[show abstract][hide abstract] ABSTRACT: Thin film surface nanostructures of semicrystalline diblock copolymer are promising for the fabrication of photonic crystals and bioanalytical devices because they might be tailorable by controlled crystallization. One approach to systematically control polymer crystallization is a self-nucleation experiment. The self-nucleation experiment for block copolymers has only been reported for the bulk and so far not for thin films. Considering the versatility of a tailorable surface nanostructure, it is promising to apply the controlled crystallization of a bulk self-nucleation experiment to thin films of a diblock copolymer. In the current study we tested the hypothesis that within two self-nucleation experiments, i.e., in the bulk and thin film, the calorimetric bulk properties of a polybutadiene-block-poly(ethylene oxide) can be correlated to the resulting thin film surface nanostructures and to understand as well as predict their formation. The calorimetric bulk properties measured by differential scanning calorimetry in the bulk self-nucleation experiment were correlated to surface nanostructures measured by atomic force microscopy of the thin film self-nucleation experiment samples. In analogy to the bulk self-nucleation experiment, we introduced a crystalline standard for the thin film self-nucleation experiment where the crystalline lamellae consisted of once-folded chains. Annealing the thin film crystalline standard promoted the thickening of crystalline lamellae on the film surface which is explained by the formation of less folded chain crystals that obtain higher melting temperatures. The crystalline lamellae thickness was steplessly variable within the range of 8–16 nm. In analogy to the Hoffman–Weeks and Gibbs–Thomson plots, we derived a function which can be used to predict the lamellae thickness as a function of the annealing temperature. Bulk and thin film self-nucleation experiments were successfully related, since thin film surface nanostructures were consistently correlated to calorimetric results. We established the dual self-nucleation experiment as a powerful tool to predictably tailor thin film nanostructures in the range of several nanometers.
[show abstract][hide abstract] ABSTRACT: Biomaterials-associated infections are primarily initiated by the adhesion of microorganisms on the biomaterial surfaces and subsequent biofilm formation. Understanding the fundamental microbial adhesion mechanisms and biofilm development is crucial for developing strategies to prevent such infections. Suitable in vitro systems for biofilm cultivation and bacterial adhesion at controllable, constant and reproducible conditions are indispensable. This study aimed (i) to modify the previously described constant-depth film fermenter for the reproducible cultivation of biofilms at non-depth-restricted, constant and low shear conditions and (ii) to use this system to elucidate bacterial adhesion kinetics on different biomaterials, focusing on biomaterials surface nanoroughness and hydrophobicity. Chemostat-grown Escherichia coli were used for biofilm cultivation on titanium oxide and investigating bacterial adhesion over time on titanium oxide, poly(styrene), poly(tetrafluoroethylene) and glass. Using chemostat-grown microbial cells (single-species continuous culture) minimized variations between the biofilms cultivated during different experimental runs. Bacterial adhesion on biomaterials comprised an initial lag-phase I followed by a fast adhesion phase II and a phase of saturation III. With increasing biomaterials surface nanoroughness and increasing hydrophobicity, adhesion rates increased during phases I and II. The influence of materials surface hydrophobicity seemed to exceed that of nanoroughness during the lag-phase I, whereas it was vice versa during adhesion phase II. This study introduces the non-constant-depth film fermenter in combination with a chemostat culture to allow for a controlled approach to reproducibly cultivate biofilms and to investigate bacterial adhesion kinetics at constant and low shear conditions. The findings will support developing and adequate testing of biomaterials surface modifications eventually preventing biomaterial-associated infections.
