A. Almaguer-flores | Universidad Nacional Autónoma de México (original) (raw)

Papers by A. Almaguer-flores

Biomedical Physics & Engineering Express

Periodontitis is a highly prevalent infectious disease that causes the progressive destruction of... more Periodontitis is a highly prevalent infectious disease that causes the progressive destruction of the periodontal supporting tissues. If left untreated, it can lead to tooth loss impairing oral function, aesthetics, and the patient’s overall quality of life. Guided and Bone Tissue Regeneration (GTR/BTR) are surgical therapies based on the placement of a membrane that prevents epithelial growth into the defect, allowing the periodontal/bone cells (including stem cells) to regenerate or restore the affected tissues. The success of these therapies is commonly affected by the local bacterial colonization of the membrane area and its fast biodegradation, causing postoperative infections and a premature rupture of the membrane limiting the regeneration process. This study presents the antibacterial and osteogenic differentiation properties of polycaprolactone-gelatin (PCL-G) electrospun membranes modified with ZnO nanoparticles (ZnO-NPs). The membranes´ chemical composition, surface rough...

SPIE Proceedings, 2017

Antibacterial studies of inorganic nanoparticles (nps) have become important due to the increased... more Antibacterial studies of inorganic nanoparticles (nps) have become important due to the increased bacterial resistance against antibiotics. We used Zinc oxide nanoparticles (ZnO nps), which possess excellent photocatalytic properties with a wide band gap (Eg), are listed as “generally recognized as safe” by the Food and Drug Administration (FDA) and have shown antibacterial activity (AA) against many bacterial strains. The AA of ZnO nps is partly attributed to the production of Reactive Oxygen Species (ROS) by photocatalysis. When ZnO nps in aqueous media are illuminated with an energy <Eg, electron-hole pairs are generated on nps surface reacting with water and Oxygen molecules to generate hydroxyl-radical (OH• ), superoxide-radical (O2 •- ) and hydrogen-peroxide (H2O2). These ROS induce cell membrane damage resulting in cell death. However, the application of inorganic nps in medical treatments is limited due to the possible long-term side effects of nps release. To prevent its release, ZnO nps were dispersed into Polycaprolactone (PCL) fibers obtained by electrospinning technique. To optimize the use of ZnO nps concentration, we developed coreshell coaxial electrospun fibers where the core corresponded to PCL and the shell to a mixture of ZnO nps/PCL. Thus, ZnO nps were only dispersed on the surface of the fibers increasing its superficial contact area. We evaluated the AA against E. coli of different electrospun ZnO nps/PCL fibers under two different conditions: UVA pre-illumination and darkness. Preliminary results suggest that the AA against E. coli is better when electrospun ZnO nps/PCL were preilluminated with UVA than under darkness conditions.

ABSTRACT Objective: Magnesium (Mg) alloys, can be use as biodegradable medical devices, eliminati... more ABSTRACT Objective: Magnesium (Mg) alloys, can be use as biodegradable medical devices, eliminating the need for a second operation for implant removal. An important feature on biomedical devices is to avoid the bacterial adhesion and subsequent biofilm formation that can cause most of the implant-failures. The aim of this study was to analyze the differences on bacterial adhesion on magnesium (Mg) alloys modified by transition metals. Methods: Oral bacterial strains (Aggregatibacter actinomycetemcomitans serotipe b, Actinomyces israelii, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum, Parvimonas micra, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis) were incubated with different surface alloys: Base (Mg-Al-Zn), Tantalum (Mg-Al-Zn-Ta), Niobium (Mg-Al-Zn-Nb), Titanium (Mg-Al-Zn-Ti) and stainless steel (SS) control during 1, 3, 7 and 10 days. Counting plate technique was used to determine the number of colony forming units (CFUs). In addition, experimental surfaces were observed by scanning electron microscopy (SEM) to determinate the surface coverage of bacteria. Significant differences were determined using T-test. Results: Bacterial cells were only counted at one day of incubation. All the magnesium alloys show very low counts, the lowest adhesion was observed on the base alloy (0.1 X 105/mL), following for the containing niobium alloy (0.5 X 105/mL). Ti and Ta containing magnesium alloys presented more bacteria attached (1 X 105/mL and 3 X 105/mL, respectively), on the SS control the counts were 77.3 X 105/mL. On the other hand, by SEM bacteria colonies were not observed in any of the days of incubation, even though in the control surfaces clear colonies were observed. Conclusions: In this study, magnesium alloys, seems to have an antibacterial effect in the oral bacterial species that were used. No significant adhesion of bacteria was observed, indicating that these surfaces can prevent the bacterial adhesion and the subsequent biofilm formation on biomedical devices made with these alloys.

