We have used the pH-induced self-assembly of a peptide-amphiphile to make a nanostructured fibrous scaffold reminiscent of extracellular matrix. The design of this peptide-amphiphile allows the nanofibers to be reversibly cross-linked to enhance or decrease their structural integrity. After cross-linking, the fibers are able to direct mineralization of hydroxyapatite to form a composite material in which the crystallographic c axes of hydroxyapatite are aligned with the long axes of the fibers. This alignment is the same as that observed between collagen fibrils and hydroxyapatite crystals in bone.

http://science.sciencemag.org/content/sci/294/5547/1684.full.pdf

Self-assembly and mineralization of peptide-amphiphile nanofibers

The inorganic part of hard tissues (bones and teeth) of mammals consists of calcium phosphate, mainly of apatitic structure. Similarly, most undesired calcifications (i.e. those appearing as a result of various diseases) of mammals also contain calcium phosphate. For example, atherosclerosis results in blood-vessel blockage caused by a solid composite of cholesterol with calcium phosphate. Dental caries result in a replacement of less soluble and hard apatite by more soluble and softer calcium hydrogenphosphates. Osteoporosis is a demineralization of bone. Therefore, from a chemical point of view, processes of normal (bone and teeth formation and growth) and pathological (atherosclerosis and dental calculus) calcifications are just an in vivo crystallization of calcium phosphate. Similarly, dental caries and osteoporosis can be considered to be in vivo dissolution of calcium phosphates. On the other hand, because of the chemical similarity with biological calcified tissues, all calcium phosphates are remarkably biocompatible. This property is widely used in medicine for biomaterials that are either entirely made of or coated with calcium phosphate. For example, self-setting bone cements made of calcium phosphates are helpful in bone repair and titanium substitutes covered with a surface layer of calcium phosphates are used for hip-joint endoprostheses and tooth substitutes, to facilitate the growth of bone and thereby raise the mechanical stability. Calcium phosphates have a great biological and medical significance and in this review we give an overview of the current knowledge in this subject.

/pdf/biological-and-medical-significance-of-calcium-phosphates-4zx1s7sv8d.pdf

Biological and medical significance of calcium phosphates.

The design of advanced, nanostructured materials at the molecular level is of tremendous interest for the scientific and engineering communities because of the broad application of these materials in the biomedical field. Among the available techniques, the layer-by-layer assembly method introduced by Decher and co-workers in 1992 has attracted extensive attention because it possesses extraordinary advantages for biomedical applications: ease of preparation, versatility, capability of incorporating high loadings of different types of biomolecules in the films, fine control over the materials’ structure, and robustness of the products under ambient and physiological conditions. In this context, a systematic review of current research on biomedical applications of layer-by-layer assembly is presented. The structure and bioactivity of biomolecules in thin films fabricated by layer-by-layer assembly are introduced. The applications of layer-bylayer assembly in biomimetics, biosensors, drug delivery, protein and cell adhesion, mediation of cellular functions, and implantable materials are addressed. Future developments in the field of biomedical applications of layer-by-layer assembly are also discussed.

/pdf/biomedical-applications-of-layer-by-layer-assembly-from-1i20r8iian.pdf

Biomedical Applications of Layer‐by‐Layer Assembly: From Biomimetics to Tissue Engineering

Multilayer thin films have garnered intense scientific interest due to their potential application in diverse fields such as catalysis, optics, energy, membranes, and biomedicine Here we review the current technologies for multilayer thin-film deposition using layer-by-layer assembly, and we discuss the different properties and applications arising from the technologies We highlight five distinct routes of assembly—immersive, spin, spray, electromagnetic, and fluidic assembly—each of which offers material and processing advantages for assembling layer-by-layer films Each technology encompasses numerous innovations for automating and improving layering, which is important for research and industrial applications Furthermore, we discuss how judicious choice of the assembly technology enables the engineering of thin films with tailor-made physicochemical properties, such as distinct-layer stratification, controlled roughness, and highly ordered packing

/pdf/technology-driven-layer-by-layer-assembly-of-nanofilms-4envvimjp4.pdf

Technology-driven layer-by-layer assembly of nanofilms

Chemistries that Facilitate Nanotechnology Kim E. Sapsford,† W. Russ Algar, Lorenzo Berti, Kelly Boeneman Gemmill,‡ Brendan J. Casey,† Eunkeu Oh, Michael H. Stewart, and Igor L. Medintz*,‡ †Division of Biology, Department of Chemistry and Materials Science, Office of Science and Engineering Laboratories, U.S. Food and Drug Administration, Silver Spring, Maryland 20993, United States ‡Center for Bio/Molecular Science and Engineering Code 6900 and Division of Optical Sciences Code 5611, U.S. Naval Research Laboratory, Washington, D.C. 20375, United States College of Science, George Mason University, 4400 University Drive, Fairfax, Virginia 22030, United States Department of Biochemistry and Molecular Medicine, University of California, Davis, School of Medicine, Sacramento, California 95817, United States Sotera Defense Solutions, Crofton, Maryland 21114, United States

Functionalizing nanoparticles with biological molecules: developing chemistries that facilitate nanotechnology.

