Bifunctional Nature Research Articles

Harnessing the potential of acyl triazoles in bifunctional cobalt-catalyzed radical cross-coupling reactions

Persistent radicals facilitate numerous selective radical coupling reactions. Here, we have identified acyl triazole as a new and versatile moiety for generating persistent radical intermediates through single-electron transfer processes. The efficient generation of these persistent radicals is facilitated by the formation of substrate-coordinated cobalt complexes, which subsequently engage in radical cross-coupling reactions. Remarkably, triazole-coordinated cobalt complexes exhibit metal-hydride hydrogen atom transfer (MHAT) capabilities with alkenes, enabling the efficient synthesis of diverse ketone products without the need for external ligands. By leveraging the persistent radical effect, this catalytic approach also allows for the development of other radical cross-coupling reactions with two representative radical precursors. The discovery of acyl triazoles as effective substrates for generating persistent radicals and as ligands for cobalt catalysis, combined with the bifunctional nature of the cobalt catalytic system, opens up new avenues for the design and development of efficient and sustainable organic transformations.

Zn, Cd and Cu Coordination Polymers for Metronidazole Sensing and for Ullmann and Chan-Lam Coupling Reactions.

Five compounds, [Zn2(bpe)(BPTA)2(H2O)2] ⋅ 2H2O (1); [Zn(bpe)(BPTA)] (2); [Cd(bpe)(BPTA)H2O] (3); [Cd(BPTA) (bpmh)] ⋅ 2H2O (4); and Cu2(BPTA)2(bpmh)3(H2O)2] ⋅ 2H2O (5) were prepared employing 2,5-bis(prop-2-yn-1-yloxy)terephthalic acid (2, 5 BPTA) as the primary ligand and 1,2-di(pyridin-4-yl)ethane (4, 4' bpe) (1-3) and 1,2-bis(pyridin-3-ylmethylene)hydrazine (bpmh) (4-5) as the secondary ligands. Single crystal studies indicated that the compounds 1, 3 and 5 have two-dimensional layer structures and compounds 2 and 4 three-dimensional structures. The luminescence behaviour of the compounds 2 and 3 were explored for the sensing of metronidazole in aqueous medium. The studies indicated that the compounds can detect metronidazole in ppm level both in solution as well as simple paper strips. The Cu compound 5 was found to lose the coordinated water molecule at 100 °C without any structural change. The coordinatively unsaturated Cu-centre were examined towards the Lewis acidic character by carrying out the Ullmann type C-C homocoupling reaction of the aromatic halide compounds. The compounds, 4 and 5, also have the Lewis basic functionality arising out the =N-N=, aza groups. The bifunctional nature of the coordination polymers (CP) was explored towards the Chan-Lam coupling reaction between phenyl boronic acid and aniline derivatives in the ethanol medium. In both the catalytic reactions, good yields and recyclability were observed. The present studies illustrated the rich diversity that the transition metal containing compounds exhibit in extended framework structures.

OsTH1 is a key player in thiamin biosynthesis in rice

Thiamin is a vital nutrient that acts as a cofactor for several enzymes primarily localized in the mitochondria. These thiamin-dependent enzymes are involved in energy metabolism, nucleic acid biosynthesis, and antioxidant machinery. The enzyme HMP-P kinase/thiamin monophosphate synthase (TH1) holds a key position in thiamin biosynthesis, being responsible for the phosphorylation of HMP-P into HMP-PP and for the condensation of HMP-PP and HET-P to form TMP. Through mathematical kinetic model, we have identified TH1 as a critical player for thiamin biofortification in rice. We further focused on the functional characterization of OsTH1. Sequence and gene expression analysis, along with phylogenetic studies, provided insights into OsTH1 bifunctional features and evolution. The indispensable role of OsTH1 in thiamin biosynthesis was validated by heterologous expression of OsTH1 and successful complementation of yeast knock-out mutants impaired in thiamin production. We also proved that the sole OsTH1 overexpression in rice callus significantly improves B1 concentration, resulting in 50% increase in thiamin accumulation. Our study underscores the critical role of OsTH1 in thiamin biosynthesis, shedding light on its bifunctional nature and evolutionary significance. The significant enhancement of thiamin accumulation in rice callus upon OsTH1 overexpression constitutes evidence of its potential application in biofortification strategies.

Orally Bioavailable Proteolysis-Targeting Chimeras: An Innovative Approach in the Golden Era of Discovering Small-Molecule Cancer Drugs.

