Biomimetic Mineralization by Combining Block Copolymer Self-Assembly and One Dimensional Crystal Nucleation

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Non-technical: This award by the Biomaterials program in the Division of Materials Research to Drexel University aims to use a "bottom-up", directed assembly method to mimic the natural bone structure, and to understand the origin of the properties of natural bone. Bone is the second most commonly transplanted tissue; over 2.2 million bone graft procedures are performed annually worldwide. Knowledge gained from the study will not only help to develop new generation bone mimics for tissue engineering, it will also shed light on novel hybrid materials design towards stronger and lighter nanocomposites. The educational component of the proposal includes: 1) developing two class modules addressing natural materials properties; 2) mentoring graduate and undergraduate students; and 3) involving high school students and teachers, particularly from underrepresented minority groups, in the proposed research activities. These educational activities encompass the following broad impacts: 1) the proposed plans will help bridge the existing gap between levels of educational developments by involving high school students and teachers in research activities; and 2) the proposed outreach program will be specifically geared towards encouraging the participation of underrepresented minority groups in the Philadelphia region.Technical: Despite various macro-structures, morphogenically different bones share similar nanostructures consisting of collagen fibrils within which organized hydroxyapatite nanocrystals are embedded with a period of 67 nm along the fibrils, and these nanocrystals are aligned parallel to the fibril axis. Synthetic soft materials have been used to successfully to control the orientation of mineral crystals. The spatial distribution of minerals in a synthetic scaffold, however, has yet to be reproduced in a biomimetic manner. The proposed design aims to mimic the hierarchical structure of natural bone on the molecular level. The investigators will combine one-dimensional nucleation and block copolymer (BCP) self-assembly to achieve this goal. By controlling crystallization of carefully selected BCP on 1D polymer nanofibers, because of depletion-induced concentration gradients, the crystal growth follows a periodic pattern with the period ranging from a few terns to hundreds of nanometers. The chemical environment in the vicinity of the BCP crystals can be tuned to allow nanoconfined biomineralization. Through this approach, for the first time, both the orientation and spatial distribution of the mineral nanocrystals can be precisely controlled. Changing BCP molecular weight also allows detailed morphological and structural control of the biomineralization process. These researchers anticipate that the unprecedented structural control will provide a new route for biomimetic design of hybrid materials in general and bone mimics in particular. The broader impact activities include mentoring high school students and teachers with a focus on underrepresented groups from the Philadelphia region.