Antimicrobial hydrogel foam dressing with controlled release of gallium maltolate for infection control in chronic wounds.

Effective treatment of infection in chronic wounds is critical to improve patient outcomes and prevent severe complications, including systemic infections, increased morbidity, and amputations. Current treatments, including antibiotic administration and antimicrobial dressings, are challenged by the increasing prevalence of antibiotic resistance and patients' sensitivity to the delivered agents. Previous studies have demonstrated the potential of a new antimicrobial agent, Gallium maltolate (GaM); however, the high burst release from the GaM-loaded hydrogel gauze required frequent dressing changes. To address this need, we developed a hydrogel foam-based wound dressing with GaM-loaded microspheres for sustained infection control. First, the minimal inhibitory and bactericidal concentrations (MIC and MBC) of GaM against two Staphylococcus aureus strains isolated from chronic wounds were identified. No significant adverse effects of GaM on dermal fibroblasts were shown at the MIC, indicating an acceptable selectivity index. For the sustained release of GaM, electrospraying was employed to fabricate microspheres with different release kinetics. Systematic investigation of loading and microsphere size on release kinetics indicated that the larger microsphere size and lower GaM loading resulted in a sustained GaM release profile over the target 5 days. Evaluation of the GaM-loaded hydrogel dressing demonstrated cytocompatibility and antibacterial activities with a zone of inhibition test. An equine distal limb wound model was developed and utilized to demonstrate the efficacy of GaM-loaded hydrogel foam in vivo. This antimicrobial hydrogel foam dressing displayed the potential to combat methicillin-resistant S. aureus (MRSA) infection with controlled GaM release to improve chronic wound healing.

A Computational Framework to Optimize the Mechanical Behavior of Synthetic Vascular Grafts.

The failure of synthetic small-diameter vascular grafts has been attributed to a mismatch in the compliance between the graft and native artery, driving mechanisms that promote thrombosis and neointimal hyperplasia. Additionally, the buckling of grafts results in large deformations that can lead to device failure. Although design features can be added to lessen the buckling potential, the addition is detrimental to decreasing compliance (e.g., reinforcing coil). Herein, we developed a novel finite element framework to inform vascular graft design by evaluating compliance and resistance to buckling. A batch-processing scheme iterated across the multi-dimensional design parameter space, which included three parameters: coil thickness, modulus, and spacing. Three types of finite element models were created in FEBio for each unique coil-reinforced graft parameter combination to simulate pressurization, axial buckling, and bent buckling, and results were analyzed to quantify compliance, buckling load, and kink radius, respectively, from each model. Importantly, model validation demonstrated that model predictions agree qualitatively and quantitatively with experimental observations. Subsequently, data for each design parameter combination were integrated into an optimization function for which a minimum value was sought. The optimization values identified various candidate graft designs with promising mechanical properties. Our investigation successfully demonstrated the model-directed framework identified vascular graft designs with optimal mechanical properties, which can potentially improve clinical outcomes by addressing device failure. In addition, the presented computational framework promotes model-directed device design for a broad range of biomaterial and regenerative medicine strategies.

Suspension electrospinning of decellularized extracellular matrix: A new method to preserve bioactivity.

Decellularized extracellular matrices (dECM) have strong regenerative potential as tissue engineering scaffolds; however, current clinical options for dECM scaffolds are limited to freeze-drying its native form into sheets. Electrospinning is a versatile scaffold fabrication technique that allows control of macro- and microarchitecture. It remains challenging to electrospin dECM, which has led researchers to either blend it with synthetic materials or use enzymatic digestion to fully solubilize the dECM. Both strategies reduce the innate bioactivity of dECM and limit its regenerative potential. Herein, we developed a new suspension electrospinning method to fabricate a pure dECM fibrous mesh that retains its innate bioactivity. Systematic investigation of suspension parameters was used to identify critical rheological properties required to instill "spinnability," including homogenization, concentration, and particle size. Homogenization enhanced particle interaction to impart the requisite elastic behavior to withstand electrostatic drawing without breaking. A direct correlation between concentration and viscosity was observed that altered fiber morphology; whereas, particle size had minimal impact on suspension properties and fiber morphology. The versatility of this new method was demonstrated by electrospinning dECM with three common decellularization techniques (Abraham, Badylak, Luo) and tissue sources (intestinal submucosa, heart, skin). Bioactivity retention after electrospinning was confirmed using cell proliferation, angiogenesis, and macrophage polarization assays. Collectively, these findings provide a framework for researchers to electrospin dECM for diverse tissue engineering applications.

