A smartphone-integrated aptasensor for pesticide detection using gold-decorated microparticles.

The increasing incidence of environmental concerns related to excessive use of pesticides, such as imidacloprid and carbendazim, poses risks to pollinators, water bodies, and human health, prompting regulatory scrutiny and bans in developed countries. In this study, we propose a portable smartphone-based biosensor for rapid and label-free colorimetric detection by using the gold-decorated polystyrene microparticles (Ps-AuNP) functionalized with specific aptamers to imidacloprid and carbendazim on a microfluidic paper-based analytical device (µ-PAD). Four aptamers were selected for the detection of these pesticides and their sensitivity and selectivity performance was evaluated. The sensitivity results show a detection limit for imidacloprid of 3.12 ppm and 1.56 ppm for carbendazim. The aptamers also exhibited high selectivity performance against other pesticides, such as thiamethoxam, fenamiphos, isoproturon, and atrazine. However, the platform presented cross-selectivity when detecting imidacloprid, carbendazim, and linuron, which is discussed herein. Overall, we present a promising platform for simple, on-site, and rapid colorimetric screening of specific pesticides, while highlighting the challenges of aptasensors in achieving selectivity amidst diverse molecular structures.

Noble-Nanoparticle-Decorated Ti3C2T x MXenes for Highly Sensitive Volatile Organic Compound Detection.

Two-dimensional transition-metal carbides and nitrides (MXenes) have been regarded as promising sensing materials because of their high surface-to-volume ratios and outstanding electronic, optical, and mechanical properties with versatile transition-metal and surface chemistries. However, weak gas-molecule adsorption of MXenes poses a serious limitation to their sensitivity and selectivity, particularly for trace amounts of volatile organic compounds (VOCs) at room temperature. To deal with these issues, Au-decorated MXenes are synthesized by a facile solution mixing method for room-temperature sensing of a wide variety of oxygen-based and hydrocarbon-based VOCs. Dynamic sensing experiments reveal that optimal decoration of Au nanoparticles (NPs) on Ti3C2T x MXene significantly elevates the response and selectivity of the flexible sensors, especially in detecting formaldehyde. Au-Ti3C2T x gas sensors exhibited an extremely low limit of detection of 92 ppb for formaldehyde at room temperature. Au-Ti3C2T x provides reliable gas response, low noise level, ultrahigh signal-to-noise ratio, high selectivity, as well as parts per billion level of formaldehyde detection. The prominent mechanism for Au-Ti3C2T x in sensing formaldehyde is elucidated theoretically from density functional theory simulations. The results presented here strongly suggest that decorating noble-metal NPs on MXenes is a feasible strategy for the development of next-generation ultrasensitive sensors for Internet of Things.

Microfluidic paper-based aptasensor devices for multiplexed detection of pathogenic bacteria.

Foodborne pathogens are major public health concerns worldwide. Paper-based microfluidic devices are versatile, user friendly and low cost. We report a novel paper-based single input channel microfluidic device that can detect more than one whole-cell foodborne bacteria at the same time, and comes with quantitative reading via image analysis. This microfluidic paper-based multiplexed aptasensor simultaneously detects E. coli O157:H7 and S. Typhimurium. Custom designed particles provide colorimetric signal enhancement and false results prevention. Several aptamers were screened and the highest-affinity aptamers were optimized and employed for detection of these bacteria in solution, both in a buffer as well as pear juice. Image analysis was used to read and quantify the colorimetric signal and measure bacteria concentration, thus rendering this paper based microfluidic device quantitative. The colorimetric results show linearity over a wide concentration range (102CFU/mL to 108CFU/mL) and a limit of detection (LOD) of 103CFU/mL and 102CFU/mL for E. coli O157:H7 and S. Typhimurium, respectively. An insignificant change in colorimetric response for non-target bacteria indicates the aptasesnors are specific. The reported multiplexed colorimetric paper-based microfluidic devices is likely to perform well for on-site rapid screening of pathogenic bacteria in water and food products.

DNA-Functionalized Ti3C2Tx MXenes for Selective and Rapid Detection of SARS-CoV-2 Nucleocapsid Gene.

