A highly sensitive molecular structural probe applied to in situ biosensing of metabolites using PEDOT:PSS.

A large amount of research within organic biosensors is dominated by organic electrochemical transistors (OECTs) that use conducting polymers such as poly(3,4-ethylene dioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS). Despite the recent advances in OECT-based biosensors, the sensing is solely reliant on the amperometric detection of the bioanalytes. This is typically accompanied by large undesirable parasitic electrical signals from the electroactive components in the electrolyte. Herein, we present the use of in situ resonance Raman spectroscopy to probe subtle molecular structural changes of PEDOT:PSS associated with its doping level. We demonstrate how such doping level changes of PEDOT:PSS can be used, for the first time, on operational OECTs for sensitive and selective metabolite sensing while simultaneously performing amperometric detection of the analyte. We test the sensitivity by molecularly sensing a lowest glucose concentration of 0.02 mM in phosphate-buffered saline solution. By changing the electrolyte to cell culture media, the selectivity of in situ resonance Raman spectroscopy is emphasized as it remains unaffected by other electroactive components in the electrolyte. The application of this molecular structural probe highlights the importance of developing biosensing probes that benefit from high sensitivity of the material's structural and electrical properties while being complimentary with the electronic methods of detection.UK EPSRC for the Plastic Electronics Centre for Doctoral Training (EP/L016702/1

Corrigendum: 3D Hybrid Scaffolds Based on PEDOT:PSS/MWCNT Composites.

[This corrects the article DOI: 10.3389/fchem.2019.00363.]

3D Hybrid Scaffolds Based on PEDOT:PSS/MWCNT Composites

Conducting polymer scaffolds combine the soft-porous structures of scaffolds with the electrical properties of conducting polymers. In most cases, such functional systems are developed by combining an insulating scaffold matrix with electrically conducting materials in a 3D hybrid network. However, issues arising from the poor electronic properties of such hybrid systems, hinder their application in many areas. This work reports on the design of a 3D electroactive scaffold, which is free of an insulating matrix. These 3D polymer constructs comprise of a water soluble conducting polymer (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNTs). The insertion of the MWCNTs in the 3D polymer matrix directly contributes to the electron transport efficiency, resulting in a 7-fold decrease in resistivity values. The distribution of CNTs, as characterized by SEM and Raman spectroscopy, further define the micro- and nano-structural topography while providing active sites for protein attachment, thereby rendering the system suitable for biological/sensing applications. The resulting scaffolds, combine high porosity, mechanical stability and excellent conducting properties, thus can be suitable for a variety of applications ranging from tissue engineering and biomedical devices to (bio-) energy storage

Conducting Polymer Scaffolds Based on Poly(3,4-ethylenedioxythiophene) and Xanthan Gum for Live-Cell Monitoring.

Conducting polymer scaffolds can promote cell growth by electrical stimulation, which is advantageous for some specific type of cells such as neurons, muscle, or cardiac cells. As an additional feature, the measure of their impedance has been demonstrated as a tool to monitor cell growth within the scaffold. In this work, we present innovative conducting polymer porous scaffolds based on poly(3,4-ethylenedioxythiophene) (PEDOT):xanthan gum instead of the well-known PEDOT:polystyrene sulfonate scaffolds. These novel scaffolds combine the conductivity of PEDOT and the mechanical support and biocompatibility provided by a polysaccharide, xanthan gum. For this purpose, first, the oxidative chemical polymerization of 3,4-ethylenedioxythiophene was carried out in the presence of polysaccharides leading to stable PEDOT:xanthan gum aqueous dispersions. Then, by a simple freeze-drying process, porous scaffolds were prepared from these dispersions. Our results indicated that the porosity of the scaffolds and mechanical properties are tuned by the solid content and formulation of the initial PEDOT:polysaccharide dispersion. Scaffolds showed interconnected pore structure with tunable sizes ranging between 10 and 150 μm and Young's moduli between 10 and 45 kPa. These scaffolds successfully support three-dimensional cell cultures of MDCK II eGFP and MDCK II LifeAct epithelial cells, achieving good cell attachment with very high degree of pore coverage. Interestingly, by measuring the impedance of the synthesized PEDOT scaffolds, the growth of the cells could be monitored

Biomimetic and electroactive 3D scaffolds for human neural crest-derived stem cell expansion and osteogenic differentiation

Abstract: Osteoporosis is a skeletal disease characterized by bone loss and bone microarchitectural deterioration. The combination of smart materials and stem cells represents a new therapeutic approach. In the present study, highly porous scaffolds are prepared by combining the conducting polymer PEDOT:PSS with collagen type I, the most abundant protein in bone. The inclusion of collagen proves to be an effective way to modulate their mechanical properties and it induces an increase in scaffolds’ electrochemical impedance. The biomimetic scaffolds support neural crest-derived stem cell osteogenic differentiation, with no need for scaffold pre-conditioning contrarily to other reports

