Electroactive scaffold

Similar to calix[n]arenes, porphyrins have been known to be one of the support pillars of supramolecular chemistry attributing suitable photoactive and electroactive properties to the molecular structures designed around them for building artificial molecular devices. Thus, various metallated and free base porphyrin-calixarene assemblies could afford attractive scaffolds for application in the areas of multipoint molecular recognition, receptors, host-guest chemistry, catalysis and photoinduced electron transfers. 

Synthesis of PEAs 146 8.6.1 Scaffolds from Electroactive Samples ... 

Scaffolds from Electroactive Samples and Electrospun Nanofibers... 

B. Guo, Y. Sun, A. Finne-Wistrand, K. Mustafa, A.-C. Albertsson, Electroactive porous tubular scaffolds with degradability and noncytotoxicity for neural tissue regenantion. Acta Biomater. 8 (1) (2012) 144-153, doi 10.1016/j.actbio.2011.09.027. 

Silica nanoparticles (Si NPs) have been successfully used for electrochemical DNA detection. As silica is inherently inactive electrochemically, these particles are either loaded with electroactive molecules and used as labels, or employed as scaffolds... 

In addition to above discussed applications, doped and undoped CPs also find extensive use in the other areas (Figure 1.66) like DSSCs, field-effect transistors (FETs), TFTs, display devices, catalysis, ECs, water purification, electroactive materials (electrorheological fluids, actuators, artificial muscles), tissue engineering scaffolds, memory devices, photocatalysis (degradation and synthesis), thermoelectric generation, electrochemical batteries, etc. [15,16,39,52,54,56,57,61,62,67,82,84,107,109, 112,113,149,153,162,169,240,244,309,314,387,401,422,423,446,514, 516,546,547,550,557,567-571], some of them will be elaborated in details in the following chapters. 

Motivated by the development of cardiac tissue engineering based on electrically active electrospun nanofibers, Fernandes and co-workers reported on the preparation of electrospun hyperbranched PLL nanofibers containing polyaniline in the form of nanotubes.Both electroactivity and biocompatibility demonstrated by the composite nanofibers opens the possibility of using this material as a scaffold in cardiac tissue engineering. 

Electrical stimulation has been shown to enhance nerve cell regeneration [124,125], the mechanisms for this effect are, however, unclear. One hypothesis is that an electrical stimulus alters the local electrical fields of extracellular matrix molecules, changing protein adsorption [126]. As early as 1994, studies into the suitability of ICPs such as PPy as neuronal scaffolds provided positive proof that these electroactive stimulus response polymers indeed have a role to play. Shastri et al. [127] showed that neurite extension of PC 12 cells was more pronounced on PPy surfaces as compared to tissue culture polystyrene. The authors also showed that the application of an electrical stimulus to the cell culture on the PPy film significantly increased the expression of neurites in the cells compared to the controls. In addition, they demonstrated through tissue compatibility and transected sciatic nerve regeneration studies in rat models that the PPy films invoke little negative response and support nerve regeneration. 

The inertness of polymers could prove very beneficial if they possessed certain bulk properties such as electrical or magnetic susceptibility that one could exploit. We believe that the electroactive polymers, namely electronically and ionically conducting polymers, piezoelectrics, and electrets, by virtue of their susceptibility to either mechanical or electromagnetic or thermal or optical phenomena, could be utilized to interface between the external world and the physiological environment and could prove quite beneficial in eliciting the desired cellular response. These polymers represents a new modality in the development of interactive scaffolds for tissue stimulation, tissue regeneration, and the development of bioartificial organs. 

Electroactive Polymers Interactive Scaffolds for Tissue Regeneration... 

Disks of PLGA-laminated polypyrrole thick (2-4 pm) films have been evaluated for their in vivo biocompatibility in rat models with excellent results. Tubular guidance channels fabricated from laminated polypyrrole films have been utilized successfully to bridge a 10-mm. sciatic nerve gap in rat models [52]. These studies have demonstrated the potential of polypyrrole scaffold in particular and electroactive polymers in general in stimulated tissue regeneration. 

Mackle, J.N., Blond, D.J., Mooney, E., Mcdonnell, C., Blau, W.J., Shaw, G., Barry, F.P., Murphy, J.M., Barron, V., 2011. In vitro characterization of an electroactive carbon-nanotube-based nanofiber scaffold for tissue engineering. Macromolecular Bioscience 11, 1272-1282. 

The physical, chemical, and electrical properties of PPy can be easily modified by various doping agents and preparation conditions. There are many available dopant ions for the generation of good quality deposited polymer films [63-64]. Two of the most common dopants that are codeposited with PPy are polystyrene-sulfonate (PSS) and sodium dodecylbenzenesulfonate (NaDBS). PPy/PSS and PPy/NaDBS polymers have been used in many applications ranging from actuators and neural scaffolds to neural electrode coatings [22, 53, 61, 65]. It is reported that electrode materials, electrolyte solution, deposition methods (current-or potential-controlled deposition), deposition time, and solution temperature during electrochemical polymerization affect both the structure and electroactivity of PPy films [66]. 

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