Single-Cell Force Spectroscopy Uncovers Root Zone- and Bacteria-Specific Interactions.

Understanding root-bacteria interactions with plant growth-promoting rhizobacteria (PGPR) is key to developing effective biofertilizers for sustainable agriculture. We performed single-cell force spectroscopy using the atomic force microscope (AFM) to study the primary attachment of two PGPR, Bacillus velezensis and Pseudomonas defensor, to different regions of Arabidopsis thaliana roots. Force measurements with individual cells uncovered distinct attachment strategies by each strain, involving binding via micrometer-long polymers from both bacteria and root surfaces.

Antimicrobial and anti-inflammatory effects of polyethyleneimine-modified polydopamine nanoparticles on a burn-injured skin model.

Chronic infections involving bacterial biofilms pose significant treatment challenges due to the resilience of biofilms against existing antimicrobials. Here, we introduce a nanomaterial-based platform for treating biofilms, both in isolation and within a biofilm-infected burn skin model. Our approach leverages biocompatible and photothermal polydopamine nanoparticles (PDNP), functionalized with branched polyethyleneimine (PEI) and loaded with the antibiotic rifampicin, to target bacteria dwelling within biofilms.

Cocktail Approach with Polyserotonin Nanoparticles and Peptides for Treatment of .

Dental plaque, formed by a biofilm, is a major contributor to cavity formation. While antimicrobial strategies exist, the growing risk of antibiotic resistance necessitates alternative therapeutic solutions. Polyserotonin nanoparticles (PSeNPs), recently recognized for their photothermal property and promising biomedical applications, open up a new avenue for antimicrobial use.

Different drug loading methods and antibiotic structure modulate the efficacy of polydopamine nanoparticles as drug nanocarriers.

The inefficient delivery of antimicrobials to their target is a significant factor contributing to antibiotic resistance. As such, smart nanomaterials that respond to external stimuli are extensively explored for precise drug delivery. Here, we investigate how drug loading methods and the structure of antibiotics impact the effectiveness of photothermally active polydopamine nanoparticles (PDNPs) as a laser-responsive drug delivery system.

Electrochemical simultaneous determination of hydroquinone, catechol, bisphenol A, and bisphenol S using a novel mesoporous nickel-modified carbon sensor.

The widespread occurrence of endocrine disruptor compounds in wastewater has garnered significant attention owing to their toxicity, even at low concentrations, and their persistence in the water body. Among various analytical techniques, electrochemical sensors become popular for the environmental monitoring of water pollutants due to their low cost, rapid detection, high sensitivity, and selectivity. In this study, the mesoporous Ni (MNi) material was synthesized with an innovative method using Pluronic™ F-127 as a soft template and applied as a modifier for the simultaneous electrochemical sensing of hydroquinone (HQ), catechol (CC), bisphenol A (BPA), and bisphenol S (BPS).

Microfluidic flow injection analysis system for the electrochemical detection of dopamine using diazonium-grafted copper nanoparticles on multi-walled carbon nanotube-modified surfaces.

In this proof-of-concept study, a microfluidic flow injection analysis (FIA) system was developed using multi-walled carbon nanotube-modified screen-printed carbon electrodes (CNTSPEs) that were modified with copper nanoparticles (CuNPs) following the electrodeposition of the diazonium salt of 4-aminothiophenol to form 4-thiophenol-conjugated CuNPs (CuNPs-CNTSPE). Transmission electron microscopy (TEM), atomic force microscopy (AFM), and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) were used to characterize the size of CuNPs, morphology and elemental analysis of CuNPs-CNTSPE, respectively. Using electrochemical impedance spectroscopy (EIS), the charge-transfer resistance (R) of CuNPs-CNTSPE was found to be 20-fold lower than that of CNTSPE.

Laser-responsive sequential delivery of multiple antimicrobials using nanocomposite hydrogels.

Precise control of antimicrobial delivery can prevent the adverse effects of antibiotics. By exploiting the photothermal activity of polydopamine nanoparticles along with the distinct transition temperatures of liposomes, a near-infrared (NIR) laser can be used to control the sequential delivery of an antibiotic and its adjuvant from a nanocomposite hydrogel-preventing bacterial growth.