Enhancing boundary detection of radiofrequency ablation lesions through photoacoustic mapping.

Atrial fibrillation (A-fib) is the most common type of heart arrhythmia, typically treated with radiofrequency catheter ablation to isolate the heart from abnormal electrical signals. Monitoring the formation of ablation-induced lesions is crucial for preventing recurrences and complications arising from excessive or insufficient ablation. Existing imaging modalities lack real-time feedback, and their intraoperative usage is in its early stages. A critical need exists for an imaging-based lesion indexing (LSI) method that directly reflects tissue necrosis formation. Previous studies have indicated that spectroscopic photoacoustic (sPA) imaging can differentiate ablated tissues from their non-ablated counterparts based on PA spectrum variation. In this paper, we introduce a method for detecting ablation lesion boundaries using sPA imaging. This approach utilizes ablation LSI, which quantifies the ratio between the signal from ablated tissue and the total tissue signal. We enhance boundary detection accuracy by adapting a regression model-based compensation. Additionally, the method was cross-validated with clinically used intraoperative monitoring parameters. The proposed method was validated with ex vivo porcine cardiac tissues with necrotic lesions created by different ablation durations. The PA-measured lesion size was compared with gross pathology. Statistical analysis demonstrates a strong correlation (R > 0.90) between the PA-detected lesion size and gross pathology. The PA-detected lesion size also exhibits a moderate to strong correlation (R > 0.75) with local impedance changes recorded during procedures. These results suggest that the introduced PA imaging-based LSI has great potential to be incorporated into the clinical workflow, guiding ablation procedures intraoperatively.

Polycaprolactone-based shape memory foams as self-fitting vaginal stents.

There is an urgent critical need for a patient-forward vaginal stent that can prevent debilitating vaginal stenosis that occurs after pelvic radiation treatments and vaginal reconstruction. To this end, we developed a self-fitting vaginal stent based on a shape-memory polymer (SMP) foam that can assume a secondary, compressed shape for ease of deployment. Upon insertion, the change in temperature and hydration initiates foam expansion to shape fit to the individual patient and restore the lumen of the stent to allow egress of vaginal secretions. To achieve rapid actuation at physiological temperature, we investigated the effect of architecture of two photocurable, polycaprolactone (PCL) macromers. Star-PCL-tetraacrylate displayed a reduced melting temperature as compared to a linear-PCL-diacrylate. Upon fabrication into high porosity foams with emulsion-templating, both compositions displayed shape fixity (>90 %) in a crimped, temporary shape. However, only the PCL star-foams displayed shape recovery (∼84 %) at 37 °C with expansion back to its permanent shape. A custom mold and curing system were then used to fabricate the PCL star-foams into hollow, cylindrical stents. The stent was crimped to its temporary insertion shape (50 % reduction in diameter, OD ∼ 11 mm) with a custom radial crimper and displayed excellent shape fixity for deployment (> 95 %) and shape recovery (∼ 100 %). To screen vaginal stents, we developed a custom benchtop pelvic model that simulated vaginal anatomy, temperatures, and pressures with an associated computational model. The crimped SMP vaginal stent was deployed in the model and expanded to walls of the canal (∼70 % increase in cross-sectional area) in less than 5 min after irrigation with warm water. The vaginal stent demonstrated retention of vaginal caliber with less than 10 % decrease in cross-sectional area under physiological pressures. Collectively, this work demonstrates the potential for SMP foams as self-fitting vaginal stents to prevent stenosis and provides new open-source tools for the iterative design of other gynecological devices. STATEMENT OF SIGNIFICANCE: Vaginal stenosis, a painful narrowing of the vaginal canal, is a common complication after pelvic radiation therapy or reconstructive surgery. To address this clinical need, we have created a self-fitting vaginal stent from a shape-memory polymer foam. The stent compresses for easy insertion and then expands to adapt to each patient's anatomy to maintain an open vaginal canal and prevent stenosis. This innovative stent provides a patient-friendly solution that could make a significant difference for women undergoing pelvic treatments by reducing pain, aiding recovery, and improving quality of life.

Design of PEG-based hydrogels as soft ionic conductors.

