Nanofibers with Incorporated Autochthonous Bacteria as Potential Probiotics for Local Treatment of Periodontal Disease.

The conventional treatment of periodontal disease does not solve the high incidence of recolonization of periodontal pockets by pathogens. Here, we introduce an innovative concept of incorporating autochthonous bacteria as potential probiotics into nanofibers for local treatment. We selected and isolated the strain 25.2.M from the oral microbiota of healthy volunteers. It was identified as Bacillus sp. based on 16S rRNA sequence analyses. The strain is nonpathogenic, produces antimicrobial substances, and can grow over the periodontal pathogen Aggregatibacter actinomycetemcomitans in vitro, making it a promising probiotic candidate. The strain 25.2.M was successfully incorporated into the nanofibers in the form of spores (107 CFU/mg), the viabilities of which were exceptional (max. change of 1 log unit) both during electrospinning and after 12 months of storage. The release of the bacteria was delayed from chitosan/poly(ethylene oxide) compared to poly(ethylene oxide) nanofibers, and the antimicrobial activity against A. actinomycetemcomitans was confirmed. The developed nanodelivery system for administration into periodontal pockets thus offers a promising approach for the inhibition of periodontal pathogens and restoration of healthy oral microbiota.

Nanofibers with genotyped Bacillus strains exhibiting antibacterial and immunomodulatory activity.

Biofilm-associated diseases such as periodontitis are widespread and challenging to treat which calls for new strategies for their effective management. Probiotics represent a promising approach for targeted treatment of dysbiosis in biofilm and modulation of host immune response. In this interdisciplinary study, nanofibers with two autochthonous Bacillus strains 27.3.Z and 25.2.M were developed. The strains were isolated from the oral microbiota of healthy individuals, and their genomes were sequenced and screened for genes associated with antimicrobial and immunomodulatory activities, virulence factors, and transferability of resistance to antibiotics. Spores of two Bacillus strains were incorporated individually or in combination into hydrophilic poly(ethylene oxide) (PEO) and composite PEO/alginate nanofibers. The nanofiber mats were characterised by a high loading of viable spores (> 7 log CFU/mg) and they maintained viability during electrospinning and 6 months of storage at room temperature. Spores were rapidly released from PEO nanofibers, while presence of alginate in the nanofibers prolonged their release. All formulations exhibited swelling, followed by transformation of the nanofiber mat into a hydrogel and polymer erosion mediating spore release kinetics. The investigated Bacillus strains released metabolites, which were not cytotoxic to peripheral blood mononuclear cells (PBMCs) in vitro. Moreover, their metabolites exhibited antibacterial activity against two periodontopathogens, an antiproliferative effect on PBMCs, and inhibition of PBMC expression of proinflammatory cytokines. In summary, the developed nanofiber-based delivery system represents a promising therapeutic approach to combat biofilm-associated disease on two fronts, namely via modulation of the local microbiota with probiotic bacteria and host immune response with their metabolites.

Electrospinning as a method for preparation of redispersible dry product with high content of magnetic nanoparticles.

One of the key technological challenges in the development of iron-oxide-based magnetic nanoparticles (MNPs) is their long-term physical stability in colloidal dispersions. This can be improved by their transformation into a dry form. Here, we introduce electrospinning as a drying method for ethanol-based and water-based MNP dispersions, which enables the preparation of high-loaded dry MNP products. The obtained easily dispersible electrospun product contained up to 50 % (w/w) of MNPs, homogeneously distributed in the fibrillar structure, which is much more compared to the products of currently available methods for drying MNP dispersions. The polymers used as building blocks of nanofibers, namely poloxamer 188 and polyethylene oxide, improved the tolerance of MNPs to high ionic strength dispersion medium and thus enhanced the short-term physical stability of MNP dispersions after reconstitution. The dry product was stable for up to 1 month at room temperature and relative humidity up to 70 %. It was in the form of a nanofiber mat, which prevented the aerosolization of MNPs and their unintentional ambient exposure. Therefore, the electrospun product with MNPs is expected to be a safer dry formulation of MNPs than the nanoparticulate powders, which are usually the final products of the conventional drying methods.

