Biomaterial Infections Research Articles

Unravelling the physicochemical and antimicrobial mechanisms of human serum albumin/tannic acid coatings for medical-grade polycaprolactone scaffolds

Biofilm-related biomaterial infections are notoriously challenging to treat and can lead to chronic infection and persisting inflammation. To date, a large body of research can be reviewed for coatings which potentially prevent bacterial infection while promoting implant integration. Yet only a very small number has been translated from bench to bedside. This study provides an in-depth analysis of the stability, antibacterial mechanism, and biocompatibility of medical grade polycaprolactone (mPCL), coated with human serum albumin (HSA), the most abundant protein in blood plasma, and tannic acid (TA), a natural polyphenol with antibacterial properties. Molecular docking studies demonstrated that HSA and TA interact mainly through hydrogen-bonding, ionic and hydrophobic interactions, leading to smooth and regular assemblies. In vitro bacteria adhesion testing showed that coated scaffolds maintained their antimicrobial properties over 3 days by significantly reducing S. aureus colonization and biofilm formation. Notably, amplitude modulation-frequency modulation (AMFM) based viscoelasticity mapping and transmission electron microscopy (TEM) data suggested that HSA/TA-coatings cause morphological and mechanical changes on the outer cell membrane of S. aureus leading to membrane disruption and cell death while proving non-toxic to human primary cells. These results support this antibiotic-free approach as an effective and biocompatible strategy to prevent biofilm-related biomaterial infections.

Melimine-Modified 3D-Printed Polycaprolactone Scaffolds for the Prevention of Biofilm-Related Biomaterial Infections.

Biomaterial-associated infections are one of the major causes of implant failure. These infections result from persistent bacteria that have adhered to the biomaterial surface before, during, or after surgery and have formed a biofilm on the implant's surface. It is estimated that 4 to 10% of implant surfaces are contaminated with bacteria; however, the infection rate can be as high as 30% in intensive care units in developed countries and as high as 45% in developing countries. To date, there is no clinical solution to prevent implant infection without relying on the use of high doses of antibiotics supplied systemically and/or removal of the infected device. In this study, melimine, a chimeric cationic peptide that has been tested in Phase I and II human clinical trials, was immobilized onto the surface of 3D-printed medical-grade polycaprolactone (mPCL) scaffolds via covalent binding and adsorption. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectra of melimine-treated surfaces confirmed immobilization of the peptide, as well as its homogeneous distribution throughout the scaffold surface. Amino acid analysis showed that melimine covalent and noncovalent immobilization resulted in a peptide density of ∼156 and ∼533 ng/cm2, respectively. Furthermore, we demonstrated that the immobilization of melimine on mPCL scaffolds by 1-ethyl-3-[3-(dimethylamino)propyl] carbodiimide hydrochloride (EDC) coupling and noncovalent interactions resulted in a reduction of Staphylococcus aureus colonization by 78.7% and 76.0%, respectively, in comparison with the nonmodified control specimens. Particularly, the modified surfaces maintained their antibacterial properties for 3 days, which resulted in the inhibition of biofilm formation in vitro. This system offers a biomaterial strategy to effectively prevent biofilm-related infections on implant surfaces without relying on the use of prophylactic antibiotic treatment.

Polycatecholamine and gentamicin as modifiers for antibacterial and blood-biocompatible polyester vascular prostheses