The formation of a new kind of biocompatible film based on poly(l-lysine) and hyaluronic acid (PLL/HA) by alternate deposition of PLL and HA was investigated. Optical waveguide lightmode spectroscopy, streaming potential measurements, atomic force microscopy, and quartz crystal microbalance (QCM) were used to analyze the different aspects of the buildup process such as the deposited mass after each new polyelectrolyte adsorption, the overall surface charge of the film, and its morphology. As for “conventional” polyelectrolyte multilayer systems, the driving force of the buildup process is the alternate overcompensation of the surface charge after each PLL and HA deposition. The construction of (PLL/HA)n films takes place over two buildup regimes. The first one is characterized by the formation of isolated islands that grow both by addition of new polyelectrolytes on their top and by mutual coalescence of the islands. The second regime sets in once a continuous film is formed after the eighth layer pair de...

Buildup Mechanism for Poly(l-lysine)/Hyaluronic Acid Films onto a Solid Surface

The buildup of the first layers of a polystyrenesulfonate (PSS)/polyallylamine (PAH) multilayer is studied in situ by means of streaming potential measurements (SPM) and by scanning angle reflectom...

In Situ Determination of the Structural Properties of Initially Deposited Polyelectrolyte Multilayers

We report here on the structural characterization of polyelectrolytes multilayer films formed by poly(l-glutamic acid) and poly(l-lysine) (PGA/PLL). The growth of this system is compared to that of poly(styrenesulfonate)/poly(allylamine hydrochloride) (PSS/PAH) multilayers by means of in situ atomic force microscopy (AFM) and by optical waveguide lightmode spectroscopy (OWLS). In contrary to the (PSS/PAH)i films that are growing linearly with the number of deposited layer pairs i, optical data evidenced that the (PGA/PLL)i films are characterized by an exponential growth. The analysis of the structure of the (PSS/PAH)i films reveals a smooth featureless surface covered by small globules. On the other hand, (PGA/PLL)i films form extended structures that appear with a vermiculate pattern. We propose a new growth mechanism based on polyelectrolyte diffusion in and out of the film coupled to the formation of polyanion/polycation complexes at the surface of the film in order to explain the whole results.

Comparison of the Structure of Polyelectrolyte Multilayer Films Exhibiting a Linear and an Exponential Growth Regime: An in Situ Atomic Force Microscopy Study

Polyetheretherketone (PEEK) is a polyaromatic semi-crystalline thermoplastic polymer with mechanical properties favorable for bio-medical applications. Polyetheretherketone forms: PEEK-LT1, PEEK-LT2, and PEEK-LT3 have already been applied in different surgical fields: spine surgery, orthopedic surgery, maxillo-facial surgery etc. Synthesis of PEEK composites broadens the physicochemical and mechanical properties of PEEK materials. To improve their osteoinductive and antimicrobial capabilities, different types of functionalization of PEEK surfaces and changes in PEEK structure were proposed. PEEK based materials are becoming an important group of biomaterials used for bone and cartilage replacement as well as in a large number of diverse medical fields. The current paper describes the structural changes and the surface functionalization of PEEK materials and their most common biomedical applications. The possibility to use these materials in 3D printing process could increase the scientific interest and their future development as well.

Polyetheretherketone (PEEK) for medical applications

We investigate the adsorption processes of a series of positively and negatively charged proteins onto the surface of polyelectrolyte multilayers. We find that proteins strongly interact with the polyelectrolyte film whatever the sign of the charge of both the multilayer and the protein. When the charges of the multilayer and the protein are similar, one usually observes the formation of protein monolayers which can become dense. We also show that when the protein and the multilayer become oppositely charged, the adsorbed amounts are usually larger and the formation of thick protein layers extending up to several times the largest dimension of the protein can be observed. Finally, we find that proteins are mainly adsorbed in a strong way on polyelectrolyte multilayers and protein surface diffusion is strongly suggested. Our results confirm that electrostatic interactions play an important role in polyelectrolyte multilayer/ protein interactions.

Frédéric Cuisinier

Papers

Buildup Mechanism for Poly(l-lysine)/Hyaluronic Acid Films onto a Solid Surface

In Situ Determination of the Structural Properties of Initially Deposited Polyelectrolyte Multilayers

Comparison of the Structure of Polyelectrolyte Multilayer Films Exhibiting a Linear and an Exponential Growth Regime: An in Situ Atomic Force Microscopy Study

Polyetheretherketone (PEEK) for medical applications

Protein Adsorption onto Auto-Assembled Polyelectrolyte Films