Engineering of Vaginal Lactobacilli to Express Fluorescent Proteins Enables the Analysis of Their Mixture in Nanofibers.

Lactobacilli are a promising natural tool against vaginal dysbiosis and infections. However, new local delivery systems and additional knowledge about their distribution and mechanism of action would contribute to the development of effective medicine. This will be facilitated by the introduction of the techniques for effective, inexpensive, and real-time tracking of these probiotics following their release. Here, we engineered three model vaginal lactobacilli (Lactobacillus crispatus ATCC 33820, Lactobacillus gasseri ATCC 33323, and Lactobacillus jensenii ATCC 25258) and a control Lactobacillus plantarum ATCC 8014 to express fluorescent proteins with different spectral properties, including infrared fluorescent protein (IRFP), green fluorescent protein (GFP), red fluorescent protein (mCherry), and blue fluorescent protein (mTagBFP2). The expression of these fluorescent proteins differed between the Lactobacillus species and enabled quantification and discrimination between lactobacilli, with the longer wavelength fluorescent proteins showing superior resolving power. Each Lactobacillus strain was labeled with an individual fluorescent protein and incorporated into poly (ethylene oxide) nanofibers using electrospinning, as confirmed by fluorescence and scanning electron microscopy. The lactobacilli retained their fluorescence in nanofibers, as well as after nanofiber dissolution. To summarize, vaginal lactobacilli were incorporated into electrospun nanofibers to provide a potential solid vaginal delivery system, and the fluorescent proteins were introduced to distinguish between them and allow their tracking in the future probiotic-delivery studies.

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.

Long-Term Sustained Ciprofloxacin Release from PMMA and Hydrophilic Polymer Blended Nanofibers.

Nanofibers represent an attractive novel drug delivery system for prolonged and controlled release. However, sustained release of hydrophilic drugs, like ciprofloxacin hydrochloride (CIP), from polymeric nanofibers is not an easy task. The present study investigates the effect of different hydrophobic polymers (PCL and PMMA) alone in monolithic nanofibers or with hydrophilic polymers (PVA, PEO, and chitosan) in blended nanofibers aiming to achieve sustained CIP release. CIP release from PCL nanofibers was 46% and from PMMA just 1.5% over 40 day period. Thus, PMMA holds great promise for modification of CIP release from blended nanofibers. PMMA blends with 10% PEO, PVA, or chitosan were used to electrospin nanofibers from solution in the mixture of acetic and formic acid. These nanofibers exhibited different drug-release profiles: PEO containing nanofiber mats demonstrated high burst effect, chitosan containing mats revealed very slow gradual release, and PVA containing mats yielded smaller burst effect with favorable sustained release. We have also shown that gradual sustain release of antibiotic like CIP can be additionally tuned over 18 days with various blend ratios of PMMA with PVA or chitosan reaching almost 100%. A mathematical model in agreement with the experimental observation revealed that the sustained CIP release from the blended nanofibers corresponded to the two-stage desorption process.

Controlled Release of Ciprofloxacin from Core-Shell Nanofibers with Monolithic or Blended Core.

Sustained controlled drug release is one of the prominent contributions for more successful treatment outcomes in the case of several diseases. However, the incorporation of hydrophilic drugs into nanofibers, a promising novel delivery system, and achieving a long-term sustained release still pose a challenging task. In this work we demonstrated a robust method of avoiding burst release of drugs and achieving a sustained drug release from 2 to 4 weeks using core-shell nanofibers with poly(methyl methacrylate) (PMMA) shell and monolithic poly(vinyl alcohol) (PVA) core or a novel type of core-shell nanofibers with blended (PVA and PMMA) core loaded with ciprofloxacin hydrochloride (CIP). It is also shown that, for core-shell nanofibers with monolithic core, drug release can be manipulated by varying flow rate of the core PVA solution, whereas for core-shell nanofibers with blended core, drug release can be manipulated by varying the ratios between PMMA and PVA in the core. During coaxial electrospinning, when the solvent from the core evaporates in concert with the solvent from the shell, the interconnected pores spanning the core and the shell are formed. The release process is found to be desorption-limited and agrees with the two-stage desorption model. Ciprofloxacin-loaded nanofiber mats developed in the present work could be potentially used as local drug delivery systems for treatment of several medical conditions, including periodontal disease and skin, bone, and joint infections.

