Macroporous materials: microfluidic fabrication, functionalization and applications

This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields

Inverted Colloidal Crystal Scaffolds New Substitutes for Bone Tissue Engineering

Bone is a highly organised and specialised connective tissue with natural ability to self-heal and regain functionality. This capacity is, however, exposed to a great number of threats that can critically damage bone’s health and trigger the need for bone substitutes. The present thesis aimed at the production of new bone scaffolds for tissue regeneration using the Inverted Colloidal Crystal (ICC) structure as model system. ICCs are 3D structures, resultant from Colloidal Crystals (CC) inverse replication, that exhibit uniform pore size, interconnected network and whose architectural design enhances the cellular environment and vascular ingrowth. Reported here is the use of organic (chitosan/chitin nanowhiskers) and inorganic (hydroxyapatite) building materials to develop scaffolds comprising ceramic, polymeric and composite matrices. Firstly, polystyrene microspheres are produced by simple microfluidic, assembled in hexagonal close packed CC and then used as templates for all scaffolds production. Ceramic based ICCs were developed using an hydroxyapatite solgel system and sintering route that allowed simultaneous template calcination and matrix formation. Polymeric based ICCs were subjected to hydrolytic degradation after being produced with different molecular weight chitosans in order to understand polymer influence on the scaffolds structural stability. Considering bone´s composite nature, ICCs were constructed using hydroxyapatite nanorods suspended in chitosan solutions. Also, structures whose materials have an imprinted liquid crystalline organization provided by chitin nanowhiskers were developed inspired by bone collagen arrangement that contributes to the tissue hierarchical architecture. The morphological, biological and mechanical evaluation of such scaffolds contributes to establish the path for the development of new ICC based products with potential to complement or replace the currently clinically used bone substitutes and in that way constitute valuable solutions for bone tissue regeneration

Inverse opal scaffolds and photoacoustic microscopy for regenerative medicine

This research centers on the fabrication, characterization, and engineering of inverse opal scaffolds, a novel class of three-dimensional (3D) porous scaffolds made of biocompatible and biodegradable polymers, for applications in tissue engineering and regenerative medicine. The unique features of an inverse opal scaffold include a highly ordered array of pores, uniform and finely tunable pore sizes, high interconnectivity, and great reproducibility. The first part of this work focuses on the fabrication and functionalization of inverse opal scaffolds based on poly(D,L-lactic-co-glycolic acid) (PLGA), a biodegradable material approved by the U.S. Food and Drug Administration (FDA). The advantages of the PLGA inverse opal scaffolds are also demonstrated by comparing with their counterparts with spherical but non-uniform pores and poor interconnectivity. The second part of this work shows two examples where the PLGA inverse opal scaffolds were successfully used as a well-defined system to investigate the effect of pore size of a 3D porous scaffold on the behavior of cell and tissue growth. Specifically, I have demonstrated that i) the differentiation of progenitor cells in vitro was dependent on the pore size of PLGA-based scaffolds and the behavior of the cells was determined by the size of individual pores where the cells resided in, and ii) the neovascularization process in vivo could be directly manipulated by controlling a combination of pore and window sizes when they were applied to a mouse model. The last part of this work deals with the novel application of photoacoustic microscopy (PAM), a volumetric imaging modality recently developed, to tissue engineering and regenerative medicine, in the context of non-invasive imaging and quantification of cells and tissues grown in PLGA inverse opal scaffolds, both in vitro and in vivo. Furthermore, the capability of PAM to monitor and quantitatively analyze the degradation of the scaffolds themselves was also demonstrated.Ph.D

Smart and Functional Polymers

This book is based on the Special Issue of the journal Molecules on “Smart and Functional Polymers”. The collected research and review articles focus on the synthesis and characterization of advanced functional polymers, polymers with specific structures and performances, current improvements in advanced polymer-based materials for various applications, and the opportunities and challenges in the future. The topics cover the emerging synthesis and characterization technology of smart polymers, core?shell structure polymers, stimuli-responsive polymers, anhydrous electrorheological materials fabricated from conducting polymers, reversible polymerization systems, and biomedical polymers for drug delivery and disease theranostics. In summary, this book provides a comprehensive overview of the latest synthesis approaches, representative structures and performances, and various applications of smart and functional polymers. It will serve as a useful reference for all researchers and readers interested in polymer sciences and technologies

3D Tissue Constructs on the Basis of Colloidal Crystals Surface Modified by Sequential Layering

