pH-sensitive hydrogels play an important role in controlled drug release applications and have the potential to impact the management of wounds. In this study, we report the fabrication of novel ...carboxylated agarose/tannic acid hydrogel scaffolds cross-linked with zinc ions for the pH-controlled release of tannic acid. The resulting hydrogels exhibited negligible release of tannic acid at neutral and alkaline pH and sustained release at acidic pH, where they also displayed maximum swelling. The hydrogels also displayed favorable antibacterial and anti-inflammatory properties, and a lack of cytotoxicity toward 3T3 fibroblast cell lines. In simulated wound assays, significantly greater cell migration and proliferation was observed for cells exposed to tannic acid hydrogel extracts. In addition, the tannic acid hydrogels were able to suppress NO production in stimulated human macrophages in a concentration-dependent manner, indicating effective anti-inflammatory activity. Taken together, the cytocompatibility, antibacterial, and anti-inflammatory characteristics of these novel pH-sensitive hydrogels make them promising candidates for wound dressings.
Neurological disorders such as Alzheimer's disease, stroke, and brain cancers are difficult to treat with current drugs as their delivery efficacy to the brain is severely hampered by the presence of ...the blood–brain barrier (BBB). Drug delivery systems have been extensively explored in recent decades aiming to circumvent this barrier. In particular, polymeric nanoparticles have shown enormous potentials owing to their unique properties, such as high tunability, ease of synthesis, and control over drug release profile. However, careful analysis of their performance in effective drug transport across the BBB should be performed using clinically relevant testing models. In this review, polymeric nanoparticle systems for drug delivery to the central nervous system are discussed with an emphasis on the effects of particle size, shape, and surface modifications on BBB penetration. Moreover, the authors critically analyze the current in vitro and in vivo models used to evaluate BBB penetration efficacy, including the latest developments in the BBB‐on‐a‐chip models. Finally, the challenges and future perspectives for the development of polymeric nanoparticles to combat neurological disorders are discussed.
This review highlights the development of polymeric nanoparticles for drug delivery to the central nervous system. The synthesis of promising polymeric nanoparticles is discussed with an emphasis on the effects of particle size, shape, and surface modification on blood–brain barrier (BBB) transfer. Moreover, current in vitro and in vivo models are discussed, including the latest advances in BBB‐on‐a‐chip models.
Metal-assisted chemical etching (MACE) affords porous silicon nanostructures control over size, shape, and porosity in a single step. Simplicity and flexibility are potential advantages over more ...traditional silicon bulk micromachining techniques. MACE-generated porous micro- and nanostructures are suitable as biomaterials through their length scales and biocompatibility.
This work provides a comprehensive overview of the MACE reaction mechanism that yields biomedically relevant silicon nanostructures – from nanowires, nanopillars, to sub-micrometer holes and pores. We discuss their biomedical applications in biosensors, cell capture and transfection arrays, and drug delivery vectors. We assess the reported benefits of the various nanostructures and discuss whether MACE provides clear and distinct advantages over other techniques.
The flexibility and simplicity of MACE comes at a cost. The reaction parameters are many and inter-related, and we lack a full model of the etching mechanism. While the cathode reaction is well understood, the anode reaction involving dissolution of the silicon remains controversial. Such uncertainties impede rational design of specific structures that address biomedical requirements. We summarize current understanding to provide design guidelines for structures used in biomedicine and review the effects of key parameters on the morphological attributes of the etched features.
•Simple and effective fabrication method of an array of gold microneedles.•Structural and electrochemical characterisation of gold microneedles.•Demonstration of the potential of microneedles array ...as electrochemical biosensors.
Here we present the simple and effective fabrication method of an array of gold microneedles (AuMNs) via the casting of conductive gold ink. To demonstrate the potential of MN arrays as electrochemical biosensors we functionalized AuMNs with an epoxy- and ferrocene-functional polymeric mediator and covalently immobilised urease. The performance of the MN array biosensor for urea detection was assessed in artificial interstitial fluid and epidermal/skin mimic, both spiked with urea. The analytical performance of MN biosensor shows that urea is detected in the range of 50–2500 µM, with a calculated limit of detection of 2.8 µM and sensitivity of 31 nA/mM. The results reveal that these MN-based biosensors may underpin the development of wearable real-time monitoring devices.
