Dimitra Sakellari

Size-Dependent Mechanisms in AC Magnetic Hyperthermia Response of Iron-Oxide Nanoparticles

This paper correlates the magnetic properties of iron-oxide nanoparticles in the size range 5-18 nm with the occurring heating loss mechanisms when magnetic nanoparticle colloidal suspensions are subjected to high-frequency ac magnetic fields. The narrow size distribution of the nanoparticles enabled their clear classification into: 1) the superparamagnetic region (as large as 10 nm) where heating is mainly attributed to Neel relaxation; 2) the intermediate superparamagnetic-ferromagnetic transition region (10-13 nm); and 3) the ferromagnetic region (above 13 nm) where hysteresis losses dominate. The results from specific loss power measurements suggest that for size and concentration optimization, superparamagnetic nanoparticles may release significant amounts of heat to the surroundings, while the hysteresis losses mechanism appears to be much more efficient and the heat transfer provided through may be easier tuned for magnetically driven hyperthermia applications.

Novel protein identification methods for biomarker discovery via a proteomic analysis of periodontally healthy and diseased gingival crevicular fluid samples

AIM To identify possible novel biomarkers in gingival crevicular fluid (GCF) samples from chronic periodontitis (CP) and periodontally healthy individuals using high-throughput proteomic analysis. MATERIALS AND METHODS Gingival crevicular fluid samples were collected from 12 CP and 12 periodontally healthy subjects. Samples were trypically digested with trypsin, eluted using high-performance liquid chromatography, and fragmented using tandem mass spectrometry (MS/MS). MS/MS spectra were analysed using PILOT_PROTEIN to identify all unmodified proteins within the samples. RESULTS Using the database derived from Homo sapiens taxonomy and all bacterial taxonomies, 432 human (120 new) and 30 bacterial proteins were identified. The human proteins, angiotensinogen, clusterin and thymidine phosphorylase were identified as biomarker candidates based on their high-scoring only in samples from periodontal health. Similarly, neutrophil defensin-1, carbonic anhydrase-1 and elongation factor-1 gamma were associated with CP. Candidate bacterial biomarkers include 33 kDa chaperonin, iron uptake protein A2 and phosphoenolpyruvate carboxylase (health-associated) and ribulose biphosphate carboxylase, a probable succinyl-CoA:3-ketoacid-coenzyme A transferase, or DNA-directed RNA polymerase subunit beta (CP-associated). Most of these human and bacterial proteins have not been previously evaluated as biomarkers of periodontal conditions and require further investigation. CONCLUSIONS The proposed methods for large-scale comprehensive proteomic analysis may lead to the identification of novel biomarkers of periodontal health or disease.

HIV infection and periodontal diseases: an overview of the post‐HAART era

HIV infection remains a global health problem of unprecedented dimensions, although the development of highly active antiretroviral therapy (HAART) has significantly modified the course of HIV disease into a manageable chronic disease with longer survival and improved quality of life in HIV-infected subjects. Among the HIV-associated infections, oral lesions have been recognized as prominent features since the beginning of the epidemic and continue to be important. Periodontal diseases strongly associated with HIV infection are classified as linear gingival erythema, necrotizing ulcerative gingivitis and necrotizing ulcerative periodontitis and are included among the cardinal oral lesions. Although oral candidiasis appears to be the infection more significantly decreased after the introduction of HAART, the current literature suggests that the prevalence and course of periodontal lesions have also been modified. Higher prevalence of opportunistic microorganisms has been frequently detected in the subgingival flora of HIV-infected individuals, probably due to the immune status of those patients, as colonization and overgrowth of atypical pathogenic species is facilitated by immunosuppression. Additional research is required regarding biological issues such as the role of oral immune factors and periodontal disease in the persistency of HIV infection, the possibility of oral transmission and the re-emerging of HIV infection.

