Clinical Perspective of Electrospun Nanofibers as a Drug Delivery Strategy for Regenerative Endodontics

Natural monoterpenes-laden electrospun fibrous scaffolds for endodontic infection eradication

This investigation aimed to synthesize poly(D,L-lactide) (PLA)-based fibrous scaffolds containing natural essential oils (i.e., linalool and citral) and determine their antimicrobial properties and cytocompatibility as a clinically viable cell-friendly disinfection strategy for regenerative endodontics. PLA-based fibrous scaffolds were fabricated via electrospinning with different concentrations of linalool and citral. The micromorphology and average diameter of the fibers was investigated through scanning electron microscopy (SEM). The chemical composition of the scaffolds was inferred by Fourier-transform infrared spectroscopy (FTIR). Antimicrobial efficacy against Enterococcus faecalis and Actinomyces naeslundii was also evaluated by agar diffusion and colony-forming units (CFU) assays. The scaffolds' cytocompatibility was determined using dental pulp stem cells (DPSCs). Statistical analyses were performed and the significance level was set at α = 5%. Linalool and citral's incorporation in the PLA fibrous scaffolds was confirmed in the FTIR spectra. SEM images indicate no morphological changes upon inclusion of the essential oils, except the reduced diameter of 40% linalool-laden fibers (p < 0.05). Importantly, significant antimicrobial properties were reported for citral-containing scaffolds for CFU/mL counts (p < 0.05), while only 20% and 40% linalool-laden scaffolds reduced CFU/mL (p < 0.05). Meanwhile, the inhibition halos were verified in a concentration-dependent manner for all monoterpenes-laden scaffolds. Citral- and linalool-laden PLA-based fibrous scaffolds showed acceptable cytocompatibility. The incorporation of natural monoterpenes did not alter the scaffolds' fibrous morphology, promoted antimicrobial action against endodontic pathogens, and preserved DPSCs viability. Linalool- and citral-laden electrospun scaffolds hold promise as naturally derived antimicrobial therapeutics for applications in regenerative endodontics.

Electrospun Azithromycin-Laden Gelatin Methacryloyl Fibers for Endodontic Infection Control

This study was aimed at engineering photocrosslinkable azithromycin (AZ)-laden gelatin methacryloyl fibers via electrospinning to serve as a localized and biodegradable drug delivery system for endodontic infection control. AZ at three distinct amounts was mixed with solubilized gelatin methacryloyl and the photoinitiator to obtain the following fibers: GelMA+5%AZ, GelMA+10%AZ, and GelMA+15%AZ. Fiber morphology, diameter, AZ incorporation, mechanical properties, degradation profile, and antimicrobial action against Aggregatibacter actinomycetemcomitans and Actinomyces naeslundii were also studied. In vitro compatibility with human-derived dental pulp stem cells and inflammatory response in vivo using a subcutaneous rat model were also determined. A bead-free fibrous microstructure with interconnected pores was observed for all groups. GelMA and GelMA+10%AZ had the highest fiber diameter means. The tensile strength of the GelMA-based fibers was reduced upon AZ addition. A similar pattern was observed for the degradation profile in vitro. GelMA+15%AZ fibers led to the highest bacterial inhibition. The presence of AZ, regardless of the concentration, did not pose significant toxicity. In vivo findings indicated higher blood vessel formation, mild inflammation, and mature and thick well-oriented collagen fibers interweaving with the engineered fibers. Altogether, AZ-laden photocrosslinkable GelMA fibers had adequate mechanical and degradation properties, with 15%AZ displaying significant antimicrobial activity without compromising biocompatibility.

