Fluorescence detecting glycopeptide antibiotics via a dynamic molecular switch

BACKGROUND

Glycopeptide antibiotics (GPAs) represented by vancomycin (VAN) are clinically used as a first-line treatment for serious infections caused by Gram-positive pathogens. The use and dosing methods of GPAs are rigorously managed for safety considerations, which calls for fast and accurate quantification approaches.

RESULT

A new sort of fluorescent probes for GPAs has been proposed, each of which was integrated by a fluorescein-based reporter and a GPAs' recognition peptide D-alanyl-D-alanine (D-Ala-D-Ala). These probes work as dynamic molecular switches, which mainly exist as non-fluorescent spirolactam forms in the absence of GPAs. GPAs binding with the dipeptide regulates the dynamic balance between fluorescence OFF lactam form and fluorescence ON ring-opened form, rendering these probes capable of GPAs detecting. The most promising one P1 exhibits excellent sensitivity and selectivity towards GPAs detection.

SIGNIFICANCE

Different to previous developments, P1 consists of a single fluorophore without the need of a fluorescence-quenching group or a secondary dye, which is the smallest fluorescent probe for GPAs up to now. P1 realizes direct VAN quantification from complex biological samples including real serums, dispensing with additional drug extraction. More interestingly, both P1 and P6 can distinguish GPAs with different peptide backbones, which has not been achieved previously.

A Vancomycin-Templated DNA-Encoded Library for Combating Drug-Resistant Bacteria

It is an urgent need to tackle the global crisis of multidrug-resistant bacterial infections. We report here an innovative strategy for large-scale screening of new antibacterial agents using a whole bacteria-based DNA-encoded library (DEL) of vancomycin derivatives via peripheral modifications. A bacterial binding affinity assay was established to select the modification fragments in high-affinity compounds. The optimal resynthesized derivatives demonstrated excellently enhanced activity against various resistant bacterial strains and provided useful structures for vancomycin derivatization. This work presents the new concept in a natural product-templated DEL and in antibiotic discovery through bacterial affinity screening, which promotes the fight against drug-resistant bacteria.

Detection of Methicillin-Resistant Staphylococcus Aureus using vancomycin conjugated silica-based fluorescent nanoprobe

Methicillin-Resistant Staphylococcus Aureus (MRSA) is a worldwide major pathogenic bacteria that has emerged over the past three decades as the leading cause of nosocomial and community-acquired infections. Biosensors can provide rapid, sensitive, and selective detection of the presence and number of bacteria in various environments. Herein, a novel fluorescence nanoprobe was designed as a biosensor for MRSA detection using dye-incorporated silica nanoparticles (FSiNP). Based on the results of specific surface area analysis using the Brauner Emmett-Teller (BET) method, the surface area of the nanoparticles was obtained at 377.127 m2/g, and the X-ray diffraction (XRD) analysis confirmed that it was in the amorphous phase. Vancomycin, as the bioreceptor, was immobilized on the silica surface through a hydrosilylation reaction, generating the biosensing platform FSiNP-Van. Each modification step was corroborated by the Fourier Transform Infra-Red (FTIR) spectroscopy. The sensing principle was based on the fluorescence-quenching mechanism of FSiNP-Van at 515 nm obtaining a rapid response time of 20 min. The FSiNP-Van nanoprobe provided a wide linear concentration range of 10-106 CFU/mL with a limit of MRSA detection calculated at 1 CFU/mL. The fluorescent nanoprobe demonstrated here is expected to find applications in point-of-care (POC) diagnostics to detect the presence of MRSA bacteria.

Versatile capillary electrophoresis method for the direct chiral separation of aliphatic and aromatic α-hydroxy acids, β-hydroxy acids and polyhydroxy acids using vancomycin as chiral selector

Hydroxy acids (HAs) are ubiquitous in nature and play significant roles in various industrial and biological processes. Most HAs harbor at least one chiral center, therefore the development of efficient chiral analysis techniques for HA stereoisomers is of crucial importance across a wide range of fields. A capillary electrophoresis (CE) method was developed for the chiral analysis and quantification of aliphatic and aromatic α‑hydroxy acid (AHA) enantiomers, aliphatic β‑hydroxy acid (BHA) enantiomers and aliphatic polyhydroxy acid (PHA) stereoisomers. Using a modified partial filling-counter current method with indirect UV detection, high resolution (Rs) was achieved with vancomycin as a chiral selector added to the background electrolyte composed of 10 mM of benzoic acid/L-histidine at pH 5 using a polyacrylamide-coated capillary. This method could be readily applied to the determination of the enantiomers of 12 aliphatic AHAs, 4 aromatic AHAs, 3 aliphatic BHAs, as well as to the determination of the stereoisomers of tartaric acid, 2,3-dihydroxybutanoic acid, 2,3,4,5-tetrahydroxypentanoic acid, and 2,3,4,5,6-pentahydroxyhexanoic acid without the need for sample derivatization. Finally, our study provides a robust and versatile strategy for the chiral and stereoselective analysis of a broad range of hydroxy acid compounds.

Multicopper Clusters Enable Oxidative Phenol Macrocyclization (OxPM) of Peptides

The biosynthesis of glycopeptide antibiotics such as vancomycin and other biologically active biaryl-bridged and diaryl ether-linked macrocyclic peptides includes key enzymatic oxidative phenol macrocyclization(s) of linear precursors. However, a simple and step-economical biomimetic version of this transformation remains underdeveloped. Here, we report highly efficient conditions for preparing biaryl-bridged and diaryl ether-linked macrocyclic peptides based on multicopper(II) clusters. The selective syntheses of ring models of vancomycin and the arylomycin cyclic core illustrate the potential of this technology to facilitate the assembly of complex antibiotic macrocyclic peptides, whose syntheses are considered highly challenging. The unprecedented ability of multicopper(II) clusters to chelate tethered diphenols and promote intramolecular over intermolecular coupling reactions demonstrates that copper clusters can catalyze redox transformations that cannot be accessed by smaller metal catalysts.

Conjugation of Vancomycin with a Single Arginine Improves Efficacy against Mycobacteria by More Effective Peptidoglycan Targeting

Drug resistant bacterial infections have emerged as one of the greatest threats to public health. The discovery and development of new antimicrobials and anti-infective strategies are urgently needed to address this challenge. Vancomycin is one of the most important antibiotics for the treatment of Gram-positive infections. Here, we introduce the vancomycin-arginine conjugate (V-R) as a highly effective antimicrobial against actively growing mycobacteria and difficult-to-treat mycobacterial biofilm populations. Further improvement in efficacy through combination treatment of V-R to inhibit peptidoglycan synthesis and ethambutol to inhibit arabinogalactan synthesis underscores the ability to identify compound synergies to more effectively target the Achilles heel of the cell-wall assembly. Moreover, we introduce mechanistic activity data and a molecular model derived from a d-Ala-d-Ala-bound vancomycin structure that we hypothesize underlies the molecular basis for the antibacterial improvement attributed to the arginine modification that is specific to peptidoglycan chemistry employed by mycobacteria and distinct from Gram-positive pathogens.

Engineered Vancomycin, with Increased Interactions with Peptidoglycan Stem Peptide, Conquers Non-tuberculosis Mycobacteria

Vancomycin-like drugs target peptidoglycan (PG) via binding to C-terminal d-Ala-d-Ala dipeptide. An engineered vancomycin has enhanced affinity for the PG stem peptide, due to probable interactions with a third residue, meso-diaminopimelic acid, in the PG. This engineered vancomycin displays enhanced killing of mycobacteria.

