High throughput LSPR and SERS analysis of aminoglycoside antibiotics

A novel strategy for therapeutic drug monitoring: application of biosensors to quantify antimicrobials in biological matrices

Over the past few years, therapeutic drug monitoring (TDM) has gained practical significance in antimicrobial precision therapy. Yet two categories of mainstream TDM techniques (chromatographic analysis and immunoassays) that are widely adopted nowadays retain certain inherent limitations. The use of biosensors, an innovative strategy for rapid evaluation of antimicrobial concentrations in biological samples, enables the implementation of point-of-care testing (POCT) and continuous monitoring, which may circumvent the constraints of conventional TDM and provide strong technological support for individualized antimicrobial treatment. This comprehensive review summarizes the investigations that have harnessed biosensors to detect antimicrobial drugs in biological matrices, provides insights into the performance and characteristics of each sensing form, and explores the feasibility of translating them into clinical practice. Furthermore, the future trends and obstacles to achieving POCT and continuous monitoring are discussed. More efforts are necessary to address the four key 'appropriateness' challenges to deploy biosensors in clinical practice, paving the way for personalized antimicrobial stewardship.

Development of Novel Peptide-Modified Silver Nanoparticle-Based Rapid Biosensors for Detecting Aminoglycoside Antibiotics

The detection and monitoring of aminoglycoside antibiotics (AGAs) have become of utmost importance due to their widespread use in human and animal therapy, as well as the associated risks of exposure, toxicity, and the emergence of antimicrobial resistance. In this study, we successfully synthesized casein hydrolysate peptides-functionalized silver nanoparticles (CHPs@AgNPs) and employed them as a novel colorimetric analytical platform to demonstrate remarkable specificity and sensitivity toward AGAs. The colorimetric and spectral response of the CHPs@AgNPs was observed at 405 and 520 nm, showing a linear correlation with the concentration of streptomycin, a representative AGA. The color changes from yellow to orange provided a visual indication of the analyte concentration, enabling quantitative determination for real-world samples. The AgNP assay exhibited excellent sensitivity with dynamic ranges of approximately 200-650 and 100-700 nM for streptomycin-spiked tap water and dairy whey with limits of detection found to be ∼98 and 56 nM, respectively. The mechanism behind the selective aggregation of CHPs@AgNPs in the presence of AGAs involves the amine groups of the target analytes acting as molecular bridges for electrostatic coupling with hydroxyl or carboxyl functionalities of adjacent NPs, driving the formation of stable NP aggregates. The developed assay offers several advantages, making it suitable for various practical applications. It is characterized by its simplicity, rapidity, specificity, sensitivity, and cost-effectiveness. These unique features make the method a promising tool for monitoring water quality, ensuring food safety, and dealing with emergent issues of antibiotic resistance.

Application of vibrational spectroscopy and nuclear magnetic resonance methods for drugs pharmacokinetics research

OBJECTIVES

The development of new methods for determining the concentration of drugs is an actual topic today. The article contains a detailed review on vibrational spectroscopy and nuclear magnetic resonance methods using for pharmacokinetic research. This study is devoted to the possibility of using vibrational spectroscopy and 1H nuclear magnetic resonance spectroscopy to determine the concentration of drugs and the use of these groups of techniques for therapeutic drug monitoring.

CONTENT

The study was conducted by using scientific libraries (Scopus, Web of Science Core Collection, Medline, GoogleScholar, eLIBRARY, PubMed) and reference literature. A search was conducted for the period from 2011 to 2021 in Russian and English, by combinations of words: 1H nuclear magnetic resonance (¹H NMR), vibrational spectroscopy, Surface-Enhanced Raman spectroscopy, drug concentration, therapeutic drug monitoring. These methods have a number of advantages and are devoid of some of the disadvantages of classical therapeutic drug monitoring (TDM) methods - high performance liquid chromatography and mass spectrometry. This review considers the possibility of using the methods of surface-enhanced Raman scattering (SERS) and ¹H NMR-spectroscopy to assess the concentration of drugs in various biological media (blood, urine), as well as to study intracellular metabolism and the metabolism of ophthalmic drugs. ¹Н NMR-spectroscopy can be chosen as a TDM method, since it allows analyzing the structure and identifying metabolites of various drugs. ¹Н NMR-based metabolomics can provide information on the side effects of drugs, predict response to treatment, and provide key information on the mechanisms of action of known and new drug compounds.

