Usefulness of low-cost infrared goggles for the assessment of spontaneous nystagmus / Utilidad de gafas infrarrojas de bajo costo para la evaluación del nistagmo espontáneo

Introduction: Due to its precision and simplicity, videonystagmography is the most used technique for evaluating eye movements in patients with vestibular complaints. However, its high cost limits its widespread use. In response, the development of low-cost goggles emerged as an alternative to traditional videonystagmography equipment. Objetives: This study aimed to compare the performance between low-cost goggles and videonystagmography in assessing spontaneous nystagmus. Materials and Methods: We conducted a cross-sectional study at the Department of Otolaryngology at the Red UC Christus. Patients referred for vestibular evaluation were assessed using both videonystagmography and a prototype of low-cost goggles. Two blinded clinicians with varying levels of expertise reviewed recordings from both tests to identify spontaneous nystagmus. Results: Of 104 participants, 56.7% exhibited spontaneous nystagmus detected by videonystagmography. The low-cost goggles demonstrated a concordance of k= 0.60 for nystagmus detection and k= 0.47 for classification when used by the less experienced clinician. The more experienced clinician achieved a concordance of k= 0.82 for detection and k= 0.73 for classification. Conclusion: While clinical assessments can be conducted without specialized equipment, videonystagmography offers a comprehensive and detailed evaluation, making it the preferred and widely utilized method. Nevertheless, low-cost goggles enable the detection of spontaneous nystagmus, demonstrating satisfactory agreement with videonystagmography.

Introducción: Debido a su precisión y simplicidad, la videonistagmografía es la técnica más utilizada para la evaluación de movimientos oculares en pacientes con queja vestibular. Sin embargo, su alto costo limita su utilización. Frente a esto, el desarrollo de gafas de bajo costo se posiciona como una alternativa al equipo tradicional de videonistagmografía. Objetivo: El objetivo de este estudio fue comparar el rendimiento entre gafas de bajo costo y videonistagmografía en la evaluación del nistagmo espontáneo. Material y Métodos: Realizamos un estudio transversal en el Servicio de Otorrinolaringología de la Red UC Christus. Los pacientes derivados para evaluación vestibular fueron evaluados con video-nistagmografía y con un prototipo de gafas de bajo costo. Dos clínicos cegados con distinta experiencia revisaron las grabaciones de ambas pruebas en busca de nistagmo espontáneo. Resultados: De 104 participantes, el 56,7% presentó nistagmo espontáneo detectado por videonistagmografía. Las gafas de bajo costo mostraron una concordancia de k= 0,60 para la detección del nistagmo y k= 0,47 para la clasificación cuando fueron utilizadas por el clínico menos experimentado. El clínico más experimentado logró una concordancia de k= 0,82 para la detección y k= 0,73 para la clasificación. Conclusión: Aunque las evaluaciones clínicas pueden realizarse sin equipo especializado, la videonistagmografía proporciona una evaluación integral y detallada, convirtiéndola en el método preferido y ampliamente utilizado. Sin embargo, las gafas económicas permiten la detección de nistagmo espontáneo, mostrando un acuerdo satisfactorio con la videonistagmografía.

[Recommendations on organization, design, characteristics and operation of neonatology services]. / Recomendaciones de organización, diseño, características y funcionamiento de servicios o unidades de neonatología.

Neonatal care has undergone important advances involving the technology for treatment and mo nitoring, the design of care spaces, the incorporation of support professionals, and, especially, the strengthening of an organizational model in networks with centers of different levels of care. Neona tal units should be located in centers with maternity services and, ideally, with pediatric ones of an equivalent level of care. This document defines the admission and transfer criteria according to the level of care and among the different levels, respectively. The evidence recommends an individual room design due to the associated benefits such as decreased occurrence and better control of health care-associated infections, improved breastfeeding, and better interaction with parents. The sugges ted room sizes favor the implementation of the family-centered care model. These recommendations establish the possibility of performing emergency surgical procedures in the neonatal unit and define the safety criteria of the physical plant. In addition, they define the human resources according to the level of care, recognizing the time dedicated to non-direct patient care activities, , and the re quirements of non-medical professionals such as psychologists, physical and respiratory therapists, occupational therapists, speech therapists, pharmacists, dietitians, and social workers. Neonatal care should be led by the neonatologist allowing the participation of general pediatricians with training and demonstrated experience in neonatal care. Midwives and neonatal nurses should have accredited formation in such area. The purpose of this document is to update the "Recommendations on the Organization, Characteristics and Operation of Neonatology Services or Units" to serve as an orien tation and guide for the design and management of neonatal care in public and private health care centers in the country.

Palatal root surgery of a maxillary molar using a piezosurgery transantral approach with simultaneous sinus lift grafting: a case report.

