Hugo De Oliveira

Magnetic responsive polymer composite materials

Magnetic responsive materials are the topic of intense research due to their potential breakthrough applications in the biomedical, coatings, microfluidics and microelectronics fields. By merging magnetic and polymer materials one can obtain composites with exceptional magnetic responsive features. Magnetic actuation provides unique capabilities as it can be spatially and temporally controlled, and can additionally be operated externally to the system, providing a non-invasive approach to remote control. We identified three classes of magnetic responsive composite materials, according to their activation mode and intended applications, which can be defined by the following aspects. (A) Their ability to be deformed (stretching, bending, rotation) upon exposure to a magnetic field. (B) The possibility of remotely dragging them to a targeted area, called magnetic guidance, which is particularly interesting for biomedical applications, including cell and biomolecule guidance and separation

Magnetic field triggered drug release from polymersomes for cancer therapeutics.

Local and temporal control of drug release has for long been a main focus in the development of novel drug carriers. Polymersomes, which can load both hydrophilic and hydrophobic species and, at the same time, be tailored to respond to a desired stimulus, have drawn much attention over the last decade. Here we describe polymersomes able to encapsulate up to 6% (w/w) of doxorubicin (DOX) together with 30% (w/w) of superparamagnetic iron oxide nanoparticles (USPIO; γ-Fe2O3). Upon internalization in HeLa cells and when a high frequency AC magnetic field (14mT at 750kHz) was applied, the developed delivery system elicited an 18% increase in cell toxicity, associated with augmented DOX release kinetics. In order to ensure that the observed cytotoxicity arose from the increased doxorubicin release and not from a pure magnetic hyperthermia effect, polymersomes loaded with magnetic nanoparticles alone were also tested. In this case, no increased toxicity was observed. We hypothesize that the magnetic field is inducing a very local hyperthermia effect at the level of the polymersome membrane, increasing drug release. This approach opens new perspectives in the development of smart delivery systems able to release drug upon demand and therefore, improving treatment control.

Smart polymersomes for therapy and diagnosis: fast progress toward multifunctional biomimetic nanomedicines

Rising from the shortcomings of modern day therapeutics there is a need for a controlled approach in carrier-mediated drug delivery. Polymeric vesicles, also called polymersomes, are powerful tools to address issues of efficacy, specificity, and controlled release of drugs to diseased tissues. These recent, biomimetic structures are able to overcome the bodys natural defences, remaining stable for extended time in circulation, have tuneable membrane properties, allowing the control of membrane permeability and therefore of drug release, and have the potential to be functionalized for active targeting of specific tissues, reducing undesirable side effects. Extensive work has been carried out in order to attain multifunctional polymeric vesicles that respond to precise triggers (e.g., temperature, pH, redox, magnetic field, etc) with a spatial and temporal monitoring what may enable unprecedented control of drug release in the body. These versatile structures can be loaded with different type of (bio)molecules and nanoparticles, from drugs to contrast agents for medical imaging, and are able to accommodate them in different subcompartments of the vesicle (i.e., hydrophobic membrane and hydrophilic core). Multimodal targeted delivery system could be obtained from this unique platform, with abilities in both drug delivery and medical imaging contrast enhancement, widening the perspectives toward theranostics. Polymersomes offer a promising route toward more effective treatments with fewer side effects and superior outcomes.

Antibody-functionalized magnetic polymersomes: in vivo targeting and imaging of bone metastases using high resolution MRI.

Multifunctional polymersomes loaded with maghemite nanoparticles and grafted with an antibody, directed against human endothelial receptor 2, are developed as novel MRI contrast agents for bone metastasis imaging. Upon administration in mice bearing bone tumor grown from human breast cancer cells, MR images show targeting and enhanced retention of antibody-labeled polymersomes at the tumor site.

In situ printing of mesenchymal stromal cells, by laser-assisted bioprinting, for in vivo bone regeneration applications

Bioprinting has emerged as a novel technological approach with the potential to address unsolved questions in the field of tissue engineering. We have recently shown that Laser Assisted Bioprinting (LAB), due to its unprecedented cell printing resolution and precision, is an attractive tool for the in situ printing of a bone substitute. Here, we show that LAB can be used for the in situ printing of mesenchymal stromal cells, associated with collagen and nano-hydroxyapatite, in order to favor bone regeneration, in a calvaria defect model in mice. Also, by testing different cell printing geometries, we show that different cellular arrangements impact on bone tissue regeneration. This work opens new avenues on the development of novel strategies, using in situ bioprinting, for the building of tissues, from the ground up.

Polymeric micelles and vesicles: biological behavior evaluation using radiolabeling techniques

Abstract The application of combined diagnosis and therapy through nanotechnology applications is attracting increasing attention worldwide. Polymeric self-assembled nanoparticles (NPs) have been studied for this purpose. Micelles and vesicles with or without a magnetic core can efficiently carry diagnostic and/or therapeutic agents to a desired target. The biological behavior of these NPs has been evaluated in this study, after radiolabeling with 99mTc. In vitro stability, in media that mimic the environment of the living body, was better for vesicles than for micelles at 1 h and decreased for both as time passed. After administration to healthy animals, all NPs presented major uptake at liver and spleen as expected. Biodistribution and imaging studies confirmed the higher uptake in these organs for the hybrid NPs and at higher extent for the ones with larger size, indicating that the magnetic load and size play an important role on in vivo distribution.