Design and development of novel mitochondrial targeted nanocarriers, DQAsomes for curcumin inhalation.

Curcumin has potent antioxidant and anti-inflammatory properties but poor absorption following oral administration owing to its low aqueous solubility. Development of novel formulations to improve its in vivo efficacy is therefore challenging. In this study, formulation of curcumin-loaded DQAsomes (vesicles formed from the amphiphile, dequalinium) for pulmonary delivery is presented for the first time. The vesicles demonstrated mean hydrodynamic diameters between 170 and 200 nm, with a ζ potential of approximately +50 mV, high drug loading (up to 61%) and encapsulation efficiency (90%), resulting in enhanced curcumin aqueous solubility. Curcumin encapsulation in DQAsomes in the amorphous state was confirmed by X-ray diffraction and differential scanning calorimetry analysis. The existence of hydrogen bonds and cation-π interaction between curcumin and vesicle building blocks, namely dequalinium molecules, were shown in lyophilized DQAsomes using FT-IR analysis. Encapsulation of curcumin in DQAsomes enhanced the antioxidant activity of curcumin compared to free curcumin. DQAsome dispersion was successfully nebulized with the majority of the delivered dose deposited in the second stage of the twin-stage impinger. The vesicles showed potential for mitochondrial targeting. Curcumin-loaded DQAsomes thus represent a promising inhalation formulation with improved stability characteristics and mitochondrial targeting ability, indicating a novel approach for efficient curcumin delivery for effective treatment of acute lung injury and the rationale for future in vivo studies.

Development of a novel in vitro cell model for evaluation of nanofiber mats immunogenicity.

Immunological safety of nanofibers remains poorly reported within the scientific literature and lacks specific in vitro testing models distinct from those used to test nanoparticles. To address the challenges of currently used conventional setups being described in the literature, we developed a novel in vitro model for nanofiber mats immunogenicity testing, which enables standardization of tested surface area, excludes nanofiber mat edges, and ensures stable contacts of cells with nanofibers during the experiment. The effect of nanofibers was assessed on peripheral blood mononuclear cells (PBMCs) by measuring their metabolic activity using MTS cell proliferation assay, where key performance parameters, i.e. cell number, phytohemagglutinin-L (PHA-L) concentration, incubation time and cell lysis were optimized. Repeatability of results obtained with non-activated and PHA-L-activated PBMCs in contact with differently thick polycaprolactone nanofiber mats was compared using both models. Our model provided more reproducible results with lower variability, exhibiting its higher reliability and accuracy than the conventional one. Furthermore, results showed the presence of thicker mats resulted in reduced metabolic activity and PBMC proliferation without any observed cytotoxicity, providing additional insights into their non-immunogenic characteristics. The developed model enables more accurate biological assessment that can support new guidelines for in vitro nanofiber testing and formulation.

Development of Nanofibers with Embedded Liposomes Containing an Immunomodulatory Drug Using Green Electrospinning.

Conventional treatments for chronic wounds are often ineffective, thus new therapeutic approaches are needed, such as the delivery of immunomodulatory drugs that can reduce inflammation, restore immune cell function, and facilitate tissue regeneration. A potential drug for such an approach is simvastatin, which has major drawbacks including poor solubility and chemical instability. With the aim of developing a dressing for wound healing, simvastatin and an antioxidant were incorporated into alginate/poly(ethylene oxide) nanofibers by green electrospinning without the use of organic solvents, thanks to their prior encapsulation into liposomes. The composite liposome-nanofiber formulations exhibited fibrillar morphology (160-312 nm) and unprecedentedly high phospholipid and drug content (76%). Transmission electron microscopy revealed dried liposomes as bright ellipsoidal spots homogeneously distributed over the nanofibers. After nanofiber hydration, the liposomes reconstituted in two size populations (~140 and ~435 nm), as revealed by cutting-edge MADLS® analysis. Lastly, in vitro assays demonstrated that composite liposome-nanofiber formulations are superior to liposomal formulations due to a better safety profile in keratinocytes and peripheral blood mononuclear cells. Furthermore, both formulations exhibited similarly advantageous immunomodulatory effects, measured as decreased inflammation in vitro. A synergistic combination of the two nanodelivery systems shows promise for the development of efficient dressings for chronic wound treatment.

