de infección del dispositivo y se conseguirá una liberación local del antimicrobiano deseado