Electrospun PLLA/PEG scaffolds Materials resemble neural network

The extensive and dynamic development of the cutting-edge technology electrospinning (from “electrostatic spinning”) has led to the creation of a new generation of advanced materials with unique features, with real potential to solve a variety of global social and economical problems. Moreover, electrospinning is the only technique that allows simple and efficient fabrication of micro- and nanosized porous scaffolds from biodegradable polymers with extremely high surface-to-volume ratios, porosity, and 3D structure. These electrospun fibrous biomaterials successfully mimic the size scales of fibers composing the extracellular matrix (ECM) of native tissues and organs [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. Therefore, it is a great challenge to fabricate electrospun fibrous scaffolds from aliphatic biodegradable polyesters because of their possible applications in tissue engineering, regenerative medicine, and wound healing.

Recently, the aliphatic biodegradable polyesters obtained from renewable resources (polylactides, polyhydroxyalkanoates, and their copolymers) have been accepted as one of the most promising biopolymers [11], [12]. Electrospinning of aliphatic polyesters is easily feasible and leads to the preparation of fibrous non-woven textiles with defined morphology. In addition, electrospun scaffolds possess a number of advantages – morphological resemblance to the ECM of the native tissues, possibility to be used as scaffolds for bone tissue engineering, etc. [13], [14], [15], [16]. However, the high hydrophobicity of aliphatic polyesters limits its range of applications. For these reasons, more effort has been aimed at blending aliphatic polyesters with appropriate agents (di- or triblock copolymers with a hydrophilic blocks, plasticizers, etc.) which are able to reduce the hydrophobicity, thus improving the overall applications of biopolymers [13], [17]. Furthermore, blending with hydrophilic homopolymers offers interesting possibilities to overcome its drawbacks, since it provides a relatively simple route for improving their performance. Hence, the selected approach provides opportunities for the simple preparation of electrospun fibers with improved hydrophilicity. Moreover, in this way a new generation of materials with varied composition and defined shape may be obtained. The proper selection of polymers and methods for their elaboration is the way to fulfill these requirements.

In our group, one focus is on identifying the possibilities for the preparation of micro- and nanofibrous biomaterials with improved properties (physical, mechanical, biological, etc.) by the suitable combination of selected polymers and by applying innovative methods and technologies. In this respect, and to the best of our knowledge, electrospinning of poly(l-lactide) (PLLA) spinning solutions mixed with hydrophilic polyethylene glycols (PEGs) have not yet been used. This is probably due to the difficult electrospinning of polymers with chain lengths shorter than is required for the formation of chain entanglements.

The cover SEM image is a result of an original, one-step method for the preparation of electrospun PLLA nanofibrous scaffolds with enhanced hydrophilicity by adding hydrophilic PEG. The PEGs with molecular weight lower than 6000 are widely used in the biomedical field because of their unique properties, including lack of toxicity and good biocompatibility [18]. In order to prepare scaffolds that mimic the size scales of fibers composing the extracellular matrix of native tissue, poly(l-lactide)/polyethylene glycol (PLLA/PEG) fibers were produced by electrospinning of their mixed solutions. In addition, the effect of the total polymer concentration on the fiber morphology and diameters was studied. It was found that at the lowest solution concentration fibers with “bead” defects are formed. The diameter and the morphology of the fibers were controlled by the polymer concentration and the composition of the spinning solution. The included PEG enhanced the hydrophilicity of the mats. The PLLA/PEG electrospun nanofibrous scaffolds were compatible with human dermal fibroblasts and osteoblast-like cell line. In long-term cultures osteoblast-like cells tended to spatially organize in tissue-like structure, thus indicating the potential of use of PLLA/PEG nanofibrous materials as tissue engineering scaffolds. Details can be found in the original article [19]. The prepared electrospun PLLA/PEG scaffold resembles a neural network and provides an efficient solution for the modulation of cellular response. The determination of the factors that impact the toxicity of electrospun fibrous materials with potential application as scaffolds in tissue engineering and regenerative medicine, as well as the control over these factors with the purpose of decreasing the toxicity of the fibrous materials, is important for the transfer of these fibrous materials from the lab to the industrial scale.

The presented SEM micrograph shows PLLA/PEG fibers resemble biological neural network. The micrograph was observed by Jeol JSM-5510 scanning electron microscope, equipped with Jeol JFC-1200 fine gold coater.


We acknowledge the use of scanning electron microscope of the Faculty of Chemistry and Pharmacy (FCP) at Sofia University “St. Kliment Ohridski” and thank Mr. Nikola Dimitrov for help.

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DOI: 10.1016/j.mattod.2019.07.001