SUMMARY AND OUTLOOK

SERS and ¹Н NMR-spectroscopy have great potential for further study and the possibility of introducing them into clinical practice, including for evaluating the efficacy and safety of drugs.

Rapid determination of isepamicin by using SERS based on BSA-protected AgNPs modified by α-Fe2O3

A surface-enhanced Raman spectroscopy (SERS) method for the determination of isepamicin (ISE) using silver nanoparticles (AgNPs) protected by bovine serum albumin (BSA) and modified by α-Fe₂O₃ as an efficient substrate was established. The synthesized substrate was characterized and verified by transmission electron microscopy (TEM), ultraviolet visible spectroscopy (UV-vis), and fourier transform infrared spectroscopy (FT-IR). The conditions affecting the Raman signal of ISE were optimized by single factor and response surface experiments. Under optimized conditions, a standard curve I_SERS = 43.08c + 63598.69 (c: nmol/L) with a linear relationship (r = 0.9976) was established between the SERS intensity and ISE concentration in the range of 20.00 - 2000.00 nmol/L. The limit of detection (LOD) for ISE was 16.58 nmol/L (S/N = 3). The recovery of ISE in the samples was 96.29 % - 104.12 %, with relative standard deviation (RSD) was 1.53 % - 3.43 % (n = 5). The SERS method was reliable and satisfactory for the quantitative analysis of ISE at low concentration.

The Role of Surface Enhanced Raman Scattering for Therapeutic Drug Monitoring of Antimicrobial Agents

The rapid quantification of antimicrobial agents is important for therapeutic drug monitoring (TDM), enabling personalized dosing schemes in critically ill patients. Highly sophisticated TDM technology is becoming available, but its implementation in hospitals is still limited. Among the various proposed techniques, surface-enhanced Raman scattering (SERS) stands out as one of the more interesting due to its extremely high sensitivity, rapidity, and fingerprinting capabilities. Here, we present a comprehensive review of various SERS-based novel approaches applied for direct and indirect detection and quantification of antibiotic, antifungal, and antituberculosis drugs in different matrices, particularly focusing on the challenges for successful exploitation of this technique in the development of assays for point-of-care tests.

Histidine Functionalized Gold Nanoparticles for Screening Aminoglycosides and Nanomolar Level Detection of Streptomycin in Water, Milk, and Whey

Aminoglycoside (AMG) antibiotics are being applied to treat infections caused by Gram-negative bacteria, mainly in livestock, and are prescribed only in severe cases because of their adverse impacts on human health and the environment. Monitoring antibiotic residues in dairy products relies on the accessibility of portable and efficient analytical techniques. Presently, high-throughput screening techniques have been proposed to detect several antimicrobial drugs having identical structural and functional features. The L-histidine functionalized gold nanoparticles (His@AuNPs) do not form a complex with other tested antibiotic classes but show high selectivity for AMG antibiotics. We used ligand-induced aggregation of His@AuNPs as a rapid and sensitive localized surface plasmon resonance (LSPR) assay for AMG antibiotics, producing longitudinal extinction shifts at 660 nm. Herein, we explore the practical application of His@AuNPs to detect streptomycin spiked in water, milk, and whey fraction of milk with nanomolar level sensitivity. The ability of the analytical method to recognize target analytes sensitively and rapidly is of great significance to perform monitoring, thus would certainly reassure widespread use of AMG antibiotics. The biosynthesis of hybrid organic–inorganic metal nanoparticles like His@AuNPs with desired size distribution, stability, and specific host–guest recognition proficiency, would further facilitate applications in various other fields.