Objectives. The present study aimed to evaluate the potential of the salivary pellicle (SP) forme... more Objectives. The present study aimed to evaluate the potential of the salivary pellicle (SP) formed on titanium (Ti) surfaces to modulate the formation of a biofilm composed of Streptococcus gordonii, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis. Materials and Methods. Ti substrates were incubated for two hours with a pool of saliva samples obtained from 10 systemically and periodontally healthy subjects. Enamel substrates were included as a biological reference. Scanning electron microscopy (SEM) and Raman spectroscopy analysis were used to analyze the formation of the salivary pellicle. After the SP formation, the surfaces were incubated for 12 hours with a mix of Streptococcus gordonii, Actinomyces naeslundii, Fusobacterium nucleatum, and Porphyromonas gingivalis. The number of bacterial cells attached to each surface was determined by the XTT assay, while bacterial viability was analyzed by fluorescence microscopy using the LIVE/DEAD® BacLightTM k...

Optics & Laser Technology

Microorganisms

The adhesion of some bacteria has been attributed to critical levels of roughness in hard tissues... more The adhesion of some bacteria has been attributed to critical levels of roughness in hard tissues, which increases the risk of developing caries. The objective of this work was to assess the effect of deciduous and permanent tooth enamel surface roughness on bacterial adhesion. One hundred and eight samples of deciduous and permanent enamel were divided into two groups (n = 54). G1_DE deciduous enamel and G2_PE permanent enamel. The surface roughness was measured by profilometry and atomic force microscopy (AFM). Subsequently, the evaluation of bacterial adherence was carried out in triplicate by means of the XTT cell viability test. Additionally, bacterial adhesion was observed using scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The average values of the micrometric roughness in both groups were similar; however, in the nanometric scale they presented significant differences. Additionally, the G1_DE group showed the highest amount of adhered S. m...

Materials

The microstructural characteristics of biodegradable Mg alloys determine their performance and ap... more The microstructural characteristics of biodegradable Mg alloys determine their performance and appropriateness for orthopedic fixation applications. In this work, the effect of the annealing treatment of a Mg-0.7Zn-0.6Ca (ZX11) alloy on the mechanical integrity, corrosive behavior, and biocompatibility-osteoinduction was studied considering two annealing temperatures, 350 and 450 °C. The microstructure showed a recrystallized structure, with a lower number of precipitates, grain size, and stronger basal texture for the ZX11-350 condition than the ZX11-450. The characteristics mentioned above induce a higher long-term degradation rate for the ZX11-450 than the ZX11-350 on days 7th and 15th of immersion. In consequence, the mechanical integrity changes within this period. The increased degradation rate of the ZX11-450 condition reduces 40% the elongation at failure, in contrast with the 16% reduction for the ZX11-350 condition. After that period, the mechanical integrity remained unch...

Journal of Cluster Science, 2021

An easy mechanochemical and eco-friendly method was employed to obtain nanocrystals with an avera... more An easy mechanochemical and eco-friendly method was employed to obtain nanocrystals with an average size of about 9 nm of zinc ferrite (ZnFe2O4) and copper ferrite (CuFe2O4). Their corresponding X-ray diffraction (XRD) patterns reveal a cubic crystal structure for ZnFe2O4, whereas in CuFe2O4 the tetragonal and cubic crystal phases coexist, the latter being the majority phase. The transmission electron microscopy (TEM) images of these nano ferrites corroborate the formation of nanocrystals with dimensions consistent with those obtained from the XRD patterns. Furthermore, their corresponding Raman spectra confirm the structure and composition of nano ferrites. In addition, both nano ferrites show an electron paramagnetic resonance (EPR) spectrum with a wide band with g ~ 2.0, characteristic of ferromagnetic oxides. Besides, the antibacterial effect of ZnFe2O4 and CuFe2O4 nanocrystals against two opportunistic pathogens, Staphylococcus epidermidis (ATCC 14,990) and Pseudomonas aeruginosa (ATCC 43,636), was tested. The minimum bactericidal concentration (MBC) results showed that ZnFe2O4 was more effective against S. epidermidis, while CuFe2O4 was for P. aeruginosa. On the other hand, when 27 mg/mL of nano ferrites were dispersed in the agar plates, the growth of S. epidermidis was 100% inhibited, whereas ZnFe2O4 and CuFe2O4 inhibited 67% and 78% of P. aeruginosa growth, respectively.