Conductive hydrogels have gained interest in biomedical applications and soft electronics. To tackle the challenge of ionic hydrogels falling short of desired mechanical properties in previous studies, our investigation aimed to understand the pivotal structural factors that impact the conductivity and mechanical behavior of polyethylene glycol (PEG)-based hydrogels with ionic conductivity. Polyether urethane diacrylamide (PEUDAm), a functionalized long-chain macromer based on PEG, was used to synthesize hydrogels with ionic conductivity conferred by incorporating ions into the liquid phase of hydrogel. The impact of salt concentration, water content, temperature, and gel formation on both mechanical properties and conductivity was characterized to establish parameters for tuning hydrogel properties. To further expand the range of conductivity available in these ionic hydrogels, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) was incorporated as a single copolymer network or double network configuration. As expected, conductivity in these ionic gels was primarily driven by ion diffusivity and charge density, which was dependent on hydrogel network formation and swelling. Copolymer network structure had minimal effect on the conductivity which was primarily driven by counter-ion equilibrium; however, the mechanical properties and equilibrium swelling was strongly dependent on network structure. The structure-property relationships elucidated here enables the rationale design of this new double network hydrogel to achieve target properties for a broad range of applications.

Injectable hydrogel electrodes as conduction highways to restore native pacing.

There is an urgent clinical need for a treatment regimen that addresses the underlying pathophysiology of ventricular arrhythmias, the leading cause of sudden cardiac death. The current report describes the design of an injectable hydrogel electrode and successful deployment in a pig model with access far more refined than any current pacing modalities allow. In addition to successful cardiac capture and pacing, analysis of surface ECG tracings and three-dimensional electroanatomic mapping revealed a QRS morphology comparable to native sinus rhythm, strongly suggesting the hydrogel electrode captures the deep septal bundle branches and Purkinje fibers. In an ablation model, electroanatomic mapping data demonstrated that the activation wavefront from the hydrogel reaches the mid-myocardium and endocardium much earlier than current single-point pacing modalities. Such uniform activation of broad swaths of tissue enables an opportunity to minimize the delayed myocardial conduction of heterogeneous tissue that underpins re-entry. Collectively, these studies demonstrate the feasibility of a new pacing modality that most closely resembles native conduction with the potential to eliminate lethal re-entrant arrhythmias and provide painless defibrillation.

Hydrogel foam dressings with angiogenic and immunomodulatory factors from mesenchymal stem cells.

Stem cell therapy and skin substitutes address the stalled healing of chronic wounds in order to promote wound closure; however, the high cost and regulatory hurdles of these treatments limit patient access. A low-cost method to induce bioactive healing has the potential to substantially improve patient care and prevent wound-induced limb loss. A previous study reported that bioactive factors derived from apoptotic-like mesenchymal stem cells (MSCs) demonstrated anti-inflammatory and proangiogenic effects and improved ischemic muscle regeneration. In this work, these MSC-derived bioactive factors were loaded into a hydrogel foam to harness immunomodulatory and angiogenic properties from MSC components to facilitate chronic wound healing without the high cost and translational challenges of cell therapies. After incorporation of bioactive factors, the hydrogel foam retained high absorbency, moisture retention, and target water vapor transmission rate. High loading efficiency was confirmed and release studies indicated that over 90% of loaded factors were released within 24 h. Ethylene oxide sterilization and 4-week storage did not affect the bioactive factor release profile or physical properties of the hydrogel foam dressing. Bioactivity retention of the released factors was also confirmed for as-sterilized, 4°C-stored, and -20°C-stored bioactive hydrogel foams as determined by relevant gene expression levels in treated pro-inflammatory (M1) macrophages. These results support the use of the bioactive dressings as an off-the-shelf product. Overall, this work reports a new method to achieve a first-line wound dressing with the potential to reduce persistent inflammation and promote angiogenesis in chronic wounds.

Hydrogel-polyurethane fiber composites with enhanced microarchitectural control for heart valve replacement.

