Gelatin hydrogels with PAMAM nanostructured surface and high density surface-localized amino groups Izabela-Cristina Stancu * Department of Polymer Chemistry and Engineering, Faculty of Applied Chemistry and Materials Science, Polytechnics University of Bucharest, Group Polymer Physics & Biomaterials, Calea Victoriei 149, Sector 1, Bucharest 010072, Romania article info Article history: Received 25 August 2009 Received in revised form 1 February 2010 Accepted 21 February 2010 Available online 25 February 2010 Keywords: Crosslinking Dendrimers Gelatin Hydrogels Nanorough surface abstract Amino-terminated PAMAM dendrimers with 16 and respectively 64 amino groups have been chemically immobilized onto the surface of glutaraldehyde (abbreviated GA) crosslinked thin gelatin scaffolds based on Schiff-base linkage formation between the amines and free aldehyde from partially unreacted GA. Crosslinking and dendrimers surface modification of hydrogels have been chemically and physically investigated using FT-IR spectroscopy and microscopy, UV–VIS, LM, AFM, swelling tests and a colorimetric technique. Two types of gelatin-based hydrogels with homogeneous nanorough surfaces and presenting an increased number of amino groups available for further chemical reactions have been obtained. The synthesis strategy presented in this work seems to open a new route for nanorough crosslinked gelatin scaffolds that could be further used for biomedical and especially for hard tissue engineering application. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction Nanomaterials include different types of materials both with dimensions under 100 nm or presenting structural features (parti- cles, fibers) under this dimensional threshold. Polyamidoamine dendrimers (PAMAM) have nano-dimensions and their immobili- zation on surfaces would lead to structural features within this dimensional range. Considering the tissue regeneration behavior, nanomaterials have been studied with respect to the proteins and cells interactions. The success of these materials is based on the initially interaction with the proteins controlling the cellular func- tions. The years 2000s have turned the attention on the stimulating effect of nanomaterials on bone regeneration process. Bone cells are naturally accustomed to nanoscale environment (hydroxyapatite, fibrilar collagen within this dimension range) and this is the main reason for enhanced cellular performance on nanomaterials. Sev- eral researches generally lead to the conclusion that the response of host organisms to the presence of nanomaterials is different and certainly superior when compared with conventional materials used until present [1–8]. For a bone graft to be successful, it seems that a biomaterial with superficial nano-features and possessing a superior surface reactivity available for growth factors and other biospecies to be immobilized could represent real advances. In this context, the chemical approach of the present work was aimed to develop biomimetic dendrimer nanostructured surfaces on poly- mer supports that seem to be appropriate for biomedical and espe- cially for bone regeneration use. A biomimetic material is defined as mimicking the biological environment of interest in order to elicit a desired cellular response. The deliverable of this research is repre- sented by innovative smart biomaterials which biomimetism is en- sured through a special surface chemistry and through a specific topography. The key parameter – the nanoroughness – is going to be achieved through surface conditioning with dendrimer molecules. Gelatin hydrogels with plane surfaces were selected as polymer supports. Gelatin is recognized as one of the most extensively stud- ied and used natural polymers for a wide range of biomedical applications like additive in pharmaceutical formulations, wound dressing, drug delivery, cell cultures and tissue engineering. The collagenic origin of this material seemed to be suitable for tissue reconstruction and this is why it was studied both as non-modified as well as modified with different bioactive molecules such as: cell adhesion peptides [9], bone sialoprotein – BSP [10], bone morpho- genic protein-2 – BMP-2 [11], growth factors [12–22], etc. Most of the studies were performed based on the non-covalent binding of the bioactive species on gelatin. Physical techniques such as mix- ing, impregnation of the hydrogel as well as electrostatic interac- tions based on charge compensation have been reported for the immobilization of a wide range of active ingredients in/on gelatin-based matrices. These methods are suitable especially for controlled release applications, but also for tissue repair. However, for in vivo applications such as localized treatment and tissue reconstruction, chemical immobilization provide important 1381-5148/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.reactfunctpolym.2010.02.005 * Tel.: +40 723 33 22 74; fax: +40 021 402 38 44. E-mail address: izabela.cristina.stancu@gmail.com Reactive & Functional Polymers 70 (2010) 314–324 Contents lists available at ScienceDirect Reactive & Functional Polymers journal homepage: www.elsevier.com/locate/react