Hydrophilic nanofibers as a supersaturating delivery system for carvedilol.

Polymer nanofibers represent a promising delivery system for poorly water-soluble drugs; however, their supersaturating potential has not been explored yet. Here, carvedilol-loaded nanofibers based on poly(ethyleneoxide) and on amphiphilic block copolymer poloxamer 407 were produced by electrospinning. These nanofibers provided high carvedilol loading and improved dissolution of carvedilol. Their dissolution resulted in a supersaturated system that was not stable, and thus to avoid carvedilol precipitation, hydroxypropyl methylcelluloses or polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer (Soluplus) were additionally incorporated into the nanofibers. The morphology of the electrospun product was not affected by incorporation of carvedilol and the polymer precipitation inhibitors, as shown by scanning electron microscopy. The hydroxypropyl methylcelluloses were not effective polymer precipitation inhibitors for carvedilol. Incorporation of Soluplus significantly extended the duration of carvedilol supersaturation (>24 h) compared to the dissolution of nanofibers without Soluplus. Moreover, after 1 h of dissolution, incorporation of Soluplus into the nanofibers provided significantly higher carvedilol concentration (94.4 ± 2.5 µg/mL) compared to the nanofibers without Soluplus (32.7 ± 5.8 µg/mL), the polymer film (24.0 ± 2.2 µg/mL), and the physical mixture (3.3 ± 0.4 µg/mL). Thus, this study shows the great potential for hydrophilic nanofibers as a delivery system for sustained carvedilol supersaturation.

Treatment challenges and delivery systems in immunomodulation and probiotic therapies for periodontitis.

Introduction: Periodontitis is a widespread illness that arises due to disrupted interplay between the oral microbiota and the host immune response. In some cases, conventional therapies can provide temporary remission, although this is often followed by disease relapse. Recent studies of periodontitis pathology have promoted the development of new therapeutics to improve treatment options, together with local application using advanced drug delivery systems.Areas covered: This paper provides a critical review of the status of current treatment approaches to periodontitis, with a focus on promising immunomodulation and probiotic therapies. These are based on delivery of small molecules, peptides, proteins, DNA or RNA, and probiotics. The key findings on novel treatment strategies and formulation of advanced delivery systems, such as nanoparticles and nanofibers, are highlighted.Expert opinion: Multitarget therapy based on antimicrobial, immunomodulatory, and probiotic active ingredients incorporated into advanced delivery systems for application to the periodontal pocket can improve periodontitis treatment outcomes. Translation of such adjuvant therapy from laboratory to patient is expected in the future.

The potential of nanofibers to increase solubility and dissolution rate of the poorly soluble and chemically unstable drug lovastatin.

Polymer nanofibers represent a promising drug delivery system. However, as a large surface area is exposed to external conditions during the electrospinning process, they are usually used to incorporate drugs with good oxidative stability. Here, we introduce a new concept for the incorporation of a drug with low oxidative stability and extremely low solubility into poloxamer 188/poly(ethylene oxide) and Soluplus/poly(ethylene oxide) nanofibers, to improve its solubility and increase its dissolution rate. The electrospun products showed different morphologies and lower initial lovastatin contents than theoretically expected, which indicated oxidative drug degradation during electrospinning. The addition of antioxidants improved the lovastatin chemical stability in the nanofibers. The highest lovastatin dissolution rate and solubility were obtained for the Soluplus-based nanofibers, where no crystalline lovastatin was detected. The accelerated stability study has revealed the chemical stability of lovastatin in the poloxamer-based nanofibers with the addition of antioxidants, whereas in the Soluplus-based nanofibers lovastatin was not completely preserved. However, appropriate packaging of the formulation and storage under normal conditions is expected to assure its stability. These Soluplus-based nanofibers developed here with antioxidants represent a promising immediate release formulation to provide improved solubility and dissolution rate for poorly soluble and chemically unstable drugs, such as lovastatin.

