A cephalosporin-chemiluminescent conjugate increases beta-lactamase detection sensitivity by four orders of magnitude

Rapid Detection of Bacterial Resistance to β-Lactam Antibiotics with a Relay-Response Chemiluminescence Assay

Bacterial resistance caused by β-lactamases has been a major threat to public health around the world, seriously weakening the efficacy of β-lactam antibiotics, the most widely used therapeutic agents against infectious diseases. To detect the bacterial resistance to β-lactam antibiotics, particularly specific type of β-lactam antibiotics, in a rapid manner, we report herein a relay-response chemiluminescence assay. This assay mainly consists of two reagents: a β-lactam-caged thiophenol and a thiophenol-sensitive chemiluminescence reporter, both of which are synthetically feasible. The selective hydrolysis of β-lactam by β-lactamase leads to the releasing of free thiophenol, which then triggers the emission of a chemiluminescence signal in a relay manner. Three thiophenol-caged β-lactams, structural analogues of cephalothin, cefotaxime, and meropenem, respectively, have been synthesized. And the application of this assay with these analogues of β-lactam antibiotics allows fast detection of β-lactamase-expressing resistant bacteria and, more impressively, provides detailed information on the resistant scope of bacteria.

Augmenting Antimicrobial Resistance Surveillance: Rapid Detection of β-Lactamase-Expressing Drug-Resistant Bacteria through Sensitized Luminescence on a Paper-Supported Hydrogel

The emergence of antimicrobial resistance (AMR) in pathogenic bacteria, expedited by the overuse and misuse of antibiotics, necessitates the development of a rapid and pan-territorially accessible diagnostic protocol for resistant bacterial infections, which would not only enable judicious prescription of drugs, leading to infection control but also augment AMR surveillance. In this study, we introduce for the first time a "turn-on" terbium (Tb3+) photoluminescence assay supported on a paper-based platform for rapid point-of-care (POC) detection of β-lactamase (BL)-producing bacteria. We strategically conjugated biphenyl-4-carboxylic acid (BCA), a potent Tb3+ sensitizer, with cephalosporin to engineer a BL substrate CCS, where the energy transfer to terbium is arrested. However, BL, a major resistance element produced by bacteria resistant to β-lactam antibiotics, triggers a spontaneous release of BCA, empowering terbium sensitization within a supramolecular scaffold supported on paper. The remarkable optical response facilitates quick assessment with a binary answer, and the time-gated signal acquisition ensues improved sensitivity with a detection limit as low as 0.1 mU/mL. Furthermore, to ensure accessibility, particularly in resource-limited areas, we have developed an in loco imaging device as an affordable alternative to high-end instruments. The integration of the assay with the device readily identified the BL-associated drug-resistant strains in the mimic urinary tract infection samples within 2 h, demonstrating its excellent potential for in-field translation. We believe that this rapid paper-based POC assay, coupled with the in loco device, can be deployed anywhere, especially in developing regions, and will enable extensive surveillance on antibiotic-resistant infections.

Bioluminogenic Probe for Rapid, Ultrasensitive Detection of β-Lactam-Resistant Bacteria

Increasingly difficult-to-treat infections by antibiotic-resistant bacteria have become a major public health challenge. Rapid detection of common resistance mechanisms before empiric antibiotic usage is essential for optimizing therapeutic outcomes and containing further spread of resistance to antibiotics among other bacteria. Herein, we present a bioluminogenic probe, D-Bluco, for rapid detection of β-lactamase activity in viable pathogenic bacteria. D-Bluco is a pro-luciferin caged by a β-lactamase-responsive cephalosporin structure and further conjugated with a dabcyl quencher. The caging and quenching significantly decreased the initial background emission and increased the signal-to-background ratio by more than 1200-fold. D-Bluco was shown to detect a broad range of β-lactamases at the femtomolar level. An ultrasensitive RAPID bioluminescence assay using D-Bluco can detect 102 to 103 colony forming unit per milliliter (cfu/mL) of β-lactamase-producing Enterobacterales in urine samples within 30 min. The high sensitivity and rapid detection make the assay attractive for the use of point-of-care diagnostics for lactam-resistant pathogens.