Microbial Pathogenesis, 2021

The in vitro antagonist growth effect of bifidobacteria were evaluated on periodontal bacteria. B... more The in vitro antagonist growth effect of bifidobacteria were evaluated on periodontal bacteria. Bifidobacterium longum, Bifidobacterium lactis and Bifidobacterium infantis biofilms were grown in single, double or triple combinations with putative periodontal pathogens P. gingivalis and F. nucleatum or beneficial bacteria S. oralis for 24, 72 and 168 h and the total counts were analyzed by checkerboard DNA-DNA hybridization. The results showed that B. infantis and B. lactis, as single species, demonstrated the best antagonist effect on F. nucleatum and P. gingivalis and no influence on S. oralis growth at 168h. All the double combinations of bifidobacteria tested demonstrated an inhibitory effect on F. nucleatum (72h) and P. gingivalis (168h) and did not affect S. oralis counts at any time. In conclusion, B. lactis and B. infantis alone or in double combinations have antagonist effect on periodontopathogens biofilms, at different times points, and minimal influence on S. oralis growth.

Materials Science and Engineering: C, 2019

We report the synthesis and in vitro evaluation of dual-function chitosan-silver nanoparticles (C... more We report the synthesis and in vitro evaluation of dual-function chitosan-silver nanoparticles (CTS-AgNPs) films with potential applications as wound dressings. We attempted to formulate nanocomposite films with appropriate AgNPs concentrations to simultaneously display antibacterial activity and suitability for cell culture. Nanocomposites were obtained by CTS-mediated in situ chemical reduction of AgNO 3. Circular-shape AgNPs (sizes ca. 7-50 nm) well distributed within the CTS matrices were obtained in concentrations from 0.018 to 0.573 wt.%. Efficacy (bacteriostatic and bactericidal properties) of CTS-AgNPs films to decrease planktonic and biofilm bacterial growth was AgNPs concentration-and bacteria strain-dependent. Films showed significant antibacterial activity against Gram-negative E. coli and P. aeruginosa and Gram-positive S. aureus. Antibacterial activity against S. epidermidis was moderated. Films suitability for cell culture was characterized using primary human fibroblasts (HF). HF displayed cell viability higher than 90% and the characteristic fusiform morphology of adhered fibroblast upon culture on films with AgNPs concentration  0.036 wt.%. HF cultured on these films also showed positive expression of tropoelastin, procollagen type I and Ki-67, characteristic proteins of extracellular matrix and proliferative cells, respectively. In vitro assays demonstrated that cytocompatibility/antibacterial properties decreased/increased as silver concentration increased, suggesting that CTS-AgNPS nanocomposite films with ≈ 0.04-0.20 wt.% might be considered as potential temporary dual-function wound dressings.

Biofilms on dental implants can cause implant failure. Patients with failed implants present a mi... more Biofilms on dental implants can cause implant failure. Patients with failed implants present a microbiota similar to that of periodontal disease; however, it remains unclear if biofilms formed on titanium (Ti) implants are similar to biofilms on teeth and how they are affected by implant surface properties like microtopography and hydrophilicity. Methods: To test this, in-vitro biofilms were formed on Ti-disk surfaces: pure-titanium (PT [Ra<0.2µm]), acid-etched (A [Ra<0.8µm]), A modified to be hydrophilic (modA), sand-blasted/acid-etched (SLA [Ra=4µm]), and hydrophilic SLA (modSLA). Disks were incubated for 24h in anaerobic conditions using human saliva (HS) or Mycoplasma-media (MM) with normal oral microbiota, including: Actinobacillus actinomycetemcomitans serotype b, Actinomyces israelii, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum ss nucleatum, Peptostreptococcus micros, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis. Col...

MRS Proceedings, 2010

Magnesium (Mg) alloys can be use as biodegradable medical devices, eliminating the need for a sec... more Magnesium (Mg) alloys can be use as biodegradable medical devices, eliminating the need for a second operation for implant removal. An important feature on biomedical devices is to avoid the bacterial adhesion and subsequent biofilm formation that cause most of the implant-failures. The aim of this study was to analyze the differences on bacterial adhesion and biofilm development on Magnesium alloys (Mg-Al-Zn) modified by different transition metals; Tantalum, Niobium and Titanium. Nine oral bacterial strains (Aggregatibacter actinomycetemcomitans serotipe b, Actinomyces israelii, Campylobacter rectus, Eikenella corrodens, Fusobacterium nucleatum, Parvimonas micra, Porphyromonas gingivalis, Prevotella intermedia and Streptococcus sanguinis) were incubated on the different alloys and commercial medical grade stainless steel (AISI 316L) was used as a control. The initial bacterial adhesion was determined after 24 hours using a counting plate technique and the subsequent biofilm develo...