Coronavirus disease 2019 (COVID-19) is an emerging human infectious disease caused by severe acute respiratory syndrome 2 (SARS-CoV-2, initially called novel coronavirus 2019-nCoV) virus. Thus, an accurate and specific diagnosis of COVID-19 is urgently needed for effective point-of-care detection and disease management. The reported promise of two-dimensional (2D) transition-metal carbides (Ti3C2Tx MXene) for biosensing owing to a very high surface area, high electrical conductivity, and hydrophilicity informed their selection for inclusion in functional electrodes for SARS-CoV-2 detection. Here, we demonstrate a new and facile functionalization strategy for Ti3C2Tx with probe DNA molecules through noncovalent adsorption, which eliminates expensive labeling steps and achieves sequence-specific recognition. The 2D Ti3C2Tx functionalized with complementary DNA probes shows a sensitive and selective detection of nucleocapsid (N) gene from SARS-CoV-2 through nucleic acid hybridization and chemoresistive transduction. The fabricated sensors are able to detect the SARS-CoV-2 N gene with sensitive and rapid response, a detection limit below 105 copies/mL in saliva, and high specificity when tested against SARS-CoV-1 and MERS. We hypothesize that the MXenes' interlayer spacing can serve as molecular sieving channels for hosting organic molecules and ions, which is a key advantage to their use in biomolecular sensing.

Optical Biosensors for Diagnostics of Infectious Viral Disease: A Recent Update.

The design and development of biosensors, analytical devices used to detect various analytes in different matrices, has emerged. Biosensors indicate a biorecognition element with a physicochemical analyzer or detector, i.e., a transducer. In the present scenario, various types of biosensors have been deployed in healthcare and clinical research, for instance, biosensors for blood glucose monitoring. Pathogenic microbes are contributing mediators of numerous infectious diseases that are becoming extremely serious worldwide. The recent outbreak of COVID-19 is one of the most recent examples of such communal and deadly diseases. In efforts to work towards the efficacious treatment of pathogenic viral contagions, a fast and precise detection method is of the utmost importance in biomedical and healthcare sectors for early diagnostics and timely countermeasures. Among various available sensor systems, optical biosensors offer easy-to-use, fast, portable, handy, multiplexed, direct, real-time, and inexpensive diagnosis with the added advantages of specificity and sensitivity. Many progressive concepts and extremely multidisciplinary approaches, including microelectronics, microelectromechanical systems (MEMSs), nanotechnologies, molecular biology, and biotechnology with chemistry, are used to operate optical biosensors. A portable and handheld optical biosensing device would provide fast and reliable results for the identification and quantitation of pathogenic virus particles in each sample. In the modern day, the integration of intelligent nanomaterials in the developed devices provides much more sensitive and highly advanced sensors that may produce the results in no time and eventually help clinicians and doctors enormously. This review accentuates the existing challenges engaged in converting laboratory research to real-world device applications and optical diagnostics methods for virus infections. The review's background and progress are expected to be insightful to the researchers in the sensor field and facilitate the design and fabrication of optical sensors for life-threatening viruses with broader applicability to any desired pathogens.

Recent Advances in Aptamer-Based Biosensors for Global Health Applications.

Since aptamers were first reported in the early 2000s, research on their use for the detection of health-relevant analytical targets has exploded. This review article provides a brief overview of the most recent developments in the field of aptamer-based biosensors for global health applications. The review provides a description of general aptasensing principles and follows up with examples of recent reports of diagnostics-related applications. These applications include detection of proteins and small molecules, circulating cancer cells, whole-cell pathogens, extracellular vesicles, and tissue diagnostics. The review also discusses the main challenges that this growing technology faces in the quest of bringing these new devices from the laboratory to the market.

Antidelaminating, Thermally Stable, and Cost-Effective Flexible Kapton Platforms for Nitrate Sensors, Mercury Aptasensors, Protein Sensors, and p-Type Organic Thin-Film Transistors.