Proteolysis-targeting chimeras (PROTACs) are an emerging therapeutic modality that show promise to open a target space not accessible to conventional small molecules via a degradation-based mechanism. PROTAC degraders, due to their bifunctional nature, which is categorized as 'beyond the Rule of Five', have gained attention as a distinctive therapeutic approach for oral administration in clinical settings. However, the development of PROTACs with adequate oral bioavailability remains a significant hurdle, largely due to their large size and less than ideal physical and chemical properties. This review encapsulates the latest advancements in orally delivered PROTACs that have entered clinical evaluation as well as developments highlighted in recent scholarly articles. The insights and methodologies elaborated upon in this review could be instrumental in supporting the discovery and refinement of novel PROTAC degraders aimed at the treatment of various human cancers.

The involvement of soluble epoxide hydrolase in the development of cardiovascular diseases through epoxyeicosatrienoic acids.

Arachidonic acid (AA) has three main metabolic pathways: the cycloxygenases (COXs) pathway, the lipoxygenases (LOXs) pathway, and the cytochrome P450s (CYPs) pathway. AA produces epoxyeicosatrienoic acids (EETs) through the CYPs pathway. EETs are very unstable in vivo and can be degraded in seconds to minutes. EETs have multiple degradation pathways, but are mainly degraded in the presence of soluble epoxide hydrolase (sEH). sEH is an enzyme of bifunctional nature, and current research focuses on the activity of its C-terminal epoxide hydrolase (sEH-H), which hydrolyzes the EETs to the corresponding inactive or low activity diol. Previous studies have reported that EETs have cardiovascular protective effects, and the activity of sEH-H plays a role by degrading EETs and inhibiting their protective effects. The activity of sEH-H plays a different role in different cells, such as inhibiting endothelial cell proliferation and migration, but promoting vascular smooth muscle cell proliferation and migration. Therefore, it is of interest whether the activity of sEH-H is involved in the initiation and progression of cardiovascular diseases by affecting the function of different cells through EETs.

Functionalized graphene oxide-modified sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) based thermal-resistance anti-fouling bi-functional cation exchange membrane for electrodialytic desalination

We report a sustainable strategy for fabricating thermal-resistance anti-fouling cation exchange membrane (CEM), using sulfonated poly (2,6-dimethyl-1,4-phenylene oxide) (SPPO), and phosphorylated graphene oxide (FGO). The GO was phosphorylated, and different CEMs (3.0–7.0 % weight ratio of FGO) were prepared to investigate their electrodialysis (ED) performance. Structural features of SPPO-FGO composite CEMs such as ̴ 21.51 % degree of sulphonation (SPPO), bi-functional (-SO3H, and -PO3H2) nature, and balanced hydrophobic-hydrophilic segments, etc., were attributed for thermal-resistance and anti-fouling membrane nature of the membrane. The presence of FGO in the SPPO polymer matrix significantly improved mechanical, thermal, oxidative stabilities, ionic conductivity (κm), and counter-ion transport number (tm+). Suitable optimized SPPO-FGO/7 % (7.0 % of FGO) showed excellent physicochemical properties (14.1 % water uptake, 3.2 % swelling ratio, and 1.76 m eq./g ion exchange capacity), along with 10.92 × 10−2 S cm−1 conductivity, and 0.95 counter-ion transport number at 30 °C. Improved i-V curves and ED performance at 60 °C, showed relatively low energy consumption (0.72 k W hr/kg of NaCl removed), and high current efficiency (99.0 %) for SPPO-FGO/7 % CEM revealed, its potential candidature for electrodialytic water desalination. Further, CEM also avoids any significant deterioration in ED performance due to the presence of cationic, anionic and zwitterionic foulants.

Hydrotreating of m-cresol: A lignin derived phenolic compound, using ruthenium decorated zeolite-β

5 wt% ruthenium-loaded Zeolite-β is found to be efficient for hydrotreating the lignin model compound, m-cresol, at 170 °C under 10 bar hydrogen pressure to give methyl cyclohexane. The catalyst has a bifunctional nature in which the redox properties of ruthenium and the strong acidic nature of Zeolite-β are instrumental in the hydrotreating of m-cresol. The well-dispersed metallic ruthenium on Zeolite-β, as evident from TEM and EDS mapping analysis, is responsible for the potential activity. The activity was retained even after six cycles and was also found to have potential for hydrotreating various other functional substrates.