Polyester (PET) prostheses are commonly used in reconstructive vascular surgery. The most serious complication after implantation is early or late infection of the graft. Therefore, there is high demand to protect prosthesis against bacterial adhesion and biofilm development. For this reason, in this work PET prostheses were first coated by highly adhesive polycatecholamine layer. The grafts were then coupled with gentamicin and studied in relation to morphological and structural properties, biological safety (contact with blood, reaction of vascular endothelial cells (HUVEC), Danio rerio fish), drug release and antibacterial activity. Among two tested catecholamine monomers, L-DOPA was found to be more effective precursor in this process than dopamine. For L-DOPA, assistance of Cu2+, Mg2+ and Na+ ions seems to increase the amount of further immobilized drug. Coated prostheses exhibited greater human endothelial cell proliferation increase and lower cytotoxic effect than uncoated. The modification reduced the hemolysis observed for pristine commercial graft and limited the rate of abnormalities in D. rerio larvae, confirming the safety of the proposed modification. The coating allowed to double the amount of immobilized antibiotic in comparison with uncoated graft which resulted in increased antibacterial activity and reduced bacterial adhesion against 4 bacterial strains prevalent in biomaterials infections. Overall, poly(L-DOPA)-coatings deposited on PET vascular grafts can effectively functionalize these prostheses for higher safety in biomedical applications.

Preparation of protamine-adsorbed calcium phosphate powders and their antibacterial property

ABSTRACT Calcium phosphates are key biomaterials in bone regeneration and dental treatment fields. Biomaterials must exhibit antibacterial properties to ensure protection against microbial infection in implantation frameworks. Various starting calcium phosphate and protamine-adsorbed calcium phosphate powders were prepared in this study to develop novel antimicrobial biomaterials exhibiting the biocompatibility of calcium phosphates and the antimicrobial property of protamine, and their properties were examined. Specifically, hydroxyapatite (HAp) and its precursors – amorphous calcium phosphate (ACP) and octacalcium phosphate (OCP) – were synthesized using the conventional wet process. Moreover, three types of protamine-adsorbed calcium phosphate powders (ACP-Protamine, OCP-Protamine, and HAp-Protamine) were prepared via adsorption of protamine (25.2, 5.28, and 19.2 mg·g−1, respectively) on the starting calcium phosphate powders in water for 48 h. The antimicrobial property of the protamine-adsorbed calcium phosphate powders against Staphylococcus aureus, a representative bacterium that causes implantation-related infection of biomaterials, was evaluated. All the examined protamine-adsorbed calcium phosphate powders exhibited antibacterial properties and, therefore, show promise as effective antimicrobial biomaterials.

Surface-Modifying Effect of Zwitterionic Polyurethane Oligomers Complexed with Metal Ions on Blood Compatibility.

To prevent unsolved problems of medical devices, we hypothesized that combinatorial effects of zwitterionic functional group and anti-bacterial metal ions can reduce effectively the thrombosis and bacterial infection of polymeric biomaterials. In this research, we designed a novel series of zwitterionic polyurethane (zPU) additives to impart anti-thrombotic properties to a polyvinyl chloride (PVC) matrix. We have synthesized zPUs by combination of various components and zPUs complexed with metal ions. Zwitterion group was prepared by reaction with 1,3-propane sultone and Nmethyldiethanolamine and metal ions were incorporated into sulfobetaine chains via molecular complexation. These zPU additives were characterized using FT-IR, 1H-NMR, elemental analysis, and thermal analysis. The PVC film blended with zPU additives were prepared by utilizing a solvent casting and hot melting process. Water contact angle demonstrated that the introduction of zwitterion group has improved hydrophilicity of polyurethanes dramatically. Protein adsorption test resulted in improved anti-fouling effects dependent on additive concentration and decreases in their effects by metal complexation. Platelet adhesion test revealed anti-fouling effects by additive blending but not significant as compared to protein resistance results. With further studies, the synthesized zPUs and zPUs complexed with metal ions are expected to be used as good biomaterials in biomedical fields. Based on our results, we can carefully estimate that the enhanced anti-fouling effect contributed to reduced platelet adhesion. Schematic explanation of the effect of zwitterionic polyurethane additives for blood-compatible and anti-bacterial bulk modification.