Sustained release of antimicrobials from double-layer nanofiber mats for local treatment of periodontal disease, evaluated using a new micro flow-through apparatus.

Periodontal disease is a widespread chronic condition associated with degradation of periodontal tissues that requires more effective approaches for its treatment. Thus, the aim was to develop a nanodelivery system for local application of antimicrobials, with evaluation in vitro using a newly developed micro flow-through apparatus that simulates local in-vivo conditions in the periodontal pocket: small resting volume, and low gingival crevicular fluid flow rate. We successfully developed a double-layer nanofiber mat composed of a chitosan/ poly(ethylene) oxide nanofiber layer with 30% ciprofloxacin, and a poly(ε-caprolactone) nanofiber layer with 5% metronidazole. The precisely designed composition enabled sustained in-vitro release of the antimicrobials according to their specific drug release mechanisms. The rate-limiting step of ciprofloxacin release was its own low solubility at pH 7.4, when there was excess of solid drug present in the delivery system. In contrast, sustained release of metronidazole was due to slow penetration of dissolution medium through the hydrophobic poly(ε-caprolactone) nanofiber layer. The double-layer nanofiber mat developed showed antibacterial activity against Escherichia coli and Aggregatibacter actinomycetemcomitans based on plate antibiogram assays. The antimicrobial concentrations released from the nanofiber mats determined using the developed apparatus were above the minimal inhibitory concentrations against the periodontal pathogens for up to 7 days, which is valuable information for prediction of the efficacy of the nanodelivery system. Although this apparatus was specifically designed for characterization of formulations associated with treatments for periodontal disease, its applicability is much wide, as for development of any delivery system for application at target sites that have similar local conditions.

Preparation of poloxamer-based nanofibers for enhanced dissolution of carvedilol.

Polymer nanofibers have become increasingly important for improvement of dissolution and bioavailability of poorly soluble drugs, representing a great challenge in pharmaceutical development. Here, we introduced a new concept of using amphiphilic polymers as fundamental excipients in electrospun nanofibers, which would improve drug solubilization and accelerate its release. Hydrophilic poloxamer-based nanofibers were developed as a novel drug delivery system for carvedilol. These nanofibers were electrospun from different liquid carvedilol dispersions, as carvedilol (nano)suspensions or ethanol solution. The electrospun products showed similar morphologies, but different mean fiber diameters (170-450 nm). Carvedilol dissolution rates from nanofibers were faster compared to its dissolution from polymer films. The electrospinning from ethanol solution resulted in the highest dissolution rate, since >90% of the drug was dissolved in the first 5 min. The type of liquid medium significantly affects also the drug crystallinity. Thus, nanofibers produced from ethanol polymer solution showed no detectable crystalline carvedilol, whereas crystalline carvedilol form II or III was detected in the other nanofiber samples investigated. In a prolonged stability study (to 1 year), the potential of nanofibers to preserve the active ingredient in the initial non-crystalline form was demonstrated. Poloxamer-based nanofibers thus represent a promising formulation for immediate release and improved dissolution rates of poorly soluble drugs.

Impact of PCL nanofiber mat structural properties on hydrophilic drug release and antibacterial activity on periodontal pathogens.

Electrospinning enables to design and manufacture novel drug delivery systems capable of advancing the local antibacterial therapy. In this study, two hydrophilic drugs - metronidazole and ciprofloxacin hydrochloride - were loaded both individually and in combination into hydrophobic poly(ε-caprolactone) (PCL) matrix using electrospinning. We aimed to develop prolonged release drug delivery systems suitable for the treatment of periodontal diseases and understand how different rarely studied structural features, such as nanofiber mat thickness, surface area, wettability, together with intrinsic properties, like solid state and localization of incorporated drugs in nanofibers, affect the drug release. Furthermore, the safety of nanofiber mats was assessed in vitro on fibroblasts, and their antibacterial activity was tested on selected strains of periodontopathogenic bacteria. The results showed that the structural properties of nanofiber mat are crucial in particular drug-polymer combinations, affecting the drug release and consequently the antibacterial activity. The hydrophobicity of a PCL nanofiber mat and its thickness are the key characteristics in prolonged hydrophilic drug release, but only when wetting is the rate-limiting step for the drug release. Combination of drugs showed beneficial effects by inhibiting the growth of all tested pathogenic bacterial strains important in periodontal diseases.