Advancing Raman spectroscopy from research to clinic: Translational potential and challenges

Raman spectroscopy has emerged as a non-invasive and versatile diagnostic technique due to its ability to provide molecule-specific information with ultrahigh sensitivity at near-physiological conditions. Despite exhibiting substantial potential, its translation from optical bench to clinical settings has been impacted by associated limitations. This perspective discusses recent clinical and biomedical applications of Raman spectroscopy and technological advancements that provide valuable insights and encouragement for resolving some of the most challenging hurdles.

Chlortetracycline-Functionalized Silver Nanoparticles as a Colorimetric Probe for Aminoglycosides: Ultrasensitive Determination of Kanamycin and Streptomycin

Aminoglycosides (AMGs) have been extensively used to treat infectious diseases caused by Gram-negative bacteria in livestock and humans. A selective and sensitive colorimetric probe for the determination of streptomycin and kanamycin was proposed based on chlortetracycline-coated silver nanoparticles (AgNPs-CTC) as the sensing element. Almost all of the tested aminoglycoside antibiotics can rapidly induce the aggregation of AgNPs, along with a color change from yellow to orange/red. The selective detection of aminoglycoside antibiotics, including tobramycin, streptomycin, amikacin, gentamicin, neomycin, and kanamycin, with other types of antibiotics, can be achieved by ultraviolet (UV) spectroscopy. This developed colorimetric assay has ability to detect various AMGs using in-depth surface plasmon resonance (SPR) studies. With this determination of streptomycin and kanamycin was achieved at the picomolar level (pM) by using a UV-visible spectrophotometer. Under aqueous conditions, the linear range of the colorimetric sensor for streptomycin and kanamycin was 1000-1,1000 and 120-480 pM, respectively. The corresponding limit of detection was 2000 pM and 120 pM, respectively. Thus, the validated dual colorimetric and ratiometric method can find various analytical applications for the ultrasensitive and rapid detection of AMG antibiotics in water samples.

A high-throughput plasmonic tongue using an aggregation assay and nonspecific interactions: classification of taste profiles in maple syrup

A simple colorimetric test detects off-flavour profiles of maple syrups in minutes, which are detectable by the naked eye. As flavour profiles are due to complex mixtures of molecules, the test uses nonspecific interactions for analysing the aggregation and color change of Au nanoparticles (AuNPs) induced by the different organic molecules contained in off-flavour maple syrup. The test was optimal with 13 nm citrate-capped AuNPs reacting 1 : 1 with pure maple syrup diluted 10 times. Under these conditions, normal flavour maple syrups did not react and the solution remained red, while off-flavoured maple syrups aggregated the AuNPs and the solution turned blue. Different classes of molecules were then tested to evaluate the types of compounds typically found in maple syrups reacting in the test, showing that sulfur- and amine-containing amino acids and aromatic amines caused aggregation of the AuNPs. The test was validated with 1818 maple syrup samples from the 2018 harvest in Quebec and 98% of the off-flavoured maple syrups were positively identified against the standard taste test. Preliminary tests were performed on site in maple sugar shacks to validate the applicability of the test on the production site.

Patterned Superhydrophobic SERS Substrates for Sample Pre-Concentration and Demonstration of Its Utility through Monitoring of Inhibitory Effects of Paraoxon and Carbaryl on AChE