Modulating On-Demand Release of Vancomycin from Implant Coatings via Chemical Modification of a Micrococcal Nuclease-Sensitive Oligonucleotide Linker

Periprosthetic infections are one of the most serious complications in orthopedic surgeries, and those caused by Staphylococcus aureus (S. aureus) are particularly hard to treat due to their tendency to form biofilms on implants and their notorious ability to invade the surrounding bones. The existing prophylactic local antibiotic deliveries involve excessive drug loading doses that could risk the development of drug resistance strains. Utilizing an oligonucleotide linker sensitive to micrococcal nuclease (MN) cleavage, we previously developed an implant coating capable of releasing covalently tethered vancomycin, triggered by S. aureus-secreted MN, to prevent periprosthetic infections in the mouse intramedullary (IM) canal. To further engineer this exciting platform to meet broader clinical needs, here, we chemically modified the oligonucleotide linker by a combination of 2'-O-methylation and phosphorothioate modification to achieve additional modulation of its stability/sensitivity to MN and the kinetics of MN-triggered on-demand release. We found that when all phosphodiester bonds within the oligonucleotide linker 5'-carboxy-mCmGTTmCmG-3-acrydite, except for the one between TT, were replaced by phosphorothioate, the oligonucleotide (6PS) stability significantly increased and enabled the most sustained release of tethered vancomycin from the coating. By contrast, when only the peripheral phosphodiester bonds at the 5'- and 3'-ends were replaced by phosphorothioate, the resulting oligonucleotide (2PS) linker was cleaved by MN more rapidly than that without any PS modifications (0PS). Using a rat femoral canal periprosthetic infection model where 1000 CFU S. aureus was inoculated at the time of IM pin insertion, we showed that the prophylactic implant coating containing either 0PS- or 2PS-modified oligonucleotide linker effectively eradicated the bacteria by enabling the rapid on-demand release of vancomycin. No bacteria were detected from the explanted pins, and no signs of cortical bone changes were detected in these treatment groups throughout the 3 month follow-ups. With an antibiotic tethering dose significantly lower than conventional antibiotic-bearing bone cements, these coatings also exhibited excellent biocompatibility. These chemically modified oligonucleotides could help tailor prophylactic anti-infective coating strategies to meet a range of clinical challenges where the risks for S. aureus prosthetic infections range from transient to long-lasting.

Antibiotic-enzyme-inorganic nanoflowers based immunoassay for the ultrasensitive detection of Staphylococcus aureus

In this work, we constructed a moderate and convenient approach for the determination of staphylococcus aureus (S. aureus) by using organic-inorganic flower-like hybrid nanoflowers and Pig IgG together in an enzyme-linked immunosorbent assay (ELISA) system. To ensure efficient capture, the hybrid nanoflowers were prepared by encapsulating horseradish peroxidase (HRP) and vancomycin (VAN) in the inorganic nanocrystal composites (calcium ion solution), just like the mimic biomineralization process. Owing to the self-assembly technique, the synthesized VAN-HRP-CaHPO₄ nanoflowers (NFs) can not only retain the ability to particularly capture the gram-positive bacteria but also enhance the stability and enzymatic activity to achieve the signal output amplification. Then, taking advantage of the integration of signal amplification elements (HRP) and biorecognition unit (VAN), the VAN-HRP-CaHPO₄ NFs were utilized as a new kind of capture & signal regent in the procedure of S. aureus detection. Based on this ELISA system, S. aureus could be clearly detected within the concentration ranging from 1.0 × 10² to 1.0 × 10⁷ CFU mL^-1. The detection limit was defined as 4.3 CFU mL^-1, which performance is superior to some commercial ELISA kits. Additionally, this system detected the S. aureus in food samples and showed an acceptable recovery. As a cost-effective and sensitive platform, this proposed assay was enable to fulfill the requirement of a quick and effective detection of S. aureus.

Preparation and modification of PS-PMMA microspheres and their application in high performance liquid chromatography

Polymer microspheres have been widely used as a stationary phase for liquid chromatography. In this work, we prepared and synthesized polystyrene-methyl methacrylate (PS-PMMA) microspheres, modified them, characterized the microspheres to have good chromatographic properties, and then used them as a high-performance liquid chromatography (HPLC) stationary phase to explore their applications. First, the PS-PMMA microspheres were hydrolyzed, and the separation of benzene homologues/alkaloids was explored. Then, on the basis of hydrolysis, diazo resin (DR) was used as a coupling agent to further modify the surface of the microspheres with amphoteric glycopeptide vancomycin. The modified microspheres were used as a HPLC stationary phase to explore the application of the stationary phase in the separation of chiral drugs. This work is important to broaden the application of functional chiral columns for antibiotics and to expand the application of PS-PMMA microspheres in HPLC.

Vancomycin as an Antibacterial Agent Capped with Silver Nanoparticles: An Experimental Potential Analysis

For the treatment of various infections, a variety of antimicrobial drugs are formulated. Nevertheless, many bacterial infections now exhibit antibiotic resistance due to the widespread utilization antibiotics. Methicillin-resistant among the most dangerous multidrug-resistant bacteria is Staphylococcus aureus (MRSA). Vancomycin became a viable therapy option due to MRSA resistance to methicillin medicines. One of the well-informed antibacterial compounds with wideband antibacterial activity is silver nanoparticles (AgNPs). AgNPs are thus suitable candidates for usage in conjunction alongside vancomycin to increase its antibacterial effect. The goal of the present research work is to boost the antibacterial potency of the glycopeptide antibiotic vancomycin towards Gram-positive (Staphylococcus aureus) but also Gram-negative (Escherichia coli) bacteria. The chemical reduction approach is used to create a colloidal solution of silver nanoparticles utilizing silver nitrate as a precursor in the environment of the ionic surfactant trisodium citrate that serves as covering including reducing reagent. Vancomycin was used to functionalize the synthesized nanoparticles and create the nanodrug complex (Van@AgNPs). The synergistic antibacterial potential of silver nanoparticles coated with vancomycin on both test pathogens was investigated using the agar well diffusion technique. The antibacterial potency for both classes of bacteria has significantly increased, according to the well diffusion test. It has been noted that this improvement is synergistic instead of additive.

Physicochemical and Microbiological Stability of Vancomycin 10-mg/mL Intravitreal Syringes

Bacterial endophthalmitis constitutes a medical emergency due to the possibility of leading to blindness unless treatment is administered quickly. The usual treatment seeks to cover both gram-positive and gram-negative bacteria by intravitreal injections of vancomycin and ceftazidime. In the present work, we sought to determine the physicochemical and microbiological stability of intravitreal syringes of vancomycin 10 mg/mL in order to be able to store them as long as possible to have immediate stock. A study was carried out at different temperatures (room temperature, refrigerator, and freezer) for six months in which the concentration and osmolarity were determined and microbiological growth was observed. Also, an accelerated degradation study was carried out at 42°C for 51 days, where only the concentration was determined. The concentrations were quantified using a high-performance liquid chromatography technique. Vancomycin 10 mg/mL in polypropylene syringes is chemically, physically, and microbiologically stable for six months if stored at -20°C and stable for 14 weeks if stored at 4°C.

Bacterial Toxin-Triggered Release of Antibiotics from Capsosomes Protects a Fly Model from Lethal Methicillin-Resistant Staphylococcus aureus (MRSA) Infection

Antibiotic resistance is a severe global health threat and hence demands rapid action to develop novel therapies, including microscale drug delivery systems. Herein, a hierarchical microparticle system is developed to achieve bacteria-activated single- and dual-antibiotic drug delivery for preventing methicillin-resistant Staphylococcus aureus (MRSA) bacterial infections. The designed system is based on a capsosome structure, which consists of a mesoporous silica microparticle coated in alternating layers of oppositely charged polymers and antibiotic-loaded liposomes. The capsosomes are engineered and shown to release their drug payloads in the presence of MRSA toxins controlled by the Agr quorum sensing system. MRSA-activated single drug delivery of vancomycin and synergistic dual delivery of vancomycin together with an antibacterial peptide successfully kills MRSA in vitro. The capability of capsosomes to selectively deliver their cargo in the presence of bacteria, producing a bactericidal effect to protect the host organism, is confirmed in vivo using a Drosophila melanogaster MRSA infection model. Thus, the capsosomes serve as a versatile multidrug, subcompartmentalized microparticle system for preventing antibiotic-resistant bacterial infections, with potential applications to protect wounds or medical device implants from infections.

Molecular dynamics simulations of the secondary-binding site in disaccharide-modified glycopeptide antibiotics

Oritavancin is a semisynthetic glycopeptide antibiotic used to treat severe infections by multidrug-resistant Gram-positive pathogens. Oritavancin is known to be a thousand times more potent than vancomycin against Gram-positive bacteria due to the additional interactions with bacterial peptidoglycan (PG) facilitated by a secondary-binding site. The presence of this secondary-binding site is evident in desleucyl-oritavancin, an Edman degradation product of oritavancin, still retaining its potency against Gram-positive bacteria, whereas desleucyl-vancomycin is devoid of any antimicrobial activities. Herein, using explicit solvent molecular dynamics (MD) simulations, steered MD simulations, and umbrella sampling, we show evidence of a secondary-binding site mediated by the disaccharide-modified hydrophobic sidechain of oritavancin interactions with the pentaglycyl-bridge segment of the PG. The interactions were characterized through comparison to the interaction of PG with chloroeremomycin, vancomycin, and the desleucyl analogs of the glycopeptides. Our results show that the enhanced binding of oritavancin to PG over the binding of the other complexes studied is due to an increase in the hydrophobic effect, electrostatic and van der Waals interactions, and not the average number of hydrogen bonds. Our ranking of the binding interactions of the biomolecular complexes directly correlates with the order based on their experimental minimum inhibitory concentrations. The results of our simulations provide insight into the modification of glycopeptides to increase their antimicrobial activities or the design of novel antibiotics against pathogenic Gram-positive bacteria.