Design and Fabrication of Magnetically Responsive Nanocarriers for Drug Delivery.

Magnetically-assisted delivery of therapeutic agents to the site of interest, which is referred to as magnetic drug targeting, has proven to be a promising strategy in a number of studies. One of the key advantages over other targeting strategies is the possibility to control remotely the distribution and accumulation of the nanocarriers after parenteral administration. However, preparation of effective and robust magnetically responsive nanocarriers based on superparamagnetic iron oxide nanocrystals (SPIONs) still represents a great scientific challenge, since spatial guidance of individual SPIONs is ineffective despite the presence of high magnetic field gradient. A strategy to overcome this issue is the clustering of SPIONs to achieve sufficient magnetic responsiveness. In this mini-review, we address current and future strategies for the design and fabrication of magnetically responsive nanocarriers based on SPIONs for magnetically-targeted drug delivery, including the underlying physical requirements, the possibility of drug loading, and the control of drug release at the targeted site.

Formulation and evaluation of chitosan/polyethylene oxide nanofibers loaded with metronidazole for local infections.

Nanofibers combined with an antimicrobial represent a powerful strategy for treatment of various infections. Local infections usually have a low fluid volume available for drug release, whereas pharmacopoeian dissolution tests include a much larger receptor volume. Therefore, the development of novel drug-release methods that more closely resemble the in-vivo conditions is necessary. We first developed novel biocompatible and biodegradable chitosan/polyethylene oxide nanofibers using environmentally friendly electrospinning of aqueous polymer solutions, with the inclusion of the antimicrobial metronidazole. Here, the focus is on the characterization of these nanofibers, which have high potential for bioadhesion and retention at the site of application. These can be used where prolonged retention of the delivery system at an infected target site is needed. Drug release was studied using three in-vitro methods: a dissolution apparatus (Apparatus 1 of the European Pharmacopoeia), vials, and a Franz diffusion cell. In contrast to other studies, here the Franz diffusion cell method was modified to introduce a small volume of medium with the nanofibers in the donor compartment, where the nanofibers swelled, eroded, and released the metronidazole, which then diffused into the receptor compartment. This set-up with nanofibers in a limited amount of medium released the drug more slowly compared to the other two in-vitro methods that included larger volumes of medium. These findings show that drug release from nanofibers strongly depends on the release method used. Therefore, in-vitro test methods should closely resemble the in-vivo conditions for more accurate prediction of drug release at a therapeutic site.

Nanofiber diameter as a critical parameter affecting skin cell response.

Electrospun polymer nanofibers have opened new opportunities in the rapidly evolving field of tissue engineering, particularly due to their topography and variability of available biomaterials. In order to better understand nanofiber influence on cell growth, the impact of their diameter was systematically examined. In this study homogenous, randomly oriented poly(vinyl alcohol) nanofibers with five different average diameters, ranging from 70nm to 1120nm, were produced, characterized and their impact on morphology, proliferation and mobility of keratinocytes and skin fibroblasts was evaluated. The results have shown that nanofiber diameter affects cell response and that this response is cell line specific. Nanofiber thickness affected size, morphology and actine organization of keratinocytes much more than fibroblasts. Specifically, the keratinocyte grown on nanofibers were more spherical and smaller compared to the control cells, while the fibroblasts were much less affect. They stayed almost unchanged and spread across growth surface. The cell proliferation determined based on their metabolic activity was the highest, when keratinocytes were grown on 305nm thick nanofibers, whereas proliferation of fibroblasts grown similar nanofibers was decreased. Finally, fibroblasts exerted higher mobility than keratinocytes. Both tested cell lines on nanofiber diameters of 300nm resulted in decreased cell mobility. These findings suggest that the control over nanofiber diameter offers promising possibility to better design the tissue scaffolds, since cells distinguish between differently sized nanofibers and respond accordingly.