Peptide-Polydopamine Nanocomposite Hydrogel for a Laser-Controlled Hydrophobic Drug Delivery.

Smart antibacterial systems, delivering antimicrobials in a highly controlled manner, are one strategy toward fighting the rise of antibiotic-resistant pathogens. Here, we engineer a laser-responsive antimicrobial nanocomposite hydrogel combining a peptide amphiphile and a photothermally active polydopamine nanoparticle (PDNP) to entrap the hydrophobic rifampicin within the hydrophilic hydrogel matrix. We show that the ability of the gelator to interact and retain rifampicin within the gel induced structural changes in its nanofiber network and mechanical properties.

Size-controlled synthesis of bioinspired polyserotonin nanoparticles with free radical scavenging activity.

Polyserotonin-based nanoparticles are a new class of bioinspired nanomaterial with recently demonstrated therapeutic potential for future clinical applications. It is therefore important to establish a robust and rapid method of synthesizing polyserotonin nanoparticles (PSeNP) in the size range ideal for in vivo utilization. Since the formation of PSeNP is base-catalyzed, here we report the influence of solution pH, in the presence of different base systems, on the kinetics of PSeNP formation and physico-chemical properties of the resulting nanoparticles.

5-Axis CNC Micromilling for Rapid, Cheap, and Background-Free NMR Microcoils.

The superior mass sensitivity of microcoil technology in nuclear magnetic resonance (NMR) spectroscopy provides potential for the analysis of extremely small-mass-limited samples such as eggs, cells, and tiny organisms. For optimal performance and efficiency, the size of the microcoil should be tailored to the size of the mass-limited sample of interest, which can be costly as mass-limited samples come in many shapes and sizes. Therefore, rapid and economic microcoil production methods are needed.

Polyacrylamide hydrogels doped with different shapes of silver nanoparticles: Antibacterial and mechanical properties.

The incorporation of nanoparticles into a hydrogel matrix enables the development of innovative smart materials with enhanced biophysical properties. In this proof-of-concept study, we encapsulated different shapes (spherical, triangular and rod) of silver nanoparticles (AgNPs) within a hydrogel matrix of polyacrylamide (PAA) and N-methylenebisacrylamide (MBA) (PAA-MBA) to investigate whether these hydrogels exhibited shape-dependent antimicrobial and mechanical properties. We examined the mechanism of adsorption of different shapes of AgNPs using time-of-flight secondary ion mass spectrometry (ToF-SIMS).

Multi-component peptide hydrogels - a systematic study incorporating biomolecules for the exploration of diverse, tuneable biomaterials.

Peptide-based supramolecular gels can be designed to be functional "smart" materials that have applications in drug delivery, tissue engineering, and supramolecular chemistry. Although many multi-component gel systems have been designed and reported, many of these applications still rely solely on single-component gel systems which limits the functionalities of the materials. Multi-component self-assembly leads to the formation of highly ordered and complex architectures while offering the possibility to generate hydrogels with interesting properties including functional complexity and diverse morphologies.

Interfacial nanomechanical heterogeneity of the E. coli biofilm matrix.

The interface between bacterial biofilms and their environment plays a vital role in the recalcitrance of biofilms to biological, chemical, and mechanical threats. Nonetheless, we know little about the physical parameters that dictate the interfacial morphology and nanomechanics of biofilms. Here, we present a robust, reproducible, and quantitative platform based on atomic force microscopy (AFM) that allows for correlated high-resolution imaging of the morphology and nanomechanical properties of an intact E.

Molecular mechanics of coiled coils loaded in the shear geometry.

Coiled coils are important nanomechanical building blocks in biological and biomimetic materials. A mechanistic molecular understanding of their structural response to mechanical load is essential for elucidating their role in tissues and for utilizing and tuning these building blocks in materials applications. Using a combination of single-molecule force spectroscopy (SMFS) and steered molecular dynamics (SMD) simulations, we have investigated the mechanics of synthetic heterodimeric coiled coils of different length (3-4 heptads) when loaded in shear geometry.

Rapid Characterization of a Mechanically Labile α-Helical Protein Enabled by Efficient Site-Specific Bioconjugation.

Atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) is a powerful yet accessible means to characterize mechanical properties of biomolecules. Historically, accessibility relies upon the nonspecific adhesion of biomolecules to a surface and a cantilever and, for proteins, the integration of the target protein into a polyprotein. However, this assay results in a low yield of high-quality data, defined as the complete unfolding of the polyprotein.

Probiotic Gut Microbiota Isolate Interacts with Dendritic Cells via Glycosylated Heterotrimeric Pili.

Mapping of the microbial molecules underlying microbiota-host interactions is key to understand how microbiota preserve mucosal homeostasis. A pivotal family of such bacterial molecules are pili. Pili are proteinaceous cell wall appendages with a well-documented role in adhesion, whilst their role in immune interaction with the host is less established.

Binding forces of Streptococcus mutans P1 adhesin.

Streptococcus mutans is a Gram-positive oral bacterium that is a primary etiological agent associated with human dental caries. In the oral cavity, S. mutans adheres to immobilized salivary agglutinin (SAG) contained within the salivary pellicle on the tooth surface.

Identification of a supramolecular functional architecture of Streptococcus mutans adhesin P1 on the bacterial cell surface.

P1 (antigen I/II) is a sucrose-independent adhesin of Streptococcus mutans whose functional architecture on the cell surface is not fully understood. S. mutans cells subjected to mechanical extraction were significantly diminished in adherence to immobilized salivary agglutinin but remained immunoreactive and were readily aggregated by fluid-phase salivary agglutinin.

Quantifying the forces guiding microbial cell adhesion using single-cell force spectroscopy.

During the past decades, several methods (e.g., electron microscopy, flow chamber experiments, surface chemical analysis, surface charge and surface hydrophobicity measurements) have been developed to investigate the mechanisms controlling the adhesion of microbial cells to other cells and to various other substrates.

Improved single molecule force spectroscopy using micromachined cantilevers.

Enhancing the short-term force precision of atomic force microscopy (AFM) while maintaining excellent long-term force stability would result in improved performance across multiple AFM modalities, including single molecule force spectroscopy (SMFS). SMFS is a powerful method to probe the nanometer-scale dynamics and energetics of biomolecules (DNA, RNA, and proteins). The folding and unfolding rates of such macromolecules are sensitive to sub-pN changes in force.

Single-cell force spectroscopy of pili-mediated adhesion.

Although bacterial pili are known to mediate cell adhesion to a variety of substrates, the molecular interactions behind this process are poorly understood. We report the direct measurement of the forces guiding pili-mediated adhesion, focusing on the medically important probiotic bacterium Lactobacillus rhamnosus GG (LGG). Using non-invasive single-cell force spectroscopy (SCFS), we quantify the adhesion forces between individual bacteria and biotic (mucin, intestinal cells) or abiotic (hydrophobic monolayers) surfaces.

Atomic force microscopy with sub-picoNewton force stability for biological applications.

Atomic force microscopy (AFM) is widely used in the biological sciences. Despite 25 years of technical developments, two popular modes of bioAFM, imaging and single molecule force spectroscopy, remain hindered by relatively poor force precision and stability. Recently, we achieved both sub-pN force precision and stability under biologically useful conditions (in liquid at room temperature).

Routine and timely sub-picoNewton force stability and precision for biological applications of atomic force microscopy.

Force drift is a significant, yet unresolved, problem in atomic force microscopy (AFM). We show that the primary source of force drift for a popular class of cantilevers is their gold coating, even though they are coated on both sides to minimize drift. Drift of the zero-force position of the cantilever was reduced from 900 nm for gold-coated cantilevers to 70 nm (N = 10; rms) for uncoated cantilevers over the first 2 h after wetting the tip; a majority of these uncoated cantilevers (60%) showed significantly less drift (12 nm, rms).

Atomic force microscopy force mapping in the study of supported lipid bilayers.

Investigating the structural and mechanical properties of lipid bilayer membrane systems is vital in elucidating their biological function. One route to directly correlate the morphology of phase-segregated membranes with their indentation and rupture mechanics is the collection of atomic force microscopy (AFM) force maps. These force maps, while containing rich mechanical information, require lengthy processing time due to the large number of force curves needed to attain a high spatial resolution.