Enantioseparation in high performance liquid chromatography: preparation and evaluation of a vancomycin-based chiral stationary phase via surface-initiated atom transfer radical polymerization

A chromatographic technique based on a chiral stationary phase (CSP) has been explored for enantioseparation. Herein, poly(glycidyl methacrylate) (poly(GMA)) brushes were grafted on the surface of silica gel via surface-initiated atom transfer radical polymerization (SI-ATRP), followed by the introduction of vancomycin as a chiral selector. The as-synthesized material was characterized by elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and thermogravimetric analysis (TGA), proving the formation of vancomycin-immobilized brushes. Then the resulting CSP was explored to separate 7 racemic drugs (bicalutamide, 1-benzyl-5-phenylbarbituric acid, chlorpheniramine maleate, fluoxetine hydrochloride, verapamil hydrochloride, benzoxazocine hydrochloride and isoprenaline hydrochloride) in high performance liquid chromatography (HPLC). Several factors affecting the enantioseparation performance of the vancomycin-immobilized CSP, including the triethylamine (TEA) content in the buffer, pH value, content of organic solvent in the mobile phase, flow rate and injection volume, were mainly optimized. Under the optimal conditions, baseline separation of fluoxetine hydrochloride (R_S = 2.52) was achieved, which was better than that on a commercial Chirobiotic V column, while enantioseparation of bicalutamide (R_S = 1.01), chlorpheniramine maleate (R_S = 0.77), 1-benzyl-5-phenylbarbituric acid (R_S = 0.67), isoprenaline hydrochloride (R_S = 0.73), verapamil hydrochloride (R_S = 0.91) and benzoxazocine hydrochloride (R_S = 1.03) was partly achieved. It was concluded that SI-ATRP is a robust way to fabricate vancomycin-based CSPs for enantioseparation.

Antibiotic-chemoattractants enhance neutrophil clearance of Staphylococcus aureus

The pathogen Staphylococcus aureus can readily develop antibiotic resistance and evade the human immune system, which is associated with reduced levels of neutrophil recruitment. Here, we present a class of antibacterial peptides with potential to act both as antibiotics and as neutrophil chemoattractants. The compounds, which we term 'antibiotic-chemoattractants', consist of a formylated peptide (known to act as chemoattractant for neutrophil recruitment) that is covalently linked to the antibiotic vancomycin (known to bind to the bacterial cell wall). We use a combination of in vitro assays, cellular assays, infection-on-a-chip and in vivo mouse models to show that the compounds improve the recruitment, engulfment and killing of S. aureus by neutrophils. Furthermore, optimizing the formyl peptide sequence can enhance neutrophil activity through differential activation of formyl peptide receptors. Thus, we propose antibiotic-chemoattractants as an alternate approach for antibiotic development.

Cyclodextrins Allow the Combination of Incompatible Vancomycin and Ceftazidime into an Ophthalmic Formulation for the Treatment of Bacterial Keratitis

Ceftazidime (CZ) and vancomycin (VA) are two antibiotics used to treat bacterial keratitis. Due to their physical incompatibility (formation of a precipitate), it is not currently possible to associate both molecules in a single container for ophthalmic administration. We firstly characterized the incompatibility then investigated if 2-hydroxypropyl-beta (HPβCD) and 2-hydroxypropyl-gamma cyclodextrins (HPγCD) could prevent this incompatibility. The impact of pH on the precipitation phenomena was investigated by analysing the supernatant solution of the mixture using high performance liquid chromatography. A characterization of the inclusion of CZ with HPγCD using ¹H nuclear magnetic resonance (NMR), and VA with HPβCD using ¹H-NMR and a solubility diagram was performed. A design of experiment was built to determine the optimal conditions to obtain a formulation that had the lowest turbidity and particle count. Our results showed that VA and CZ form an equimolar precipitate below pH 7.3. The best formulation obtained underwent an in-vitro evaluation of its antibacterial activity. The impact of HPCDs on incompatibility has been demonstrated through the inclusion of antibiotics and especially VA. The formulation has been shown to be able to inhibit the incompatibility for pH higher than 7.3 and to possess unaltered antibacterial activity.

Prevention the formation of biofilm on orthopedic implants by melittin thin layer on chitosan/bioactive glass/vancomycin coatings

Methicillin-resistant and Vancomycin-resistant Staphylococcus aureus bacteria (MRSA and VRSA, respectively) can seriously jeopardizes bone implants. This research aimed to examine the potential synergistic effects of Melittin and vancomycin in preventing MRSA and VRSA associated bone implant infections. Chitosan/bioactive glass nanoparticles/vancomycin composites were coated on hydrothermally etched titanium substrates by casting method. The composite coatings were coated by Melittin through drop casting technique. Melittin raised the proliferation of MC3T3 cells, making it an appropriate option as osteoinductive and antibacterial substance in coatings of orthopedic implants. Composite coatings having combined vancomycin and Melittin eliminated both planktonic and adherent MRSA and VRSA bacteria, whereas coatings containing one of them failed to kill the whole VRSA bacteria. Therefore, chitosan/bioactive glass/vancomycin/Melittin coating can be used as a bone implant coating because of its anti-infective properties.

In vitro evaluation of antibacterial efficacy of vancomycin-loaded suture tapes and cerclage wires

Usage of implants containing antibiotic agents has been a common strategy to prevent implant related infections in orthopedic surgery. Unfortunately, most implants with microbial repellent properties are characterized by accessibility limitations during daily clinical practice. Aim of this in vitro study was to investigate whether suture tapes and cerclage wires, which were treated with vancomycin, show a sustainable antibacterial activity. For this purpose, we used 24 stainless steel wire cerclages and 24 ultra-high molecular weight polyethylene and polyester suture tape test bodies. The test bodies were incubated for 30 min. in 100 mg/ml vancomycin solution or equivalent volumes of 0.9% NaCl. After measuring the initial solution uptake of the test bodies, antibacterial efficacy via agar diffusion test with Staphylococcus aureus and vancomycin elution tests were performed 1, 2, 3, and 6 days after incubation. Vancomycin-loaded tapes as well as vancomycin-loaded cerclage wires demonstrated increased bacterial growth inhibition when compared to NaCl-treated controls. Vancomycin-loaded tapes showed an additional twofold and eightfold increase of bacterial growth inhibition compared to vancomycin-loaded wires at day 1 and 2, respectively. Elution tests at day 1 revealed high levels of vancomycin concentration in vancomycin loaded tapes and wires. Additionally, the concentration in vancomycin loaded tapes was 14-fold higher when compared to vancomycin loaded wires. Incubating suture tapes and cerclage wires in vancomycin solution showed a good short-term antibacterial activity compared to controls. Considering the ease of vancomycin application on suture tapes or wires, our method could represent an attractive therapeutic strategy in biofilm prevention in orthopedic surgery.

Autoclaving of Poloxamer 407 hydrogel and its use as a drug delivery vehicle

With antibiotic-resistant bacteria becoming increasingly prevalent, biomaterials capable of targeted, in situ drug delivery are urgently needed. The synthetic polymer Poloxamer 407 (P407) is of particular interest due to its thermoreversible gelation. Clinical use of P407 typically involves sterilization via autoclaving, but the effects of these extreme environmental conditions on hydrogel water content, rheological properties and efficacy as a drug delivery vehicle remain unknown. The aim of this study was to investigate the effects of autoclaving on the properties of P407 hydrogel. Autoclaving reduced hydrogel water content due to evaporation, thus increasing the polymer weight fraction of the hydrogels. In contrast, except for a reduction in gelation temperature following autoclaving, autoclaved hydrogels had similar rheological properties as nonautoclaved hydrogels. In vitro, autoclaving did not hinder the hydrogel's efficacy as a carrier for vancomycin antibiotic, and P407 (with and without vancomycin) had a bactericidal effect on planktonic Staphylococcus aureus. An in vivo pilot study using P407 to deliver bacteriophage highlighted the need for additional understanding of the functionality of the hydrogel for surgical applications. In conclusion, P407 hydrogel water content and gelation temperature were reduced by autoclave sterilization, while other rheological properties and the efficacy of the biomaterial as a delivery vehicle for vancomycin in vitro were unaffected.

