This study aimed to evaluate the in vitro performance of activated platelet-rich plasma associated with porous sponges of chitosan as a composite scaffold for proliferation and osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells. The sponges were prepared by controlled freezing (−20, −80, or −196°C) and lyophilization of chitosan solutions (1, 2, or 3% w/v). The platelet-rich plasma was obtained from controlled centrifugation of whole blood and activated with calcium and autologous serum. The composite scaffolds were prepared by embedding the sponges with the activated platelet-rich plasma. The results showed the performance of the scaffolds was superior to that of activated platelet-rich plasma alone, in terms of delaying the release of growth factors and increased proliferation of the stem cells. The best preparation conditions of chitosan composite scaffolds that coordinated the physicochemical and mechanical properties and cell proliferation were 3% (w/v) chitosan and a −20°C freezing temperature, while −196°C favored osteogenic differentiation. Although the composite scaffolds are promising for regenerative medicine, the structures require stabilization to prevent the collapse observed after five days.

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Due to their minimally invasive implantation procedures, injectable scaffolds have being widely investigated and are considered promising in tissue engineering [1]. From the clinical perspective, the use of injectable scaffolds is advantageous because it minimizes patient discomfort, the risk of infection and scarring, and the cost of treatment [2]. Furthermore, injectable scaffolds can homogeneously fill the defect or repair point and can incorporate cells and various therapeutic agents such as growth factors prior to injection [3]. From the biomaterial perspective, adequate injectable scaffolds must be nontoxic, biodegradable, and sterilizable. Moreover, they must solidify under mild conditions, show mechanical strength and resistance to in situ forces and allow for the incorporation of bioactive molecules. Various types of biodegradable materials have been proposed for the preparation of injectable scaffolds used in tissue engineering. Considerable attention has been given to chitosan-based materials, primarily due to their similarities with the extracellular matrix, chemical versatility, good biological performance, and specific cellular interactions [4]. Chitosan scaffolds has been prepared as hydrogels by physical associatiation [5], coordination with metal ions [6] and chemical crosslinking [7]. However, the use of chemical crosslinking

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