PLoS ONE 01/2014; 9(1):e84837. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Background: Certain coatings such as titanium may improve the biocompatibility of hernia meshes. The coating with biopolymers such as polyethylenimine (PEI) can also improve the material characteristics of implants. This approach has, however, not yet been explored. Thus, it was the aim of the present work to clarify if and how hernia meshes with their three-dimensional structure can be successfully coated with PEI and with which technique this coating can be best analysed. Methods: Commercially available meshes made from polypropylene, polyester and ePTFE have been coated with PEI. The coating was analysed via cell proliferation test (mouse fibroblasts), electron microscopy, X-ray photoelectron spectroscopy (XPS) and fluorescence microscopy. Cell viability and cytotoxicity were tested by the MTT test. Results: With the PEI surface modification, mouse fibroblasts grow faster and in greater numbers on the mesh surface. XPS as well as fluorescence microscopy show weaknesses in their applicability and meaningfulness because of the three-dimensional mesh structure while XPS showed overall better results. Optical proof in the electron microscope after cell fixation was not unambiguously accomplished with the techniques used here. In the MTT test, no cellular damage from the PEI coating was detected after 24 hours. Conclusion: The present results show for the first time that PEI coating of hernia meshes is possible and effective. The PEI coating can be achieved in a fast and cost-efficient way. Further investigations are necessary with respect to coating quality and cytotoxicity before such a coating may be used in the clinical routine. In conclusion, PEI is a promising polymer that warrants further research as a coating for medical implants.
Zentralblatt für Chirurgie 12/2013; · 0.69 Impact Factor
[show abstract][hide abstract] ABSTRACT: Aligned multi-wall carbon nanotube (MWCNT)/polymer composite films were created in a one-step process. 5 wt% MWCNT/semi-crystalline polymer composite films of approximately 100nm thickness were obtained by melt-drawing. The matrix polymers were isotactic polypropylene (iPP), poly(1-butene) (PB-1) and high density polyethylene (HDPE). Transmission electron microscopy (TEM) investigations revealed an exceptionally high degree of local MWCNT alignment with an angular deviation of <10°<10° (HDPE) and <20°<20° (iPP and PB-1) parallel to the films’ drawing direction for a broad range of drawing velocities. For HDPE, the lamellar polymer-crystals at the interface between the MWCNT and the polymer film were identified as the nano-hybrid shish-kebab morphology by selected area electron diffraction. Based on the direct visualization of the MWCNT disentanglement process in the TEM, a polymer physics-based model for the unraveling of MWCNT entanglements, a source of aligned MWCNTs, is proposed that explains differences in MWCNT alignment encountered for different matrix polymers. The melt-drawing mediated MWCNT alignment provides both an innovative approach for the fabrication of applicable MWCNT containing films and a versatile tool for studying the interface in MWCNT/polymer composites.
[show abstract][hide abstract] ABSTRACT: The surface topography is of great importance for the biological performance of titanium based implants
since it may influence the initial adsorption of proteins, cell response, as well as microbial adhesion.
A recently described technique for the preparation of titanium thin films with an adjustable surface
roughness on the nanometer scale is the physical vapor deposition (PVD). The aims of this study were
to statistically evaluate the reproducibility of nanorough titanium thin films prepared by PVD using an
atomic force microscopy (AFM) based approach, to test the microbial adhesion in dependence of the
nanoscale surface roughness and to critically discuss the parameters used for the characterization of the
titanium surfaces with respect to AFM microscope settings. No statistically significant differences were
found between the surface nanoroughnesses of the PVD prepared titanium thin films. With increasing
surface nanoroughness, the coverage by Escherichia coli decreased and the microbial cells were increasingly patchy distributed. The calculated roughness values significantly increased with increasing AFM
scan size, while image resolution and pixel density had no influence on this effect. Our study shows that
PVD is a suitable tool to reproducibly prepare titanium thin films with a well-defined surface topography
on the nanometer scale. These surfaces are, thus, a suitable 2D model system for studies addressing the
interaction between surface nanoroughness and the biological system. First results show that surface
roughness even on the very low nanometer scale has an influence on bacterial adhesion behavior. These
findings give new momentum to biomaterials research and will support the development of biomaterials
surfaces with anti-infectious surface properties.