A synergistic antibacterial platform: combining mechanical and photothermal effects based on Van-MoS2-Au nanocomposites

Herein, we successfully developed a new multifunctional antibacterial system, which combined mechano-bactericidal (Au-nanostars) and photothermal (MoS₂) mechanism. Meanwhile, the targeting molecule of vancomycin was modified on the surface of MoS₂-Au nanocomposites (Van-MoS₂-Au), that generally yield high efficiency in antibacterial performance due to their effective working radii. Van-MoS₂-Au nanocomposites were capable of completely destroying both gram-negative (E. coli) and gram-positive (B. subtilis) bacteria under 808 NIR laser irradiation for 20 min, and nearly no bacterial growth was detected after 12 h incubation. Moreover, these nanocomposites could destruct the refractory biofilm as well, which was a much more difficult medical challenge. The new antibacterial nanomaterials might offer many biomedical applications because of the biocompatibility and strong antibacterial ability.

Study on the anti-infection ability of vancomycin cationic liposome combined with polylactide fracture internal fixator

A polylactide composite fracture fixator loaded with vancomycin cationic liposome (PLA@VL) was prepared by reverse evaporation method. The method of cationic liposome encapsulating vancomycin could effectively improve antibacterial property and achieve drug sustained release effect, so as to reduce toxicity of antibiotics in vivo. Scanning electron microscope (SEM) was used to observe morphology and Fourier transform infrared spectroscopy (FTIR) was used to detect the composition of the internal fixator. In vitro drug release model, in vitro degradation model and body fluid osteogenesis model were designed in this study. On the other hand, the experiments of inhibition zone and MC3T3-E1 osteoblasts in mice were conducted to explore antibacterial property, cell activity and adhesion of the PLA@VL composite internal fixator. Alkaline phosphatase (ALP) staining method and alizarin red assay were used to detect the osteogenic induction ability of the composite internal fixator. Finally, mice fracture models were established to verify osteogenic and anti-infection abilities of the composite internal fixator in vivo. The results showed that MC3T3-E1 cells had better adhesion and proliferation abilities on the PLA@VL composite internal fixator than on the PLA fixator, which indicated that the PLA@VL composite internal fixator possessed excellent osteogenic and anti-infection abilities both in vivo and in vitro. Therefore, the above experiments showed that the fracture internal fixator combined with vancomycin cationic liposome had better biocompatibility, antibacterial ability and osteogenic ability, which provides a promising anti-infection material for the clinical field of fracture.

Green Algae as a Drug Delivery System for the Controlled Release of Antibiotics

New strategies to efficiently treat bacterial infections are crucial to circumvent the increase of resistant strains and to mitigate side effects during treatment. Skin and soft tissue infections represent one of the areas suffering the most from these resistant strains. We developed a new drug delivery system composed of the green algae, Chlamydomonas reinhardtii, which is generally recognized as safe, to target specifically skin diseases. A two-step functionalization strategy was used to chemically modify the algae with the antibiotic vancomycin. Chlamydomonas reinhardtii was found to mask vancomycin and the insertion of a photocleavable linker was used for the release of the antibiotic. This living drug carrier was evaluated in presence of Bacillus subtilis and, only upon UVA1-mediated release, growth inhibition of bacteria was observed. These results represent one of the first examples of a living organism used as a drug delivery system for the release of an antibiotic by UVA1-irradiation.

Near-Infrared-Controlled Nanoplatform Exploiting Photothermal Promotion of Peroxidase-like and OXD-like Activities for Potent Antibacterial and Anti-biofilm Therapies

Nanozymes that mimic peroxidase (POD) activity can convert H₂O₂ into bactericidal free radicals, which is referred to as chemodynamic therapy (CDT). High glutathione (GSH) levels in the infectious tissue severely limit the performance of CDT. Herein, we report a near-infrared-controlled antibacterial nanoplatform that is based on encapsulating tungsten sulfide quantum dots (WS₂QDs) and the antibiotic vancomycin in a thermal-sensitive liposome. The system exploits the photothermal sensitivity of the WS₂QDs to achieve selective liposome rupture for the targeted drug delivery. We determined that WS₂QDs show a strong POD-like activity under physiological conditions and the oxidase-like activity, which can oxidate GSH to further improve the CDT efficacy. Moreover, we found that increased temperature promotes multiple enzyme-mimicking activities of WS₂QDs. This platform exerts antibacterial effects against Gram-positive Mu50 (a vancomycin-intermediate Staphylococcus aureus reference strain) and Gram-negative Escherichia coli and disrupts biofilms for improved penetration of therapeutic agents inside biofilms. In vivo studies with mice bearing Mu50-caused skin abscess revealed that this platform confers potent antibacterial activity without obvious toxicity. Accordingly, our work illustrates that the photothermal and nanozyme properties of WS₂QDs can be deployed alongside a conventional therapeutic to achieve synergistic chemodynamic/photothermal/pharmaco therapy for powerful antibacterial effects.

Rose Bengal Crosslinking to Stabilize Collagen Sheets and Generate Modulated Collagen Laminates

For medical application, easily accessible biomaterials with tailored properties are desirable. Collagen type I represents a biomaterial of choice for regenerative medicine and tissue engineering. Here, we present a simple method to modify the properties of collagen and to generate collagen laminates. We selected three commercially available collagen sheets with different thicknesses and densities and examined the effect of rose bengal and green light collagen crosslinking (RGX) on properties such as microstructure, swelling degree, mechanical stability, cell compatibility and drug release. The highest impact of RGX was measured for Atelocollagen, for which the swelling degree was reduced from 630% (w/w) to 520% (w/w) and thickness measured under force application increased from 0.014 mm to 0.455 mm, indicating a significant increase in mechanical stability. Microstructural analysis revealed that the sponge-like structure was replaced by a fibrous structure. While the initial burst effect during vancomycin release was not influenced by crosslinking, RGX increased cell proliferation on sheets of Atelocollagen and on Collagen Solutions. We furthermore demonstrate that RGX can be used to covalently attach different sheets to create materials with combined properties, making the modification and combination of readily available sheets with RGX an attractive approach for clinical application.

Vancomycin-loaded nanoparticles against vancomycin intermediate and methicillin resistant Staphylococcus aureus strains

Bacterial infections represent one of the leading causes of mortality in the world. Among causative pathogens, S. aureus is prominently known as the underlying cause of many multidrug resistant infections that are often treated with the first-line choice antibiotic vancomycin (VCM). Loading antibiotics into polymeric nanoparticles (Np) displays promise as an alternative method to deliver therapy due to the greater access and accumulation of the antibiotic at the site of the infection as well as reducing toxicity, irritation and degradation. The aim of this work was to prepare, characterize and evaluate VCM-loaded nanoparticles (VNp) for use against S. aureus strains. Moreover, conjugation of Nps with holo-transferrin (h-Tf) was investigated as an approach for improving targeted drug delivery. VNp were prepared by double emulsion solvent evaporation method using PLGA and PVA or DMAB as surfactants. The particles were characterized for size distribution, Zeta Potential, morphology by transmission electron microscopy, encapsulation yield and protein conjugation efficiency. Process yield and drug loading were also investigated along with an in vitro evaluation of VNp antimicrobial effects against S. aureus strains. Results showed that Np were spontaneously formed with a mean diameter lower than 300 nm in a narrow size distribution that presented a spherical shape. The bioconjugation with h-Tf did not appear to increase the antimicrobial effect of VNp. However, non-bioconjugated Np presented a minimal inhibitory concentration lower than free VCM against a MRSA (Methicillin-resistant S. aureus) strain, and slightly higher against a VISA (VCM intermediate S. aureus) strain. VNp without h-Tf showed potential to assist in the development of new therapies against S. aureus infections.

Synthesis of Antiviral Perfluoroalkyl Derivatives of Teicoplanin and Vancomycin

The limited scope of antiviral drugs and increasing problem of antiviral drug resistance represent a global health threat. Glycopeptide antibiotics and their lipophilic derivatives have emerged as relevant inhibitors of diverse viruses. Herein, we describe a new strategy for the synthesis of dual hydrophobic and lipophobic derivatives of glycopeptides to produce selective antiviral agents without membrane-disrupting activity. Perfluorobutyl and perfluorooctyl moieties were attached through linkers of different length to azido derivatives of vancomycin aglycone and teicoplanin pseudoaglycone, and the new derivatives were evaluated against a diverse panel of viruses. The teicoplanin derivatives displayed strong anti-influenza virus activity at nontoxic concentrations. Some of the perfluoroalkylated glycopeptides were also active against a few other viruses such as herpes simplex virus or coronavirus. These data encourage further exploration of glycopeptide analogues for broad antiviral application.

