DOI: 10.1002/adem.200900092 Matrix Assisted Pulsed Laser Evaporation (MAPLE) of Poly(D,L lactide) (PDLLA) on Three Dimensional Bioglass 1 Structures By Valeria Califano * , Francesco Bloisi, Luciano R. M. Vicari, Darmawati M. Yunos, Xanthipi Chatzistavrou and Aldo R. Boccaccini Introduction Tissue engineering and the related discipline of regen- erative medicine remain a flourishing area of research with potential new treatments for many more diseases [1] . The advances involve researchers in a multitude of disciplines, including cell biology, biomaterials science, imaging, and characterization of surfaces and cell material interactions. [1,2] Tissue regeneration is required where damage has occurred to tissues and organs due to disease or injury. In a common tissue engineering strategy, bioresorbable scaffolds made of engi- neered biomaterials are used to give a temporary mechanical support for natural tissue regeneration, effectively acting as an artificial extracellular matrix since they allow ideal conditions for cell survival and proliferation. [2–5] Such materials must show adequate properties from both the biological and mechanical points of view, [5] in particular bone engineering requires scaffolds with a controllable interconnected porosity to direct the cells to grow into the desired physical structure of the tissue. Simultaneously, bone scaffolds must be sufficiently strong and not collapse during handling and after implanta- tion. Both natural and synthetic materials are been investi- gated for tissue-engineering of bone. 45S5 Bioglass is a commercially available bioactive glass developed and first studied by Hench et al. [6] The main advantage of Bioglass is its high bioactivity due to its optimized composition comprising SiO 2 (45 wt%), Na 2 O (24.5 wt%), CaO (24.5 wt%), and P 2 O 5 (6 wt%). The disadvantage of Bioglass, being a very brittle material, is the mechanical weakness and low fracture toughness. Since it was first synthesized, this material has been largely studied and applied, mainly as small implant, bone filler, and coating. [7] However, in the last years it has been also investigated for bone tissue engineering scaffolds, on its own [8] or in combination with polymers. [9,10] Several approaches have been proposed in order to improve the mechanical properties of Bioglass based scaffolds, mainly combining it with synthetic polyesters. [10] Polylactides, polyglycolides, and their copolymers have found a wide range of biomedical applications due to their biocompatibility and biodegradability. [11] In particular, poly- lactides derived from lactic acid, degrade in the human body via a hydrolytic reaction first producing oligomers and then lactic acids, of which the L-lactic acid is a natural intermediate in carbohydrate metabolism. Both poly(L-lactide) (PLLA) and poly(D-lactide) (PDLA) are semi-crystalline, while poly- (D,L-lactide) (PDLLA), consisting of racemic lactate units, is amorphous. Although the mechanical properties of PLLA and PDLA are superior with respect to PDLLA, those polymers are brittle at room temperature. [13] Due to its relatively high rate of degradation and biocompatibility, PDLLA has been exten- sively studied for in-vivo biomedical applications, especially for controlled drug delivery systems and tissue engineering scaffolds. [3] PDLLA has been also considered as coating material to improve the mechanical properties of brittle bioactive glass scaffolds for bone tissue engineering. [10] In using a polymeric coating in order to improve the mechanical properties of scaffolds, it must be taken into account that the porosity of the structure must be maintained, e.g., high control of coating thickness and homogeneous covering of the foam struts should be achieved. This requirement has induced us to use for this purpose matrix assisted pulsed laser evaporation (MAPLE) technique, inspired by pulsed laser deposition (PLD), but well suited for polymeric or organic materials. [12,13] In PLD, a solid target of the material to be deposited is ablated by a pulsed laser beam and the ablated material is deposited onto the desired substrate. In MAPLE, a technique first developed at the U.S. Naval Research Laboratory, [12] the target is a frozen solution of the molecules to be deposited in a highly volatile and light-absorbing solvent. MAPLE provides a softer mechanism of ablation with respect to PLD allowing the deposition of intact polymer molecules both if the laser energy is absorbed by the solvent (solute ejection due to abrupt solvent vaporization) [14] and if it is absorbed by the solute itself COMMUNICATION [*] Dr. V. Califano Instituto Motori CNR, Via G. Marconi 8. 80125 Napoli, Italy E-mail: valeriacalifano@hotmail.com Prof. F. Bloisi Universita`degli Studi di Napoli Federico II, Dipartimento di Scienze Fisiche, Facolta`di Ingegneria, Napoli, Italy Prof. L. R. M. Vicari CNR/INFM-Coherentia, Napoli, Italy D. M. Yunos, Dr. X. Chatzistavrou, Prof. Dr. Ing. A. R. Boccaccini Department of Materials, Imperial College London, London, UK ADVANCED ENGINEERING MATERIALS 2009, 11, No. 8 ß 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 685