[show abstract][hide abstract] ABSTRACT: OBJECTIVE: Bacteria persisting in the root canal system may thwart endodontic therapy. It is therefore interesting to know whether clinically available root canal sealers have an antimicrobial effect. The objective of the present in vitro study was to investigate the antibacterial effect of various sealers on the endodontologically detectable species Enterococcus faecalis (E. faecalis), Fusobacterium nucleatum (F. nucleatum) and Porphyromonas gingivalis (P. gingivalis). METHODS: The antibacterial effectiveness of the sealers was tested by means of the agar diffusion test (ADT) and the direct contact test (DCT). Eight different sealers (AH Plus(®), Hermetic(®), RoekoSeal(®), Sealapex(®), Apexit Plus(®), 2Seal(®), EndoREZ(®) and ProRoot MTA(®)) and two temporary sealers (Calxyl(®) and Gangraena Merz(®)) were tested. At first, 100μl of bacterial suspension (BS) of each individual micro-organism (optical density (OD) 0.5) was applied separately to Schaedler agar plates for the ADT. Subsequently, freshly mixed and set sealer was applied. After 48h of incubation, the inhibition zones were measured. Further, 18mg of sealer were put into each well of 48-well cell culture plates and overlaid with 400μl of Schaedler liquid medium and 100μl of BS (OD 0.5) in monoculture. Bacterial growth was determined by the DCT from the optical density of the liquid by photospectrometry after 2, 4, 6, 8, 10, 12 and 24h. RESULTS: For the application, the sealer Hermetic(®), a significant suppression of the species E. faecalis, F. nucleatum and P. gingivalis was detected in both the ADT and the DCT. AH Plus(®) showed a suppressive effect on E. faecalis and F. nucleatum in the DCT. With all other sealers tested, E. faecalis was not suppressible. RoekoSeal(®), Calxyl(®) and Gangraena-Merz(®) showed no antibacterial effect on the tested species whatsoever. SIGNIFICANCE: We have shown in both ADT and DCT that some root canal sealers suppress the growth of E. faecalis in vitro.
Dental materials: official publication of the Academy of Dental Materials 03/2013; · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: OBJECTIVES: The majority of modern resin-based oral restorative biomaterials are cured via photopolymerization processes. A variety of light sources are available for this light curing of dental materials, such as composites or fissure sealants. Quartz-tungsten-halogen (QTH) light curing units (LCUs) have dominated light curing of dental materials for decades and are now almost entirely replaced by modern light emitting diode light curing units (LED LCUs). Exactly 50 years ago, visible LEDs were invented. Nevertheless, it was not before the 1990s that LEDs were seriously considered by scientists or manufactures of commercial LCUs as light sources to photopolymerize dental composites and other dental materials. The objective of this review paper is to give an overview of the scientific development and state-of-the-art of LED photopolymerization of oral biomaterials. METHODS: The materials science of LED LCU devices and dental materials photopolymerized with LED LCU, as well as advantages and limits of LED photopolymerization of oral biomaterials, are discussed. This is mainly based on a review of the most frequently cited scientific papers in international peer reviewed journals. The developments of commercial LED LCUs as well as aspects of their clinical use are considered in this review. RESULTS: The development of LED LCUs has progressed in steps and was made possible by (i) the invention of visible light emitting diodes 50 years ago; (ii) the introduction of high brightness blue light emitting GaN LEDs in 1994; and (iii) the creation of the first blue LED LCUs for the photopolymerization of oral biomaterials. The proof of concept of LED LCUs had to be demonstrated by the satisfactory performance of resin based restorative dental materials photopolymerized by these devices, before LED photopolymerization was generally accepted. Hallmarks of LED LCUs include a unique light emission spectrum, high curing efficiency, long life, low energy consumption and compact device form factor. SIGNIFICANCE: By understanding the physical principles of LEDs, the development of LED LCUs, their strengths and limitations and the specific benefits of LED photopolymerization will be better appreciated.