Vancomycin Resistance Is Overcome by Conjugation of Polycationic Peptides

Multidrug-resistant bacteria represent one of the biggest challenges facing modern medicine. The increasing prevalence of glycopeptide resistance compromises the efficacy of vancomycin, for a long time considered as the last resort for the treatment of resistant bacteria. To reestablish its activity, polycationic peptides were conjugated to vancomycin. By site-specific conjugation, derivatives that bear the peptide moiety at four different sites of the antibiotic were synthesized. The most potent compounds exhibited an approximately 1000-fold increased antimicrobial activity and were able to overcome the most important types of vancomycin resistance. Additional blocking experiments using d-Ala-d-Ala revealed a mode of action beyond inhibition of cell-wall formation. The antimicrobial potential of the lead candidate FU002 for bacterial infection treatments could be demonstrated in an in vivo study. Molecular imaging and biodistribution studies revealed that conjugation engenders superior pharmacokinetics.

Comparative Stability Study of Unit-dose Vancomycin Hydrochloride Oral Solutions in Plastic Capped Oral Syringes and Plastic Sealed Dosage Cups

The objective of this study was to evaluate the stability of vancomycin hydrochloride oral solution prepared using FIRST Vancomycin and FIRVANQ compounding kits, prepared in oral syringes and heat-sealed dosing cups, stored at refrigerated and room temperatures. Triplicate batches of vancomycin hydrochloride oral solution (50 mg/mL) were prepared using FIRST Vancomycin and FIRVANQ kits, aliquoted into plastic oral syringes and sealed dosing cups, stored at refrigerated and room temperatures for a total of eight sample groups. Additionally, remaining samples from FIRVANQ batches were unit-dosed in clear Luer-Lok syringes and stored under refrigeration as a ninth batch. Samples were removed and analyzed for vancomycin recovery using a previously validated high-performance liquid chromatography with ultraviolet detection method over a 30-day period. Recovery was quantitatively assessed by comparing to a freshly prepared United States Pharmacopeia reference standard on each day of sampling. Stability was defined as recovery of 90% to 110% of labeled amount. For all batches and storage conditions tested, the percent recovery of vancomycin remained within the 90% to 110% range throughout the entire 30-day study period. Statistically significant differences based on storage conditions were detected between some test groups, with higher recoveries associated with refrigerated storage. The stability of FIRVANQ is comparable to the solution prepared using the FIRST Vancomycin kit. FIRST Vancomycin and FIRVANQ solutions can be unit dosed, using capped oral syringes or sealed plastic cups, and stored at room temperature or under refrigeration for up to 30 days, which helps improve pharmacy workflow and reduce errors.

Physical Compatibility of Medications Used in Critically Ill Patients with Balanced Fluid Solutions

Using balanced fluids for resuscitation in patients with septic shock may lead to improved patient outcomes. However, compatibility data on co-administering balanced fluids via y-site connector with other intravenous medications is lacking. The purpose of this study was to examine the physical compatibility of frequently used intravenous medications for patients with septic shock with balanced fluids, Plasma-Lyte A, and Lactated Ringers, using a simulated y-site. Medications studied were acyclovir, amiodarone, ampicillin, aztreonam, cefepime, ceftriaxone, ciprofloxacin, heparin, hydrocortisone, gentamicin, levofloxacin, meropenem, piperacillin-tazobactam, tobramycin, and vancomycin. All medications were assessed with Plasma-Lyte A; amiodarone, ampicillin, cefepime, hydrocortisone, and levofloxacin were also assessed for compatibility with Lactated Ringers, based on missing or conflicting compatibility data. The medications were diluted to maximum concentrations used for patient administration and mixed with the balanced fluid solution in equal volumes. Physical compatibility was determined by assessing samples visually against light and dark backgrounds and using a laboratory turbidimeter. Assessments occurred at time of mixing and at 15-minute intervals up to one hour. Amiodarone demonstrated turbidimetric incompatibility when combined with Plasma- Lyte A or Lactated Ringers and should not be co-administered with either of these fluids via y-site connector. Each remaining study drug displayed visible and turbidimetric compatibility with the assessed balanced fluid. Acyclovir, ampicillin, aztreonam, cefepime, ceftriaxone, ciprofloxacin, gentamicin, heparin, hydrocortisone, levofloxacin, meropenem, piperacillin-tazobactam, tobramycin, and vancomycin exhibited physical compatibility with Plasma- Lyte A in a simulated y-site for up to one hour. Ampicillin, cefepime, hydrocortisone, and levofloxacin were also physically compatible with Lactated Ringers.

In vivo photothermal inhibition of methicillin-resistant Staphylococcus aureus infection by in situ templated formulation of pathogen-targeting phototheranostics

Bacterial infection has caused a serious threat to human public health. Methicillin-resistant Staphylococcus aureus (MRSA) is a representative drug-resistant bacterium, which is difficult to eradicate completely, resulting in high infection probability with severe mortality. Herein, pathogen-targeting phototheranostic nanoparticles, Van-OA@PPy, are developed for efficient elimination of MRSA infection. Van-OA@PPy nanoparticles are fabricated from the in situ templated formation of polypyrrole (PPy) in the presence of ferric ions (Fe³⁺) and a polymer template, hydrophilic poly(2-hydroxyethyl methacrylate-co-N,N-dimethyl acrylamide), P(HEMA-co-DMA). PPy nanoparticles are further coated with vancomycin conjugated oleic acid (Van-OA) to afford the resultant pathogen-targeting Van-OA@PPy. A high photothermal conversion efficiency of ∼49.4% is achieved. MRSA can be efficiently killed due to sufficient nanoparticle adhesion and fusion with MRSA, followed by photothermal therapy upon irradiation with an 808 nm laser. Remarkable membrane damage of MRSA is observed, which contributes greatly to the inhibition of MRSA infection. Furthermore, the nanoparticles have high stability and good biocompatibility without causing any detectable side effects. On the other hand, residual Fe³⁺ and PPy moieties in Van-OA@PPy endow the nanoparticles with magnetic resonance (MR) imaging and photoacoustic (PA) imaging potency, respectively. The current strategy has the potential to inspire further advances in precise diagnosis and efficient elimination of MRSA infection in biomedicine.

Electrodeposited Assembly of Additive-Free Silk Fibroin Coating from Pre-Assembled Nanospheres for Drug Delivery

Electrophoretically deposited (EPD) polymer-based coatings have been extensively reported as reservoirs in medical devices for delivery of therapeutic agents, but control over drug release remains a challenge. Here, a simple but uncommon assembly strategy for EPD polymer coatings was proposed to improve drug release without introducing any additives except the EPD matrix polymer precursor. The added value of the proposed strategy was demonstrated by developing a novel EPD silk fibroin (SF) coating assembled from pre-assembled SF nanospheres for an application model, that is, preventing infections around percutaneous orthopedic implants via local delivery of antibiotics. The EPD mechanism of this nanosphere coating involved oxidation of water near the substrate to neutralize SF nanospheres, resulting in irreversible deposition. The deposition process and mass could be easily controlled using the applied EPD parameters. In comparison with the EPD SF coating assembled in a conventional way (directly obtained from SF molecule solutions), this novel coating had a similar adhesion strength but exhibited a more hydrophobic nanotopography to induce better fibroblastic response. Moreover, the use of nanospheres as building blocks enabled 1.38 and 21 times enhancement on the antibiotic release amount and time (of 95% maximum dug release), respectively, while retaining drug effectiveness and showing undetectable cytotoxicity. This unexpected release kinetics was found attributable to the electrostatic and hydrophobic interactions between the drug and nanospheres and a negligible initial dissolution effect on the nanosphere coating. These results illustrate the promising potential of the pre-assembled strategy on EPD polymer coatings for superior control over drug delivery.

Facile Assembly of Multifunctional Antibacterial Nanoplatform Leveraging Synergistic Sensitization between Silver Nanostructure and Vancomycin

The emergence of antibiotic-resistant bacterial strains renders the conventional antibiotic therapy less efficient. The integration of two distinct bactericides into one compact platform provides a promising strategy to realize a combinational antimicrobial therapy. In this work, an efficient chemo-Ag nanohybrid antibacterial platform was facilely developed based on the integration of vancomycin-carrying polydopamine with silver nanoparticles (PDA@Van-Ag). The as-synthesized antibacterial nanohybrid inherited the intrinsic properties of both bactericides to achieve a synergistic antibacterial performance against both Staphylococcus aureus and Escherichia coli strains by attacking bacteria from two distinct fronts. Through this combinational therapy, the efficiency of antibiotic against S. aureus was significantly improved by reducing drug dosage with less opportunity for imparting drug resistance. In addition, this antibacterial nanohybrid, with innate photothermal properties, could achieve auxiliary hyperthermia-assisted bacterial inactivation in the meantime. Furthermore, the outstanding in vivo bacteria-killing activity and wound-healing acceleration were demonstrated in a S. aureus-infected mouse skin defect model. Taken together, this bactericidal nanohybrid could achieve sustained antibiotic release and wipe out bacteria more effectively in a synergistic way, thus reducing the emergence of antibiotic resistance. This work holds great potential to advance the development of novel antibacterial agents and combinational strategies as a promising supplement of antibiotics in the near future.