Comparing Antibiotic Pastes with Electrospun Nanofibers as Modern Drug Delivery Systems for Regenerative Endodontics

Nanomaterials have various features that make these types of materials able to be applied in different biomedical applications like, diagnosis, treatment, and drug delivery. Using such materials in endodontic filed both to face the challenges that occur during treatment processes and to make these materials have an antibacterial effect without showing any harm on the host cells. The approach of nanofibers loaded with various antibacterial drugs offers a potential treatment method to enhance the elimination procedure of intracanal biofilms. Clinically, many models of bacterial biofilms have been prepared under in vitro conditions for different aims. The process of drug delivery from polymeric nanofibers is based on the principle that the releasing ratio of drug molecules increases due to the increase in the surface area of the hosted structure. In our review, we discuss diverse approaches of loading/releasing drugs on/from nanofibers and we summarized many studies about electrospun nanofibers loaded various drugs applied in the endodontic field. Moreover, we argued both the advantages and the limitations of these modern endodontic treatment materials comparing them with the traditional ones.

Drug Delivery Assessment of a Novel Triple Antibiotic-Eluting Injectable Platelet-Rich Fibrin Scaffold: An In Vitro Study

BACKGROUND

Intracanal disinfection is a critical, yet challenging goal for long-term success in regenerative-based treatments. This in-vitro study aimed to assess the release profile of triple antibiotic- eluting Injectable Platelet-Rich Fibrin (I-PRF) constructs in 28 days.

METHODS

I-PRF scaffolds containing triple antibiotic mixture [Metronidazole (MET), Ciprofloxacin (CIP), and Minocycline (MINO)] by immersion (group one), I-PRF scaffolds containing triple antibiotic mixture by integration (group two), and antibiotic-free I-PRF scaffolds (group three) were fabricated. The antibiotic release from the scaffolds was measured using High-Performance Liquid Chromatography (HPLC) (the mobile phase of 0.1% formic acid and methanol (35:65 v/v), a C18 analytical column (150 × 4.6 mm, 5 μm) at a flow rate of 0.7 mL/min, at 25ºC) at days 1, 3, 7, 14, 21, and 28.

RESULTS

Retention times for MINO, CIP, and MET were achieved as 2.3, 2.6, and 3.1 min, respectively. The maximum UV absorbance values for CIP, MET, and MINO were 268 nm, 278 nm, and 350 nm, respectively. The results of the first group showed burst release within the first 24 hours followed by sustained maintenance of all three antibiotics up to 14 days. MINO and MET were still detectable in the third week. The second group could not sustainably release the antibiotics.

CONCLUSION

The developed method for the simultaneous identification and quantification of each antibiotic in I-PRF was sensitive and quick. Overall, group one could take up the antibiotics in adequate quantities and then subsequently release them over the study period.

Curcumin-A Natural Medicament for Root Canal Disinfection: Effects of Irrigation, Drug Release, and Photoactivation

INTRODUCTION

Curcumin incorporation into polymeric fibers was tested for its antimicrobial properties and potential use in root canal disinfection.

METHODS

Curcumin-modified fibers were processed via electrospinning and tested against a 7-day old established Actinomyces naeslundii biofilm. The medicaments tested were as follows: curcumin-modified fibers at 2.5 and 5.0 mg/mL, curcumin-based irrigant at 2.5 and 5.0 mg/mL, saline solution (negative control), and the following positive controls: 2% chlorhexidine, 1% sodium hypochlorite, and triple antibiotic paste (TAP, 1 mg/mL). All medicaments, except for the positive controls, were allocated according to the light exposure protocol (ie, photoactivation with a light-emitting diode every 30 seconds for 4 minutes or without photoactivation). After treatment, the medicaments were removed, and 1 mL saline solution was added; the biofilm was scraped from the well and used to prepare a 1:2000 dilution. Spiral plating was performed using anaerobic blood agar plates. After 24 hours, colony-forming units (colony-forming units/mL, n = 11/group) were counted to determine the antimicrobial effects.

RESULTS

Data exhibited significant antimicrobial effects on the positive control groups followed by the curcumin irrigants and, lastly, the photoactivated curcumin-modified fibers. There was a significant reduction of viable bacteria in curcumin-based irrigants, which was greater than the TAP-treated group. Curcumin-free fibers, saline, and the nonphotoactivated curcumin-modified fibers did not display antimicrobial activity.

CONCLUSIONS

Curcumin seems to be a potential alternative to TAP when controlling infection, but it requires a minimal concentration (2.5 mg/mL) to be effective. Photoactivation of curcumin-based medicaments seems to be essential to obtain greater antibiofilm activity.