We describe a patterned surface-enhanced Raman spectroscopy (SERS) substrate with the ability to pre-concentrate target molecules. A surface-adsorbed nanosphere monolayer can serve two different functions. First, it can be made into a SERS platform when covered by silver. Alternatively, it can be fashioned into a superhydrophobic surface when coated with a hydrophobic molecular species such as decyltrimethoxy silane (DCTMS). Thus, if silver is patterned onto a latter type of substrate, a SERS spot surrounded by a superhydrophobic surface can be prepared. When an aqueous sample is placed on it and allowed to dry, target molecules in the sample become pre-concentrated. We demonstrate the utility of the patterned SERS substrate by evaluating the effects of inhibitors to acetylcholinesterase (AChE). AChE is a popular target for drugs and pesticides because it plays a critical role in nerve signal transduction. We monitored the enzymatic activity of AChE through the SERS spectrum of thiocholine (TC), the end product from acetylthiocholine (ATC). Inhibitory effects of paraoxon and carbaryl on AChE were evaluated from the TC peak intensity. We show that the patterned SERS substrate can reduce both the necessary volumes and concentrations of the enzyme and substrate by a few orders of magnitude in comparison to a non-patterned SERS substrate and the conventional colorimetric method.

Silver nanoparticle probe for colorimetric detection of aminoglycoside antibiotics: picomolar-level sensitivity toward streptomycin in water, serum, and milk samples

BACKGROUND

The low cost of aminoglycoside (AMG) antibiotics facilitates their excessive use in animal husbandry and the agriculture sector. This scenario has led to the occurrence of residues in the food chain. After several years of AMG use in antibacterial therapy, resistance to streptomycin has begun to appear. Most of the detection methods developed for AMG antibiotics lacks specificity. A broad target specific nanoprobe would be ideal for detecting the entire class of AMGs. A rapid and sensitive method for the detection of AMGs is urgently needed.

RESULTS

Gallic acid-coated silver nanoparticles (AgNPs) were demonstrated as a nanoprobe for the colorimetric detection of AMGs (yellow to orange / red). A linear dynamic range of 50-650 pmol L^-1 was achieved readily by ratiometric spectrophotometry (A₅₆₀ /A₄₀₀ ) with a limit of detection (LOD) as low as 36 pmol L^-1 . The amine-groups of the AMGs function as molecular linkers, so that electrostatic coupling interactions between neighboring particles drive the formation of AgNP aggregates. The assay can also be applied for the determination of streptomycin residues in serum and milk samples.

CONCLUSION

This study revealed the potential of an AgNP probe for the rapid and cost-effective detection of low-molecular-weight target analytes, such as the AMGs. A ligand-induced aggregation of AgNPs coated with gallic acid was reported to be a rapid and sensitive assay for AMGs. Analysis of streptomycin was demonstrated with excellent picomolar-level sensitivity. Thus, the validated method can find practical applications in the ultrasensitive detection of AMGs in complex and diagnostic settings. © 2019 Society of Chemical Industry.

Comparative study of serum sample preparation methods in aggregation-based plasmonic sensing

The use of nanoparticle-based colorimetric methods has received considerable attention for clinical analysis in biofluids. Sample preparation methods are surveyed here to minimize the impact of the sample matrix on the performance of a nanoparticle aggregation assay.

A review on recent advances in the applications of surface-enhanced Raman scattering in analytical chemistry

This review is focused on recent developments of surface-enhanced Raman scattering (SERS) applications in Analytical Chemistry. The work covers advances in the fabrication methods of SERS substrates, including nanoparticles immobilization techniques and advanced nanopatterning with metallic features. Recent insights in quantitative and sampling methods for SERS implementation and the development of new SERS-based approaches for both qualitative and quantitative analysis are discussed. The advent of methods for pre-concentration and new approaches for single-molecule SERS quantification, such as the digital SERS procedure, has provided additional improvements in the analytical figures-of-merit for analysis and assays based on SERS. The use of metal nanostructures as SERS detection elements integrated in devices, such as microfluidic systems and optical fibers, provided new tools for SERS applications that expand beyond the laboratory environment, bringing new opportunities for real-time field tests and process monitoring based on SERS. Finally, selected examples of SERS applications in analytical and bioanalytical chemistry are discussed. The breadth of this work reflects the vast diversity of subjects and approaches that are inherent to the SERS field. The state of the field indicates the potential for a variety of new SERS-based methods and technologies that can be routinely applied in analytical laboratories.