Exploring the Structural Space of Chemiluminescent 1,2-Dioxetanes

Chemiluminescent molecules which emit light in response to a chemical reaction are powerful tools for the detection and measurement of biological analytes and enable the understanding of complex biochemical processes in living systems. Triggerable chemiluminescent 1,2-dioxetanes have been studied and tuned over the past decades to advance quantitative measurement of biological analytes and molecular imaging in live cells and animals. A crucial determinant of success for these 1,2-dioxetane based sensors is their chemical structure, which can be manipulated to achieve desired chemical properties. In this Perspective, we survey the structural space of triggerable 1,2-dioxetane and assess how their design features affect chemiluminescence properties including quantum yield, emission wavelength, and decomposition kinetics. Based on this appraisal, we identify some structural modifications of 1,2-dioxetanes that are ripe for exploration in the context of chemiluminescent biological sensors.

Complementation Dependent Enzyme Prodrug Therapy Enables Targeted Activation of Prodrug on HER2-Positive Cancer Cells

Antibodies have been explored for decades for the delivery of small molecule cytotoxins directly to diseased cells. In antibody-directed enzyme prodrug therapy (ADEPT), antibodies are armed with enzymes that activate nontoxic prodrugs at tumor sites. However, this strategy failed clinically due to off-target toxicity associated with the enzyme prematurely activating prodrug systemically. We describe here the design of an antibody-fragment split enzyme platform that regains activity after binding to HER2, allowing for site-specific activation of a small molecule prodrug. We evaluated a library of fusion constructs for efficient targeting and complementation to identify the most promising split enzyme pair. The optimal pair was screened for substrate specificity among chromogenic, fluorogenic, and prodrug substrates. Evaluation of this system on HER2-positive cells revealed 7-fold higher toxicity of the activated prodrug over prodrug treatment alone. Demonstrating the potential of this strategy against a known clinical target provides the basis for a unique therapeutic platform in oncology.

β-Lactamase-Mediated Fragmentation: Historical Perspectives and Recent Advances in Diagnostics, Imaging, and Antibacterial Design

The discovery of β-lactam (BL) antibiotics in the early 20th century represented a remarkable advancement in human medicine, allowing for the widespread treatment of infectious diseases that had plagued humanity throughout history. Yet, this triumph was followed closely by the emergence of β-lactamase (BLase), a bacterial weapon to destroy BLs. BLase production is a primary mechanism of resistance to BL antibiotics, and the spread of new homologues with expanded hydrolytic activity represents a pressing threat to global health. Nonetheless, researchers have developed strategies that take advantage of this defense mechanism, exploiting BLase activity in the creation of probes, diagnostic tools, and even novel antibiotics selective for resistant organisms. Early discoveries in the 1960s and 1970s demonstrating that certain BLs expel a leaving group upon BLase cleavage have spawned an entire field dedicated to employing this selective release mechanism, termed BLase-mediated fragmentation. Chemical probes have been developed for imaging and studying BLase-expressing organisms in the laboratory and diagnosing BL-resistant infections in the clinic. Perhaps most promising, new antibiotics have been developed that use BLase-mediated fragmentation to selectively release cytotoxic chemical "warheads" at the site of infection, reducing off-target effects and allowing for the repurposing of putative antibiotics against resistant organisms. This Review will provide some historical background to the emergence of this field and highlight some exciting recent reports that demonstrate the promise of this unique release mechanism.

Chemiluminescent spiroadamantane-1,2-dioxetanes: Recent advances in molecular imaging and biomarker detection

Triggered chemiluminescence emission of spiroadamantane-1,2-dioxetanes to detect bioanalytes has fueled the emerging popularity of chemiluminescence imaging in live animals and cells. Recently, a structural evolution of the dioxetane scaffolds towards near-infrared emitters has been observed, and efforts have been made for quantitative and semi-quantitative detection of a wide range of analytes. In this review, we summarize the current chemiluminescence imaging developments of spiroadamantane-1,2-dioxetanes. Specifically, we look at examples which depict whole animal or cellular chemiluminescence imaging of small molecules and enzymes, as well as those that portray their potential diagnostic and therapeutic abilities, with an emphasis on analyte quantification and experimental parameters.

Small-molecule fluorescent probes: big future for specific bacterial labeling and infection detection

Bacterial infections remain a global healthcare problem that is particularly attributed to the spread of antibiotic resistance and the evolving pathogenicity. Accurate and swift approaches for infection diagnosis are urgently needed to facilitate antibiotic stewardship and effective medical treatment. Direct optical imaging for specific bacterial labeling and infection detection offers an attractive prospect of precisely monitoring the infectious disease status and therapeutic response in real time. This feature article focuses on the recent advances of small-molecule probes developed for fluorescent imaging of bacteria and infection, which covers the probe design, responsive mechanisms and representative applications. In addition, the perspective and challenges to advance small-molecule fluorescent probes in the field of rapid drug-resistant bacterial detection and clinical diagnosis of bacterial infections are discussed. We envision that the continuous advancement and clinical translations of such a technique will have a strong impact on future anti-infective medicine.