The inkjet printing of metal electrodes on polymer films is a desirable manufacturing process due to its simplicity but is limited by the lack of thermal stability and serious delaminating flaws in various aqueous and organic solutions. Kapton, adopted worldwide due to its superior thermal durability, allows the high-temperature sintering of nanoparticle-based metal inks. By carefully selecting inks (Ag and Au) and Kapton substrates (Kapton HN films with a thickness of 135 µm and a thermal resistance of up to 400 °C) with optimal printing parameters and simplified post-treatments (sintering), outstanding film integrity, thermal stability, and antidelaminating features were obtained in both aqueous and organic solutions without any pretreatment strategy (surface modification). These films were applied in four novel devices: a solid-state ion-selective (IS) nitrate (NO3-) sensor, a single-stranded DNA (ssDNA)-based mercury (Hg2+) aptasensor, a low-cost protein printed circuit board (PCB) sensor, and a long-lasting organic thin-film transistor (OTFT). The IS NO3- sensor displayed a linear sensitivity range between 10-4.5 and 10-1 M (r2 = 0.9912), with a limit of detection of 2 ppm for NO3-. The Hg2+ sensor exhibited a linear correlation (r2 = 0.8806) between the change in the transfer resistance (RCT) and the increasing concentration of Hg2+. The protein PCB sensor provided a label-free method for protein detection. Finally, the OTFT demonstrated stable performance, with mobility values in the linear (µlin) and saturation (µsat) regimes of 0.0083 ± 0.0026 and 0.0237 ± 0.0079 cm2 V-1 S-1, respectively, and a threshold voltage (Vth) of -6.75 ± 3.89 V.

Two C-terminal sequence variations determine differential neurotoxicity between human and mouse α-synuclein.

BACKGROUND: α-Synuclein (aSyn) aggregation is thought to play a central role in neurodegenerative disorders termed synucleinopathies, including Parkinson's disease (PD). Mouse aSyn contains a threonine residue at position 53 that mimics the human familial PD substitution A53T, yet in contrast to A53T patients, mice show no evidence of aSyn neuropathology even after aging. Here, we studied the neurotoxicity of human A53T, mouse aSyn, and various human-mouse chimeras in cellular and in vivo models, as well as their biochemical properties relevant to aSyn pathobiology. METHODS: Primary midbrain cultures transduced with aSyn-encoding adenoviruses were analyzed immunocytochemically to determine relative dopaminergic neuron viability. Brain sections prepared from rats injected intranigrally with aSyn-encoding adeno-associated viruses were analyzed immunohistochemically to determine nigral dopaminergic neuron viability and striatal dopaminergic terminal density. Recombinant aSyn variants were characterized in terms of fibrillization rates by measuring thioflavin T fluorescence, fibril morphologies via electron microscopy and atomic force microscopy, and protein-lipid interactions by monitoring membrane-induced aSyn aggregation and aSyn-mediated vesicle disruption. Statistical tests consisted of ANOVA followed by Tukey's multiple comparisons post hoc test and the Kruskal-Wallis test followed by a Dunn's multiple comparisons test or a two-tailed Mann-Whitney test. RESULTS: Mouse aSyn was less neurotoxic than human aSyn A53T in cell culture and in rat midbrain, and data obtained for the chimeric variants indicated that the human-to-mouse substitutions D121G and N122S were at least partially responsible for this decrease in neurotoxicity. Human aSyn A53T and a chimeric variant with the human residues D and N at positions 121 and 122 (respectively) showed a greater propensity to undergo membrane-induced aggregation and to elicit vesicle disruption. Differences in neurotoxicity among the human, mouse, and chimeric aSyn variants correlated weakly with differences in fibrillization rate or fibril morphology. CONCLUSIONS: Mouse aSyn is less neurotoxic than the human A53T variant as a result of inhibitory effects of two C-terminal amino acid substitutions on membrane-induced aSyn aggregation and aSyn-mediated vesicle permeabilization. Our findings highlight the importance of membrane-induced self-assembly in aSyn neurotoxicity and suggest that inhibiting this process by targeting the C-terminal domain could slow neurodegeneration in PD and other synucleinopathy disorders.

Sulfur-Doped Titanium Carbide MXenes for Room-Temperature Gas Sensing.