HtrAs are essential for the survival of the haloarchaeon Natrinema gari J7-2 in response to heat, high salinity, and toxic substances.

Bacterial and eukaryotic HtrAs can act as an extracytoplasmic protein quality control (PQC) system to help cells survive in stress conditions, but the functions of archaeal HtrAs remain unknown. Particularly, haloarchaea route most secretory proteins to the Tat pathway, enabling them to fold properly in well-controlled cytoplasm with cytosolic PQC systems before secretion. It is unclear whether HtrAs are required for haloarchaeal survival and stress response. The haloarchaeon Natrinema gari J7-2 encodes three Tat signal peptide-bearing HtrAs (NgHtrA, NgHtrB, and NgHtrC), and the signal peptides of NgHtrA and NgHtrC contain a lipobox. Here, the in vitro analysis reveals that the three HtrAs show different profiles of temperature-, salinity-, and metal ion-dependent proteolytic activities and could exhibit chaperone-like activities to prevent the aggregation of reduced lysozyme when their proteolytic activities are inhibited at low temperatures or the active site is disrupted. The gene deletion and complementation assays reveal that NgHtrA and NgHtrC are essential for the survival of strain J7-2 at elevated temperature and/or high salinity and contribute to the resistance of this haloarchaeon to zinc and inhibitory substances generated from tryptone. Mutational analysis shows that the lipobox mediates membrane anchoring of NgHtrA or NgHtrC, and both the membrane-anchored and free extracellular forms of the two enzymes are involved in the stress resistance of strain J7-2, depending on the stress conditions. Deletion of the gene encoding NgHtrB in strain J7-2 causes no obvious growth defect, but NgHtrB can functionally substitute for NgHtrA or NgHtrC under some conditions.IMPORTANCEHtrA-mediated protein quality control plays an important role in the removal of aberrant proteins in the extracytoplasmic space of living cells, and the action mechanisms of HtrAs have been extensively studied in bacteria and eukaryotes; however, information about the function of archaeal HtrAs is scarce. Our results demonstrate that three HtrAs of the haloarchaeon Natrinema gari J7-2 possess both proteolytic and chaperone-like activities, confirming that the bifunctional nature of HtrAs is conserved across all three domains of life. Moreover, we found that NgHtrA and NgHtrC are essential for the survival of strain J7-2 under stress conditions, while NgHtrB can serve as a substitute for the other two HtrAs under certain circumstances. This study provides the first biochemical and genetic evidence of the importance of HtrAs for the survival of haloarchaea in response to stresses.

RAFT step-growth polymerization via the Z-group approach and deconstruction by RAFT interchange.

Recycling vinyl polymers is essential to mitigate the environmental impact of plastic waste. However, typical polymerization strategies to construct vinyl polymers lack the ability to incorporate degradable linkers throughout the main chain. We report a RAFT step-growth polymerization through the Z-group approach that is directly carried out by using a common class of symmetric trithiocarbonate based RAFT agents and commercially available bismaleimide monomers. Such synthesized RAFT step-growth polymers contain embedded RAFT agents in every structural unit, allowing chain expansion of the step-growth backbone via controlled chain growth to yield linear multiblock (co)polymers. These polymers can undergo deconstruction via the RAFT interchange process with exogeneous RAFT agents, generating smaller uniform species with narrow molecular weight distribution. In addition, the telechelic bifunctional RAFT agent nature after deconstruction allows repolymerization, showing a promising method for recycling common vinyl polymers.

Biochemical unravelling of the endoxylanase activity in a bifunctional GH39 enzyme cloned and expressed from thermophilic Geobacillus sp. WSUCF1

The glycoside hydrolase family 39 (GH39) proteins are renowned for their extremophilic and multifunctional enzymatic properties, yet the molecular mechanisms underpinning these unique characteristics continue to be an active subject of research. In this study, we introduce WsuXyn, a GH39 protein with a molecular weight of 58 kDa, originating from the thermophilic Geobacillus sp. WSUCF1. Previously reported for its exceptional thermostable β-xylosidase activity, WsuXyn has recently demonstrated a significant endoxylanase activity (3752 U·mg−1) against beechwood xylan, indicating towards its bifunctional nature. Physicochemical characterization revealed that WsuXyn exhibits optimal endoxylanase activity at 70 °C and pH 7.0. Thermal stability assessments revealed that the enzyme is resilient to elevated temperatures, with a half-life of 168 h. Key kinetic parameters highlight the exceptional catalytic efficiency and strong affinity of the protein for xylan substrate. Moreover, WsuXyn-mediated hydrolysis of beechwood xylan has achieved 77 % xylan conversion, with xylose as the primary product. Structural analysis, amalgamated with docking simulations, has revealed strong binding forces between xylotetraose and the protein, with key amino acid residues, including Glu278, Tyr230, Glu160, Gly202, Cys201, Glu324, and Tyr283, playing pivotal roles in these interactions. Therefore, WsuXyn holds a strong promise for biodegradation and value-added product generation through lignocellulosic biomass conversion.