Novel approaches for the deposition and the patterning of materials towards the fabrication of organic electronic devices

International audienc

Deposition and characterization of organic materials for organic electronics applications

The present thesis aims in the development and characterization of organic thin films as the active channel towards the realization of OFETs. We herein investigated new and innovative solution-based techniques for the deposition of the organic semiconductors and we examined both the morphological and structural properties of the resulting films towards the improvement of the electrical behavior of the fabricated devices. The organic materials examined, include the p-type TIPS-pentacene (TIPS-PEN) and diF-TES-anthradithiophene (diF-TES-ADT), as well as n-type napthalene-bisimide derivative (NBI-4-n-BuPh). In the initial steps of this study, we examined the methodology and the overall procedure followed, towards the development of all the critical layers of the OFETs, based on simple vacuum and solution -based methods, including all the appropriate surface modifications. Following, we investigated a commonly used and large-scale compatible technique, blade coating. Specifically, we examined two alternative approaches towards the deposition of the organic layer, based in the incorporation of dielectric polymers towards the improvement of the rheological behavior of the semiconducting solution. In the first approach, the semiconductor:polymer (TIPS-PEN:PS/ PMMA) blends led in high-quality crystalline structures, with excellent electrical characteristics and field-effect mobility up to 0.47 cm2/Vs. In the second approach, polymeric buffer layers were incorporated between the semiconductor and the insulator to improve the poor adhesion of the semiconductor to the dielectric layer. This, along with the use of an innovative method namely “non-isotropic solvent evaporation” for the controlled crystallization of TIPS-PEN, resulted in highly oriented and homogenous crystalline structures and led to the realization of high performance OFETs with field-effect mobility up to 0.52 ±0.11 cm2/Vs, low threshold voltage, on/off current ratio >104 and enhanced stability both under electrical stress and ambient conditions. A new and innovative method was also studied in the present thesis, the electrostatic deposition. Specifically, two different function modes of this technique were examined. In the first approach, electrostatic spraying deposition was applied in order to produce micro-droplets of the organic materials with desired sizes and to control their crystallization behavior. In the second approach, electrospinning deposition was applied towards the fabrication of a polymeric (PVA) fiber-based mesh to control the crystalline growth of the either blade-coated or spin-coated TIPS-PEN films. Indeed a substantial improvement in the morphological and structural characteristics of the resulting films was observed, with the spin-coated film showing a remarkable enhancement in the structural order of its crystalline domains, exhibiting one of the highest field-effect mobility (0.11 cm2/Vs) reported for spin-coated TIPS-PEN OFETs. In the last part of this work, high performance n-type OFETs were fabricated based on a new semiconducting material, NBI-4-n-BuPh. Specifically, zone-casting was applied for the deposition of NBI-4-n-BuPh, in order to develop well-oriented crystalline structures. The synergy of the architecture (bottom-contact/top-gate) along with the use of Parylene-C as dielectric layer and the high quality of the crystal domains resulted in devices with excellent electrical characteristics and remarkable environmental stability. All the above findings open up new possibilities for research in other related organic materials as well as their fabrication processes.