Optical Biosensors for Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is a fundamental tool when administering drugs that have a limited dosage or high toxicity, which could endanger the lives of patients. To carry out this monitoring, one can use different biological fluids, including blood, plasma, serum, and urine, among others. The help of specialized methodologies for TDM will allow for the pharmacodynamic and pharmacokinetic analysis of drugs and help adjust the dose before or during their administration. Techniques that are more versatile and label free for the rapid quantification of drugs employ biosensors, devices that consist of one element for biological recognition coupled to a signal transducer. Among biosensors are those of the optical biosensor type, which have been used for the quantification of different molecules of clinical interest, such as antibiotics, anticonvulsants, anti-cancer drugs, and heart failure. This review presents an overview of TDM at the global level considering various aspects and clinical applications. In addition, we review the contributions of optical biosensors to TDM.

Protection of silver and gold LSPR biosensors in corrosive NaCl environment by short alkanethiol molecules; characterized by extinction spectrum, helium ion microscopy and SERS

We investigated the utility of localized surface plasmon resonance sensors in a biologically relevant environment containing NaCl. Our sensors are fabricated by depositing gold or silver on a monolayer of adsorbed monodisperse SiO₂ nanospheres. While silver nanostructures are rather unstable in air and water as assessed by drifts in the extinction peak, even gold nanostructures have been found to drift at elevated NaCl concentrations. In an attempt to protect these nanostructures against NaCl, we modified them with alkanethiols with different lengths in the vapor phase and found that shorter chain alkanethiols such as 1-butanethiol are particularly effective against even 250 mM NaCl, rather than longer-chain alkanethiols more suitable for robust SAM formation. A vapor phase treatment method, in contrast to widely used solution phase treatment methods, was selected with the intention of reducing the solvent effect, i.e. destruction of intricate nanostructures upon contact with a solvent when nanostructures have been prepared in a vacuum system. Moreover, the treatment with 1-butanethiol led to an enhanced sensitivity as expressed by peak shift in nm per refractive index unit, nm per RIU. We show the results of evaluating alkanethiol-protected silver and gold nanostructures by extinction spectroscopy, helium ion microscopy and surface-enhanced Raman spectroscopy. The vapor phase treatment method with short chain alkanethiols is an effective way to protect intricate gold and silver nanostructures prepared in a vacuum system.

We investigated the utility of localized surface plasmon resonance sensors in a biologically relevant environment containing NaCl.

Bimetallic cerium/copper organic framework-derived cerium and copper oxides embedded by mesoporous carbon: Label-free aptasensor for ultrasensitive tobramycin detection

We reported a novel bimetallic cerium/copper-based metal organic framework (Ce/Cu-MOF) and its derivatives pyrolyzed at different temperatures, followed by exploiting them as the scaffold of electrochemical aptamer sensors for extremely sensitive detection of trace tobramycin (TOB) in human serum and milk. After the calcination at high temperature, the meal coordination centers (Ce and Cu) were transferred to metal oxides containing various chemical valences, such as Ce(III), Ce(IV), Cu(II) and Cu(0), which were embedded within the mesoporous carbon network originated from the organic ligands (represented by CeO₂/CuO_x@mC). Owning to the strong synergistic effect among the metal oxides, mesoporous carbon, and small cavities and open channels of MOF, the as-prepared CeO₂/CuO_x@mC nanocomposites not only possess good electrochemical activity but also exhibit strong bioaffinity toward the aptamer strands. By comparing the electrochemical biosensing peroformances using on the Ce/Cu-MOF- and the series of CeO₂/CuO_x@mC-based aptasensors, the constructed CeO₂/CuO_x@mC₉₀₀-based (calcinated at 900 °C) aptasensor exhibits an extremely low detection limit of 2.0 fg mL^-1 within a broad linear TOB concentration range from 0.01 pg mL^-1 to 10 ng mg L^-1. It demonstrates that the proposed aptasensor is substantially superior to those previously reported in the literature, along with high selectivity, good stability and reproducibility, and acceptable applicability in human serum and milk. Thereby, the newly fabricated aptasensing approach based on bimetallic CeO₂/CuO_x@mC has a considerable potential for the quantitative detection of antibiotics in the food safety and biomedical field.