Dental materials: official publication of the Academy of Dental Materials 03/2013; · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: The propagation of the Click-reaction concept in synthetic chemistry, particularly the Cu-catalyzed cycloaddition between azides and alkynes, led to numerous applications in materials science, bio-, medicinal, and polymer chemistry. Often copper salts or complexes are applied as catalysts. In the present case those have been replaced by heterogeneous catalysts using porous glasses as support materials. Loading the supports with Cu using wet-impregnation technique led to Cu-loadings of 80% on theoretical basis, whereas other support materials revealed lower metal loads. Characterization of the catalyst morphology by SEM identified Cu-agglomerates at the surface. A 2 eV-shift of the binding energy of the Cu 2p core levels in the catalysts’ XPS spectra and the disappearance of satellite peaks led to the assumption that reduction of Cu(II) to Cu(I) or Cu(0) occurred during catalyst application. Indeed, working without a reducing agent (sodium ascorbate) resulted in decreased catalyst activity regarding the model reaction. The microwave-assisted cycloaddition of benzyl azide with phenylacetylene in water led to full conversion after 10 or 20 min at 120 or 100 °C, respectively. Reaction is characterized by excellent regioselectivity forming the 1,4-triazole almost exclusively. Optimization of the reaction conditions with respect to time and catalyst loading affords maximal TOF >635 h−1. Recycling studies revealed that up to four reapplications of the catalyst are possible without lost of activity.
[show abstract][hide abstract] ABSTRACT: We synthesized nano-scaled periodic ripple patterns on silicon and titanium dioxide (TiO(2)) surfaces by xenon ion irradiation, and performed adsorption experiments with human plasma fibrinogen (HPF) on such surfaces as a function of the ripple wavelength. Atomic force microscopy showed the adsorption of HPF in mostly globular conformation on crystalline and amorphous flat Si surfaces as well as on nano-structured Si with long ripple wavelengths. For short ripple wavelengths the proteins seem to adsorb in a stretched formation and align across or along the ripples. In contrast to that, the proteins adsorb in a globular assembly on flat and long-wavelength rippled TiO(2), but no adsorbed proteins could be observed on TiO(2) with short ripple wavelengths due to a decrease of the adsorption energy caused by surface curvature. Consequently, the adsorption behavior of HPF can be tuned on biomedically interesting materials by introducing a nano-sized morphology while not modifying the stoichiometry/chemistry.
[show abstract][hide abstract] ABSTRACT: One key for the successful integration of implants into the human body is the control of protein adsorption by adjusting surface properties at different length scales. This is particularly important for titanium oxide constituting one of the most common biomedical interfaces. As for titania (TiO(2)) the interface is largely defined by its crystal surface structure it is crucial to understand how the surface crystallinity affects the structure, properties and function of protein layers mediating the subsequent biological reaction. For rutile TiO(2) we demonstrate that the conformation and relative amount of human plasma fibrinogen (HPF) and the structure of adsorbed HPF layers depend on the crystal surface nanostructure by employing thermally etched multi-faceted TiO(2) surfaces. Thermal etching of polycrystalline TiO(2) facilitates a nanoscale crystal faceting and, thus, the creation of different surface nanostructures on a single specimen surface. Atomic force microscopy shows that HPF arranges into networks and thin globular layers on flat and irregular crystal grain surfaces, respectively. On a third, faceted category we observed an alternating conformation of HPF on neighboring facets. The bulk grain orientation obtained from electron back scatter diffraction and thermodynamic mechanisms of surface reconstruction during thermal etching suggest the grain and facet surface specific arrangement and relative amount of adsorbed proteins to depend on the associated on-site free crystal surface energy. Implications for potentially favorable TiO(2) crystal facets regarding the inflammatory response and hemostasis are discussed in view of an advanced surface design of future implants.