Η παρούσα διδακτορική διατριβή εστιάζεται στην ανάπτυξη και τον χαρακτηρισμό λεπτών υμενίων οργανικών και ανόργανων υλικών για την κατασκευή OFETs. H μελέτη που πραγματοποιήθηκε, εστιάστηκε τόσο στην διερεύνηση νέων τεχνικών εναπόθεσης του ενεργού στρώματος του ημιαγωγού όσο και στη βελτίωση των μορφολογικών και δομικών χαρακτηριστικών των παραγόμενων υμενίων. Ως ενεργά υλικά, εφαρμόστηκαν κατά κύριο λόγο διαλυτοί οργανικοί ημιαγωγοί p-τύπου όπως το TIPS-pentacene (TIPS-PEN) και το diF-TES-anthradithiophene (diF-TES-ADT), καθώς και n-τύπου όπως ένα παράγωγο του naphthalene-bisimide (NBI-4-n-BuPh). Στα πρωταρχικά στάδια της μελέτης αυτής εξετάστηκε η μεθοδολογία ανάπτυξης και τροποποίησης των κρίσιμων στρωμάτων προκειμένου να καθοριστεί το πρωτόκολλο κατασκευής διατάξεων OFETs. Στη συνέχεια μελετήθηκε η κατασκευή OFETs βασισμένων στο TIPS-PEN, χρησιμοποιώντας μια μέθοδο ανάπτυξης ευρείας κλίμακας, αυτή της επίστρωσης λεπίδας (blade-coating). Για την εναπόθεση του ενεργού στρώματος, δοκιμάστηκαν δυο διαφορετικές προσεγγίσεις, οι οποίες στηρίζονται στην χρήση πολυμερικών διηλεκτρικών υλικών, προκειμένου να βελτιωθεί η ρεολογική συμπεριφορά του διαλύματος του ημιαγωγού κατά την ανάπτυξη του. Στη πρώτη περίπτωση, η χρήση μιγμάτων TIPS-PEN και πολυμερούς (PS ή PMMA) σε ισόποση αναλογία, οδήγησε στον σχηματισμό ποιοτικότερων κρυσταλλικών δομών, γεγονός που επιβεβαιώθηκε από τις εξαιρετικές τιμές ευκινησίας φορέων φορτίου έως 0.47 cm2/Vs. Στη δεύτερη περίπτωση, η χρήση των παραπάνω πολυμερών ως ενδιάμεσα βοηθητικά στρώματα μεταξύ του ημιαγωγού και του μονωτικού στρώματος, βελτίωσε σημαντικά την πρόσφυση του ημιαγωγού στον μονωτικό στρώμα του οξειδίου. Αυτό, σε συνδυασμό με τη χρήση μιας καινοτόμου μεθόδου επιλεκτικής κρυσταλλοποίησης (“μη-ισότροπη εξάτμιση διαλύτη”) οδήγησε στην επίτευξη επιθυμητού ομοαξονικού κρυσταλλικού προσανατολισμού και υψηλής ομοιομορφίας σε μακροσκοπική κλίμακα. Οι διατάξεις OFETs εμφάνισαν υψηλές τιμές ευκινησίας φορέων φορτίου (0.52 cm2/Vs), χαμηλή τάση κατωφλίου και λόγους ρευμάτων >104 καθώς και ενισχυμένη σταθερότητά τόσο σε ηλεκτρική καταπόνηση, όσο και σε παρατεταμένη παραμονή σε συνθήκες ατμόσφαιρας. Ακολούθως, εξετάστηκε η εφαρμογή της μεθόδου ηλεκτροστατικής εναπόθεσης για την κατασκευή OFETs. Ειδικότερα, μελετήθηκαν δυο διαφορετικές καταστάσεις λειτουργίας της τεχνικής, αυτή του ηλεκτροστατικού ψεκασμού καθώς και αυτή της ηλεκτροστατικής ινοποίησης. Κατά τον ηλεκτροστατικό ψεκασμό, οι βελτιστοποιημένες παράμετροι ανάπτυξης των παραγόμενων σταγονιδίων συντέλεσαν στην δημιουργία ποιοτικών κρυσταλλικών υμενίων επάνω σε διαφορετικά υποστρώματα. Η λειτουργία της ηλεκτροστατικής ινοποίησης χρησιμοποιήθηκε για τη δημιουργία ενός βοηθητικού πλέγματος πολυμερικών ινών (PVA), με στόχο τον έλεγχο της κρυσταλλικής μορφολογίας των οργανικών ημιαγωγών. Η βελτίωση των δομικών και μορφολογικών χαρακτηριστικών, επιβεβαιώθηκε από τη μέγιστη τιμή ευκινησίας που επιτεύχθηκε (0.11 cm2/Vs) και αποτελεί μια από τις μεγαλύτερες που έχουν αναφερθεί στη βιβλιογραφία για TIPS-PEN OFETs από spin-coating. Τέλος, κατασκευάστηκαν n-τύπου OFETs υψηλής απόδοσης και σταθερότητας, βασισμένα στο NBI-4-n-BuPh. Για την ανάπτυξη του ενεργού στρώματος εφαρμόστηκε η τεχνική zone-casting. Ο συνδυασμός της γεωμετρίας bottom-contact/top-gate, της χρήσης του Parylene-C ως μονωτικού στρώματος και της υψηλής ποιότητας κρυστάλλων που προέκυψαν από την τεχνική ανάπτυξης, οδήγησε σε σταθερές διατάξεις n-τύπου με ευκινησίες ηλεκτρονίων από τις υψηλότερες που έχουν αναφερθεί. Συμπερασματικά, μέσω της παρούσας διατριβής πραγματοποιήθηκε η κατασκευή λειτουργικών διατάξεων OFETs υψηλής απόδοσης με χρήση υγρών τεχνικών, οι οποίες προσαρμόστηκαν κατάλληλα ώστε να επιτευχθεί η βέλτιστη κρυσταλλική μορφολογία του ημιαγώγιμου στρώματος. Τα αποτελέσματα που προέκυψαν αναμένεται να δώσουν σημαντική ώθηση για περαιτέρω διερεύνηση συναφών οργανικών ημιαγώγιμων ενώσεων καθώς και διαδικασιών ανάπτυξης τους