Toxicology Letters, 2016

Introduction: The use of nanoparticles (NPs) is among the most promising strategies to overcome i... more Introduction: The use of nanoparticles (NPs) is among the most promising strategies to overcome infections within the medical and dental area. Bismuth subsalicylate (BSS) has been used as an antimicrobial agent against H. pylori infections. However, there is not enough information regarding the antibacterial effect of BBS-NPs in other relevant bacteria strains and their toxic effects in mammalian cells. Objective: The aim of this study was to evaluate the in vitro cytotoxicity of BSS-NPs against cultures of four strains of bacteria of medical importance and in cell cultures of human gingival fibroblast. Materials and methods: BSS-NPs were synthesized by laser ablation and the physico-chemical characterization was performed by UV-Vis spectroscopy, Dynamic light scattering (LDS), Laser Doppler Anemometer (LDA) and Transmission Electron Microscopy (TEM). To evaluate the antibacterial effect, BSS-NPs were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis using XTT assay in 24 h. Cell cultures of human gingival fibroblast (HGF-1) were used to measure cell viability by MTS and LDH assays for 24 h. Results: The UV-Vis spectra indicated the presence of salicylic acid functional groups that are present in the BSS chemical structure. LDS measurement reported a diameter in water of between 1.2 and 220 nm and the zeta potential of −9.09 which was obtained by LDA. The use of TEM allowed to observe nanoparticles, with a crystal structure and primary particle size of 10 nm. The results of antibacterial effect indicated a significant growth inhibition in all strains tested (∼89%), being more effective against P. aeruginosa with a 90% at a concentration of 60 g/mL of BSS-NPs. Cell viability assays showed that BSS-NPs did not compromise HGF-1 viability, 96% of mitochondrial activity and 5% of LDH release was observed at 60 g/mL. Conclusions: BSS-NPs showed an efficient antibacterial effect in bacteria strains of dental importance and a low toxicity in cell mammalian cultures; thus BBS-NPs could be a good antimicrobial agent for medical-dental applications.

Revista Odontológica Mexicana, 2010

Introduction: Periodontal diseases are infections, caused by microorganisms that colonize oral su... more Introduction: Periodontal diseases are infections, caused by microorganisms that colonize oral surfaces in a complex structure called biofilm. Purpose: To describe the microbial composition of subgingival plaque samples in Mexican subjects with chronic periodontitis. Methods: 56 patients (33 with chronic periodontitis and 23 periodontally healthy) were included in the study. Subgingival plaque samples were evaluated using the “checkerboard” DNADNA hybridization technique. Results: Mean DNA probe counts were significantly higher in chronic periodontitis subjects for P. gingivalis (p < 0.001), T. forsythensis (p < 0.01) and for T. denticola and A. actinomycetemcomitans (p < 0.05). Chronic periodontitis subjects also exhibited significantly higher proportions of “red” complex species and significantly lower proportions of Actinomyces species and microorganisms included in the “yellow” complex when compared with healthy subjects. Conclusions: Due to the complexity of the subgin...

Journal of Nanoparticle Research, 2015

The antimicrobial properties of bismuth subsalicylate (BSS) nanoparticles against four opportunis... more The antimicrobial properties of bismuth subsalicylate (BSS) nanoparticles against four opportunistic pathogens; E. coli, P. aeruginosa, S. aureus, and S. epidermidis were determined. BSS nanoparticles were synthesized by pulse laser ablation of a solid target in distilled water under different conditions. The nanoparticles were characterized using high-resolution transmission electron microscopy and absorption spectra and small angle X-ray scattering. The analysis shows that the colloids maintained the BSS structure and presented average particle size between 20 and 60 nm, while the concentration ranges from 95 to 195 mg/L. The antibacterial effect was reported as the inhibition ratio of the bacterial growth after 24 h and the cell viability was measured using the XTT assay. The results showed that the inhibition ratio of E. coli and S. epidermidis was dependant on the NPs size and/ or concentration, meanwhile P. aeruginosa and S. aureus were more sensitive to the BSS nanoparticles independently of both the size and the concentration. In general, the BSS colloids with average particle size of 20 nm were the most effective, attaining inhibition ratios [80 %, similar or larger than those obtained with the antibiotic used as control. The results suggest that the BSS colloids could be used as effective antibacterial agents with potential applications in the medical area.