Surface-enhanced Raman scattering investigation of bovine serum albumin by Au nanoparticles with different sizes

BACKGROUND

Surface-enhanced Raman scattering (SERS) has become a useful spectroscopic tool for studying biomolecule structures. The main types of plasmonic substrates used in biological systems are Au nanoparticles (AuNPs), whose surface plasmon resonance depends on the nanoparticle size, morphology, particle interspace, and so on.

METHODS

In this study, AuNP colloids with different sizes were synthesized and used as the sensors to probe SERS signals of different biomarkers and biomolecules.

RESULTS

The results showed that an AuNP colloid of ~50 nm had excellent SERS effects in probing various molecules, and could be preserved for about 3 months with excellent repeatability and reproducibility (RSD <5%) in terms of the probed signal intensity (rhodamine 6G and crystal violet). Meanwhile, the fabricated AuNPs were applied to study the SERS signals and structural information of bovine serum albumin (BSA) in aqueous solution. It was found that SERS could rapidly provide the structural information and vibration characteristics of BSA.

CONCLUSION

It was concluded that biocompatible AuNP colloid may be a promising biosensor in the rapid and label-free detection of biological systems.

Enhancement of Gold Nanoparticle Coupling with a 2D Plasmonic Crystal at High Incidence Angles

2D nanoplasmonic substrates excited in transmission spectroscopy are ideal for several biosensing, metamaterial, and optical applications. We show that their excellent properties can be further improved with plasmonic coupling of Au nanoparticles (AuNPs) on gold-coated nanodisk arrays excited at large incidence angles of up to 50°. The Bragg modes (BM) thereby strongly couple to AuNP immobilized on the plasmonic substrate due to shorter decay length of the plasmon at higher incidence angles, leading to a further enhanced field between the AuNP and the plasmonic substrate. The field was highest and two hotspots were created at orthogonal positions for AuNP located close to the corner of the Au film and Au nanodisk, which was also observed for AuNP dimers. Hybridization between single-stranded DNA (ssDNA) immobilized on the surface of the AuNPs and the capture ssDNA on the gold-coated nanodisk arrays led to at least a 5-fold signal improvement and a 7-fold lower limit of detection at 7 pM for ssDNA-functionalized AuNPs at large incident angles. Thus, we demonstrate that higher field strength can be accessed and the significant advantages of working with high incidence angles with AuNP on a 2D plasmonic crystal in plasmonic sensing.

Hybridization conditions of oligonucleotide-capped gold nanoparticles for SPR sensing of microRNA

MicroRNA (miRNA) sensing, especially the miRNA-200 family, is increasingly targeted for cancer diagnostics. As the sensing schemes often rely on nanoparticles functionalized with a specific oligonucleotide, we investigate the hydribization conditions using the common case of surface plasmon resonance (SPR) sensing of miRNA and a gold nanoparticle (Au NP) competitor. In this type of assays, the Au NPs compete with the microRNA to bind the capture probe immobilized on the gold surface. In our study, we simplify and improve the detection procedure by adopting 11-mercaptoundecanoic acid (11-MUA) as linker to the gold surface, not only omitting the blocking step of 6-mercapto-1-hexanol (MCH), but also increasing the probe density. We report that the response in our SPR sensing studies increased with the size of Au NPs according to the plasmon ruler equation, but the larger AuNPs of 32 nm lacked colloidal stability. In addition, decreasing the ratio of oligonucleotide to Au NPs and the addition of polyethylene glycol (PEG) to hybridization buffer also favored a better response in SPR sensing of miRNA. The optimization led to an improved detection sensitivity in our competition method and a detection limit as low as 500 pM for miRNA-200b without amplification of miRNA and use of other amplification schemes.