Contribution of Nanotechnology to Improved Treatment of Periodontal Disease.

Periodontal disease is chronic inflammation of periodontal tissues resulting in formation of periodontal pockets, periodontal attachment loss and progressive destruction of the ligament and alveolar bone. This review gives an update on periodontal disease pathogenesis, which is important for the development of novel methods and delivery systems for its treatment. The available treatment approaches, including removal of dental plaque, modulation of the host inflammatory response, and regeneration of periodontal tissue, are reviewed and their drawbacks discussed. Furthermore the latest achievements involving development of nanomedicines, which represent a new approach to better treatment of periodontal disease, are highlighted. They enable local drug delivery to particular tissues, cells, or subcellular compartments in periodontal pockets, either to biofilm pathogens or host cells, as well as control the release of incorporated drugs, usually antibiotic or anti-inflammatory. Specific examples of the nanocarriers or nanomaterials such as liposomes, lipid and polymeric nanoparticles, nanocrystals, dendrimers, and nanofibers under development for the treatment of periodontal disease are also clearly reviewed. Nanofibers are of special interest as nanodelivery systems and scaffolds for the regeneration of periodontal tissue. Finally, the future outlook of novel therapeutic approaches involving nanodelivery systems in the treatment of periodontal disease is provided.

Electrospun polycaprolactone nanofibers as a potential oromucosal delivery system for poorly water-soluble drugs.

The number of poorly water-soluble drug candidates is rapidly increasing; this represents a major challenge for the pharmaceutical industry. As a consequence, novel formulation approaches are required. Furthermore, if such a drug candidate is intended for the therapy of a specific group of the population, such as geriatric or pediatric, the formulation challenge is even greater, with the need to produce a dosage form that is acceptable for specific patients. Therefore, the goal of our study was to explore electrospun polycaprolactone (PCL) nanofibers as a novel nanodelivery system adopted for the oromucosal administration of poorly water-soluble drugs. The nanofibers were evaluated in comparison with polymer films loaded with ibuprofen or carvedilol as the model drugs. Scanning electron microscopy revealed that the amount of incorporated drug affects the diameter and the morphology of the nanofibers. The average fiber diameter increased with a higher drug loading, whereas the morphology of the nanofibers was noticeably changed in the case of nanofibers with 50% and 60% ibuprofen. The incorporation of drugs into the electrospun PCL nanofibers was observed to reduce their crystallinity. Based on the morphology of the nanofibers and the films, and the differential scanning calorimetry results obtained in this study, it can be assumed that the drugs incorporated into the nanofibers were partially molecularly dispersed in the PCL matrix and partially in the form of dispersed nanocrystals. The incorporation of both model drugs into the PCL nanofibers significantly improved their dissolution rates. The PCL nanofibers released almost 100% of the incorporated ibuprofen in 4h, whereas only up to 77% of the incorporated carvedilol was released during the same time period, indicating the influence of the drug's properties, such as molecular weight and solubility, on its release from the PCL matrix. The obtained results clearly demonstrated the advantages of the new nanodelivery system compared to the drug-loaded polymer films that were used as the reference formulation. As a result, electrospinning was shown to be a very promising nanotechnology-based approach to the formulation of poorly water-soluble drugs in order to enhance their dissolution. In addition, the great potential of the produced drug-loaded PCL nanofiber mats for subsequent formulation as oromucosal drug delivery systems for children and the elderly was confirmed.

Development and bioevaluation of nanofibers with blood-derived growth factors for dermal wound healing.