Bifunctional Co active site on dilute CoCu plasmonic alloy for light-driven H2 production from methanol and water

Catalytic H2 production from CH3OH and H2O is acknowledged as a promising strategy in the growth of future hydrogen economy, yet its industrialization still faces significant challenges of substantial energy consumption. To overcome the high barrier of CH3OH/H2O activation, we report a low-cost plasmonic Co–Cu alloy catalyst for producing H2 efficiently through a light-driven process, bringing an outstanding generation rate of 6225.1 μmol g−1 min−1 (31.1 μmol min−1) without external thermal energy input. The bifunctional nature of Co active sites on Cu favors the adsorption of CH3OH and lowers the energy barrier for H2O dissociation simultaneously. Moreover, the Co–Cu interface exploits the hot-carrier-induced reactant activation upon visible light irradiation, enormously decreasing the apparent activation energy from 100.8 to 68.2 kJ mol−1. Our study unveils a novel method to harness renewable solar energy for H2 production, and will provide numerous opportunities for constructing a robust and sustainable catalytic process.

Promotional effects of phosphotungstic acid on CePO4 catalyst for the selective catalytic reduction of NOx with NH3

CePO4 was prepared using the co-precipitation method. Recognizing the bifunctional nature of hetero-polyacid (salt), with both acidic and redox properties, it was modified by using phosphotungstic acid (HPW), and the HPW/CePO4 catalysts were synthesized using the impregnation technique. Various advanced techniques were employed to investigate aspects such as catalytic activity, microstructure, surface properties, and reaction mechanisms. These methods included NH3-SCR, XRD, XPS, SEM, BET, NH3-TPD, H2-TPR, and In-situ DRIFTs. Experimental findings indicated that the HPW-modified CePO4 catalysts exhibited enhanced SCR activity. Among them, the reaction activity window for NOx conversion of the W: Ce 0.05 catalyst was found to be 300∼400 °C, which represented the best activity temperature window. Following the incorporation of HPW, the HPW/CePO4 catalysts demonstrated an increased presence of Brønsted acidic sites, which concurrently led to a significant reduction in SO2 adsorption. The W: Ce 0.05 catalyst possessed the highest ratios of Oα/(Oα+Oβ+Oγ) and Ce4+/(Ce3++Ce4+). These ratios effectively regulated the sequestration and release of reactive oxygen species, thereby enhancing the activation of NH3. Consequently, this promoted the catalyst's low-temperature NH3-SCR reactivity. Lastly, the reaction process was examined using in-situ DRIFTs. The study revealed the generation of -NH2 intermediates at the Lewis acid sites of the W: Ce 0.05 catalyst. These intermediates subsequently underwent reactions with gaseous NO via the Eley-Rideal mechanism. This approach not only amplified the low-temperature catalytic efficacy of the catalysts but also bolstered their resilience to SO2, thereby fostering the long-term stability of the NH3-SCR reaction.

Structural Analysis of Non-native Peptide-Based Catalysts Using 2D NMR-Guided MD Simulations.

Proteins and enzymes generally achieve their functions by creating well-defined 3D architectures that pre-organize reactive functionalities. Mimicking this approach to supramolecular pre-organization is leading to the development of highly versatile artificial chemical environments, including new biomaterials, medicines, artificial enzymes, and enzyme-like catalysts. The use of β-turn and α-helical motifs is one approach that enables the precise placement of reactive functional groups to enable selective substrate activation and reactivity/selectivity that approaches natural enzymes. Our recent work has demonstrated that helical peptides can serve as scaffolds for pre-organizing two reactive groups to achieve enzyme-like catalysis. In this study, we used CYANA and AmberTools to develop a computational approach for determining how the structure of our peptide catalysts can lead to enhancements in reactivity. These results support our hypothesis that the bifunctional nature of the peptide enables catalysis by pre-organizing the two catalysts in reactive conformations that accelerate catalysis by proximity. We also present evidence that the low reactivity of monofunctional peptides can be attributed to interactions between the peptide-bound catalyst and the helical backbone, which are not observed in the bifunctional peptide.