A Simple Surface-Enhanced Raman Spectroscopic Method for on-Site Screening of Tetracycline Residue in Whole Milk

Therapeutic and subtherapeutic use of veterinary drugs has increased the risk of residue contamination in animal food products. Antibiotics such as tetracycline are used for mastitis treatment of lactating cows. Milk expressed from treated cows before the withdrawal period has elapsed may contain tetracycline residue. This study developed a simple surface-enhanced Raman spectroscopic (SERS) method for on-site screening of tetracycline residue in milk and water. Six batches of silver colloid nanoparticles were prepared for surface enhancement measurement. Milk-tetracycline and water-tetracycline solutions were prepared at seven concentration levels (1000, 500, 100, 10, 1, 0.1, and 0.01 ppm) and spiked with silver colloid nanoparticles. A 785 nm Raman spectroscopic system was used for spectral measurement. Tetracycline vibrational modes were observed at 1285, 1317 and 1632 cm-1 in water-tetracycline solutions and 1322 and 1621 cm-1 (shifted from 1317 and 1632 cm-1, respectively) in milk-tetracycline solutions. Tetracycline residue concentration as low as 0.01 ppm was detected in both the solutions. The peak intensities at 1285 and 1322 cm-1 were used to estimate the tetracycline concentrations in water and milk with correlation coefficients of 0.92 for water and 0.88 for milk. Results indicate that this SERS method is a potential tool that can be used on-site at field production for qualitative and quantitative detection of tetracycline residues.

Plasma-Assisted Large-Scale Nanoassembly of Metal-Insulator Bioplasmonic Mushrooms

Large-scale plasmonic substrates consisting of metal-insulator nanostructures coated with a biorecognition layer can be exploited for enhanced label-free sensing by utilizing the principle of localized surface plasmon resonance (LSPR). Most often, the uniformity and thickness of the biorecognition layer determine the sensitivity of plasmonic resonances as the inherent LSPR sensitivity of nanomaterials is limited to 10-20 nm from the surface. However, because of time-consuming nanofabrication processes, there is limited work on both the development of large-scale plasmonic materials and the subsequent surface functionalizing with biorecognition layers. In this work, by exploiting properties of reactive ions in an SF₆ plasma environment, we are able to develop a nanoplasmonic substrate containing ∼10⁶/cm² mushroom-like structures on a large-sized silicon dioxide substrate (i.e., 2.5 cm by 7.5 cm). We further investigate the underlying mechanism of the nanoassembly of gold on glass inside the plasma environment, which can be expanded to a variety of metal-insulator systems. By incorporating a novel microcontact printing technique, we deposit a highly uniform biorecognition layer of proteins on the nanoplasmonic substrate. The bioplasmonic assays performed on these substrates achieve a limit of detection of 10^-17 g/mL (∼66 zM) for biomolecules such as antibodies (∼150 kDa). Our simple nanofabrication procedure opens new opportunities in fabricating versatile bioplasmonic materials for a wide range of biomedical and sensing applications.

Colorimetric aptasensors for determination of tobramycin in milk and chicken eggs based on DNA and gold nanoparticles

Colorimetric aptasensors were designed for detection of tobramycin (TOB) based on unmodified gold nanoparticles (AuNPs) and single-strand DNA (ssDNA). In the absence of TOB, the DNA aptamer was coated on the surface of AuNPs to keep it against salt-induced aggregation. In the presence of TOB, aptamer will bind with TOB and detach from the surface of AuNPs because of higher affinities between aptamer and TOB. Then less protection of DNA may result in the aggregation of AuNPs by salt and an apparent color change from red to purple-blue. The developed aptasensors showed a high selectivity and sensitivity for TOB detection. The linearity range and the detection limit were 40-200 nM and 23.3 nM respectively. The validity of the procedure and applicability of aptasensors were successfully used to detect TOB in milk and chicken eggs, and the results were excellent in accord with the values obtained by spectrofluorimetric detection.