We demonstrate a fabrication breakthrough to produce large-area arrays of vertically aligned silicon nanowires (VA-SiNWs) with full tunability of the geometry of the single nanowires and of the whole ...array, paving the way toward advanced programmable designs of nanowire platforms. At the core of our fabrication route, termed “Soft Nanoparticle Templating”, is the conversion of gradually compressed self-assembled monolayers of soft nanoparticles (microgels) at a water–oil interface into customized lithographical masks to create VA-SiNW arrays by means of metal-assisted chemical etching (MACE). This combination of bottom-up and top-down techniques affords excellent control of nanowire etching site locations, enabling independent control of nanowire spacing, diameter and height in a single fabrication route. We demonstrate the fabrication of centimeter-scale two-dimensional gradient photonic crystals exhibiting continuously varying structural colors across the entire visible spectrum on a single silicon substrate, and the formation of tunable optical cavities supported by the VA-SiNWs, as unambiguously demonstrated through numerical simulations. Finally, Soft Nanoparticle Templating is combined with optical lithography to create hierarchical and programmable VA-SiNW patterns.
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•Skin biofluids contain a wealth of molecular information related to an individual’s health and wellbeing state.•These biofluids (i.e. sweat, interstitial fluid, blood) may be ...on-invasively accessed and analysed using wearable technology.•Novel wearable biosensors are able to detect physiological levels of biomarkers for disease diagnosis and health monitoring.•Advancements in nano- and micro-technologies have greatly contributed to the development of wearable biosensors.•This review highlights the challenges and opportunities on wearable biosensing systems, and anticipates research directions.
The skin, as the largest and most accessible organ in the human body, contains biofluids rich in biomarkers useful not only in diagnosis and monitoring of diseases, but also in profiling an individual’s wellbeing. Advancements in micro- and nanotechnology research have underpinned the development of multifunctional wearable sensing devices. Those sensors may allow monitoring of physiological parameters from different skin sections such as epidermis, dermis and hypodermis by sampling various bodily fluids. Our review summarizes current advances in wearable biosensors for on-skin analysis of sweat, transdermal monitoring of interstitial fluid and analysis of subcutaneous fluids via implanted devices. The review is divided into three main parts describing biosensors acting on the different skin sections. Each part focuses on recent scientific and technological advancements in the wearable biosensing field by highlighting critical challenges as well as providing information on how these barriers are being addressed by the research community.
A turn-on orange-red fluorescent nanosensor based on rhodamine B derivative-functionalized graphene quantum dots (RBD-GQDs) has been successfully synthesized for Fe3+ detection with high sensitivity ...and selectivity. By connecting with GQDs, the water solubility, sensitivity, photostability, and biocompatibility of RBD are drastically improved. The most distinctive feature of the RBD-GQDs, which sets them apart from other previously reported fluorophores or GQDs, is that they with the detection limits as low as 0.02 μM are demonstrated as a Fe3+ turn-on fluorescent nanosensor in cancer stem cells. Fe3+ binding to such GQDs (RBD-GQDs-Fe3+) with orange-red fluorescence of 43% quantum yield were demonstrated to be the biomarkers for cancer stem cell imaging.
Silicon, in its various forms, finds widespread use in electronic, optical, and structural materials. Research on uses of silicon and silica has been intense for decades, raising the question of how ...much diversity is left for innovation with this element. Shape variation is particularly well examined. Here, we review the principles revealed by diatom frustules, the porous silica shells of diatoms, microscopic, unicellular algae. The frustules have nanometer‐scale detail, and the almost 100 000 species with unique frustule morphologies suggest nuanced structural and optical functions well beyond the current ranges used in advanced materials. The unique frustule morphologies have arisen through tens of millions of years of evolutionary selection, and so are likely to reflect optimized design and function. Performing the structural and optical equivalent of data mining, and understanding and adopting these designs, affords a new paradigm in materials science, an alternative to combinatorial materials synthesis approaches in spurring the development of new material and more nuanced materials.
The world's smallest silica nanofabrication factories: a remarkable diversity of shapes and pore architectures of diatom biosilica irrefutably demonstrates precision and brilliance of natural design at the micro and nanoscale, providing a range of lessons that current and future nanotechnology researchers can learn from diatoms.
Abnormal dopamine neurotransmission is associated with several neurological and psychiatric disorders such as Parkinson's disease, schizophrenia, attention deficiency and hyperactivity disorder, and ...addiction. Developing highly sensitive, selective, and fast dopamine monitoring methods is of high importance especially for the early diagnosis of these diseases. Herein, we report a new ultrasensitive electrochemical sensing platform for
monitoring of cell-secreted dopamine using Au-coated arrays of micropyramid structures integrated directly into a Petri dish. This approach enables the monitoring of dopamine released from cells in real-time without the need for relocating cultured cells. According to the electrochemical analyses, our dopamine sensing platform exhibits excellent analytical characteristics with a detection limit of 0.50 ± 0.08 nM, a wide linear range of 0.01-500 μM, and a sensitivity of 0.18 ± 0.01 μA/μM. The sensor also has remarkable selectivity toward DA in the presence of different potentially interfering small molecules. The developed electrochemical sensor has great potential for
analysis of neuronal cells as well as early diagnosis of different neurological diseases related to abnormal levels of dopamine.
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