A Comprehensive Review on Processing, Development and Applications of Organofunctional Silanes and Silane-Based Hyperbranched Polymers.

Since the last decade, hyperbranched polymers (HBPs) have gained wider theoretical interest and practical applications in sensor technology due to their ease of synthesis, highly branched structure but dimensions within nanoscale, a larger number of modified terminal groups and lowering of viscosity in polymer blends even at higher HBP concentrations. Many researchers have reported the synthesis of HBPs using different organic-based core-shell moieties. Interestingly, silanes, as organic-inorganic hybrid modifiers of HBP, are of great interest as they resulted in a tremendous improvement in HBP properties like increasing thermal, mechanical and electrical properties compared to that of organic-only moieties. This review focuses on the research progress in organofunctional silanes, silane-based HBPs and their applications since the last decade. The effect of silane type, its bi-functional nature, its influence on the final HBP structure and the resultant properties are covered in detail. Methods to enhance the HBP properties and challenges that need to be overcome in the near future are also discussed.

Silicalite-1 Layer Secures the Bifunctional Nature of a CO2 Hydrogenation Catalyst.

Close proximity usually shortens the travel distance of reaction intermediates, thus able to promote the catalytic performance of CO2 hydrogenation by a bifunctional catalyst, such as the widely reported In2O3/H-ZSM-5. However, nanoscale proximity (e.g., powder mixing, PM) more likely causes the fast deactivation of the catalyst, probably due to the migration of metals (e.g., In) that not only neutralizes the acid sites of zeolites but also leads to the reconstruction of the In2O3 surface, thus resulting in catalyst deactivation. Additionally, zeolite coking is another potential deactivation factor when dealing with this methanol-mediated CO2 hydrogenation process. Herein, we reported a facile approach to overcome these three challenges by coating a layer of silicalite-1 (S-1) shell outside a zeolite H-ZSM-5 crystal for the In2O3/H-ZSM-5-catalyzed CO2 hydrogenation. More specifically, the S-1 layer (1) restrains the migration of indium that preserved the acidity of H-ZSM-5 and at the same time (2) prevents the over-reduction of the In2O3 phase and (3) improves the catalyst lifetime by suppressing the aromatic cycle in a methanol-to-hydrocarbon conversion step. As such, the activity for the synthesis of C2 + hydrocarbons under nanoscale proximity (PM) was successfully obtained. Moreover, an enhanced performance was observed for the S-1-coated catalyst under microscale proximity (e.g., granule mixing, GM) in comparison to the S-1-coating-free counterpart. This work highlights an effective shielding strategy to secure the bifunctional nature of a CO2 hydrogenation catalyst.

Synthesis of etheric ester based biofuel additive over bifunctional metal/zeolite catalysts comprising NiRe nanoparticles and Beta zeolite

Biomass derived etheric ester compounds show promising applications as renewable fuel additives and solvents. In this study, we reported the preparation of bifunctional transition metal/zeolite catalysts comprising Ni-Re bimetal nanoparticles and Beta zeolites prepared via conventional wet-impregnation method. The bifunctional nature makes it possible for the synthesis of ethyl-4-ethoxy pentanoate (EEP) as etheric ester starting from ethyl levulinate (EL) in presence of H2 with good performance. The textural properties and acidity of the catalysts were characterized by several techniques: XRD, TEM, STEM-Mapping, H2-TPR and XPS. The addition of ReOx increased the dispersion and reducibility of NiO·NH3-TPD and in-situ FT-IR of pyridine adsorption confirmed that the NiReOx/Beta catalyst affords large amount of Lewis acid sites and certain amount of Bronsted acid sites. The attained Bronsted acid sites in BEA topology may be the key sites contributing to the etherification. Under optimized reaction conditions, namely 160 °C, 1 MPa H2 and reaction time of 2 h, almost full conversion of EL with 83% yield of EEP could be achieved in ethanol.

Anaerobic Hydroxylation of C(sp3)-H Bonds Enabled by the Synergistic Nature of Photoexcited Nitroarenes.