Two-dimensional titanium carbide MXenes, Ti3C2Tx, possess high surface area coupled with metallic conductivity and potential for functionalization. These properties make them especially attractive for the highly sensitive room-temperature electrochemical detection of gas analytes. However, these extraordinary materials have not been thoroughly investigated for the detection of volatile organic compounds (VOCs), many of which hold high relevance for disease diagnostics and environmental protection. Furthermore, the insufficient interlayer spacing between MXene nanoflakes could limit their applicability and the use of heteroatoms as dopants could help overcome this challenge. Here, we report that S-doping of Ti3C2Tx MXene leads to a greater gas-sensing performance to VOCs compared to their undoped counterparts, with unique selectivity to toluene. After S-doped and pristine materials were synthesized, characterized, and used as electrode materials, the as-fabricated sensors were subjected to room-temperature dynamic impedimetric testing in the presence of VOCs with different functional groups (ethanol, hexane, toluene, and hexyl-acetate). Unique selectivity to toluene was obtained by both undoped and doped Ti3C2Tx MXenes, but an enhancement of response in the range of ∼214% at 1 ppm to ∼312% at 50 ppm (3-4 folds increase) was obtained for the sulfur-doped sensing material. A clear notable response to 500 ppb toluene was also obtained with sulfur-doped Ti3C2Tx MXene sensors along with excellent long-term stability. Our experimental measurements and density functional theory analysis offer insight into the mechanisms through which S-doping influences VOC analyte sensing capabilities of Ti3C2Tx MXenes, thus opening up future investigations on the development of high-performance room-temperature gas sensors.

Surface Functionalization of Ti3C2Tx MXene with Highly Reliable Superhydrophobic Protection for Volatile Organic Compounds Sensing.

Two-dimensional (2D) transition-metal carbides (Ti3C2Tx MXene) have received a great deal of attention for potential use in gas sensing showing the highest sensitivity among 2D materials and good gas selectivity. However, one of the long-standing challenges of the MXenes is their poor stability against hydration and oxidation in a humid environment, limiting their long-term storage and applications. Integration of an effective protection layer with MXenes shows promise for overcoming this major drawback. Herein, we demonstrate a surface functionalization strategy for Ti3C2Tx with fluoroalkylsilane (FOTS) molecules through surface treatment, providing not only a superhydrophobic surface, mechanical/environmental stability but also enhanced sensing performance. The experimental results show that high sensitivity, good repeatability, long-term stability, and selectivity and faster response/recovery property were achieved by the FOTS-functionalized when Ti3C2Tx was integrated into chemoresistive sensors sensitive to oxygen-containing volatile organic compounds (ethanol, acetone). FOTS functionalization provided protection to sensing response when the dynamic response of the Ti3C2Tx-F sensor to 30 ppm of ethanol was measured over in the 5 to 80% relative humidity range. Density functional theory simulations suggested that the strong adsorption energy of ethanol on Ti3C2Tx-F and the local structure deformation induced by ethanol adsorption, contributing to the gas-sensing enhancement. This study offers a facile and practical solution for developing highly reliable MXene based gas-sensing devices with response that is stable in air and in the presence of water.

Ionic Strength Influences on Biofunctional Au-Decorated Microparticles for Enhanced Performance in Multiplexed Colorimetric Sensors.

The rising development of biosensors offers a great potential for health, food, and environmental monitoring. However, in many colorimetric platforms, there is a performance limitation stemming from the tendency of traditional Au nanoparticles toward nonspecific aggregation in response to changing ionic strength (salt concentration). This work puts forward a new type of colorimetric aptamer-functionalized labeling of microparticles, which allows to leverage an increase in ionic strength as a positive driver of enhanced detection performance of analytical targets. The resulting device is a cost-effective, instrument-free, portable, and reliable aptasensor that serves as basis for the fabrication of universal paper-based colorimetric platforms with the capability of multiplex, multireplicates and provides quantitative colorimetric detection. A controlled fabrication process was demonstrated by keeping 90% of the signal obtained from the as-fabricated devices (n = 40) within ± 1 standard deviation (SD) (relative SD = 5.69%) and following a mesokurtic normal-like distribution (p = 0.385). We propose for the first time a salt-induced aggregation mechanism for highly stable multilayered label particles (ssDNA-PEI-Au-PS) as the basis of the detection scheme. The use of DNA aptamers as capture biomolecules and PEI as an encapsulating agent allows for a sensitive and highly specific colorimetric response. As a proof of concept, multiplexed detection of mercury (Hg2+) and arsenic (As3+) was demonstrated. In addition, we introduced a robust image analysis algorithm for testing zone segmentation and color signal quantification that allowed for analytical detection, reaching a limit of detection of 1 ppm for both targeted analytes, with enough evidence (p > 0.05) to prove the high specificity of the fabricated device versus a pool of possible interferent ions.