Polymeric heart valves offer the potential to overcome the limited durability of tissue based bioprosthetic valves and the need for anticoagulant therapy of mechanical valve replacement options. However, developing a single-phase material with requisite biological properties and target mechanical properties remains a challenge. In this study, a composite heart valve material was developed where an electrospun mesh provides tunable mechanical properties and a hydrogel coating confers an antifouling surface for thromboresistance. Key biological responses were evaluated in comparison to glutaraldehyde-fixed pericardium. Platelet and bacterial attachment were reduced by 38% and 98%, respectively, as compared to pericardium that demonstrated the antifouling nature of the hydrogel coating. There was also a notable reduction (59%) in the calcification of the composite material as compared to pericardium. A custom 3D-printed hydrogel coating setup was developed to make valve composites for device-level hemodynamic testing. Regurgitation fraction (9.6 ± 1.8%) and effective orifice area (1.52 ± 0.34 cm2 ) met ISO 5840-2:2021 requirements. Additionally, the mean pressure gradient was comparable to current clinical bioprosthetic heart valves demonstrating preliminary efficacy. Although the hemodynamic properties are promising, it is anticipated that the random microarchitecture will result in suboptimal strain fields and peak stresses that may accelerate leaflet fatigue and degeneration. Previous computational work has demonstrated that bioinspired fiber microarchitectures can improve strain homogeneity of valve materials toward improving durability. To this end, we developed advanced electrospinning methodologies to achieve polyurethane fiber microarchitectures that mimic or exceed the physiological ranges of alignment, tortuosity, and curvilinearity present in the native valve. Control of fiber alignment from a random fiber orientation at a normalized orientation index (NOI) 14.2 ± 6.9% to highly aligned fibers at a NOI of 85.1 ± 1.4%. was achieved through increasing mandrel rotational velocity. Fiber tortuosity and curvilinearity in the range of native valve features were introduced through a post-spinning annealing process and fiber collection on a conical mandrel geometry, respectively. Overall, these studies demonstrate the potential of hydrogel-polyurethane fiber composite as a heart valve material. Future studies will utilize the developed advanced electrospinning methodologies in combination with model-directed fabrication toward optimizing durability as a function of fiber microarchitecture.

The accumulation and growth of Pseudomonas aeruginosa on surfaces is modulated by surface mechanics via cyclic-di-GMP signaling.

Attachment of bacteria onto a surface, consequent signaling, and accumulation and growth of the surface-bound bacterial population are key initial steps in the formation of pathogenic biofilms. While recent reports have hinted that surface mechanics may affect the accumulation of bacteria on that surface, the processes that underlie bacterial perception of surface mechanics and modulation of accumulation in response to surface mechanics remain largely unknown. We use thin and thick hydrogels coated on glass to create composite materials with different mechanics (higher elasticity for thin composites; lower elasticity for thick composites) but with the same surface adhesivity and chemistry. The mechanical cue stemming from surface mechanics is elucidated using experiments with the opportunistic human pathogen Pseudomonas aeruginosa combined with finite-element modeling. Adhesion to thin composites results in greater changes in mechanical stress and strain in the bacterial envelope than does adhesion to thick composites with identical surface chemistry. Using quantitative microscopy, we find that adhesion to thin composites also results in higher cyclic-di-GMP levels, which in turn result in lower motility and less detachment, and thus greater accumulation of bacteria on the surface than does adhesion to thick composites. Mechanics-dependent c-di-GMP production is mediated by the cell-surface-exposed protein PilY1. The biofilm lag phase, which is longer for bacterial populations on thin composites than on thick composites, is also mediated by PilY1. This study shows clear evidence that bacteria actively regulate differential accumulation on surfaces of different stiffnesses via perceiving varied mechanical stress and strain upon surface engagement.

Hydroxyapatite nanoparticle-modified porous bone grafts with improved cell attachment.

Emulsion-templated foams have displayed promise as injectable bone grafts; however, the use of a surfactant as an emulsifier resulted in relatively small pores and impedes cell attachment. Hydroxyapatite nanoparticles were explored as an alternative stabilizer to address these limitations. To this end, hydroxyapatite nanoparticles were first modified with myristic acid to generate the appropriate balance of hydrophobicity to stabilize a water-in-oil emulsion of neopentyl glycol diacrylate and 1,4-butanedithiol. In situ surface modification of the resulting foam with hydroxyapatite was confirmed with elemental mapping and transmission electron microscopy. Nanoparticle-stabilized foams displayed improved human mesenchymal stem cell viability (91 ± 5%) over surfactant-stabilized foams (23 ± 11%). Although the pore size was appropriate for bone grafting applications (115 ± 71 µm), the foams lacked the interconnected architecture necessary for cell infiltration. We hypothesized that a co-stabilization approach with both surfactant and nanoparticles could be used to achieve interconnected pores while maintaining improved cell attachment and larger pore sizes. A range of hydroxyapatite nanoparticle and surfactant concentrations were investigated to determine the effects on microarchitecture and cell behavior. By balancing these interactions, a co-stabilized foam was identified that possessed large, interconnected pores (108 ± 67 µm) and improved cell viability and attachment. The co-stabilized foam was then evaluated as an injectable bone graft including network formation, microscale integration with bone, push out strength, and compressive properties. Overall, this work demonstrated that in situ surface modification with nHA improved cell attachment while retaining desirable bone grafting features and injectability.