Construction and Characterizations of Antibacterial Surfaces Based on Self-Assembled Monolayer of Antimicrobial Peptides (Pac-525) Derivatives on Gold

Background: Infection that is related to implanted biomaterials is a serious issue in the clinic. Antimicrobial peptides (AMPs) have been considered as an ideal alternative to traditional antibiotic drugs, for the treatment of infections, while some problems, such as aggregation and protein hydrolysis, are still the dominant concerns that compromise their antimicrobial efficiency in vivo. Methods: In this study, antimicrobial peptides underwent self-assembly on gold substrates, forming good antibacterial surfaces, with stable antibacterial behavior. The antimicrobial ability of AMPs grafted on the surfaces, with or without glycine spaces or a primer layer, was evaluated. Results: Specifically, three Pac-525 derivatives, namely, Ac-CGn-KWRRWVRWI-NH2 (n = 0, 2, or 6) were covalently grafted onto gold substrates via the self-assembling process for inhibiting the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Furthermore, the alkanethiols HS(CH)10SH were firstly self-assembled into monolayers, as a primer layer (SAM-SH) for the secondary self-assembly of Pac-525 derivatives, to effectively enhance the bactericidal performance of the grafted AMPs. The -(CH)10-S-S-G6Pac derivative was highly effective against S. aureus and E. coli, and reduced the viable amount of E. coli and S. aureus to 0.4% and 33.2%, respectively, after 24 h of contact. In addition, the immobilized AMPs showed good biocompatibility, promoting bone marrow stem cell proliferation. Conclusion: the self-assembled monolayers of the Pac-525 derivatives have great potential as a novel therapeutic method for the treatment of implanted biomaterial infections.

Antimicrobial Potential of Strontium Hydroxide on Bacteria Associated with Peri-Implantitis

Background: Peri-implantitis due to infection of dental implants is a common complication that may cause significant patient morbidity. In this study, we investigated the antimicrobial potential of Sr(OH)2 against different bacteria associated with peri-implantitis. Methods: The antimicrobial potential of five concentrations of Sr(OH)2 (100, 10, 1, 0.1, and 0.01 mM) was assessed with agar diffusion test, minimal inhibitory concentration (MIC), and biofilm viability assays against six bacteria commonly associated with biomaterial infections: Streptococcus mitis, Staphylococcus epidermidis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Escherichia coli, and Fusobacterium nucleatum. Results: Zones of inhibition were only observed for, 0.01, 0.1, and 1 mM of Sr(OH)2 tested against P. gingivalis, in the agar diffusion test. Growth inhibition in planktonic cultures was achieved at 10 mM for all species tested (p < 0.001). In biofilm viability assay, 10 and 100 mM Sr(OH)2 showed potent bactericidal affect against S. mitis, S. epidermidis, A. actinomycetemcomitans, E. coli, and P. gingivalis. Conclusions: The findings of this study indicate that Sr(OH)2 has antimicrobial properties against bacteria associated with peri-implantitis.

Effect of pre-existing diseases on COVID-19 infection and role of new sensors and biomaterials for its detection and treatment.

The entire world is suffering from a new type of viral disease, occurred by severe acute respiratory syndrome coronavirus‐2 (SARS‐CoV‐2). The present article briefly discussed the genome sequencing and interaction of host cells with SARS‐CoV‐2. The influence of pre‐existing diseases such as diabetes, heart disease and age of the patients on COVID‐19 infection is reviewed. The possible treatments of SARS‐CoV‐2 including antiviral drugs, Chinese traditional treatment and plasma therapy are elaborately discussed. The proper vaccine for COVID‐19 is not available till date. However, the trials of pre‐existing antiviral vaccines such as, chloroquine/hydroxychloroquine, remdesivir, ritonavir and lopinavir and their consequences are briefly presented. Further, the importance of new materials and devices for the detection and treatment of COVID‐19 has also been reviewed. The polymerase chain reaction (PCR)‐based, and non‐PCR based devices are used for the detection of COVID‐19 infection. The non‐PCR based devices provide rapid results as compared to PCR based devices.

Potential Application of Protamine for Antimicrobial Biomaterials in Bone Tissue Engineering.