Selective Detection of Ethylene by MoS2-Carbon Nanotube Networks Coated with Cu(I)-Pincer Complexes.

The plant hormone ethylene (C2) can induce premature fruit ripening and flower senescence at levels below 1 ppm, which has motivated efforts to develop cost-effective methods for C2 monitoring during the transport and storage of climacteric fruits. Here, we describe a nanocomposite film composed of exfoliated MoS2, single-walled carbon nanotubes (SCNTs), and Cu(I)-tris(mercaptoimidazolyl)borate complexes (Cu-Tm) for real-time detection of C2 at levels down to 100 ppb. A copercolation network of MoS2 and SCNTs was deposited onto interdigitated Ag electrodes printed on plastic substrates and then coated with Cu-Tm with a final conductance in the 0.5 mS range. Reversible changes in relative conductance (-ΔG/G0) were measured upon C2 exposure with a linear response at sub-ppm levels. The thin-film sensors were highly selective toward C2, and they responded weakly to other volatile organic compounds or water at similar partial pressures. A mechanism is proposed in which Cu-Tm behaves as a chemically sensitive n-type dopant for MoS2, based on spectroscopic characterization and density functional theory modeling. Cu-Tm-coated MoS2/SCNT sensors were also connected to a battery-powered wireless transmitter and used to monitor C2 production from various fruit samples, validating their utility as practical, field-deployable sensors.

Nisin infusion into surface cracks in oxide coatings to create an antibacterial metallic surface.

The efficacy of surface topology and chemistry on the ability for a surface to retain antimicrobial performance via the immobilization of a peptide was evaluated. A nanosecond pulsed laser was used to create oxide films on Ti-6Al-4V and 304L stainless steel. The laser conditions employed created a mudflat cracked surface on titanium, but no cracks on the steel. An antimicrobial peptide, nisin, was infused into the cracked and uncracked oxide surfaces to provide antimicrobial activity against Gram-positive bacteria; Listeria monocytogenes was chosen as the model microorganism. Release tests in distilled water at room temperature show that nisin is slowly liberated from the uncracked stainless steel surface, while there was no evidence of nisin liberation from the cracked titanium alloy surfaces, likely due to immobilization of the peptide into the artificially created micro-cracks on the surface of this alloy. Surfaces treated with nisin became active and exhibit anti-microbial performance against L. monocytogenes; this behavior is mostly retained after scrubbing/washing and simple immersion in water.

Microfluidic rapid and autonomous analytical device (microRAAD) to detect HIV from whole blood samples.

While identifying acute HIV infection is critical to providing prompt treatment to HIV-positive individuals and preventing transmission, existing laboratory-based testing methods are too complex to perform at the point of care. Specifically, molecular techniques can detect HIV RNA within 8-10 days of transmission but require laboratory infrastructure for cold-chain reagent storage and extensive sample preparation performed by trained personnel. Here, we demonstrate our point-of-care microfluidic rapid and autonomous analysis device (microRAAD) that automatically detects HIV RNA from whole blood. Inside microRAAD, we incorporate vitrified amplification reagents, thermally-actuated valves for fluidic control, and a temperature control circuit for low-power heating. Reverse transcription loop-mediated isothermal amplification (RT-LAMP) products are visualized using a lateral flow immunoassay (LFIA), resulting in an assay limit of detection of 100 HIV-1 RNA copies when performed as a standard tube reaction. Even after three weeks of room-temperature reagent storage, microRAAD automatically isolates the virus from whole blood, amplifies HIV-1 RNA, and transports amplification products to the internal LFIA, detecting as few as 3 × 105 HIV-1 viral particles, or 2.3 × 107 virus copies per mL of whole blood, within 90 minutes. This integrated microRAAD is a low-cost and portable platform to enable automated detection of HIV and other pathogens at the point of care.