Photonic monitoring of treatment during infection and sepsis: development of new detection strategies and potential clinical applications

Despite the strong decline in the infection-associated mortality since the development of the first antibiotics, infectious diseases are still a major cause of death in the world. With the rising number of antibiotic-resistant pathogens, the incidence of deaths caused by infections may increase strongly in the future. Survival rates in sepsis, which occurs when body response to infections becomes uncontrolled, are still very poor if an adequate therapy is not initiated immediately. Therefore, approaches to monitor the treatment efficacy are crucially needed to adapt therapeutic strategies according to the patient's response. An increasing number of photonic technologies are being considered for diagnostic purpose and monitoring of therapeutic response; however many of these strategies have not been introduced into clinical routine, yet. Here, we review photonic strategies to monitor response to treatment in patients with infectious disease, sepsis, and septic shock. We also include some selected approaches for the development of new drugs in animal models as well as new monitoring strategies which might be applicable to evaluate treatment response in humans in the future. Figure Label-free probing of blood properties using photonics.

Electrochemical biosensing based on protein-directed carbon nanospheres embedded with SnOx and TiO2 nanocrystals for sensitive detection of tobramycin

A series of nanocomposites comprised of homogeneous mesoporous carbon nanospheres embedded with SnO_x (x = 0, 1, or 2) and TiO₂ nanocrystals using bovine serum albumin (BSA) as template followed by calcinated at different temperatures (300, 500, 700, and 900°C) were prepared, and were denoted as SnO_x@TiO₂@mC. Then a novel electrochemical biosensing strategy for detecting tobramycin (TOB) based on the nanocomposites was constructed. The as-prepared SnO_x@TiO₂@mC nanocomposites not only possess high specific surface area and good electrochemical activity but also exhibit strong bioaffinity with the aptamer strands, therefore, they were applied as the scaffold for anchoring TOB-targeted aptamer and further used to sensitively detect trace TOB in aqueous solutions. By comparing the electrochemical biosensing responses toward TOB detection based on the four SnO_x@TiO₂@mC nanocomposites, the biosensing system constructed with SnO_x@TiO₂@mC₉₀₀ (derived at 900°C) demonstrated the highest determination efficiency, high selectivity, and good stability. In particular, the new proposed aptasensing method based on SnO_x@TiO₂@mC nanocomposite exhibits considerable potential for the quantitative detection of TOB in the biomedical field.

Identification and Quantification of Intravenous Therapy Drugs Using Normal Raman Spectroscopy and Electrochemical Surface-Enhanced Raman Spectroscopy

Errors in intravenous (IV) drug therapies can cause human harm and even death. There are limited label-free methods that can sensitively monitor the identity and quantity of the drug being administered. Normal Raman spectroscopy (NRS) provides a modestly sensitive, label-free, and completely noninvasive means of IV drug sensing. In the case that the analyte cannot be detected within its clinical range with Raman, a label-free surface-enhanced Raman spectroscopy (SERS) approach can be implemented to detect the analyte of interest. In this work, we demonstrate two individual cases where we use NRS and electrochemical SERS (EC-SERS) to detect IV therapy analytes within their clinically relevant ranges. We implement NRS to detect gentamicin, a commonly IV-administered antibiotic and EC-SERS to detect dobutamine, a drug commonly administered after heart surgery. In particular, dobutamine detection with EC-SERS was found to have a limit of detection 4 orders of magnitude below its clinical range, highlighting the excellent sensitivity of SERS. We also demonstrate the use of hand-held Raman instrumentation for NRS and EC-SERS, showing that Raman is a highly sensitive technique that is readily applicable in a clinical setting.