Development of local vancomycin delivery system from fibrin gel to prevent Staphylococcus aureus biofilms graft infection

Prosthetic vascular graft infection is one of the most severe vascular surgery complications. Fibrin gel (FG) has many useful characteristics as biocompatibility, biodegradation, adhesion, and haemostasis to develop the local antibiotic delivery system. In this study, human plasma was collected from peripheral blood that was used to create fibrin gel by supplement ion Ca²⁺. Antibiotic-containing fibrin gel was then evaluated in some characteristics such as surface structure, biodegradation, antibiotic delivery, cytotoxicity, and bacterial biofilm prevention in vitro and in vivo. The results showed that fibrin gel was excellent material for the extended delivery of antibiotics. Most importantly, antibiotic-containing fibrin gel was not toxic for human fibroblast cells in vitro and inhibited bacterial biofilm growth in vitro and in vivo. This research is the first step in developing an antibiotic delivery system for effective graft infection treatments.

Enantioselective potential of teicoplanin- and vancomycin-based superficially porous particles-packed columns for supercritical fluid chromatography

Application of the superficially porous particles (SPPs) grafted with chiral selectors can substantially improve resolution in chromatographic techniques. In this work, we carried out a deeper study on supercritical fluid chromatography systems with 2.7 µm SPPs bonded with teicoplanin and vancomycin. Fast separations of the majority of enantiomers of phytoalexins, substituted tryptophans, and ketamine derivatives, as representatives of important biologically active and structurally diverse chiral compounds have been achieved. The chromatographic behavior of the structurally different analytes served to characterize these separation systems. The influence of separation conditions, namely mobile phase composition, i.e. type of co-solvent and additive on retention, enantioselective resolution and enantioselectivity was examined. The success rate of baseline and partial separations in individual groups of compounds differed with the chiral stationary phase and also with mobile phase composition. The best, baseline separations for the phytoalexins were achieved on the TeicoShell column using methanol as a co-solvent and trifluoroacetic acid as an additive if used. Mostly partial separations were achieved on the vancomycin-based column for all groups of analytes. Complementary separation behavior of these CSPs was confirmed for the majority of the chiral compounds examined in this work.

Electrochemical Aptamer-Based Sensors for Improved Therapeutic Drug Monitoring and High-Precision, Feedback-Controlled Drug Delivery

The electrochemical aptamer-based (E-AB) sensing platform appears to be a convenient (rapid, single-step, and calibration-free) and modular approach to measure concentrations of specific molecules (irrespective of their chemical reactivity) directly in blood and even in situ in the living body. Given these attributes, the platform may thus provide significant opportunities to render therapeutic drug monitoring (the clinical practice in which dosing is adjusted in response to plasma drug measurements) as frequent and convenient as the measurement of blood sugar has become for diabetics. The ability to measure arbitrary molecules in the body in real time could even enable closed-loop feedback control over plasma drug levels in a manner analogous to the recently commercialized controlled blood sugar systems. As initial exploration of this, we describe here the selection of an aptamer against vancomycin, a narrow therapeutic window antibiotic for which therapeutic monitoring is a critical part of the standard of care, and its adaptation into an electrochemical aptamer-based (E-AB) sensor. Using this sensor, we then demonstrate: (i) rapid (seconds) and convenient (single-step and calibration-free) measurement of plasma vancomycin in finger-prick-scale samples of whole blood, (ii) high-precision measurement of subject-specific vancomycin pharmacokinetics (in a rat animal model), and (iii) high-precision, closed-loop feedback control over plasma levels of the drug (in a rat animal model). The ability to not only track (with continuous-glucose-monitor-like measurement frequency and convenience) but also actively control plasma drug levels provides an unprecedented route toward improving therapeutic drug monitoring and, more generally, the personalized, high-precision delivery of pharmacological interventions.

Dual polymer networks: a new strategy in expanding the repertoire of hydrogels for biomedical applications

Inspired by the double network hydrogel systems we report the formulation of dual networks, which expands the repertoire of this class of materials for potential biomedical applications. The tough dual network hydrogels were designed through sequential interpenetrating polymer formation, applying green chemistry and low-cost methods, devoid of any initiator-activator complexes that may pose risks in biomedical applications. The dual networks were synthesized in two steps, firstly the water soluble poly(vinyl alcohol) was subjected to cryogelation that formed the first network, which was then expanded by intrusion of a dilute solution of sodium alginate and complexed with a solution of calcium chloride under ambient conditions and further freeze-thawed. These hydrogels are flexible, ductile and porous with the ability to absorb and retain fluids as well as possess the versatility to easily incorporate biological molecules/drugs/antibiotics to be applied in tissue matrices or drug delivery systems. The dual network hydrogels can be tailored to have varying mechanical properties, shapes, size, thickness and particularly can be made physically porous if required, to suit the users intended application.

Improved Intestinal Mucus Permeation of Vancomycin via Incorporation Into Nanocarrier Containing Papain-Palmitate

The aim of this study was to improve intestinal mucus permeation of a peptide antibiotic via incorporation into papain-palmitate-modified self-emulsifying drug delivery systems (SEDDS) as nanocarrier. Vancomycin as a peptide antibiotic was lipidized by hydrophobic ion pair formation using sodium bis-2-ethylhexyl-sulphosuccinate before incorporation in SEDDS comprising Capmul MCM, propylenglycol, and Kolliphor EL (2:1:2). As mucolytic agent, 0.5% papain-palmitate was introduced in SEDDS formulation containing the vancomycin-sodium bis-2-ethylhexyl-sulphosuccinate ion pair. The formulation was evaluated regarding droplet size, zeta potential, and cytotoxicity using Caco-2 cells previous to intestinal mucus permeation studies using Transwell diffusion and rotating tube method. The hydrophobic ion pair product yielded from surfactant to drug ratio of 3:1 provided a 25-fold increase in lipophilicity, drug payload in SEDDS of 5%, and log D_{SEDDS/release medium} of 2.2. The formulation exhibited a droplet size and zeta potential of 221.5 ± 14.8 nm and -4.2 ± 0.8 mV, respectively. Cytotoxicity study showed that SEDDS formulations were not toxic. Introducing 0.5% papain-palmitate increased the mucus permeability of SEDDS 2.8-fold and 3.3-fold in Transwell diffusion and rotating tube studies, respectively. According to these results, papain decorated SEDDS might be a potential strategy to improve the mucus permeating properties of peptide antibiotics.

Characterization and Antibiofilm Activity of Mannitol-Chitosan-Blended Paste for Local Antibiotic Delivery System

Mannitol, a polyalcohol bacterial metabolite, has been shown to activate dormant persister cells within bacterial biofilm. This study sought to evaluate an injectable blend of mannitol, chitosan, and polyethylene glycol for delivery of antibiotics and mannitol for eradication of Staphylococcal biofilm. Mannitol blends were injectable and had decreased dissociation and degradation in the enzyme lysozyme compared to blends without mannitol. Vancomycin and amikacin eluted in a burst response, with active concentrations extended to seven days compared to five days for blends without mannitol. Mannitol eluted from the paste in a burst the first day and continued through Day 4. Eluates from the mannitol pastes with and without antibiotics decreased viability of established S. aureus biofilm by up to 95.5% compared to blends without mannitol, which only decreased biofilm when loaded with antibiotics. Cytocompatibility tests indicated no adverse effects on viability of fibroblasts. In vivo evaluation of inflammatory response revealed mannitol blends scored within the 2–4 range at Week 1 (2.6 ± 1.1) and at Week 4 (3.0 ± 0.8), indicative of moderate inflammation and comparable to non-mannitol pastes (p = 0.065). Clinically, this paste could be loaded with clinician-selected antibiotics and used as an adjunctive therapy for musculoskeletal infection prevention and treatment.