3D Hybrid Scaffolds Based on PEDOT:PSS/MWCNT Composites

Conducting polymer scaffolds combine the soft-porous structures of scaffolds with the electrical properties of conducting polymers. In most cases, such functional systems are developed by combining an insulating scaffold matrix with electrically conducting materials in a 3D hybrid network. However, issues arising from the poor electronic properties of such hybrid systems, hinder their application in many areas. This work reports on the design of a 3D electroactive scaffold, which is free of an insulating matrix. These 3D polymer constructs comprise of a water soluble conducting polymer (PEDOT:PSS) and multi-walled carbon nanotubes (MWCNTs). The insertion of the MWCNTs in the 3D polymer matrix directly contributes to the electron transport efficiency, resulting in a 7-fold decrease in resistivity values. The distribution of CNTs, as characterized by SEM and Raman spectroscopy, further define the micro- and nano-structural topography while providing active sites for protein attachment, thereby rendering the system suitable for biological/sensing applications. The resulting scaffolds, combine high porosity, mechanical stability and excellent conducting properties, thus can be suitable for a variety of applications ranging from tissue engineering and biomedical devices to (bio-) energy storage

Conducting Polymer Scaffolds Based on Poly(3,4-ethylenedioxythiophene) and Xanthan Gum for Live-Cell Monitoring.

Conducting polymer scaffolds can promote cell growth by electrical stimulation, which is advantageous for some specific type of cells such as neurons, muscle, or cardiac cells. As an additional feature, the measure of their impedance has been demonstrated as a tool to monitor cell growth within the scaffold. In this work, we present innovative conducting polymer porous scaffolds based on poly(3,4-ethylenedioxythiophene) (PEDOT):xanthan gum instead of the well-known PEDOT:polystyrene sulfonate scaffolds. These novel scaffolds combine the conductivity of PEDOT and the mechanical support and biocompatibility provided by a polysaccharide, xanthan gum. For this purpose, first, the oxidative chemical polymerization of 3,4-ethylenedioxythiophene was carried out in the presence of polysaccharides leading to stable PEDOT:xanthan gum aqueous dispersions. Then, by a simple freeze-drying process, porous scaffolds were prepared from these dispersions. Our results indicated that the porosity of the scaffolds and mechanical properties are tuned by the solid content and formulation of the initial PEDOT:polysaccharide dispersion. Scaffolds showed interconnected pore structure with tunable sizes ranging between 10 and 150 μm and Young's moduli between 10 and 45 kPa. These scaffolds successfully support three-dimensional cell cultures of MDCK II eGFP and MDCK II LifeAct epithelial cells, achieving good cell attachment with very high degree of pore coverage. Interestingly, by measuring the impedance of the synthesized PEDOT scaffolds, the growth of the cells could be monitored

Bacterial Membrane Mimetics: From Biosensing to Disease Prevention and Treatment.

Peer reviewed: TruePlasma membrane mimetics can potentially play a vital role in drug discovery and immunotherapy owing to the versatility to assemble facilely cellular membranes on surfaces and/or nanoparticles, allowing for direct assessment of drug/membrane interactions. Recently, bacterial membranes (BMs) have found widespread applications in biomedical research as antibiotic resistance is on the rise, and bacteria-associated infections have become one of the major causes of death worldwide. Over the last decade, BM research has greatly benefited from parallel advancements in nanotechnology and bioelectronics, resulting in multifaceted systems for a variety of sensing and drug discovery applications. As such, BMs coated on electroactive surfaces are a particularly promising label-free platform to investigate interfacial phenomena, as well as interactions with drugs at the first point of contact: the bacterial membrane. Another common approach suggests the use of lipid-coated nanoparticles as a drug carrier system for therapies for infectious diseases and cancer. Herein, we discuss emerging platforms that make use of BMs for biosensing, bioimaging, drug delivery/discovery, and immunotherapy, focusing on bacterial infections and cancer. Further, we detail the synthesis and characteristics of BMs, followed by various models for utilizing them in biomedical applications. The key research areas required to augment the characteristics of bacterial membranes to facilitate wider applicability are also touched upon. Overall, this review provides an interdisciplinary approach to exploit the potential of BMs and current emerging technologies to generate novel solutions to unmet clinical needs