Polymersomes for theranostics

In spite of the clear potential of personalized medicine, its pace of implementation has not yet fulfilled initial hopes. Polymeric vesicles, also named polymersomes, are presented as versatile systems able to address issues of efficacy, specificity and controlled release of drugs in a wide range of pathological scenarios that might show the way to novel therapies. Extensive work has endowed these biomimetic structures with the ability to overcome the bodys natural defences, remain stable for an extended time in circulation, tuneable membrane properties for controlled drug release, and the ability to be functionalized for active targeting and therefore reducing undesirable side effects. Additionally, this unique platform has the ability to integrate both drug delivery and medical imaging capabilities, widening the perspectives towards theranostics. Polymersomes hold promise for more effective treatments with both fewer side effects and superior outcomes.

Self-assembled core–shell micelles from peptide-b-polymer molecular chimeras towards structure–activity relationships

The aim of this contribution is to design, produce and characterize size-tuneable core-shell micelles from amphiphilic Tat-b-poly(trimethylene carbonate) (Tat-b-PTMC) molecular chimeras, and to explore their biological properties. Because the extensive characterization of nanomaterials is a pre-requisite to understand and rationalize their ensuing properties, we present a detailed description of Tat-b-PTMC micelles thanks to light scattering, AFM imaging and small angle neutron scattering analyses. In vitro, Tat-b-PTMC micelles were found to be rapidly and efficiently internalized by HeLa cells, with cellular uptake kinetics being mostly related to Tat peptide content and, to a lesser extent, to nanoparticle size. We also demonstrated that, after a first membrane-binding step, Tat-b-PTMC micelles were taken up by cells via an energy-dependent endocytotic process.

A new composite hydrogel combining the biological properties of collagen with the mechanical properties of a supramolecular scaffold for bone tissue engineering.

Tissue engineering is a promising alternative to autografts, allografts, or biomaterials to address the treatment of severe and large bone lesions. Classically, tissue engineering products associate a scaffold and cells and are implanted or injected into the lesion. These cells must be embedded in an appropriate biocompatible scaffold, which offers a favourable environment for their survival and differentiation. Here, we designed a composite hydrogel composed of collagen I, an extracellular matrix protein widely used in several therapeutic applications, which we associated with a physical hydrogel generated from a synthetic small amphiphilic molecule. This composite showed improved mechanical and biological characteristics as compared with gels obtained from each separate compound. Incorporation of the physical hydrogel prevented shrinkage of collagen and cell diffusion out of the gel and yielded a gel with a higher elastic modulus than those of gels obtained with each component alone. The composite hydrogel allowed cell adhesion and proliferation in vitro and long‐term cell survival in vivo. Moreover, it promoted the differentiation of human adipose‐derived stem cells in the absence of any osteogenic factors. In vivo, cells embedded in the composite gel and injected subcutaneously in immunodeficient mice produced lamellar osteoid tissue and differentiated into osteoblasts. This study points this new composite hydrogel as a promising scaffold for bone tissue engineering applications.

The proangiogenic potential of a novel calcium releasing composite biomaterial: Orthotopic in vivo evaluation

Insufficient angiogenesis remains a major hurdle in current bone tissue engineering strategies. An extensive body of work has focused on the use of angiogenic factors or endothelial progenitor cells. However, these approaches are inherently complex, in terms of regulatory and methodologic implementation, and present a high cost. We have recently demonstrate the potential of electrospun poly(lactic acid) (PLA) fiber-based membranes, containing calcium phosphate (CaP) ormoglass particles, to elicit angiogenesis in vivo, in a subcutaneous model in mice. Here we have devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a (Hydroxypropyl)methyl cellulose (HPMC) matrix, with the capacity to release calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. The bone regeneration kinetics was dependent on the Ca2+ release rate, with the faster Ca2+ release composite gel showing improved bone repair at 3weeks, in relation to control. In the same line, improved angiogenesis could be observed for the same gel formulation at 6weeks post implantation. This methodology allows to integrate two fundamental processes for bone tissue regeneration while using a simple, cost effective, and safe approach. STATEMENT OF SIGNIFICANCE In current bone tissue engineering approaches the achievement of sufficient angiogenesis, during tissue regeneration, is a major limitation in order to attain full tissue functionality. Recently, we have shown that calcium ions, released by the degradation of calcium phosphate ormoglasses (CaP), are effective angiogenic promoters, in both in vitro and in a subcutaneous implantation model. Here, we devised an injectable composite, containing CaP glass-ceramic particles, dispersed within a HPMC matrix, enabling the release of calcium in a more sustained fashion. We show that by tuning the release of calcium in vivo, in a rat bone defect model, we could improve both bone formation and increase angiogenesis. This simple and cost effective approach holds great promise to translate to the clinics.