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.

Influence of Excipient Composition on Survival of Vaginal Lactobacilli in Electrospun Nanofibers.

The lack of appropriate delivery systems hinders the use of probiotics in the treatment of vaginal infections. Therefore, the development of a new delivery system for the local administration of vaginal probiotics is necessary. In this study, we selected three vaginal lactobacilli, i.e., Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii, and incorporated them into nanofibers using electrospinning. Polyethylene oxide (PEO) was used as a carrier polymer to produce nanofibers. It was supplemented with alginate and sucrose selected from a group of carbohydrates for their growth-promoting effect on lactobacilli. The interaction between excipients and lactobacilli was evaluated thermally and spectroscopically. Bacterial survival in polymer solutions and in nanofibers immediately after electrospinning and after storage varied among species and was dependent on the formulation. Sucrose improved the survival in polymer solutions and preserved the viability of L. crispatus and L. jensenii immediately after electrospinning, and L. gasseri and L. jensenii during storage. Blending PEO with alginate did not improve species viability. However, the three lactobacilli in the nanofibers retained some viability after 56 days, indicating that composite multifunctional nanofibers can maintain the viability of vaginal lactobacilli and can be used as a potential solid delivery system for vaginal administration of probiotics.

Incorporation of Ethylcellulose Microparticles Containing a Model Drug with a Bitter Taste into Nanofibrous Mats by the Electrospinning Technique-Preliminary Studies.

Electrospinning is considered a simple and comprehensive technique to formulate ultrafine fibres by using an electric field. Polymeric nanofibers constitute promising materials in biomedical applications as drug delivery systems. For their preparation, both natural and synthetic polymers are utilised. Owing to the potential use of electrospun nanofibers as an orodispersible drug dosage form, ethylcellulose microparticles containing the antihistamine drug rupatadine fumarate, prepared by the spray drying technique to conceal the drug's bitter taste, were incorporated into nanofibers. The obtained nanofibrous mats were evaluated for morphology, mechanical strength, disintegration time, the drug solid state and acceptability in terms of taste masking efficiency. Preliminary studies showed that hypromellose used as a single polymer was not a suitable substance for the manufacturing of nanofibers. Therefore, in order to facilitate the obtention of homogeneous nonwovens, different grades of polyethylene oxide (2,000,000-2M-Da and 4,000,000-4M-Da) were added, which improved the quality of the prepared mats. Nanofibers of the most satisfactory quality were obtained from hypromellose (6.5% w/v) and PEO (2M, 0.5% w/v). SEM image analysis has shown that the nanofibers were homogeneous and smooth and possessed a fast disintegration time (below 30 s) and an adequate drug content with a simultaneous taste-masking effect (as indicated by the in vivo and in vitro methods). However, further studies are necessary to refine their mechanical characteristics.

Microstructure and Electrical Conductivity of Electrospun Titanium Oxynitride Carbon Composite Nanofibers.

Titanium oxynitride carbon composite nanofibers (TiON/C-CNFs) were synthesised with electrospinning and subsequent heat treatment in ammonia gas. In situ four-probe electrical conductivity measurements of individual TiON/C-CNFs were performed. Additionally, the TiON/C-CNFs were thoroughly analysed with various techniques, such as X-ray and electron diffractions, electron microscopies and spectroscopies, thermogravimetric analysis and chemical analysis to determine the crystal structure, morphology, chemical composition, and N/O at. ratio. It was found that nanofibers were composed of 2-5 nm sized titanium oxynitride (TiON) nanoparticles embedded in an amorphous carbon matrix with a small degree of porosity. The average electrical conductivity of a single TiON/C-CNF was 1.2 kS/m and the bulk electrical conductivity of the TiON/C-CNF fabric was 0.053 kS/m. From the available data, the mesh density of the TiON/C-CNF fabric was estimated to have a characteristic length of 1.0 µm and electrical conductivity of a single TiON/C-CNF was estimated to be from 0.45 kS/m to 19 kS/m. The electrical conductivity of the measured TiON/C-CNFs is better than that of amorphous carbon nanofibers and has ohmic behaviour, which indicates that it can effectively serve as a new type of support material for electrocatalysts, batteries, sensors or supercapacitors.