The aim of our work was to produce a modern nanomaterial with incorporated blood-derived growth factors, produced by electrospinning, applicable in treatment of chronic wounds. Platelet-rich plasma was chosen as a natural source of growth factors. Results showed that platelet-rich plasma stimulates keratinocyte and fibroblast cell growth in vitro. Its optimal concentration in growth medium was 2% (v/v) for both types of skin cells, while higher concentrations caused alterations in cell morphology, with reduced cell mobility and proliferation. In the next step hydrophilic nanofibers loaded with platelet-rich plasma were produced from chitosan and poly(ethylene oxide), using electrospinning. The morphology of nanofibers was stable in aqueous conditions for 72 h. It was shown that electrospinning does not adversely affect the biological activity of platelet-rich plasma. The effects of nanofibers with incorporated platelet-rich plasma on cell proliferation, survival, morphology and mobility were examined. Nanofibers limited cell mobility, changed morphology and stimulated cell proliferation. Despite of the small amount of blood-derived growth factors introduced in cell culture via platelet-rich plasma-loaded nanofibers, such nanofibrillar support significantly induced cell proliferation, indicating synergistic effect of nanotopography and incorporated growth factors. The overall results confirm favorable in vitro properties of produced nanofibers, indicating their high potential as a nanomaterial suitable for delivery of platelet-rich plasma in wound healing applications.

The impact of relative humidity during electrospinning on the morphology and mechanical properties of nanofibers.

Electrospinning is an efficient and flexible method for nanofiber production, but it is influenced by many systemic, process, and environmental parameters that govern the electrospun product morphology. This study systematically investigates the influence of relative humidity (RH) on the electrospinning process. The results showed that the morphology of the electrospun product (shape and diameter) can be manipulated with precise regulation of RH during electrospinning. Because the diameter of nanofibers correlates with their rigidity, it was shown that RH control can lead to manipulation of material mechanical properties. Finally, based on the solution's rheological parameter-namely, phase shift angle-we were able to predict the loss of homogenous nanofiber structure in correlation with RH conditions during electrospinning. This research addresses the mechanism of RH impact on the electrospinning process and offers the background to exploit it in order to better control nanomaterial properties and alter its applicability.

Nanofibers and their biomedical use.

The idea of creating replacement for damaged or diseased tissue, which will mimic the physiological conditions and simultaneously promote regeneration by patients' own cells, has been a major challenge in the biomedicine for more than a decade. Therefore, nanofibers are a promising solution to address these challenges. These are solid polymer fibers with nanosized diameter, which show improved properties compared to the materials of larger dimensions or forms and therefore cause different biological responses. On the nanometric level, nanofibers provide a biomimetic environment, on the micrometric scale three-dimensional architecture with the desired surface properties regarding the intended application within the body, while on the macrometric scale mechanical strength and physiological acceptability. In the review, the development of nanofibers as tissue scaffolds, modern wound dressings for chronic wound therapy and drug delivery systems is highlighted. Research substantiates the effectiveness of nanofibers for enhanced tissue regeneration, but ascertains that evidences from clinical studies are currently lacking. Nevertheless, due to the development of nano- and bio-sciences, products on the market can be expected in the near future.

Targeting intracellular compartments by magnetic polymeric nanoparticles.

Superparamagnetic iron oxide nanoparticles (SPIONs) show a great promise for a wide specter of bioapplications, due to their characteristic magnetic properties exhibited only in the presence of magnetic field. Their advantages in the fields of magnetic drug targeting and imaging are well established and their safety is assumed, since iron oxide nanoparticles have already been approved for in vivo application, however, according to many literature reports the bare metal oxide nanoparticles may cause toxic effects on treated cells. Therefore, it is reasonable to prevent the direct interactions between metal oxide core and surrounding environment. In the current research ricinoleic acid coated maghemite nanoparticles were successfully synthesized, characterized and incorporated in the polymeric matrix, resulting in nanosized magnetic polymeric particles. The carrier system was shown to exhibit superparamagnetic properties and was therefore responsive towards external magnetic field. Bioevaluation using T47-D breast cancer cells confirmed internalization of magnetic polymeric nanoparticles (MNPs) and their intracellular localization in various subcellular compartments, depending on presence/absence of external magnetic field. However, the number of internalized MNPs observed by fluorescent and transmission electron microscopy was relatively low, making such way of targeting effective only for delivery of highly potent drugs. The scanning electron microscopy of treated cells revealed that MNPs influenced the cell adhesion, when external magnetic field was applied, and that treatment resulted in damaged apical plasma membrane right after exposure to the magnetic carrier. On the other hand, MNPs showed only reversibly reduced cellular metabolic activity in concentrations up to 200 µg/ml and, in the tested concentration the cell cycle distribution was within the normal range, indicating safety of the established magnetic carrier system for the treated cells.