Prevalence and distribution of Aggregatibacter actinomycetemcomitans serotypes and the JP2 clone in a Greek population

AIM to investigate the distribution of Aggregatibacter actinomycetemcomitans serotypes and the prevalence of the JP2 clone in subgingival samples of Greek subjects. MATERIALS AND METHODS two hundred and twenty eight subjects participated in the present study. Each contributed with one pooled subgingival sample from the mesiobuccal surface of the four first molars. Samples were analysed using polymerase chain reaction for five serotypes of A. actinomycetemcomitans and the JP2 clone, using primers and conditions described previously. Subjects were stratified according to periodontal status (untreated periodontitis, non-periodontitis and periodontitis patients receiving supportive treatment). Comparisons between and within groups were performed by applying non-parametric tests (Kruskall-Wallis, Pearson χ(2) , z-test with Bonferronis corrections and Kramers V-test) at p=0.05 level. RESULTS a. actinomycetemcomitans was detected statistically more frequently in untreated patients (27.5%) compared with the other two groups (11.7% for non-periodontitis and 10% for periodontitis patients receiving supportive treatment). No statistical differences were observed concerning the distribution of serotypes among groups (z-test with Bonferronis corrections p>0.05). Serotype c was more predominant within the periodontally diseased groups (Kramers V-test p<0.05). The JP2 clone was not detected. CONCLUSIONS a. actinomycetemcomitans serotype b was not statistically correlated with periodontal disease in the investigated sample and the utility of microbiological testing before antimicrobial administration is emphasized.

Discovery of biomarker combinations that predict periodontal health or disease with high accuracy from GCF samples based on high‐throughput proteomic analysis and mixed‐integer linear optimization

AIM To identify optimal combination(s) of proteomic based biomarkers in gingival crevicular fluid (GCF) samples from chronic periodontitis (CP) and periodontally healthy individuals and validate the predictions through known and blind test sets. MATERIALS AND METHODS GCF samples were collected from 96 CP and periodontally healthy subjects and analysed using high-performance liquid chromatography, tandem mass spectrometry and the PILOT_PROTEIN algorithm. A mixed-integer linear optimization (MILP) model was then developed to identify the optimal combination of biomarkers which could clearly distinguish a blind subject sample as healthy or diseased. RESULTS A thorough cross-validation of the MILP model capability was performed on a training set of 55 samples and greater than 99% accuracy was consistently achieved when annotating the testing set samples as healthy or diseased. The model was then trained on all 55 samples and tested on two different blind test sets, and using an optimal combination of 7 human proteins and 3 bacterial proteins, the model was able to correctly predict 40 out of 41 healthy and diseased samples. CONCLUSIONS The proposed large-scale proteomic analysis and MILP model led to the identification of novel combinations of biomarkers for consistent diagnosis of periodontal status with greater than 95% predictive accuracy.

Prevalence of tetM, tetQ, nim and blaTEM genes in the oral cavities of Greek subjects: a pilot study

AIM To investigate the prevalence of tetM, tetQ, nim and bla(TEM) antimicrobial resistance genes in subgingival and tongue samples of Greek subjects. MATERIALS AND METHODS Fifty-four subjects participated in the present study. Participants each contributed with one pooled subgingival sample from the mesiobuccal surface of the four first molars and one sample from the tongue. Samples were analysed using polymerase chain reaction for tetM, tetQ, nim and bla(TEM) genes using the primers and conditions described previously. Subjects were stratified according to periodontal status (health, gingivitis or periodontitis). Intake of any antibiotic for medical or dental reasons during the previous 12 months was also recorded (self-reported). Comparisons within and between groups were performed by applying non-parametric tests (z-test with Bonferroni corrections). RESULTS A high prevalence of tetM, tetQ and bla(TEM) genes was detected in both tongue and subgingival samples (48.1-82.2%). No differences were observed across genes between periodontally healthy, gingivitis or periodontitis cases, and no statistical correlation was observed between the presence of the bla(TEM) gene and the intake of beta-lactams during the last 12 months (Fishers exact test, p>0.05). CONCLUSIONS Findings from the present study suggest a high prevalence of tetM, tetQ and bla(TEM), but not nim resistance genes in subgingival and tongue samples from Greek subjects.