[show abstract][hide abstract] ABSTRACT: Advances have been achieved in the design and biomechanical performance of orthopedic implants in the last decades. These include anatomically shaped and angle-stable implants for fracture fixation or improved biomaterials (e.g. ultra-high-molecular-weight polyethylene) in total joint arthroplasty. Future modifications need to address the biological function of implant surfaces. Functionalized surfaces can promote or reduce osseointegration, avoid implant-related infections or reduce osteoporotic bone loss. To this end, polyelectrolyte multilayer structures have been developed as functional coatings and intensively tested in vitro previously. Nevertheless, only a few studies address the effect of polyelectrolyte multilayer coatings of biomaterials in vivo. The aim of the present work is to evaluate the effect of polyelectrolyte coatings of titanium alloy implants on implant anchorage in an animal model. We test the hypotheses that (1) polyelectrolyte multilayers have an effect on osseointegration in vivo; (2) multilayers of chitosan/hyaluronic acid decrease osteoblast proliferation compared to native titanium alloy, and hence reduce osseointegration; (3) multilayers of chitosan/gelatine increase osteoblast proliferation compared to native titanium alloy, hence enhance osseointegration. Polyelectrolyte multilayers on titanium alloy implants were fabricated by a layer-by-layer self-assembly process. Titanium alloy (Ti) implants were alternately dipped into gelatine (Gel), hyaluronic acid (HA) and chitosan (Chi) solutions, thus assembling a Chi/Gel and a Chi/HA coating with a terminating layer of Gel or HA, respectively. A rat tibial model with bilateral placement of titanium alloy implants was employed to analyze the bones' response to polyelectrolyte surfaces in vivo. 48 rats were randomly assigned to three groups of implants: (1) native titanium alloy (control), (2) Chi/Gel and (3) Chi/HA coating. Mechanical fixation, peri-implant bone area and bone contact were evaluated by pull-out tests and histology at 3 and 8weeks. Shear strength at 8weeks was statistically significantly increased (p<0.05) in both Chi/Gel and Chi/HA groups compared to the titanium alloy control. No statistically significant difference (p>0.05) in bone contact or bone area was found between all groups. No decrease of osseointegration of Chi/HA-coated implants compared to non-coated implants was found. The results of polyelectrolyte coatings in a rat model showed that the Chi/Gel and Chi/HA coatings have a positive effect on mechanical implant anchorage in normal bone.
[show abstract][hide abstract] ABSTRACT: Human dental erosion caused by acids is a major factor for tooth decay. Adding polymers to acidic soft drinks is one important approach to reduce human dental erosion caused by acids. The aim of this study was to investigate the thickness and the structure of polymer layers adsorbed in vitro on human dental enamel from polymer modified citric acid solutions.
The polymers propylene glycol alginate (PGA), highly esterified pectin (HP) and gum arabic (GA) were used to prepare polymer modified citric acids solutions (PMCAS, pH 3.3). With these PMCAS, enamel samples were treated for 30, 60 and 120s respectively to deposit polymer layers on the enamel surface. Profilometer scratches on the enamel surface were used to estimate the thickness of the polymer layers via atomic force microscopy (AFM). The composition of the deposited polymer layers was investigated with X-ray photoelectron spectroscopy (XPS). In addition the polymer-enamel interaction was investigated with zeta-potential measurements and scanning electron microscopy (SEM).
It has been shown that the profilometer scratch depth on the enamel with deposited polymers was in the range of 10nm (30s treatment time) up to 25nm (120s treatment time). Compared to this, the unmodified CAS-treated surface showed a greater scratch depth: from nearly 30nm (30s treatment time) up to 60nm (120s treatment time). Based on XPS measurements, scanning electron microscopy (SEM) and zeta-potential measurements, a model was hypothesized which describes the layer deposited on the enamel surface as consisting of two opposing gradients of polymer molecules and hydroxyapatite (HA) particles.
In this study, the structure and composition of polymer layers deposited on in vitro dental enamel during treatment with polymer modified citric acid solutions were investigated. Observations are consistent with a layer consisting of two opposing gradients of hydroxyapatite particles and polymer molecules. This leads to reduced erosive effects of citric acid solutions on dental enamel surfaces.