Surface Functionalization of Layered Molybdenum Disulfide for the Selective Detection of Volatile Organic Compounds at Room Temperature.

Semiconducting two-dimensional (2D) transition-metal dichalcogenides (TMDCs) are considered promising sensing materials due to the high surface-to-volume ratio and active sensing sites. However, the reported strategies for 2D TMDCs toward sensing of volatile organic compounds (VOCs) present with some drawbacks. These include high operation temperatures, low gas response, and complex fabrication, limiting the development of room-temperature gas sensors. In this study, 2D MoS2 nanoflakes were prepared by liquid-phase exfoliation, and their surface was functionalized with Au nanoparticles (NPs) through a facile solution mixing method. MoS2 decorated with Au NPs with an average size of 10 nm was used as a material platform for an electrochemical sensor to detect a wide variety of VOCs at room temperature. Through dynamic sensing tests, the enhancement of gas-sensing performance in terms of response and selectivity, especially in detecting oxygen-based VOCs (acetone, ethanol, and 2-propanol), was demonstrated. After Au functionalization, the response of the gas sensor to acetone improved by 131% (changing from 13.7% for pristine MoS2 to 31.6% for MoS2-Au(0.5)). Sensing tests under various relative humidity values (10-80%), bending or long-term conditions, indicated the sound robustness and flexibility of the sensor. Density functional theory simulations suggested that the adsorption energy of VOC molecules on MoS2-Au is significantly higher than that on pristine MoS2, contributing to the gas-sensing enhancement; a VOC-sensing mechanism for Au-decorated MoS2 nanoflakes was proposed for the first time for the highly sensitive and selective detection of oxygen-based VOCs.

Aptamer-based SERS biosensor for whole cell analytical detection of E. coli O157:H7.

Infectious outbreaks caused by foodborne pathogens such as E. coli O157:H7 are still imposing a heavy burden for global food safety, causing acute illnesses and significant industrial impact worldwide. Despite the growth of biosensors as a research field, continuous innovation on detection strategies, novel materials and enhanced limits of detection, most of the platforms developed at the laboratory scale never will get to meet the market. The use of aptamers as capture biomolecules has been proposed as a promising alternative to overcome the harsh environmental conditions of industrial manufacturing processes, and to enhance the performance under real, complex, conditions. In this work, we present the feasibility of using aptameric DNA sequences, covalently conjugated to 4-aminothiophenol-gold nanoparticle complexes for the sensitive and highly specific detection of E. coli O157:H7 via surface enhanced Raman spectroscopy (SERS) analysis. Low concentrations of E. coli O157:H7 were detected and quantified within 20 min in both pure culture (∼101 CFU mL-1) and ground beef samples (∼102 CFU mL-1). The SERS intensity response showed a strong negative linear correlation (r2 = 0.995) with increasing concentrations of E. coli O157:H7 (ranging from 102 to 106 CFU mL-1). High specificity was achieved at genus (L. monocytogenes, S. aureus S. typhimurium) species (E. coli B1201) and serotype (E. coli O55:H7) level, demonstrating with 95% of confidence that the interferent microorganisms tested generated a Raman signal response not significantly different from the background (p = 0.786). This work evaluates the incorporation of aptameric DNA sequences as bio capture molecules exclusively. The successful performance presented using non-modified citrate reduced GNPs, is promising for potential low-cost, high-throughput applications. The findings might be applied simultaneously to the detection of a wide variety of foodborne pathogens in a multiplexed fashion employing unique Raman probes and strain-specific aptamer sequences.

Inkjet Printed Nanopatterned Aptamer-Based Sensors for Improved Optical Detection of Foodborne Pathogens.