Bacterial infection of biomaterials is a serious problem in the field of medical devices. It is urgently necessary to develop new biomaterials with bactericidal activity. Antimicrobial peptides and proteins (AMPs), alternative antibacterial agents, are expected to overcome the bacterial resistance. The aim of this study was to develop a new intelligent material in bone tissue engineering based on protamine-loaded hydroxyapatite (protamine/HAp) that uses AMPs rather than antibiotics. It was found that the adsorption of protamine to HAp followed the Langmuir adsorption model and was due to electrostatic and/or hydrophobic interactions. In vitro bacterial adhesion and growth on protamine/HAp was inhibited in a protamine dose-dependent manner. Adherent bacteria exhibited an aberrant morphology for high dosages of protamine/HAp, resulting in the formation of large aggregates and disintegration of the membrane. The released protamine from protamine/HAp also prevented the growth of planktonic bacteria in vitro. However, a high dosage of protamine from powders at loading concentrations over 1000 μg·mL−1 induced a cytotoxic effect in vitro, although those exhibited no apparent cytotoxicity in vivo. These data revealed that protamine/HAp (less than 1000 μg·mL−1) had both antimicrobial activity and biocompatibility and can be applied for bone substitutes in orthopedic fields.

Role of 4-Hexylresorcinol in the Field of Tissue Engineering

4-hexylresorcinol (4-HR), as a derivative of phenolic lipids, has biological and pharmacological properties that are beneficial when used with a biomaterial. It has antimicrobial and antiseptic activity and can thus prevent contamination and infection of biomaterials. 4-HR suppresses the nuclear factor kappa B (NF-κB) signaling pathway related to osteoclast differentiation. The suppression of NF-κB increases the bone formation marker and contributes to new bone formation. The tumor necrosis factor-α (TNF-α) is a pro-inflammatory cytokine produced by macrophages and suppressed by 4-HR. Suppression of TNF-α decreases osteoclast activity and promotes wound healing. 4-HR increases the vascular endothelial growth factor and has an anti-thrombotic effect. When incorporated into silk vascular patches, it promotes endothelium wound healing. Recently, 4-HR has exhibited biological properties and has been successfully incorporated into various biomaterials. Consequently, it is a useful pharmacological chemical that can be used with biomaterials in the field of tissue engineering.

Multifunctional Coatings and Nanotopographies: Toward Cell Instructive and Antibacterial Implants.

In biomaterials science, it is nowadays well accepted that improving the biointegration of dental and orthopedic implants with surrounding tissues is a major goal. However, implant surfaces that support osteointegration may also favor colonization of bacterial cells. Infection of biomaterials and subsequent biofilm formation can have devastating effects and reduce patient quality of life, representing an emerging concern in healthcare. Conversely, efforts toward inhibiting bacterial colonization may impair biomaterial-tissue integration. Therefore, to improve the long-term success of medical implants, biomaterial surfaces should ideally discourage the attachment of bacteria without affecting eukaryotic cell functions. However, most current strategies seldom investigate a combined goal. This work reviews recent strategies of surface modification to simultaneously address implant biointegration while mitigating bacterial infections. To this end, two emerging solutions are considered, multifunctional chemical coatings and nanotopographical features.

Prevention of Biomaterial Infection by Pre-Operative Incubation with Human Cells.