A cell growth matrix for optimizing 3D organization nutrient delivery, controlling release of differentiation factors and facilitating attachment of cells to a scaffold Colloidal crystals and inverted colloidal crystals are used to form an ordered structure for use as a scaffold for tissue engineering. The porosity of the cell growth matrix may be modified by the selection of particles of appropriate diameter. Further, the surface of colloidal crystals can be easily modified to accommodate many organic species including biomolecules. Layer-by-layer materials are used for tissue engineering to control cell development by using sequential layering of bioactive species wherein the number and order of LBL layers deposited between layers containing a particular protein are controlled. LBL may also be used for timed release of bioactive species. Increased control differentiation factors release and control of cell attachments to the scaffold are achieved to better mimic natural tissue development

Hydrogel microparticles from lithographic processes: Novel materials for fundamental and applied colloid science

In recent years, there has been a surge in methods to synthesize geometrically and chemically complex microparticles. Analogous to atoms, the concept of a “periodic table” of particles has emerged and continues to be expanded upon. Complementing the natural intellectual curiosity that drives the creation of increasingly intricate particles is the pull from applications that take advantage of such high-value materials. Complex particles are now being used in fields ranging from diagnostics and catalysis, to self-assembly and rheology, where material composition and microstructure are closely linked with particle function. This is especially true of polymer hydrogels, which offer an attractive and broad class of base materials for synthesis. Lithography affords the ability to engineer particle properties a priori and leads to the production of homogenous ensembles of particles. This review summarizes recent advances in synthesizing hydrogel microparticles using lithographic processes and highlights a number of emerging applications. We discuss advantages and limitations of current strategies, and conclude with an outlook on future trends in the field.National Science Foundation (U.S.) (Grant DMR-1006147)Novartis-MIT Center for Continuous ManufacturingNational Institute for Biomedical Imaging and Bioengineering (U.S.) (Grant R21EB008814

Nanocomposites of Polymers and Inorganic Particles

The book covers all of the specific aspects of this topic, ranging from preparatory approaches, functionalization strategies of NPs and polymers, processing and integration of nanocomposites in additive manufacturing materials, and technological methodologies to obtain functional multiphase materials for advanced application

Hierarchical Templates and Their Application to Multimodal Porous Materials Fabrication

Hierarchical materials offer great promise for high-performance sensors and catalysis carriers. Well-defined hierarchically porous materials are promising candidates for a wide range of applications relating to biosensors, separations, drug delivery, surface-enhanced Raman scattering (SERS), etc. Research on synthetic methodologies is expanding. However, fabrication of hierarchical porous structures with tunable pore dimension and shape, controllable pore distribution and interconnectivity is still a challenging task in materials science. One of the main tasks of this work is to establish a facile and reliable approach of making well-defined hierarchically porous materials. Then, based on those multimodal porous structures, different functions and applications can be realized. This work utilizes a direct hard templating method to obtain hierarchical porous structures with a well-defined bimodal distribution of the pores based on hierarchical templates. The hierarchical templates were prepared by synthetically joining appropriately functionalized commercially available polystyrene (PS) latex spheres together. Two different coupling reactions were used to form the hierarchical templates: carbodiimide-assisted coupling of COOH groups with NH2 groups and base-assisted coupling of epoxy groups with NH2 groups. Two different morphologies of templates, raspberry-like and strawberry-like were made. The template can be defined by the sizes of both the core and the satellite spheres, and altering the coverage of satellites on the core . The main advantage of this strategy is the tailorability of the size and shape of the hierarchical templates, which allows an easy and independent adjustment to the multiporosity of the material structure design. Also, the monodispersed hierarchical templates are constructed of only one material, can be isolated, and can be assembled using standard template packing procedures that have been used for unimodal porous material fabrication described in published literature. Based on the predefined monodispersed hierarchical templates, multimodal porous silica, bimodal porous gold film and porous capsules were fabricated in this work as representative 3D, 2D, and 0D hierarchical porous structures, respectively. Because the template was predefined as one whole body, the connectivity between the big pores and small pores is guaranteed. The way the templates are packed together on a surface also ensures connections between each template-shaped pore cluster . The uniform interconnectivity and ordered arrangement among the pores allows the different modals of pores to communicate with each other. The different hierarchical porous materials made in this work were characterized with SEM, TEM, AFM, XPS, STEM, gas adsorption, and mercury intrusion porosity. The results indicate that the multimodal porous materials can be successfully fabricated using predefined hierarchical templates. The different arrangement (3D, 2D, 0D) of those templates and the independent tailorability of the pore sizes provide more flexibility and control on the hierarchical porous material fabrication. The main parts of this work are as follows: (1) Fabrication and characterization of morphology controllable hierarchical templates (2) Fabrication and characterization of various multimodal porous structures of different materials based on the obtained templates (3) Study of the application of hierarchical porous gold electrode obtained and (4) The comparison between conventional porous structures and hierarchical porous structures