In vitro and in vivo characterization of temoporfin-loaded PEGylated PLGA nanoparticles for use in photodynamic therapy.

AIMS: In this study we evaluated temoporfin-loaded polyethylene glycol (PEG) Poly-(D,L-lactide-co-glycolide) (PLGA) nanoparticles (NPs) as a new formulation for potential use in cancer treatment. MATERIALS & METHODS: NPs were characterized for their photophysical properties, temoporfin release, cellular uptake and intracellular localization, and dark and photocytotoxicities of temoporfin by using A549, MCF10A neoT and U937 cell lines. In vivo imaging was performed on athymic nude-Foxn1 mice. RESULTS: Temoporfin was highly aggregated within the NPs and the release of temoporfin monomers was faster from PEGylated PLGA NPs than from non-PEGylated ones. PEGylation significantly reduced the cellular uptake of NPs by the differentiated promonocytic U937 cells, revealing the stealth properties of the delivery system. Dark cytotoxicity of temoporfin delivered by NPs was less than that of free temoporfin in standard solution (Foscan(®), Biolitec AG [Jena, Germany]), whereas phototoxicity was not reduced. Temoporfin delivered to mice by PEGylated PLGA NPs exhibits therapeutically favorable tissue distribution. CONCLUSION: These encouraging results show promise in using PEGylated PLGA NPs for improving the delivery of photosensitizers for photodynamic therapy.

Proinflammatory effects of bare and PEGylated ORMOSIL-, PLGA- and SUV-NPs on monocytes and PMNs and their modulation by f-MLP.

AIMS: We wanted to test the proinflammatory effects of vinyltriethoxysilane-based organically modified silica nanoparticles (ORMOSIL-NPs) in vitro on blood leukocytes. MATERIALS & METHODS: Cell selectivity, cytokines/chemokines and O(2) (-) production were analyzed using nonpolyethylene glycol (PEG)ylated and PEGylated ORMOSIL-NPs, poly(lactic-co-glycolic acid) (PLGA)-NPs and small unilamellar vesicles (SUV)-NPs. RESULTS: ORMOSIL-NPs mostly bound to monocytes while other NPs to all leukocyte types similarly. Cell capture of PEGylated-NPs decreased strongly (ORMOSIL), moderately (PLGA) and weakly (SUV). Bare ORMOSIL-NPs effectively stimulated the production of IL-1ß/IL-6/TNF-α/IL-8 by monocytes and of IL-8 by polymorphonuclear leukocytes (PMNs). NP PEGylation inhibited such effects only partially. Formyl-methionine-leucine phenylalanine (f-MLP) further increased the release of cytokines/chemokines by monocytes/PMNs primed with bare and PEGylated ORMOSIL-NPs. PEGylated SUV-NPs, bare and PEGylated ORMOSIL- and PLGA-NPs sensitize PMNs and monocytes to secrete O(2) (-) upon f-MLP stimulation. CONCLUSION: ORMOSIL-NPs are preferentially captured by circulating monocytes but stimulate both monocytes and PMNs per se or by sensitizing them to another agonist (f-MLP). PEG-coating confers stealth effects but does not completely eliminate leukocyte activation. Safe nanomedical applications require the evaluation of both intrinsic and cooperative proinflammatory potential of NPs.