A photoexcited-nitroarene-mediated anaerobic C-H hydroxylation of aliphatic systems is reported. The success of this reaction is due to the bifunctional nature of the photoexcited nitroarene, which serves as the C-H bond activator and the oxygen atom source. Compared to previous methods, this approach is cost- and atom-economical due to the commercial availability of the nitroarene, the sole mediator of the reaction. Because of the anaerobic conditions of the transformation, a noteworthy expansion in substrate scope can be obtained compared to prior reports. Mechanistic studies support that the photoexcited nitroarenes engage in successive hydrogen atom transfer and radical recombination events with hydrocarbons, leading to N-arylhydroxylamine ether intermediates. Spontaneous fragmentation of these intermediates leads to the key oxygen atom transfer products.

Ti@MoS2 incorporated Polypropylene/Nylon fabric-based porous, breathable triboelectric nanogenerator as respiration sensor and ammonia gas sensor applications

High output and non-interrupted power supply from fabric-based nanogenerators still remain a major challenge in developing self-powered wearable electronic applications. Addressing this, we demonstrate a low-cost, lead-free triboelectric nanogenerator based on hydrothermally grown Titanium (Ti) functionalized Molybdenum Disulfide (MoS2) interspersed polypropylene (PP) cloth and sandwiched with Nylon cloth for a highly sensitive respiration sensor and self-powered ammonia gas sensor. The nanogenerator with the device configuration Cu/Ti@MoS2/PP: Nylon /Ag is attached to a respiratory mask, and the open-circuit voltage (Voc) and short-circuit current density (JSC) during respiration cycles were obtained as 29.3 V and 42.7 µA/cm2 respectively. A significant difference in the breath pattern of human respiration cycles. Further, a fully self-powered ammonia gas sensor was demonstrated by integrating the triboelectric nanogenerator with Ti@MoS2/PP ammonia sensor. The self-powered Ti- MoS2 on PP cloth-based gas sensor driven by TENG displays an excellent response with a wide dynamic sensing range of ammonia gas from 200 ppb to 2600 ppb at room temperature, with a high sensitivity, selectivity and a rapid response time. This study explores the bifunctional nature of Ti@MoS2 nanoparticles as a respiratory mask and a self-powered ammonia gas sensor fabricated with excellent potential for self-powered health diagnostic applications.

Amplification and Quantitation of Telomeric Extrachromosomal Circles.

Telomeres are structures that cap the ends of linear chromosomes and play critical roles in maintaining genome integrity and establishing the replicative lifespan of cells. In stem and cancer cells, telomeres are actively elongated by either telomerase or the alternative lengthening of telomeres (ALT) pathway. This pathway is characterized by several hallmark features, including extrachromosomal C-rich circular DNAs that can be probed to assess ALT activity. These so-called C-circles are the product of ALT-associated DNA damage repair processes and simultaneously serve as potential templates for iterative telomere extension. This bifunctional nature makes C-circles highly sensitive and specific markers of ALT. Here, we describe a C-circle assay, adapted from previous reports, that enables the quantitation of C-circle abundance in mammalian cells subjected to a wide range of experimental perturbations. This protocol combines the Quick C-circle Preparation (QCP) method for DNA isolation with fluorometry-based DNA quantification, rolling circle amplification (RCA), and detection of C-circles using quantitative PCR. Moreover, the inclusion of internal standards with well-characterized telomere maintenance mechanisms (TMMs) allows for the reliable benchmarking of cells with unknown TMM status. Overall, our work builds upon existing protocols to create a generalizable workflow for in vitro C-circle quantitation and ascertainment of TMM identity.

Review: 3-Aminopropyltriethoxysilane (APTES) Deposition Methods on Oxide Surfaces in Solution and Vapor Phases for Biosensing Applications.

Surface functionalization and bioreceptor immobilization are critical processes in developing a highly sensitive and selective biosensor. The silanization process with 3-aminopropyltriethoxysilane (APTES) on oxide surfaces is frequently used for surface functionalization because of beneficial characteristics such as its bifunctional nature and low cost. Optimizing the deposition process of the APTES layer to obtain a monolayer is crucial to having a stable surface and effectively immobilizing the bioreceptors, which leads to the improved repeatability and sensitivity of the biosensor. This review provides an overview of APTES deposition methods, categorized into the solution-phase and vapor-phase, and a comprehensive summary and guide for creating stable APTES monolayers on oxide surfaces for biosensing applications. A brief explanation of APTES is introduced, and the APTES deposition methods with their pre/post-treatments and characterization results are discussed. Lastly, APTES deposition methods on nanoparticles used for biosensors are briefly described.