Salivary concentration of free LL-37 in edentulism, chronic periodontitis and healthy periodontium

OBJECTIVE The antimicrobial peptide LL-37, a component of innate immunity, has an important role in maintaining oral health. This study aimed to investigate the concentration of free LL-37 in whole saliva of periodontally healthy, edentulous and chronic periodontitis subjects. DESIGN Unstimulated whole saliva was sampled from 154 subjects (76 periodontally healthy, 20 edentulous, and 58 subjects with chronic periodontitis). All participants were in good general health. The salivary LL-37 was determined by ELISA. RESULTS The median salivary concentrations of free LL-37 were 30.5, 22.5, and 1.8ng/ml for the healthy, the chronic periodontitis and the edentulous group, respectively. The differences in concentration between the edentulous and the others were statistically significant (Mann-Whitney test, p<0.001). In the healthy subjects, women displayed significantly higher peptide concentrations compared to men (Mann-Whitney test, p<0.05). The intra-subject variation in LL-37 concentration was wider for the healthy (range 0.75-285ng/ml) and chronic periodontitis patients (range 1-207ng/ml) than for the edentulous subjects (range 0.15-4.4ng/ml). CONCLUSIONS The present findings show that edentulism correlates with a substantial decrease in salivary levels of free LL-37, thus indicating the considerable contribution of the gingival tissues in the secretion of the peptide in the oral environment.

Proteomics for the discovery of biomarkers and diagnosis of periodontitis: a critical review

Periodontitis is a common chronic and destructive disease whose pathogenetic mechanisms remain unclear. Due to their sensitivity and global scale, proteomics studies offer the opportunity to uncover critical host and pathogen activity indicators and can elucidate clinically applicable biomarkers for improved diagnosis and treatment of the disease. This review summarizes the literature of proteomics studies on periodontitis and comprehensively discusses commonly found candidate biomarkers. Key considerations in the design of an experimental proteomics platform are also outlined. The applicability of protein biomarkers across the progression of periodontitis and unexplored areas of research are highlighted.

Prevalence of Staphylococcus aureus and methicillin resistant Staphylococcus aureus (MRSA) in the oral cavity

OBJECTIVE To assess the prevalence of Staphylococcus aureus and methicillin resistant Staphylococcus aureus (MRSA) in plaque and tongue samples from systemically healthy subjects with periodontal health, gingivitis or chronic periodontitis. METHODS After screening 720 potentially eligible subjects, 154 systemically healthy participants were ultimately enrolled in the current study. Subgingival samples were taken from the first molars and the tongue and analyzed for the presence of S. aureus and MRSA by polymerase chain reaction (PCR), using primers and conditions previously described in the literature. In addition, samples were taken from deep periodontal pockets of chronic periodontitis patients. Statistical analysis was performed by applying non-parametric tests (Kruskal-Wallis for clinical parameters, and z-test with Bonferroni corrections for distributions of assessed parameters). All comparisons were set at the 0.05 significance level. RESULTS S. aureus was detected in 18% of all participants and in 10% of the samples tested. No significant differences were found in its distribution among the three investigated groups (z-test for proportions with Bonferroni corrections, p>0.05). The mecA gene was not present in any of the S. aureus found. CONCLUSIONS S. aureus can be found in the oral environment regardless of the periodontal conditions and therefore should be considered as a member of the transient flora not participating in periodontal pathology. Subgingival sites and tongue surfaces seem to be an unusual habitat of MRSA.

Prevalence of β-lactam (blaTEM) and Metronidazole (nim) Resistance Genes in the Oral Cavity of Greek Subjects

Objectives: The aim of this study is to investigate the prevalence of blaTEM and nim genes that encode resistance to β-lactams and nitroimidazoles, respectively, in the oral cavity of systemically healthy Greek subjects. Materials and Methodology: After screening 720 potentially eligible subjects, 154 subjects were recruited for the study, including 50 periodontally healthy patients, 52 cases of gingivitis and 52 cases of chronic periodontitis. The clinical parameters were assessed with an automated probe. Various samples were collected from the tongue, first molars and pockets >6mm, and analysed by polymerase chain reaction-amplification of the blaTEM and nim genes, using primers and conditions previously described in the literature. Results: There was a high rate of detection of blaTEM in plaque and tongue samples alike in all periodontal conditions (37% of plaque and 60% of tongue samples, and 71% of participants). The blaTEM gene was detected more frequently in the tongue samples of the periodontally healthy (56%) and chronic periodontitis (62%) groups compared to the plaque samples from the same groups (36% and 29%, respectively; z-test with Bonferroni corrections-tests, P<0.05). The nim gene was not detected in any of the 343 samples analysed. Conclusion: The oral cavity of Greek subjects often harbours blaTEM but not nim genes, and therefore the antimicrobial activity of β-lactams might be compromised.