Antibiotic resistance is a serious medical, economical and public health problem. No information ... more Antibiotic resistance is a serious medical, economical and public health problem. No information is available about the presence of bacterial resistance in dental plaque in the mexican population. Objective: To determine the proportion of bacterial species resistant to amoxicillin, doxycycline, metronidazole and clindamycin in subgingival plaque samples of mexican subjects with chronic periodontitis. Methods: After initial screening and clinical monitoring, two samples of subgingival plaque were taken from the distal surface of two molar. The two samples were dispersed and serially diluted in PRAS Ringer's solution and plated on enriched Tripticase soy blood agar supplemented or not with one of the antibiotics that were tested. After 7 days of anaerobic incubation, colonies were counted on both the antibiotic-containing and no antibiotic media for determining the proportion of antibiotic resistant isolates in the samples. Results: The proportion of resistance was 3.5 for amoxici...

Clinical Implant Dentistry and Related Research, 2014

Dental implants will be exposed to a complex ecosystem once they are placed in the oral cavity. T... more Dental implants will be exposed to a complex ecosystem once they are placed in the oral cavity. The bacterial colonization and biofilm formation on these devices will depend not only on the physicochemical surface implant properties but also on the periodontal health conditions of the patients, as these devices are exposed. The aim of this study was to correlate the subgingival microbial profile with the composition of initial biofilm formed on different microstructured titanium (Ti) surfaces. Ten periodontitis and 10 periodontally healthy subjects were included in this study. The subjects wore a removable acrylic device with four different fixed Ti surfaces for 48 hours. Microbial samples of subgingival plaque and the biofilm formed on each Ti surface were individually analyzed by the checkerboard DNA-DNA hybridization technique. Despite the roughness or hydrophilicity of the Ti surfaces, a characteristic pattern of bacterial adhesion was observed on each of the study groups. However, significant differences in the proportion of the species that colonized the Ti surfaces were found between the periodontitis and periodontally healthy groups. Treponema denticola, Neisseria mucosa, Eikenella corrodens, and Tannerella forsythia were detected in higher proportions on the Ti disks placed in the periodontitis subjects, while significant higher proportions of Capnocytophaga sputigena, Fusobacterium periodonticum, Prevotella melaninogenica, and Streptococcus mitis were detected on the Ti disks placed in the periodontally healthy group. The results obtained in this study shows that the composition and the proportion of the species that initially colonize Ti surfaces are highly influenced by the periodontal status more than the surface characteristics of the Ti implant.

MRS Proceedings, 2012

ABSTRACTBismuth has been used as an antimicrobial agent for treating gastrointestinal disorders, ... more ABSTRACTBismuth has been used as an antimicrobial agent for treating gastrointestinal disorders, and has been used in the eradication of Helicobacter pylori. The aim of the present study was to analyze the antimicrobial activity of different Bi compounds against opportunistic pathogens. Ten bismuth compounds were tested with three different concentrations (60, 30 and 10%), against pure cultures of the following bacterial strains: Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Staphylococcus epidermidis. The results show that Bismuth subsalicylate, Bismuth trioxide and Bismuth subgallate had a good antibacterial activity however, Bismuth subsalicylate was the most effective in the inhibition of the four bacterial strains tested. In this study we confirm the antibacterial properties of Bi-based compounds for other bacteria than H. pylori.

MRS Proceedings, 2009

ABSTRACTInfection due microbes on implant surfaces has a strong influence on healing and long ter... more ABSTRACTInfection due microbes on implant surfaces has a strong influence on healing and long term viability of dental implants. The prevention and control of biofilms can be achieved by reducing the bacterial adhesion on the surface. The coating of medical devices with silver, or the addition of silver nanoparticles, are two possible ways to prevent device-associated infections. On the other hand, amorphous carbon films, in its different forms and compositions, have been studied as beneficial surface modification for implant materials. However, the bacterial adhesion on these films by oral bacteria in comparison to standard surfaces (Ti and SS) has been seen to be relatively high. In the oral cavity, the microbial ecology is complex and consists of hundreds of bacterial species, and therefore it is recommendable to study bacteria adhesion using various strains. In this work, we tested the biocompatibility and the anti-microbial properties of amorphous carbon films with the addition...