Biodegradable nanofibrous drug delivery systems: effects of metronidazole and ciprofloxacin on periodontopathogens and commensal oral bacteria

Abstract

Objectives: The purposes of this study were to fabricate biodegradable polydioxanone (PDS II®) electrospun periodontal drug delivery systems (hereafter referred to as matrices) containing either metronidazole (MET) or ciprofloxacin (CIP) and to investigate the effects of antibiotic incorporation on both periodontopathogens and commensal oral bacteria.

Materials and methods: Fibrous matrices were processed from PDS polymer solution by electrospinning. Antibiotic-containing PDS solutions were prepared to obtain four distinct groups: 5 wt.% MET, 25 wt.% MET, 5 wt.% CIP, and 25 wt.% CIP. Pure PDS was used as a control. High-performance liquid chromatography (HPLC) was done to evaluate MET and CIP release. Dual-species biofilms formed by Lactobacillus casei (Lc) and Streptococcus salivarius (Ss) were grown on the surface of all electrospun matrices. After 4 days of biofilm growth, the viability of bacteria on biofilms was assessed. Additionally, antimicrobial properties were evaluated against periodontopathogens Fusobacterium nucleatum (Fn) and Aggregatibacter actinomycetemcomitans (Aa) using agar diffusion assay.

Results: A three-dimensional interconnected porous network was observed in the different fabricated matrices. Pure PDS showed the highest fiber diameter mean (1,158 ± 402 nm) followed in a descending order by groups 5 wt.% MET (1,108 ± 383 nm), 25 wt.% MET (944 ± 392 nm), 5 wt.% CIP (871 ± 309 nm), and 25 wt.% CIP (765 ± 288 nm). HPLC demonstrated that groups containing higher amounts (25 wt.%) of incorporated drugs released more over time, while those with lower levels (5 wt.%) the least. No inhibitory effect of the tested antibiotics was detected on biofilm formation by the tested commensal oral bacteria. Meanwhile, CIP-containing matrices inhibited growth of Fn and Aa.

Conclusion: CIP-containing matrices led to a significant inhibition of periodontopathogens without negatively impairing the growth of periodontal beneficial bacteria.

Clinical relevance: Based on the proven in vitro inhibition of periodontitis-related bacteria, future in vivo research using relevant animal models is needed to confirm the effectiveness of these drug delivery systems.

Fig. 1

(a) Macrophotograph of the dual-species biofilm experimental set up on modified 24-wells tissue culture plates. Note the distinct PDS-based nanofibrous samples that were electrospun directly on cover borosilicate glass (solid arrow) slips attached to acrylic blocks (dotted arrow) using dental wax previously glued to the lid of the tissue culture plate. Representative SEM micrographs (b–d) of electrospun PDS matrices. (b) PDS control, (c) PDS + 25 wt.% MET, and (d) PDS + 25 wt.% CIP. Note the three-dimensional nanofibrous structure with an evident interconnected porous network.

Fig. 2

(a) Mean drug release ± SD (in μg) and the (b) percentage of drug release from the antibiotic-containing PDS-based electrospun matrices based on initial sample weight.

Fig. 3

Representative SEM micrographs of the electrospun PDS matrices following exposure to the dual-species biofilm. (a) PDS control, (b) PDS + 25% MET, and (c) PDS + 25% CIP. Note the presence of biofilm over the nanofibrous structure regardless of the material composition. (d) Mean counts of viable cells with error bars indicating SD (CFU/mL) on biofilms. No significant differences in counts of L. casei and S. salivarius were found among the tested conditions (p>0.05).

Fig. 4

(a) Growth inhibition of Aa and Fn following 5 days exposure to electrospun matrices incorporated with 5 or 25 wt.% of MET or CIP. *represents a statistical difference of groups tested against Aa in comparison to pure PDS used as a negative control. designates a statistical difference of groups tested against Fn and the control. Data was generated from a one-way ANOVA followed by Tukey’s (p<0.05). (b–c) Representative macrophotographs showing growth inhibition of Aa and Fn, respectively.