Base de la física y de la química de la biotecnología - Marcel De Cuiper and Jeff W. M . Bulte

BIOMIMETIC MATERIALS SYNTHESIS


ALEKSEY NEDOLUZHKO AND TREVOR DOUGLAS
Department of Chemistry, Temple University
Philadelphia, PA 19122-2585 USA





Abstract

The study of mineral formation in biological systems, biomineralisation, provides inspiration for novel approaches to the synthesis of new materials. Biomineralisation relies on extensive organic-inorganic interactions to induce and control the synthesis of inorganic solids. Living systems exploit these interactions and utilise organised organic scaffolds to direct the precise patterning of inorganic materials over a wide range of length scales. Fundamental studies of biomineral and model systems have revealed some of the key interactions which take place at the organic-inorganic interface. This has led to extensive use of the principles at work in biomineralisation for the creation of novel materials. A biomimetic approach to materials synthesis affords control over the size, morphology and polymorph of the mineral under mild synthetic conditions.
In this review, we present examples of organic-inorganic systems of different kinds, employed for the synthesis of inorganic structures with a controlled size and morphology, such as individual semiconductor and metal nanoparticles with a narrow size distribution, ordered assemblies of the nanoparticles, and materials possessing complex architectures resembling biominerals. Different synthetic strategies employing organic substances of various kinds to control crystal nucleation and growth and/or particle assembly into structures organised at a larger scale are reviewed. Topics covered include synthesis of solid nanoparticles in micelles, vesicles, protein shells, organisation of nanocrystals using biomolecular recognition, synthesis of nanoparticle arrays using ordered organic templates.


1. Introduction

The rapidly growing field of biomimetic materials chemistry has developed largely from the fundamental study of biomineralisation [ 1], the formation of mineral structures in biological systems. Many living organisms synthesise inorganic minerals and are able to tailor the choice of material and morphology to suit a particular function. In addition, the overall material is often faithfully reproduced from generation to generation. The control exerted in the formation of these biominerals has captured the attention of materials scientists because of the degree of hierarchical order, from the nanometer to the meter length scale, present in most of these structures [2]. Biominerals are usually formed through complementary molecular interactions, the “organic-matrix mediated” mineralization proposed by Lowenstam [3]. These interactions between organic and inorganic phases are mediated by the organisms through the spatial localisation of the organic template, the availability of inorganic precursors, the control of local conditions such as pH and ionic strength, and a cellular processing which results in the assembly of complex structures. Our understanding of some of the fundamental principles at work in biomineralisation allows us to mimic these processes for the synthesis of inorganic materials of technological interest.
The biomimetic approach to materials chemistry follows two broad divisions that remain a challenge to the synthetic chemist. On the one hand mineral formation is dominated by molecular interactions leading to nucleation and crystal growth. On the other hand there is the assembly of mineral components into complex shapes and structures (tectonics [4]) which impart a new dimension to the properties of the material. So, interactions must be controlled at both the molecular length scale (Å) – to ensure crystal fidelity of the individual materials, as well as at organismal length scales (cm or m). The fidelity of materials over these dramatic length scales is not necessarily the same. An intense effort in biomimetic materials chemistry is focussed (often simultaneously) on these two length scales. There is not yet a generalised approach to the processing of materials from the molecular level into complex macroscopic forms that can be used for advanced materials with direct applications.




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