A user's guide to degradation testing of polyethylene glycol-based hydrogels: From in vitro to in vivo studies.

Poly(ethylene glycol) (PEG)-based hydrogels have gained significant attention in the field of biomedical applications due to their versatility and antifouling properties. Acrylate-derivatized PEG hydrogels (PEGDA) are some of the most widely studied hydrogels; however, there has been debate around the degradation mechanism and predicting resorption rates. Several factors influence the degradation rate of PEG hydrogels, including backbone and endgroup chemistry, macromer molecular weight, and polymer concentration. In addition to hydrogel parameters, it is necessary to understand the influence of biological and environmental conditions (e.g., pH and temperature) on hydrogel degradation. Rigorous methods for monitoring degradation in both in vitro and in vivo settings are also critical to hydrogel design and development. Herein, we provide guidance on tailoring PEG hydrogel chemistry to achieve target hydrolytic degradation kinetics for both resorbable and biostable applications. A detailed overview of accelerated testing methods and hydrogel degradation characterization is provided to aid researchers in experimental design and interpreting in vitro-in vivo correlations necessary for predicting hydrogel device performance.

Interpenetrating network design of bioactive hydrogel coatings with enhanced damage resistance.

Bioactive hydrogel coatings offer a promising route to introduce sustained thromboresistance to cardiovascular devices without compromising bulk mechanical properties. Poly(ethylene glycol)-based hydrogels provide antifouling properties to limit acute thromobosis and incorporation of adhesive ligands can be used to promote endothelialization. However, conventional PEG-based hydrogels at stiffnesses that promote cell attachment can be brittle and prone to damage in a surgical setting, limiting their utility in clinical applications. In this work, we developed a durable hydrogel coating using interpenetrating networks of polyether urethane diacrylamide (PEUDAm) and poly(N-acryloyl glycinamide) (pNAGA). First, diffusion-mediated redox initiation of PEUDAm was used to coat electrospun polyurethane fiber meshes with coating thickness controlled by the immersion time. The second network of pNAGA was then introduced to enhance damage resistance of the hydrogel coating. The durability, thromboresistance, and bioactivity of the resulting multilayer grafts were then assessed. The IPN hydrogel coatings displayed resistance to surgically-associated damage mechanisms and retained the anti-fouling nature of PEG-based hydrogels as indicated by reduced protein adsorption and platelet attachment. Moreover, incorporation of functionalized collagen into the IPN hydrogel coating conferred bioactivity that supported endothelial cell adhesion. Overall, this conformable and durable hydrogel coating provides an improved approach for cardiovascular device fabrication with targeted biological activity.

Bacterial mechanosensing of surface stiffness promotes signaling and growth leading to biofilm formation by Pseudomonas aeruginosa.

The attachment of bacteria onto a surface, consequent signaling, and the accumulation and growth of the surface-bound bacterial population are key initial steps in the formation of pathogenic biofilms. While recent reports have hinted that the stiffness of a surface may affect the accumulation of bacteria on that surface, the processes that underlie bacterial perception of and response to surface stiffness are unknown. Furthermore, whether, and how, the surface stiffness impacts biofilm development, after initial accumulation, is not known. We use thin and thick hydrogels to create stiff and soft composite materials, respectively, with the same surface chemistry. Using quantitative microscopy, we find that the accumulation, motility, and growth of the opportunistic human pathogen Pseudomonas aeruginosa respond to surface stiffness, and that these are linked through cyclic-di-GMP signaling that depends on surface stiffness. The mechanical cue stemming from surface stiffness is elucidated using finite-element modeling combined with experiments - adhesion to stiffer surfaces results in greater changes in mechanical stress and strain in the bacterial envelope than does adhesion to softer surfaces with identical surface chemistry. The cell-surface-exposed protein PilY1 acts as a mechanosensor, that upon surface engagement, results in higher cyclic-di-GMP levels, lower motility, and greater accumulation on stiffer surfaces. PilY1 impacts the biofilm lag phase, which is extended for bacteria attaching to stiffer surfaces. This study shows clear evidence that bacteria actively respond to different stiffness of surfaces where they adhere via perceiving varied mechanical stress and strain upon surface engagement.