Preparation and characterization of innovative electrospun nanofibers loaded with pharmaceutically applicable ionic liquids.

Keeping up with cutting edge research in the field of drug delivery, the overall goal of this study was to develop innovative electrospun nanofibers loaded with ionic liquids (ILs) as active pharmaceutical ingredients (APIs). For the first time, a novel approach was examined by combining biocompatible polymer, poly (ethylene oxide) (PEO), and pharmaceutical ILs in an electrospinning process to develop nanofibers with high drug loading (up to 47%). Firstly, two well-known local anaesthetic drugs, lidocaine and procaine, were modified into ILs with the salicylate, forming lidocaine salicylate and procaine salicylate. Its dual-functional nature and increased water solubility for 4- to 10-fold depending on the drug used contribute to overcoming current hurdles encountered by APIs such as poor solubility, low bioavailability, and polymorphism of the solid-state. Nanofibers were formulated using solutions tested for density, viscosity, electrical conductivity, and small-angle X-ray scattering by varying PEO molecular weight and the PEO to IL mass ratio. Scanning electron microscopy showed the surface morphology of the obtained nanofibers, while Fourier transform infrared spectroscopy and differential scanning calorimetry confirmed IL in the nanofibers in an amorphous state. Thus, nanofibers with incorporated IL represent well-known drugs in the new form and a novel dermal application delivery system.

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.

Particle properties and drug metastable solubility of simvastatin containing PVP matrix particles prepared by electrospraying technique.

In this work the preparation of drug loaded polymeric nanoparticles using electrospraying method and their subsequent characterization is presented. Our purpose was to incorporate the drug with extremely low solubility and low oxidative stability into polyvinylpyrolidone nanoparticles in order to improve its solubility and preserve its chemical stability and hence evaluate the ability of the technology to stabilize such systems in nanoparticulate form. Through the initial screening and optimization of process parameters and polymer solution properties, we detected different morphologies of electrosprayed product particles, where the use of lower molecular weight polymer resulted in a higher process instability as well as in a broader particle size distribution. On the other hand, the solution containing polyvinylpyrolidone with higher molecular weight showed sensitivity to different flow rates and electric field changes, which again resulted in differing the particle size and morphology. The electrosprayed products, prepared by sufficient process stability and having adequately narrow size distribution span, showed lower initial simvastatin contents than theoretically expected, which indicated an oxidative drug degradation already during the electrospraying process. The addition of antioxidants improved simvastatin chemical stability in the particles, during the process itself as well as after accelerated stability study. With an addition of butylated hydroxyanisole antioxidant mixture into initial polymer solution more than 95% of the drug content was preserved after one month at accelerated conditions, whereas in formulations without antioxidants simvastatin content was less than 6%. Antioxidants addition however did not influence only simvastatin stability but also simvastatin solubility. Surprisingly, antioxidants addition did decrease drug solubility in buffers (pH=4 and pH=6.8) for more than a half without any solid state changes of simvastatin. Potential hydrophobic interaction between simvastatin and antioxidants are hindering the drug solubility in the respective buffer, despite drug being in amorphous state.

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.

Core-shell nanofibers as drug delivery systems.

Core-shell nanofibers have grown in popularity over the last decade owing to their special features and their many applications in biomedicine. They can be produced by electrospinning of immiscible polymer blends or emulsions through a single nozzle or by electrospinning using a coaxial nozzle. Several of the electrospinning parameters allow great versatility for the compositions and diameters of core-shell nanofibers to be produced. Morphology of core-shell nanofibers can be investigated using transmission electron microscopy and, in some cases, scanning electron microscopy. Several studies have shown that core-shell nanofibers have some advantages over monolithic nanofibers, such as better drug, protein, gene or probiotic incorporation into the nanofibers, greater control over drug release, and maintenance of protein structure and activity during electrospinning. We herein review the production and characterization of core-shell nanofibers, the critical parameters that affect their development, and their advantages as delivery systems.

