Polydopamine Nanosphere with In-Situ Loaded Gentamicin and Its Antimicrobial Activity

Polydopamine surface functionalization of 3D printed resin material for enhanced polystyrene adhesion towards insulation layers for 3D microelectrode arrays (3D MEAs)

3D printing involves the use of photopolymerizable resins, which are toxic and typically have incompatible properties with materials such as polystyrene (PS), which present limitations for biomedical applications. We present a method to dramatically improve the poor adhesion between the PS insulative layer on 3D printed Microelectrode Array (MEA) substrates by functionalizing the resin surface with polydopamine (PDA), a mussel-inspired surface chemistry derivative. A commercial 3D printing prepolymer resin, FormLabs Clear (FLC), was printed using a digital light processing (DLP) printer and then surface functionalized with PDA by alkali-induced aqueous immersion deposition and self-polymerization. It was observed that the adhesion of the PS to FLC was improved due to the precision emanating from the DLP method and further improved after the functionalization of DLP printed substrates with PDA at 1, 12, and 24 h time intervals. The adhesion of PS was evaluated through scotch tape peel testing and instron measurements of planar substrates and incubation testing with qualitative analysis of printed culture wells. The composition and topology of the samples were studied to understand how the properties of the surface change after PDA functionalization and how this contributes to the overall improvement in PS adhesion. Furthermore, the surface energies at each PDA deposition time were calculated from contact angle studies as it related to adhesion. Finally, biocompatibility assays of the newly modified surfaces were performed using mouse cardiac cells (HL-1) to demonstrate the biocompatibility of the PDA functionalization process. PDA surface functionalization of 3D DLP printed FLC resin resulted in a dramatic improvement of thin film PS adhesion and proved to be a biocompatible solution for improving additive manufacturing processes to realize biosensors such as in vitro MEAs.

3D printing involves the use of toxic photopolymerizable resins which typically have incompatible properties with polystyrene for biomedical applications. Herein, we use 3D printing tricks and polydopamine to dramatically improve adhesion.

Research Progress on Polydopamine Nanoparticles for Tissue Engineering

Tissue engineering is an interdisciplinary field that aims to develop biological substitutes for the replacement, repair, or enhancement of tissue function. The physical and chemical characteristics of biomaterials exert a profound influence on the biological responses and the following biofunction. Nanostructured coatings have been widely applied as an effective surface modification strategy to improve the bioactivity of biomaterials. Especially, polydopamine and polydopamine-derived nanoparticles are found with excessive adhesiveness, redox activity, photothermal conversion capacity, paramagnetism and conductivity other than excellent biocompatibility, and hydrophilicity. In this article, advances about polydopamine nanoparticles in tissue engineering applications are reviewed, including the repair of bone, cartilage, skin, heart, and nerve, to provide strategies for future biomaterial design.

A dry electroencephalogram electrode for applications in steady-state visual evoked potential-based brain-computer interface systems

High-efficiency electroencephalogram (EEG) dry electrodes are a key component of brain-computer interface (BCI) technology because of their direct contact with the scalp. In this study, a semi-flexible polydopamine (PDA)/Pt-TiO₂ electrode is prepared for the dry-contact acquisition of EEG signals. The PDA biofilm adheres strongly to the scalp and maintains a dynamic balance of water and ions. The Pt nanoparticles and TiO₂ nanotube array together result in fast electron transfer. Therefore, the interface impedance between the dry PDA/Pt-TiO₂ electrode and scalp is as low as 19.63-24.53 kΩ. The spontaneous EEG signal collected simultaneously using the dry PDA/Pt-TiO₂ and wet Ag/AgCl electrodes had a correlation coefficient of up to 99.9%. In a steady-state visual evoked potential (SSVEP)-based BCI system, the dry electrode was used to collect EEG feedback signals for stimulations at 27 different frequencies in the range of 7-19.25 Hz. For these feedback signals, O1, Oz, and O2 channels in the occipital area exhibited high signal-to-noise ratios of 11.3, 11.8, and 11 dB, respectively. A volunteer wore an EEG headband with three PDA/Pt-TiO₂ dry electrodes and successfully controlled the robotic arm of the SSVEP-BCI system in the untrained mode. The dry PDA/Pt-TiO₂ electrode-based EEG cap is comfortable to wear, the identification signals of the SSVEP paradigm are accurate, and it is suitable for controlling external devices including a keyboard in the SSVEP-BCI system.

Bio-Applications of Multifunctional Melanin Nanoparticles: From Nanomedicine to Nanocosmetics

Bioinspired nanomaterials are ideal components for nanomedicine, by virtue of their expected biocompatibility or even complete lack of toxicity. Natural and artificial melanin-based nanoparticles (MNP), including polydopamine nanoparticles (PDA NP), excel for their extraordinary combination of additional optical, electronic, chemical, photophysical, and photochemical properties. Thanks to these features, melanin plays an important multifunctional role in the design of new platforms for nanomedicine where this material works not only as a mechanical support or scaffold, but as an active component for imaging, even multimodal, and simple or synergistic therapy. The number of examples of bio-applications of MNP increased dramatically in the last decade. Here, we review the most recent ones, focusing on the multiplicity of functions that melanin performs in theranostics platforms with increasing complexity. For the sake of clarity, we start analyzing briefly the main properties of melanin and its derivative as well as main natural sources and synthetic methods, moving to imaging application from mono-modal (fluorescence, photoacoustic, and magnetic resonance) to multi-modal, and then to mono-therapy (drug delivery, anti-oxidant, photothermal, and photodynamic), and finally to theranostics and synergistic therapies, including gene- and immuno- in combination to photothermal and photodynamic. Nanomedicine aims not only at the treatment of diseases, but also to their prevention, and melanin in nature performs a protective action, in the form of nanopigment, against UV-Vis radiations and oxidants. With these functions being at the border between nanomedicine and cosmetics nanotechnology, recently examples of applications of artificial MNP in cosmetics are increasing, paving the road to the birth of the new science of nanocosmetics. In the last part of this review, we summarize and discuss these important recent results that establish evidence of the interconnection between nanomedicine and cosmetics nanotechnology.