Dental materials: official publication of the Academy of Dental Materials 08/2012; 28(10):1089-97. · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: One approach to create novel amphiphilic surface nanostructures with typical lateral pattern dimensions in the order of 10 nm is to employ double crystalline co-oligomers with domain sizes largely determined by the block length of extended molecular chains. The aim of the study was to test the hypothesis that the extended chain bulk morphology of an asymmetric polyethylene-block-poly(ethylene oxide) (PE-b-PEO) co-oligomer can be induced at its thin film surface. Furthermore, we explored the central role of the extended oligomer orientation and the surface affinity to achieve an amphiphilic: surface nanostructure. The co-oligomer was drop-cast from dilute solution onto hydrophobic, neutral and hydrophilic substrates. Atomic-force microscopy revealed that independent of the substrate chemistry, the film thickness was quantized in integral multiples of the calculated extended chain length. At the same time, the terraces exhibited lateral domains that coarsen with increasing substrate hydrophobicity. Altho
[show abstract][hide abstract] ABSTRACT: The nanostructure of thermally annealed thin films of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blends on hydrophobic and hydrophilic substrates was studied to unravel the relationship between the substrate properties and the phase structure of polymer blends in confined geometry. Indeed, the nature of the employed substrates was found to affect the extent of phase separation, the PCBM aggregation state and the texture of the whole system. In particular, annealing below the melting temperature of the polymer yielded the formation of PCBM nanometric crystallites on the hydrophobic substrates, while mostly amorphous microscopic aggregates were formed on the hydrophilic ones. Moreover, while an enhanced in-plane orientation of P3HT lamellae was promoted on hydrophobic substrates, a markedly tilted geometry was produced on the hydrophilic ones. The observed effects were interpreted in terms of a simple model connecting the interface free energy for the blend films to the different polymer chain mobility and diffusion velocity of PCBM molecules on the different substrates.
[show abstract][hide abstract] ABSTRACT: The study was aimed at investigating the cytotoxicity of different composites as a function of composite shade and the light curing unit (LCU) employed.
Non-polymerized and polymerized samples of the composites Grandio(®) (VOCO, Cuxhaven), Solitaire(®) (Heraeus Kulzer, Hanau) and Filtek Z 250(®) (3M/Espe, Seefeld) in two markedly differing shades (A2, C2) were prepared. Polymerization was performed with two LCUs: Heliolux II (Ivoclar/Vivadent, Ellwangen) and Swiss Master Light (EMS, Nyon, Switzerland). To obtain composite extracts, the samples were immersed in cell culture medium (DMEM--Dulbecco's Modified Eagle Medium), which was replaced daily up to the 7th day of the experiment, and then on the 14th, 21st and 28th day. After incubation of human gingival fibroblasts (HGF) with the extracts obtained, cytotoxicity was determined using the MTT test.
With the non-polymerized samples, essentially no influence of the composite shades investigated on HGF viability was detected, with the exception of the Solitaire material, where a higher cytotoxicity of the shade C2 in the non-polymerized state was found at the end of the observation period. After polymerization of the different composites, the cytotoxic reaction observed for the extracts of shade C2 was stronger than that observed for A2. After polymerization with the Heliolux II (HLX) LCU, the extracts of composites Grandio and Solitaire C2 were significantly more toxic than those of the A2 shade (p<0.01). Polymerization with the Swiss Master Light (SML) reduces this cytotoxic effect. The extracts of the Grandio composite showed the least cytotoxic effect throughout the observation period, irrespective of the LCU used. For the extracts of the Z250 specimens, the cytotoxicity observed was generally higher.
The results show that the shade of the composite has an influence on its cytotoxicity and that this cytotoxicity is also influenced by the light curing unit used. It was observed that composites of the darker shade (C2) had a higher cytotoxicity, which varied with the LCU employed.
Dental materials: official publication of the Academy of Dental Materials 03/2012; 28(3):312-9. · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: Cervical tooth erosion is increasingly observed among adults and frequently associated with dentin sensitivity (DS). This study evaluated the effectiveness on DS of a biomimetic mineralization system (BIMIN) in comparison to the current standard treatment (Gluma(®) Desensitizer, Gluma).