A novel patient-specific three-dimensional drug delivery construct for regenerative endodontics

Evoked bleeding (EB) clinical procedure, comprising a disinfection step followed by periapical tissue laceration to induce the ingrowth of undifferentiated stem cells from the periodontal ligament and alveolar bone, is currently the only regenerative-based therapeutic approach to treating pulp tissue necrosis in undeveloped (immature) permanent teeth approved in the United States. Yet, the disinfection step using antibiotic-based pastes leads to cytotoxic, warranting a biocompatible strategy to promote root canal disinfection with no or minimal side-effects to maximize the regenerative outcomes. The purpose of this investigation was to develop a tubular three-dimensional (3D) triple antibiotic-eluting construct for intracanal drug delivery. Morphological (scanning electron microscopy), chemical (Fourier transform infrared spectroscopy), and mechanical (tensile testing) characteristics of the polydioxanone-based triple antibiotic-eluting fibers were assessed. The antimicrobial properties of the tubular 3D constructs were determined in vitro and in vivo using an infected (Actinomyces naeslundii) dentin tooth slice model and a canine method of periapical disease, respectively. The in vitro data indicated significant antimicrobial activity and the ability to eliminate bacterial biofilm inside dentinal tubules. In vivo histological findings demonstrated that, using the EB procedure, the tubular 3D triple antibiotic-eluting construct allowed the formation of an appropriate environment that led to apex closure and the ingrowth of a thin layer of osteodentin-like tissue into the root canal. Taken together, these findings indicate that our novel drug delivery construct is a promising biocompatible disinfection strategy for immature permanent teeth with necrotic pulps. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1576-1586, 2019.

Comparative Evaluation of the Cytotoxic and Angiogenic Effects of Minocycline and Clindamycin: An In Vitro Study

INTRODUCTION

This study aimed to compare the cytocompatibility and angiogenic potential of 2 antibiotics (clindamycin [CLIN] and minocycline [MINO]) at distinct concentrations on dental pulp stem cells (DPSCs) and human umbilical vein endothelial cells (HUVECs).

METHODS

DPSCs and HUVECs were exposed to cell culture media modified with CLIN or MINO at concentrations ranging from 30 μg/mL-1000 μg/mL. Cell toxicity and proliferation were investigated using the lactate dehydrogenase and tetrazolium reduction assays, respectively. A capillarylike tube formation in vitro assay was conducted to determine the angiogenic potential associated with each antibiotic. Additionally, selected morphometric angiogenesis parameters were determined using dedicated software (WimTube; Onimagin Technologies SCA, Córdoba, Spain). All statistical analyses were performed using 1-way analysis of variance and the Tukey post hoc test (α= .05).

RESULTS

The collected data showed that compared with the control (cell culture media, alpha-minimum essential medium Eagle) increasing the antibiotic concentration significantly decreased cell viability and proliferation of both DPSCs and HUVECs. In terms of angiogenic potential, when tested at 30 μg/mL and 50 μg/mL, CLIN significantly amplified tube formation when compared with MINO with angiogenesis parameters (ie, tube length and tube number) similar to the effect promoted by exogenous vascular endothelial growth factor (50 ng/mL).

CONCLUSIONS

CLIN was less cytotoxic when compared with MINO at higher concentrations. Of note, CLIN did not hinder the proangiogenic activity induced by vascular endothelial growth factor to the same extent as MINO, suggesting that the replacement of MINO by CLIN might translate into positive implications in the overall regenerative outcome.

Animal Models for Stem Cell-Based Pulp Regeneration: Foundation for Human Clinical Applications

IMPACT STATEMENT

Animal models are essential for tissue regeneration studies. This review summarizes and discusses the small and large animal models, including mouse, ferret, dog, and miniswine that have been utilized to experiment and to demonstrate stem cell-mediated dental pulp tissue regeneration. We describe the models based on the location where the tissue regeneration is tested-either ectopic, semiorthotopic, or orthotopic. Developing and utilizing optimal animal models for both mechanistic and translational studies of pulp regeneration are of critical importance to advance this field.