The increasing incidence of infectious outbreaks from contaminated food and water supply continues imposing a global burden for food safety, creating a market demand for on-site, disposable, easy-to-use, and cost-efficient devices. Despite of the rapid growth of biosensors field and the generation of breakthrough technologies, more than 80% of the platforms developed at lab-scale never will get to meet the market. This work aims to provide a cost-efficient, reliable, and repeatable approach for the detection of foodborne pathogens in real samples. For the first time an optimized inkjet printing platform is proposed taking advantage of a carefully controlled nanopatterning of novel carboxyl-functionalized aptameric ink on a nitrocellulose substrate for the highly efficient detection of E. coli O157:H7 (25 colony forming units (CFU) mL-1 in pure culture and 233 CFU mL-1 in ground beef) demonstrating the ability to control the variation within ±1 SD for at least 75% of the data collected even at very low concentrations. From the best of the knowledge this work reports the lowest limit of detection of the state of the art for paper-based optical detection of E. coli O157:H7, with enough evidence (p > 0.05) to prove its high specificity at genus, species, strain, and serotype level.

Investigation of porosity on mechanical properties, degradation and in-vitro cytotoxicity limit of Fe30Mn using space holder technique.

Bioresorbable metallic implants are considered to be a new generation of transient fixation devices, which provide strong mechanical support during healing as well as effective integration with the host bone tissues, free of secondary surgery. We evaluated the microstructures and mechanical properties of iron­manganese alloys (Fe30Mn) with 0-, 5-, 10-, and 60-volume percent porosity, which was produced through ammonium bicarbonate (NH4HCO3) decomposition. We also investigated the influence of porosity concentration on the corrosion rate and cytotoxicity of the alloy. The average value of maximum compressive strength was 2-fold greater in the 0-vol% scaffolds than that in 60-vol% scaffolds. Scaffolds with 60-vol% porosity exhibited the highest average value of corrosion rate in a potentiodynamic polarization test among the four groups. However, the group influenced cellular viability negatively in a subsequent cytotoxicity test. Fe30Mn scaffolds with 10-vol% NH4HCO3 are considered promising resorbable scaffolds based on the results of compression tests, corrosion experiments and cytotoxicity studies.

Hybrid plasmonic Au-TiN vertically aligned nanocomposites: a nanoscale platform towards tunable optical sensing.

Tunable plasmonic structure at the nanometer scale presents enormous opportunities for various photonic devices. In this work, we present a hybrid plasmonic thin film platform: i.e., a vertically aligned Au nanopillar array grown inside a TiN matrix with controllable Au pillar density. Compared to single phase plasmonic materials, the presented tunable hybrid nanostructures attain optical flexibility including gradual tuning and anisotropic behavior of the complex dielectric function, resonant peak shifting and change of surface plasmon resonances (SPRs) in the UV-visible range, all confirmed by numerical simulations. The tailorable hybrid platform also demonstrates enhanced surface plasmon Raman response for Fourier-transform infrared spectroscopy (FTIR) and photoluminescence (PL) measurements, and presents great potentials as designable hybrid platforms for tunable optical-based chemical sensing applications.

In Vivo Evaluation of Biodegradability and Biocompatibility of Fe30Mn Alloy.

OBJECTIVES: This study aims to evaluate the biodegradability and biocompatibility of an alloy of iron and manganese (Fe30Mn) in a bone model in vivo. METHODS: Resorption of a Fe30Mn wire was compared with traditional permanent 316L stainless steel (SS) wire after bilateral transcondylar femoral implantation in 12 rats. Evaluation of biodegradation over 6 months was performed using radiography, post-mortem histology and microscopic implant surface analysis. RESULTS: Corrosion and resorption of the novel iron-manganese implant with formation of an iron oxide corrosion layer was noted on all post-mortem histological sections and macroscopic specimens (corrosion fraction of 0.84 and 0 for Fe30Mn and 316L SS, respectively). Increased bone ongrowth was observed at the wire-bone interface (bone ongrowth fraction of 0.61 and 0.34 for Fe30Mn and 316L SS, respectively). Occasionally, poorly stained newly formed bone and necrotic bone in contact with corrosion was seen. In bone marrow, Fe30Mn alloy was scored as a mild local irritant compared with 316L SS (biocompatibility score of 8.8 and 5.3, respectively). There was no evidence of systemic adverse reaction. CLINICAL SIGNIFICANCE: Resorbable iron-manganese alloys may offer a promising alternative to permanent metallic implants. Further in vivo studies to control implant resorption at a rate suitable for fracture healing and to confirm the biocompatibility and biosafety of the resorbable Fe30Mn metallic implant are necessary prior to use in clinical settings.