One-Step Synthesis of Epoxy Group-Terminated Organosilica Nanodots: A Versatile Nanoplatform for Imaging and Eliminating Multidrug-Resistant Bacteria and Their Biofilms

Multidrug-resistant bacteria (MRB) and their biofilms, both of which develop high levels of drug tolerance, cause severe threats to global health. This study demonstrates that biocompatible fluorescent silicon-containing nanodots can be a multifunctional platform for simultaneously imaging and eliminating MRB and their biofilms. Ultrasmall epoxy group (oxirane)-functionalized organosilica nanodots (OSiNDs) with a high photoluminescence quantum yield of ≈31% are synthesized via a simple one-step hydrothermal treatment of an epoxy group-containing silane molecule, 3-glycidoxypropyltrimethoxysilane, and an organic dye, rose bengal. The resultant OSiNDs can be employed as a universal imaging reagent for visualizing various bacteria/biofilms, including MRB and their biofilms. Moreover, the epoxy group-terminated OSiNDs can be conjugated with amine-containing reagents only via the simple stirring of the mixtures at an elevated temperature (e.g., 60 °C) for several hours (e.g., 3 h) without the addition of activating reagents. The amine-containing antibiotic vancomycin (Van) can thus be easily conjugated with the OSiNDs, and the obtained OSiNDs-Van can successfully inhibit the growth of MRB and even eliminate their biofilms. Collectively, the present work may give new impetus to the development of novel antibacterial and anti-biofilm agents for overcoming the drug resistance of bacteria.

Vancomycin- and Strontium-Loaded Microspheres with Multifunctional Activities against Bacteria, in Angiogenesis, and in Osteogenesis for Enhancing Infected Bone Regeneration

Biomaterials that have capacities to simultaneously induce bone regeneration and kill bacteria are in demand because bone defects face risks of severe infection in clinical therapy. To meet the demand, multifunctional biodegradable microspheres are fabricated, which contain vancomycin to provide antibacterial activity and strontium-doped apatite to provide osteocompatibility. Moreover, the strontium component shows activity in promoting angiogenesis, which further favors osteogenesis. For producing the microspheres, vancomycin is loaded into mesoporous silica and embedded in polylactide-based microspheres via the double emulsion technique and the strontium-doped apatite is deposited onto the microspheres via biomineralization in strontium-containing simulated body fluid. Sustained release behaviors of both vancomycin and Sr²⁺ ions are achieved. The microspheres exhibit strong antibacterial effect against Staphylococcus aureus, while demonstrating excellent cell/tissue compatibility. Studies of differentiation confirm that the introduction of strontium element strengthens the angiogenic and osteogenic expressions of mesenchymal stromal cells. Subcutaneous injection of the microspheres into rabbit's back confirms their effectiveness in inducing neovascularization and ectopic osteogenesis. Finally, an infected rabbit femoral condyle defect model is created with S. aureus infection and the multifunctional microspheres are injected, which display significant antibacterial activity in vivo and achieve efficient new bone formation in comparison with biomineralized microspheres without vancomycin loading. The vancomycin- and strontium-loaded microspheres, being biomineralized, injectable, and biodegradable, are attractive because of their flexibility in integrating multiple functions into one design, whose potentials in treating infected bone defects are highly expected.

In Situ Gelling Hydrogel with Anti-Bacterial Activity and Bone Healing Property for Treatment of Osteomyelitis

Background

Despite the development of progressive surgical techniques and antibiotics, osteomyelitis is a big challenge for orthopedic surgeons. The main aim of this study is to fabricate an in situ gelling hydrogel that permits sustained release of antibiotic (for control of infection) and growth factor (for induction of new bone formation) for effective treatment of osteomyelitis.

Methods

An in situ gelling alginate (ALG)/hyaluronic acid (HA) hydrogel containing vancomycin (antibiotic) and bone morphogenetic protein-2 (BMP-2; growth factor) was prepared by simple mixing of ALG/HA/Na₂HPO₄ solution and CaSO₄/vancomycin/BMP-2 solution. The release behaviors of vancomycin and BMP-2, anti-bacterial effect (in vitro); and therapeutic efficiency for osteomyelitis and bone regeneration (in vivo, osteomyelitis rat model) of the vancomycin and BMP-2-incorporated ALG/HA hydrogel were investigated.

Results

The gelation time of the ALG/HA hydrogel was controlled into approximately 4 min, which is sufficient time for handling and injection into osteomyelitis lesion. Both vancomycin and BMP-2 were continuously released from the hydrogel for 6 weeks. From the in vitro studies, the ALG/HA hydrogel showed an effective anti-bacterial activity without significant cytotoxicity for 6 weeks. From an in vivo animal study using Sprague-Dawley rats with osteomyelitis in femur as a model animal, it was demonstrated that the ALG/HA hydrogel was effective for suppressing bacteria (Staphylococcus aureus) proliferation at the osteomyelitis lesion and enhancing bone regeneration without additional bone grafts.

Conclusions

From the results, we suggest that the in situ gelling ALG/HA hydrogel containing vancomycin and BMP-2 can be a feasible therapeutic tool to treat osteomyelitis.

Vancomycin-Iridium (III) Interaction: An Unexplored Route for Enantioselective Imine Reduction

The chiral structure of antibiotic vancomycin (Van) was exploited as an innovative coordination sphere for the preparation of an IrCp* based hybrid catalysts. We found that Van is able to coordinate iridium (Ir(III)) and the complexation was demonstrated by several analytical techniques such as MALDI-TOF, UV, Circular dichroism (CD), Raman IR, and NMR. The hybrid system so obtained was employed in the Asymmetric Transfer Hydrogenation (ATH) of cyclic imines allowing to obtain a valuable 61% e.e. (R) in the asymmetric reduction of quinaldine 2. The catalytic system exhibited a saturation kinetics with a calculated efficiency of K_cat/K_M = 0.688 h⁻¹mM⁻¹.

Fast super/subcritical fluid chromatographic enantioseparations on superficially porous particles bonded with broad selectivity chiral selectors relative to fully porous particles

Superficially porous particles (SPPs) have shown advantages in enantiomeric separations in HPLC by conserving selectivity while providing higher efficiency separations with significantly reduced analysis times. The question arises as to whether the same advantages can be found to the same extent in super/subcritical fluid chromatography. In this work, the low viscosity advantage of carbon dioxide/MeOH mixtures is coupled with high-efficiency 2.7 μm superficially porous particles for enantiomeric separations. Given the fact that the viscosity of the mobile phase is typically ten times lower than liquid mobile phases it is possible to use flow rates as high as 14 mL/min on 5 cm packed columns. Superficially porous particles (SPPs) were grafted with teicoplanin (TeicoShell), a chemically modified macrocyclic glycopeptide (NicoShell), vancomycin (VancoShell), and isopropyl derivatized cyclofructan-6 (LarihcShell-P). One hundred chiral analytes were separated in a very short time frame, as little as 0.2 min (13 s). Even shorter separations can be obtained with advances in SFC instrumentation. The LarihcShell-P is the only chiral crown ether-based selector which showed high selectivity for primary amines. The Teicoshell column offered unique separations for acidic and neutral analytes. The NicoShell and the VancoShell were useful in separating amine (secondary and tertiary) containing pharmaceutical drugs and controlled substances. By chemically modifying a macrocyclic glycopeptide (NicoShell) we report the first enantiomeric separation of nicotine under SFC conditions within 3 min with a resolution of >3. Additionally, van Deemter plots are constructed comparing the fully porous particles and superficially porous particles bonded with the same chiral selectors. In toto the SPP advantages also were found for SFC. However instrumental shortcomings involving extra column effects and pressure limitations need to be addressed by instrument manufacturers to realize the full advantages of SPPs and other smaller particle supports.

In vitro testing of a first-in-class tri-alkylnorspermidine-biaryl antibiotic in an anti-biofilm silicone coating

Biofilm-related infection is among the worst complication to prosthetic joint replacement procedures; once established on the implant surface, biofilms show strong recalcitrance to clinical antibiotic therapy, frequently requiring costly revision procedures and prolonged systemic antibiotics for their removal. A well-designed active release coating might assist host immunity in clearing bacterial contaminants within the narrow perioperative window and ultimately prevent microbial colonization of the joint prosthesis. A first-in-class compound (CZ-01127) was tested as the active release agent in a silicone (Si) coating using an in vitro dynamic flow model of surgical site contamination and compared with analogous coatings containing clinical gold-standard antibiotics vancomycin and gentamicin; the CZ-01127 coating outperformed both vancomycin and gentamicin coatings and was the only to decrease the methicillin-resistant Staphylococcus aureus (MRSA) inocula below detectable limits for the first 3 days. The antimicrobial activity of CZ-01127, and for comparison vancomycin and gentamicin, were characterized against both planktonic and biofilm MRSA using the minimum inhibitory concentration (MIC) assay, serial passages, and serial dilution tests against established biofilms grown with a CBR 90 CDC biofilm reactor. Despite a similar MIC (1 µg/ml) and behavior in a 25-day serial passage analysis, CZ-01127 displayed much greater bactericidal activity against established biofilms and was the only to decrease biofilm colony forming units (CFUs) below detectable limits at the highest concentration tested (500 µg/ml). Coating release profiles were characterized using ATR-FTIR and displayed burst release kinetics within the decisive period of the perioperative window suggesting the silicon carrier is broadly useful for screening antibiotic compound for local delivery applications. STATEMENT OF SIGNIFICANCE: With an aging population, an increasing number of people are undergoing total joint replacement procedures in which diseased joint tissues are replaced with permanent metallic implants. Some of these procedures are burdened by costly and debilitating infections. A promising approach to prevent infections is the use of an antimicrobial coating on the surface of the implant which releases antibiotics into the surgical site to prevent infection. In this study, we tested a new antibiotic compound formulated in a silicone coating. Data showed that this compound was more effective at killing pathogenic methicillin resistant Staphylococcus aureus (MRSA) bacteria than two clinical gold-standard antibiotics-vancomycin and gentamicin-and could be a promising agent for antimicrobial coating technologies.