Cells of tissues and biofilm forming bacteria compete for the living space on the surface of an implant. We hypothesized the incubation of the implant (titanium, polydimethylsiloxane, and polystyrene surface) with human cells before implantation as a strategy to prevent bacterial adhesion and biofilm formation. After 24 hours of incubation with human osteogenic sarcoma SaOS-2 cells (1 × 105 cells/mL), the materials were incubated for 4.5 hours or two days with Staphylococcus aureus in serial 1:10 dilutions of 108 colony-forming units/mL. The bacterial adherence and biofilm biomass on materials pre-incubated with SaOS-2 cells were compared with our previous results on materials incubated only with bacteria or in simultaneous co-culture of SaOS-2 cells and S. aureus. Fluorescent microscopy and crystal violet stain were used. The number of viable SaOS-2 and bacterial cells present was tested using colorimetric methods (MTT, LDH) and drop plate method, respectively. The pre-treatment with human cells was associated with a reduction of bacterial colonization of the biomaterial at 4.5 hours and 48 hours compared with the non-pre-treated materials. The presence of bacteria decreased the number of viable human cells on all materials. ( Supplementary Fig. 1 ; see online supplementary materials at www.liebertpub.com/sur ). These results suggest that the pre-operative incubation of prostheses with host cells could prevent infection of biomaterials.

Multicenter, Prospective, Longitudinal Study of the Recurrence, Surgical Site Infection, and Quality of Life After Contaminated Ventral Hernia Repair Using Biosynthetic Absorbable Mesh: The COBRA Study.

Objective:The aim of the study was to evaluate biosynthetic absorbable mesh in single-staged contaminated (Centers for Disease Control class II and III) ventral hernia (CVH) repair over 24 months.Background:CVH has an increased risk of postoperative infection. CVH repair with synthetic or biologic meshes has reported chronic biomaterial infections and high hernia recurrence rates.Methods:Patients with a contaminated or clean-contaminated operative field and a hernia defect at least 9 cm2 had a biosynthetic mesh (open, sublay, retrorectus, or intraperitoneal) repair with fascial closure (n = 104). Endpoints included overall Kaplan-Meier estimates for hernia recurrence and postoperative wound infection rates at 24 months, and the EQ-5D and Short Form 12 Health Survey (SF-12). Analyses were conducted on the intent-to-treat population, and health outcome measures evaluated using paired t tests.Results:Patients had a mean age of 58 years, body mass index of 28 kg/m2, 77% had contaminated wounds, and 84% completed 24-months follow-up. Concomitant procedures included fistula takedown (n = 24) or removal of infected previously placed mesh (n = 29). Hernia recurrence rate was 17% (n = 16). At the time of CVH repair, intraperitoneal placement of the biosynthetic mesh significantly increased the risk of recurrences (P ≤ 0.04). Surgical site infections (19/104) led to higher risk of recurrence (P < 0.01). Mean 24-month EQ-5D (index and visual analogue) and SF-12 physical component and mental scores improved from baseline (P < 0.05).Conclusions:In this prospective longitudinal study, biosynthetic absorbable mesh showed efficacy in terms of long-term recurrence and quality of life for CVH repair patients and offers an alternative to biologic and permanent synthetic meshes in these complex situations.

Protein adsorption, platelet adhesion, and bacterial adhesion to polyethylene-glycol-textured polyurethane biomaterial surfaces.

Traditional strategies for surface modification to enhance the biocompatibility of biomaterials often focus on a single route utilizing either chemical or physical approaches. This study combines the chemical and physical treatments as applied to poly(urethane urea) (PUU) biomaterials to enhance biocompatibility at the interface for inhibiting platelet-related thrombosis or bacterial adhesion-induced microbial infections. PUU films were first textured with submicron patterns by a soft lithography two-stage replication process, and then were grafted with polyethylene glycol (PEG). A series of biological response experiments including protein adsorption, platelet adhesion/activation, and bacterial adhesion/biofilm formation showed that PEG-grafted submicron textured biomaterial surfaces were resistant to protein adsorption, and greatly increased the efficiency in reducing both platelet adhesion/activation and bacterial adhesion/biofilm formation due to the additive effects of physical topography and grafted PEG. Results suggest that a combination of chemical modification and surface texturing will be more efficient in preventing biomaterial-associated thrombosis and infection of biomaterials. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 668-678, 2017.