PEG-Based Hydrogel Coatings: Design Tools for Biomedical Applications.

Device failure due to undesired biological responses remains a substantial roadblock in the development and translation of new devices into clinical care. Polyethylene glycol (PEG)-based hydrogel coatings can be used to confer antifouling properties to medical devices-enabling minimization of biological responses such as bacterial infection, thrombosis, and foreign body reactions. Application of hydrogel coatings to diverse substrates requires careful consideration of multiple material factors. Herein, we report a systematic investigation of two coating methods: (1) traditional photoinitiated hydrogel coatings; (2) diffusion-mediated, redox-initiated hydrogel coatings. The effects of method, substrate, and compositional variables on the resulting hydrogel coating thickness are presented. To expand the redox-based method to include high molecular weight macromers, a mechanistic investigation of the role of cure rate and macromer viscosity was necessary to balance solution infiltration and gelation. Overall, these structure-property relationships provide users with a toolbox for hydrogel coating design for a broad range of medical devices.

High porosity PEG-based hydrogel foams with self-tuning moisture balance as chronic wound dressings.

A major challenge in chronic wound treatment is maintaining an appropriate wound moisture balance throughout the healing process. Wound dehydration hinders wound healing due to impeded molecule transport and cell migration with associated tissue necrosis. In contrast, wounds that produce excess fluid contain high levels of reactive oxygen species and matrix metalloproteases that impede cell recruitment, extracellular matrix reconstruction, and angiogenesis. Dressings are currently selected based on the relative amount of wound exudate with no universal dressing available that can maintain appropriate wound moisture balance to enhance healing. This work aimed to develop a high porosity poly(ethylene glycol) diacrylate hydrogel foam that can both rapidly remove exudate and provide self-tuning moisture control to prevent wound dehydration. A custom foaming device was used to vary hydrogel foam porosity from 25% to 75% by adjusting the initial air-to-solution volume ratio. Hydrogel foams demonstrated substantial improvements in water uptake volume and rate as compared to bulk hydrogels while maintaining similar hydration benefits with slow dehydration rates. The hydrogel foam with the highest porosity (~75%) demonstrated the greatest water uptake and rate, which outperformed commercial dressing products, Curafoam® and Silvercel®, in water absorption, moisture retention, and exudate management. Investigation of the water vapor transmission rates of each dressing at varied hydration levels was characterized and demonstrated the dynamic moisture-controlling capability of the hydrogel foam dressing. Overall, the self-tuning moisture control of this hydrogel foam dressing holds great promise to improve healing outcomes for both dry and exudative chronic wounds.

Wound swabs versus biopsies to detect methicillin resistant Staphylococcus aureus in experimental equine wounds.

OBJECTIVE: To compare: (1) the load and diversity of cultivatable bacterial species isolated from tissue biopsies with cultures from surface swabs, and (2) the ability of each technique to detect methicillin-resistant Staphylococcus aureus (MRSA) in a model of MRSA-infected equine wounds. STUDY DESIGN: Experimental in vivo study. ANIMALS: Three light-breed adult horses. METHODS: Four 2.5 × 2.5 cm full-thickness skin wounds were created on the dorsolateral aspect of each forelimb. Five days later, each wound was inoculated with a pure culture of MRSA (ATCC 43300). One hundred microlitres of 0, 5 × 108 , 5 × 109 or 5 × 1010 colony forming units (CFU)/ml was used to inoculate each wound. Surface swabs (Levine technique) and tissue biopsy samples (3 mm punch biopsy) were obtained at 2, 7, 14, and 21 days after inoculation. Quantitative aerobic culture was performed using routine clinical techniques. RESULTS: A similar bacterial profile was identified from the culture of each wound-sampling technique and there was moderate correlation (R = 0.49, P < .001) between the bacterial bioburdens. Agreement was fair (κ = 0.31; 95% CI, 0.129-0.505) between the sampling techniques in identification of MRSA. Methicillin-resistant Staphylococcus aureus was isolated more frequently (P = .016) from cultures of tissue biopsies (79%; 76/96) than from surface swabs (62%; 60/96). CONCLUSION: Bacterial load and diversity did not differ between sampling techniques but MRSA was detected more often from the cultures of tissue biopsies. CLINICAL SIGNIFICANCE: Tissue biopsy should be preferred to culture swab in wounds where MRSA is suspected.