Mechanism of formation governs the mechanism of release of antibiotics from calcium phosphate nanopowders and cements in a drug-dependent manner

The kinetics of drug release from hydroxyapatite (HAp) cements could be tuned by controlling the kinetics of crystallization of their HAp precursor powders during synthesis. Here it is shown that this history of formation affects not only the kinetics, but also the mechanism of release. Cements composed of two HAp powders precipitated under different conditions, one (HAp2) taking twice longer to transform from the amorphous to the crystalline state than the other (HAp1), were mixed at different ratios to tune their drug release kinetics and tested for the release mechanism in conjunction with compositional and microstructural analyses. While the cement component converting to the amorphous phase during gelation (HAp2) exhibited a faster, but also more anomalous, non-Fickian mechanism of release of vancomycin, the cement component retaining its crystalline state all throughout gelation, setting and hardening (HAp1) stabilized at the ideal, Fickian diffusion case corresponding to the Korsmeyer-Peppas exponent value of 0.45 ± 0.02. This effect got reversed for the other antibiotic studied as a drug, ciprofloxacin, in which case HAp2 exhibited the ideal, Fickian diffusion with n = 0.45 ± 0.02 and the increase in the content of the cement component retaining its crystallinity during gelation, setting and hardening (HAp1) steadily shifted the mechanism of release to more anomalous, non-Fickian types. This has indicated that the molecular structure of the drug is an essential determinant of the mechanism of release and that the design of a carrier for a universally tunable release of drugs based on the passive transport is likely impossible. Preliminary assays involving the addition of chitosan or gelatin as polymeric components to HAp led to the inclusion of swelling and erosion as additional effects by which the drug escapes the carrier and shifted the release toward less diffusional and more multimodal mechanisms. With regard to the microstructural and compositional effects governing the release mechanism and kinetics, the retention of a finite concentration of slit-like pores of the amorphous precursor in HAp2 and its lower surface energy and lesser drug binding potential in the gelled, amorphous state, but also its possibly less stable and more diffusive particle surface and higher structural water content were elaborated as potential reasons explaining the distinct rates and mechanisms of release from the two HAp powders with different histories of formation.

HLA-A*32:01 is strongly associated with vancomycin-induced drug reaction with eosinophilia and systemic symptoms

BACKGROUND

Vancomycin is a prevalent cause of the severe hypersensitivity syndrome drug reaction with eosinophilia and systemic symptoms (DRESS), which leads to significant morbidity and mortality and commonly occurs in the setting of combination antibiotic therapy, affecting future treatment choices. Variations in HLA class I in particular have been associated with serious T cell-mediated adverse drug reactions, which has led to preventive screening strategies for some drugs.

OBJECTIVE

We sought to determine whether variation in the HLA region is associated with vancomycin-induced DRESS.

METHODS

Probable vancomycin-induced DRESS cases were matched 1:2 with tolerant control subjects based on sex, race, and age by using BioVU, Vanderbilt's deidentified electronic health record database. Associations between DRESS and carriage of HLA class I and II alleles were assessed by means of conditional logistic regression. An extended sample set from BioVU was used to conduct a time-to-event analysis of those exposed to vancomycin with and without the identified HLA risk allele.

RESULTS

Twenty-three subjects met the inclusion criteria for vancomycin-associated DRESS. Nineteen (82.6%) of 23 cases carried HLA-A*32:01 compared with 0 (0%) of 46 of the matched vancomycin-tolerant control subjects (P = 1 × 10-8) and 6.3% of the BioVU population (n = 54,249, P = 2 × 10-16). Time-to-event analysis of DRESS development during vancomycin treatment among the HLA-A*32:01-positive group indicated that 19.2% had DRESS and did so within 4 weeks.

CONCLUSIONS

HLA-A*32:01 is strongly associated with vancomycin-induced DRESS in a population of predominantly European ancestry. HLA-A*32:01 testing could improve antibiotic safety, help implicate vancomycin as the causal drug, and preserve future treatment options with coadministered antibiotics.

Evaluation of collagen/hydroxyapatite electrospun layers loaded with vancomycin, gentamicin and their combination: Comparison of release kinetics, antimicrobial activity and cytocompatibility

The aim of this study was to develop a biodegradable nanostructured electrospun layer based on collagen (COL), hydroxyapatite nanoparticles (HA), vancomycin hydrochloride (V), gentamicin sulphate (G) and their combination (VG) for the treatment of prosthetic joint infections and the prevention of infection during the joint replacement procedure. COL/HA layers containing different amounts of HA (0, 5 and 15 wt%) were tested for the in vitro release kinetics of antibiotics, antimicrobial activity against MRSA, gentamicin-resistant Staphylococcus epidermidis and Enterococcus faecalis isolates and cytocompatibility using SAOS-2 bone-like cells. The results revealed that the COL/HA layers released high concentrations of vancomycin and gentamicin for 21 days and performed effectively against the tested clinically-relevant bacterial isolates. The presence of HA in the collagen layers was found not to affect the release kinetics of the vancomycin from the layers loaded only with vancomycin or its combination with gentamicin. Conversely, the presence of HA slowed down the release of gentamicin from the COL/HA layers loaded with gentamicin and its combination with vancomycin. The combination of both antibiotics exerted a positive effect on the prolongation of the conversion of vancomycin into its degradation products. All the layers tested with different antibiotics exhibited potential antibacterial activity with respect to both the tested staphylococci isolates and enterococci. The complemental effect of vancomycin was determined against both gentamicin-resistant Staphylococcus epidermidis and Enterococcus faecalis in contrast to the application of gentamicin as a single agent. This combination was also found to be more effective against MRSA than is vancomycin as a single agent. Importantly, this combination of vancomycin and gentamicin in the COL/HA layers exhibited sufficient cytocompatibility to SAOS-2, which was independent of the HA content. Conversely, only gentamicin caused the death of SAOS-2 independently of HA content and only vancomycin stimulated SAOS-2 behaviour with an increased concentration of HA in the COL/HA layers. In conclusion, COL/HA layers with 15 wt% of HA impregnated with vancomycin or with a combination of vancomycin and gentamicin offer a promising treatment approach and the potential to prevent infection during the joint replacement procedures.

Application of Sub-2 Micron Particle Silica Hydride Derivatized with Vancomycin for Chiral Separations by Nano-Liquid Chromatography

1.8 μm Silica hydride particles have been derivatized with vancomycin and applied to the enantioseparation of some racemic herbicides and nonsteroidal anti-inflammatory drugs (NSAIDs) by nano-liquid chromatography. The chiral stationary phase (CSP) was packed for only 11 cm and the enantiomers were separated utilizing a laboratory-assembled instrumentation. The new CSP was very effective for the separation of the above mentioned acidic compounds, while poor resolutions were obtained for basic compounds. Mixtures of acetate buffer with methanol or acetonitrile allowed the chiral resolution of all compounds. Fast chiral separation of a NSAIDs-related compound can be achieved in less than 60 s.

A chemoselective strategy for late-stage functionalization of complex small molecules with polypeptides and proteins

Conjugates between proteins and small molecules enable access to a vast chemical space that is not achievable with either type of molecule alone; however, the paucity of specific reactions capable of functionalizing proteins and natural products presents a formidable challenge for preparing conjugates. Here we report a strategy for conjugating electron-rich (hetero)arenes to polypeptides and proteins. Our bioconjugation technique exploits the electrophilic reactivity of an oxidized selenocysteine residue in polypeptides and proteins, and the electron-rich character of certain small molecules to provide bioconjugates in excellent yields under mild conditions. This conjugation chemistry enabled the synthesis of peptide-vancomycin conjugates without the prefunctionalization of vancomycin. These conjugates have an enhanced in vitro potency for resistant Gram-positive and Gram-negative pathogens. Additionally, we show that a 6 kDa affibody protein and a 150 kDa immunoglobulin-G antibody could be modified without diminishing bioactivity.