The effect of silver or gallium doped titanium against the multidrug resistant Acinetobacter baumannii

Implant-related infection of biomaterials is one of the main causes of arthroplasty and osteosynthesis failure. Bacteria, such as the rapidly-emerging Multi Drug Resistant (MDR) pathogen Acinetobacter Baumannii, initiate the infection by adhering to biomaterials and forming a biofilm. Since the implant surface plays a crucial role in early bacterial adhesion phases, titanium was electrochemically modified by an Anodic Spark Deposition (ASD) treatment, developed previously and thought to provide osseo-integrative properties. In this study, the treatment was modified to insert gallium or silver onto the titanium surface, to provide antibacterial properties.The material was characterized morphologically, chemically, and mechanically; biological properties were investigated by direct cytocompatibility assay, Alkaline Phosphatase (ALP) activity, Scanning Electron Microscopy (SEM), and Immunofluorescent (IF) analysis; antibacterial activity was determined by counting Colony Forming Units, and viability assay.The various ASD-treated surfaces showed similar morphology, micrometric pore size, and uniform pore distribution. Of the treatments studied, gallium-doped specimens showed the best ALP synthesis and antibacterial properties.This study demonstrates the possibility of successfully doping the surface of titanium with gallium or silver, using the ASD technique; this approach can provide antibacterial properties and maintain high osseo-integrative potential.

Anti-biofilm activity of ultrashort cinnamic acid peptide derivatives against medical device-related pathogens.

The threat of antimicrobial resistance has placed increasing emphasis on the development of innovative approaches to eradicate multidrug-resistant pathogens. Biofilm-forming microorganisms, for example, Staphylococcus epidermidis and Staphylococcus aureus, are responsible for increased incidence of biomaterial infection, extended hospital stays and patient morbidity and mortality. This paper highlights the potential of ultrashort tetra-peptide conjugated to hydrophobic cinnamic acid derivatives. These peptidomimetic molecules demonstrate selective and highly potent activity against resistant biofilm forms of Gram-positive medical device-related pathogens. 3-(4-Hydroxyphenyl)propionic)-Orn-Orn-Trp-Trp-NH2 displays particular promise with minimum biofilm eradication concentration (MBEC) values of 125 µg/ml against methicillin sensitive (ATCC 29213) and resistant (ATCC 43300) S. aureus and activity shown against biofilm forms of Escherichia coli (MBEC: 1000 µg/ml). Kill kinetics confirms complete eradication of established 24-h biofilms at MBEC with 6-h exposure. Reduced cell cytotoxicity, relative to Gram-positive pathogens, was proven via tissue culture (HaCaT) and haemolysis assays (equine erythrocytes). Existing in nature as part of the immune response, antimicrobial peptides display great promise for exploitation by the pharmaceutical industry in order to increase the library of available therapeutic molecules. Ultrashort variants are particularly promising for translation as clinical therapeutics as they are more cost-effective, easier to synthesise and can be tailored to specific functional requirements based on the primary sequence allowing factors such as spectrum of activity to be varied.

Development of a standardized and safe airborne antibacterial assay, and its evaluation on antibacterial biomimetic model surfaces.

Bacterial infection of biomaterials is a major concern in medicine, and different kinds of antimicrobial biomaterial have been developed to deal with this problem. To test the antimicrobial performance of these biomaterials, the airborne bacterial assay is used, which involves the formation of biohazardous bacterial aerosols. We here describe a new experimental set-up which allows safe handling of such pathogenic aerosols, and standardizes critical parameters of this otherwise intractable and strongly user-dependent assay. With this new method, reproducible, thorough antimicrobial data (number of colony forming units and live-dead-stain) was obtained. Poly(oxonorbornene)-based Synthetic Mimics of Antimicrobial Peptides (SMAMPs) were used as antimicrobial test samples. The assay was able to differentiate even between subtle sample differences, such as different sample thicknesses. With this new set-up, the airborne bacterial assay was thus established as a useful, reliable, and realistic experimental method to simulate the contamination of biomaterials with bacteria, for example in an intraoperative setting.