Effects of Electrospinning on the Viability of Ten Species of Lactic Acid Bacteria in Poly(Ethylene Oxide) Nanofibers.

Lactic acid bacteria can have beneficial health effects and be used for the treatment of various diseases. However, there remains the challenge of encapsulating probiotics into delivery systems with a high viability and encapsulation efficacy. The electrospinning of bacteria is a novel and little-studied method, and further investigation of its promising potential is needed. Here, the morphology, zeta potential, hydrophobicity, average cell mass, and growth characteristics of nine different species of Lactobacillus and one of Lactococcus are characterized. The electrospinning of polymer solutions containing ~10 log colony forming units (CFU)/mL lactic acid bacteria enabled the successful incorporation of all bacterial species tested, from the smallest (0.74 µm; Lactococcus lactis) to the largest (10.82 µm; Lactobacillus delbrueckii ssp. bulgaricus), into poly(ethylene oxide) nanofibers with an average diameter of ~100 nm. All of these lactobacilli were viable after incorporation into nanofibers, with 0 to 3 log CFU/mg loss in viability, depending on the species. Viability correlated with the hydrophobicity and extreme length of lactic acid bacteria, whereas a horizonal or vertical electrospinning set-up did not have any role. Therefore, electrospinning represents a promising method for the incorporation of lactic acid bacteria into solid delivery systems, while drying the bacterial dispersion at the same time.

Effect of Solution Composition Variables on Electrospun Alginate Nanofibers: Response Surface Analysis.

Alginate is a promising biocompatible and biodegradable polymer for production of nanofibers for drug delivery and tissue engineering. However, alginate is difficult to electrospin due to its polyelectrolyte nature. The aim was to improve the 'electrospinability' of alginate with addition of exceptionally high molecular weight poly(ethylene oxide) (PEO) as a co-polymer. The compositions of the polymer-blend solutions for electrospinning were varied for PEO molecular weight, total (alginate plus PEO) polymer concentration, and PEO proportion in the dry alginate-PEO polymer mix used. These were tested for rheology (viscosity, complex viscosity, storage and loss moduli) and conductivity, and the electrospun nanofibers were characterized by scanning electron microscopy. One-parameter-at-a-time approach and response surface methodology (RSM) were used to optimize the polymer-blend solution composition to obtain defined nanofibers. Both approaches revealed that the major influence on nanofiber formation and diameter were total polymer concentration and PEO proportion. These polymer-blend solutions of appropriate conductivity and viscosity enabled fine-tuning of nanofiber diameter. PEO molecular weight of 2-4 million Da greatly improved the electrospinnability of alginate, producing nanofibers with >85% alginate. This study shows that RSM can be used to design nanofibers with optimal alginate and co-polymer contents to provide efficient scaffold material for regenerative medicine.

Development of electrospun nanofibers that enable high loading and long-term viability of probiotics.

The interest in probiotics has grown in recent years due to increased awareness of the importance of microbiota for human health. We present the development of monolithic poly(ethylene oxide) and composite poly(ethylene oxide)/lyoprotectant nanofibers loaded with the probiotic Lactobacillus plantarum ATCC 8014. High loading was achieved for L. plantarum cells (up to 7.6 × 108 colony-forming unit/mg) that were either unmodified or expressing mCherry fluorescent protein. The initial concentration of L. plantarum in poly(ethylene oxide) solution was reported, for the first time, as the most critical parameter for its high viability after electrospinning, whereas the applied electric voltage and relative humidity during electrospinning did not vitally impact upon L. plantarum viability. The presence of amorphous lyoprotectant (especially trehalose) in the nanofibers promoted L. plantarum survival due to lyoprotectant interactions with L. plantarum cells. L. plantarum cells in nanofibers were stable over 24 weeks at low temperature, thereby achieving stability comparable with that in lyophilizates. The poly(ethylene oxide) nanofibers released almost all of the L. plantarum cells over 30 min, which will be adequate for their local administration. Our integrated approach enabled development of a promising nanodelivery system that provides high loading and long-term viability of L. plantarum in nanofibers, for local delivery to re-establish the microbiota balance e.g. in vagina.

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.