Clindamycin-modified Triple Antibiotic Nanofibers: A Stain-free Antimicrobial Intracanal Drug Delivery System

INTRODUCTION

A biocompatible strategy to promote bacterial eradication within the root canal system after pulpal necrosis of immature permanent teeth is critical to the success of regenerative endodontic procedures. This study sought to synthesize clindamycin-modified triple antibiotic (metronidazole, ciprofloxacin, and clindamycin [CLIN]) polymer (polydioxanone [PDS]) nanofibers and determine in vitro their antimicrobial properties, cell compatibility, and dentin discoloration.

METHODS

CLIN-only and triple antibiotic CLIN-modified (CLIN-m, minocycline-free) nanofibers were processed via electrospinning. Scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and tensile testing were performed to investigate fiber morphology, antibiotic incorporation, and mechanical strength, respectively. Antimicrobial properties of CLIN-only and CLIN-m nanofibers were assessed against several bacterial species by direct nanofiber/bacteria contact and over time based on aliquot collection up to 21 days. Cytocompatibility was measured against human dental pulp stem cells. Dentin discoloration upon nanofiber exposure was qualitatively recorded over time. The data were statistically analyzed (P < .05).

RESULTS

The mean fiber diameter of CLIN-containing nanofibers ranged between 352 ± 128 nm and 349 ± 128 nm and was significantly smaller than PDS fibers. FTIR analysis confirmed the presence of antibiotics in the nanofibers. Hydrated CLIN-m nanofibers showed similar tensile strength to antibiotic-free (PDS) nanofibers. All CLIN-containing nanofibers and aliquots demonstrated pronounced antimicrobial activity against all bacteria. Antibiotic-containing aliquots led to a slight reduction in dental pulp stem cell viability but were not considered toxic. No visible dentin discoloration upon CLIN-containing nanofiber exposure was observed.

CONCLUSIONS

Collectively, based on the remarkable antimicrobial effects, cell-friendly, and stain-free properties, our data suggest that CLIN-m triple antibiotic nanofibers might be a viable alternative to minocycline-based antibiotic pastes.

Antimicrobial Efficacy of Triple Antibiotic-eluting Polymer Nanofibers against Multispecies Biofilm

The elimination of microbial flora in cases of immature permanent teeth with necrotic pulp is both key and a challenging goal for the long-term success of regenerative therapy. Recent research has focused on the development of cell-friendly intracanal drug delivery systems. This in vitro study aimed to investigate the antimicrobial action of 3-dimensional (3D) tubular-shaped triple antibiotic-eluting nanofibrous constructs against a multispecies biofilm on human dentin. Polydioxanone polymer solutions, antibiotic-free or incorporated with metronidazole, ciprofloxacin, and minocycline, were electrospun into 3D tubular-shaped constructs. A multispecies biofilm consisting of Actinomyces naeslundii, Streptococcus sanguinis, and Enterococcus faecalis was forced inside the dentinal tubules via centrifugation in a dentin slice in vitro model. The infected specimens were exposed to 2 experimental groups (ie, 3D tubular-shaped triple antibiotic-eluting constructs and triple antibiotic paste [TAP]) and 2 control groups (7-day biofilm untreated and antibiotic-free 3D tubular-shaped constructs). Biofilm elimination was quantitatively analyzed with confocal laser scanning microscopy. Confocal laser scanning microscopic (CLSM) analysis showed a dense population of viable (green) bacteria adhered to dentin and penetrated into the dentinal tubules. Upon 3D tubular-shaped triple antibiotic-eluting nanofibrous construct exposure, nearly complete elimination of viable bacteria on the dentin surface and inside the dentinal tubules was shown in the CLSM images, which was similar (P < .05) to the bacterial death promoted by the TAP group but significantly greater when compared with both the antibiotic-free 3D tubular-shaped constructs and the control (saline). The proposed 3D tubular-shaped antibiotic-eluting construct showed pronounced antimicrobial effects against the multispecies biofilm tested and therefore holds significant clinical potential as a disinfection strategy before regenerative endodontics.