Characterization and Activity of an Immobilized Antimicrobial Peptide Containing Bactericidal PEG-Hydrogel

A single step immobilization-polymerization strategy of a highly active antimicrobial peptide into a soft hydrogel network on a poly(ethylene terephthalate) surface using thiol-ene chemistry is described. The bactericidal hydrogel was molecularly characterized via Coomassie and Lowry assay protein staining agents as well as by X-ray photoelectron spectroscopy. The bactericidal activity was established against Staphylococcus aureus and Staphylococcus epidermidis, two bacterial strains commonly associated with biomaterial infections. To gain further insight into the biological stability, the hydrogels were incubated with human serum prior to activity testing without loss of activity. These studies revealed a promising bactericidal hydrogel with good stability under physiological conditions.

Ultrashort cationic naphthalene-derived self-assembled peptides as antimicrobial nanomaterials.

Self-assembling dipeptides conjugated to naphthalene show considerable promise as nanomaterial structures, biomaterials, and drug delivery devices. Biomaterial infections are responsible for high rates of patient mortality and morbidity. The presence of biofilm bacteria, which thrive on implant surfaces, are a huge burden on healthcare budgets, as they are highly resistant to current therapeutic strategies. Ultrashort cationic self-assembled peptides represent a highly innovative and cost-effective strategy to form antibacterial nanomaterials. Lysine conjugated variants display the greatest potency with 2% w/v NapFFKK hydrogels significantly reducing the viable Staphylococcus epidermidis biofilm by 94%. Reducing the size of the R-group methylene chain on cationic moieties resulted in reduction of antibiofilm activity. The primary amine of the protruding R-group tail may not be as readily available to interact with negatively charged bacterial membranes. Cryo-SEM, FTIR, CD spectroscopy, and oscillatory rheology provided evidence of supramolecular hydrogel formation at physiological pH (pH 7.4). Cytotoxicity assays against murine fibroblast (NCTC 929) cell lines confirmed the gels possessed reduced cytotoxicity relative to bacterial cells, with limited hemolysis upon exposure to equine erythrocytes. The results presented in this paper highlight the significant potential of ultrashort cationic naphthalene peptides as future biomaterials.

A zebrafish high throughput screening system used for Staphylococcus epidermidis infection marker discovery

BackgroundStaphylococcus epidermidis bacteria are a major cause of biomaterial-associated infections in modern medicine. Yet there is little known about the host responses against this normally innocent bacterium in the context of infection of biomaterials. In order to better understand the factors involved in this process, a whole animal model with high throughput screening possibilities and markers for studying the host response to S. epidermidis infection are required.ResultsWe have used a zebrafish yolk injection system to study bacterial proliferation and the host response in a time course experiment of S. epidermidis infection. By combining an automated microinjection system with complex object parametric analysis and sorting (COPAS) technology we have quantified bacterial proliferation. This system was used together with transcriptome analysis at several time points during the infection period. We show that bacterial colony forming unit (CFU) counting can be replaced by high throughput flow-based fluorescence analysis of embryos enabling high throughput readout. Comparison of the host transcriptome response to S. epidermidis and Mycobacterium marinum infection in the same system showed that M. marinum has a far stronger effect on host gene regulation than S. epidermidis. However, multiple genes responded differently to S. epidermidis infection than to M. marinum, including a cell adhesion gene linked to specific infection by staphylococci in mammals.ConclusionsOur zebrafish embryo infection model allowed (i) quantitative assessment of bacterial proliferation, (ii) identification of zebrafish genes serving as markers for infection with the opportunistic pathogen S. epidermidis, and (iii) comparison of the transcriptome response of infection with S. epidermidis and with the pathogen M. marinum. As a result we have identified markers that can be used to distinguish common and specific responses to S. epidermidis. These markers enable the future integration of our high throughput screening technology with functional analyses of immune response genes and immune modulating factors.