Tuning Electrostatic Gating of Semiconducting Carbon Nanotubes by Controlling Protein Orientation in Biosensing Devices

The ability to detect proteins through gating conductance by their unique surface electrostatic signature holds great potential for improving biosensing sensitivity and precision. Two challenges are: (1) defining the electrostatic surface of the incoming ligand protein presented to the conductive surface; (2) bridging the Debye gap to generate a measurable response. Herein, we report the construction of nanoscale protein-based sensing devices designed to present proteins in defined orientations; this allowed us to control the local electrostatic surface presented within the Debye length, and thus modulate the conductance gating effect upon binding incoming protein targets. Using a β-lactamase binding protein (BLIP2) as the capture protein attached to carbon nanotube field effect transistors in different defined orientations. Device conductance had influence on binding TEM-1, an important β-lactamase involved in antimicrobial resistance (AMR). Conductance increased or decreased depending on TEM-1 presenting either negative or positive local charge patches, demonstrating that local electrostatic properties, as opposed to protein net charge, act as the key driving force for electrostatic gating. This, in turn can, improve our ability to tune the gating of electrical biosensors toward optimized detection, including for AMR as outlined herein.

Tuning Electrostatic Gating of Semiconducting Carbon Nanotubes by Controlling Protein Orientation in Biosensing Devices

The ability to detect proteins through gating conductance by their unique surface electrostatic signature holds great potential for improving biosensing sensitivity and precision. Two challenges are: (1) defining the electrostatic surface of the incoming ligand protein presented to the conductive surface; (2) bridging the Debye gap to generate a measurable response. Herein, we report the construction of nanoscale protein-based sensing devices designed to present proteins in defined orientations; this allowed us to control the local electrostatic surface presented within the Debye length, and thus modulate the conductance gating effect upon binding incoming protein targets. Using a β-lactamase binding protein (BLIP2) as the capture protein attached to carbon nanotube field effect transistors in different defined orientations. Device conductance had influence on binding TEM-1, an important β-lactamase involved in antimicrobial resistance (AMR). Conductance increased or decreased depending on TEM-1 presenting either negative or positive local charge patches, demonstrating that local electrostatic properties, as opposed to protein net charge, act as the key driving force for electrostatic gating. This, in turn can, improve our ability to tune the gating of electrical biosensors toward optimized detection, including for AMR as outlined herein.

Advances in activity-based diagnostics for infectious disease and microbiome health

In the human body, pathogens and the endogenous microbiome produce enzymes that aid in replication and survival. The activity from these enzymes as well as energy-dependent transport processes can be used as functional biomarkers for pathogen identification, antimicrobial treatment monitoring, and surveillance of microbiome health. To produce visual and/or quantifiable readouts from this activity, concepts from chemical biology and nanomedicine have been utilized to develop signal-producing probes for patient samples or for direct administration in vivo. In the context of infection, activity-based diagnostics offer several potential advantages over current diagnostics including the ability to differentiate between active infection and sterile inflammation, which is made possible by targeting microbial enzymes with orthogonal activity to that of the host. In this review, we discuss new developments in the making of activity-based infection diagnostics and the beginnings of microbiome activity-based diagnostics.

β-Lactamase triggered visual detection of bacteria using cephalosporin functionalized biomaterials

We report the conjugation of a chromogenic cephalosporin β-lactamase (βL) substrate to polymers and integration into biomaterials for facile, visual βL detection. Identification of these bacterial enzymes, which are a leading cause of antibiotic resistance, is critical in the treatment of infectious diseases. The βL substrate polymer conjugate undergoes a clear to deep yellow color change upon incubation with common pathogenic Gram-positive and Gram-negative bacteria species. We have demonstrated the feasibility of formulating hydrogels with the βL substrate covalently tethered to a poly(ethylene glycol) (PEG) polymer matrix, exhibiting a visible color change in the presence of βLs. This approach has the potential to be used in diagnostic biomaterials for point-of-care detection of βL-producing bacteria, helping combat the spread of drug resistant microbes.