In this single-blind, 2-arm study, 40 patients with confirmed cervical DS were randomized to either the test group or the positive control group. A Visual-Analog-Scale (VAS) was used to assess DS following stimulation of the exposed dentin with a 2-s air blast. Assessments were made at baseline (pre-treatment), 2 days, 4, 8 and 12 weeks, and 12 months after treatment. Two-stage replicas were obtained from the treated teeth and gold sputtered at baseline, and 2 days, 3 and 12 months after treatment. Surface topography of the treated cervical lesions and occlusion of dentinal tubules were investigated using scanning electron microscopy (SEM).
Both treatments led to a statistically significant reduction (P<0.0001) in DS that persisted over the entire 12-month observation period. Differences in DS between the treatments were not statistically significant. SEM photomicrographs demonstrated that a mineral layer concealed the dentinal tubules in the test group. In contrast, numerous dentinal tubules remained visible in cervical defects that were treated with Gluma.
A biomimetic mineralization kit was successfully used to treat patients exhibiting DS. The effect was similar to using Gluma, and was likely the result of the deposition of an enamel-like layer on the exposed cervical dentin.
Dental materials: official publication of the Academy of Dental Materials 02/2012; 28(4):457-64. · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: We aimed to achieve detailed biomaterials characterization of a drug delivery system for local periodontitis treatment based on electrospun metronidazole-loaded resorbable polylactide (PLA) fibers.
PLA fibers loaded with 0.1-40% (w/w) MNA were electrospun and were characterized by SEM and DSC. HPLC techniques were used to analyze the release profiles of metronidazole (MNA) from these fibers. The antibacterial efficacy was determined by measuring inhibition zones of drug-containing aliquots from the same electrospun fiber mats in an agar diffusion test. Three pathogenic periodontal bacterial strains: Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were studied. Cytotoxicity testing was performed with human gingival fibroblasts by: (i) counting viable cells via live/dead staining methods and (ii) by exposing cells directly onto the surface of MNA-loaded fibers.
MNA concentration influenced fiber diameters and thus w/w surface areas: diameter being minimal and area maximal at 20% MNA. HPLC showed that these 20% MNA fibers had the fastest initial MNA release. From the third day, MNA release was slower and nearly linear with time. All fiber mats released 32-48% of their total drug content within the first 7 days. Aliquots of media taken from the fiber mats inhibited the growth of all three bacterial strains. MNA released up to the 28th day from fiber mats containing 40% MNA significantly decreased the viability of F. nucleatum and P. gingivalis and up to the 2nd day also for the resistant A. actinomycetemcomitans. All of the investigated fibers and aliquots showed excellent cytocompatibility.
This study shows that MNA-loaded electrospun fiber mats represent an interesting class of resorbable drug delivery systems. Sustained drug release properties and cytocompatibility suggest their potential clinical applicability for the treatment of periodontal diseases.
Dental materials: official publication of the Academy of Dental Materials 02/2012; 28(2):179-88. · 2.88 Impact Factor
[show abstract][hide abstract] ABSTRACT: Using fibrinogen (Fg) protein as a probe molecule, mapping using accumulated probe trajectories (MAPT) is performed on nanostructured melt-drawn high-density poly(ethylene) (HDPE) films composed of well-oriented crystalline patches separated by amorphous regions. The spatially grouped molecular trajectories allow for identification of regions with distinct surface properties (i.e., crystalline vs. amorphous) while simultaneously determining the characteristic dynamic protein behavior within those regions. In the presence of solution with a sufficiently high Fg concentration, discrete patches of a dense, ordered protein layer form (presumably on crystalline HDPE regions), leading to a dramatic rise in the surface residence time (by more than two orders of magnitude) of molecules incorporated into the film. Within this ordered Fg layer, individual molecules exhibit slow anisotropic lateral diffusion; the mobility is restricted by the nanostructure boundaries of the underlying HDPE. On HDPE films at low Fg surface coverage, or on films that have been rendered hydrophilic with Ar plasma, short surface residence times and fast, isotropic diffusion are observed. These results demonstrate the ability of spatially resolved single-molecule tracking to provide mechanistic information about biomolecule-surface interactions in a highly heterogeneous environment.