AIM: To report a case involving transantral palatal root piezoelectric surgery followed by a sinus floor augmentation procedure with the purpose of minimizing and managing complications associated with sinus lining perforations and optimizing bone regeneration at the site of the surgical defect. SUMMARY: An asymptomatic 28-year-old male patient with the diagnosis of chronic apical periodontitis on a previously root filled right maxillary first molar (FDI tooth 16) and second premolar (No. 15) was managed by transantral apical surgery. Cone-beam computerized tomography (CBCT) revealed the position of the palatal root of the first molar within the maxillary sinus. The case highlights the management of the palatal root and the handling of a perforation of the Schneiderian membrane through a combination of piezosurgery and a sinus lift grafting procedure involving a second-generation of platelet concentrates. No postoperative complications were observed. Sinus bone augmentation after a 26-month recall period was confirmed by CBCT in the clinically asymptomatic teeth. KEY LEARNING POINTS: The selective bone tissue cutting and enhanced visibility obtained by piezoelectric surgery in comparison with current rotary techniques make this technology the preferred tool for apical surgery when the mucosal lining of the maxillary sinus could be compromised. The wound healing and physical properties of the platelet-rich fibrin membranes in combination with an allograft material can be considered as sinus bone graft options when a transantral approach is performed on a palatal root of a maxillary molar. A preoperative tomographic examination is essential for apical surgery using a transantral approach with sinus bone augmentation, because of the information obtained from the axial and coronal views on the CBCT scan.

Thoracoscopic cryoanalgesia: A new strategy for postoperative pain control in minimally invasive pectus excavatum repair. / Crioanalgesia toracoscópica: nueva estrategia para el control del dolor postoperatorio en cirugía del pectus excavatum.

OBJECTIVE: Recent publications report early discharge and low opioid requirements after minimally invasive pectus excavatum repair treated with bilateral intercostal nerve cryoablation. Our aim is to report our initial experience with this technique. MATERIAL AND METHODS: Retrospective analysis of medical records of patients undergoing bilateral thoracoscopic cryoanalgesia during minimally invasive pectus excavatum repair within our institution from September 2018 to March 2019. TECHNIQUE: A cryoprobe was applied at -70 ºC for 2 minutes each from the 3rd to the 7th intercostal nerves bilaterally under thoracoscopic control. Postoperative pain was assessed using a visual analogue scale (VAS). RESULTS: Twenty-one patients were included. Ninety percent were male, the mean age being 15.2 ± 4.29 years, and the mean weight being 53.6 ± 15.33 kg. The average Haller index was 5.1 ± 2.97, and the mean repair index was 37.6 ± 13.77%. The mean number of implants introduced was 2.55 ± 0.74. The mean duration of cryoanalgesia was 39.9 ± 21.1. No patients received epidural anesthesia. Mean postoperative stay was 1.64 ± 0.73 days. Seventy-one percent of the patients required 1 dose of opioids at the most for postoperative pain control. According to the VAS, the average pain score on postoperative days 1, 3, 7, and 21 was 2.55, 2.01, 0.5, and 0.06, respectively. CONCLUSIONS: Bilateral thoracoscopic cryoanalgesia during minimally invasive pectus excavatum repair leads to early discharge and good postoperative pain control in all cases. Cryoanalgesia has become our treatment of choice for pain control in the thoracoscopic repair of pectus excavatum.

INTRODUCCION: Publicaciones recientes reportaron el alta temprana y bajos requerimientos de opioides para el control del dolor postoperatorio en la reparación mínimamente invasiva del pectus excavatum tras crioablación bilateral de nervios intercostales. Nuestro objetivo es describir nuestra experiencia inicial con esta técnica. MATERIAL Y METODOS: Análisis retrospectivo de historias clínicas de pacientes sometidos a crioanalgesia toracoscópica bilateral durante la reparación mínimamente invasiva del pectus excavatum en nuestra institución desde septiembre de 2018 a marzo de 2019. TECNICA: Se aplicó una criosonda a -70°C bajo visión toracoscópica durante 2 minutos del 3º al 7º espacio intercostal, de manera bilateral. El dolor postoperatorio fue evaluado con una Escala Visual Analógica. RESULTADOS: Se incluyeron 21 pacientes, de los cuales el 90% era de sexo masculino con una edad media de 15,2 ± 4,29 años y un peso de 53,6 ± 15,33 kg. El índice de Haller promedio fue de 5,1 ± 2,97 y el índice de corrección de 37,6 ± 13,77%. El número promedio de implantes fue de 2,55 ± 0,74. La duración media de la crioanalgesia fue de 39,9 ± 21,1 minutos. Ninguno recibió anestesia peridural. El tiempo de internación postquirúrgico fue de 1,64 ± 0,73. La necesidad de rescate con opiáceos fue menor a 1 dosis en el 71,3%. La puntuación de dolor en los días postoperatorios 1, 3, 7 y 21 fue, en promedio, de 2,55; 2,01; 0,5 y 0,06, respectivamente. CONCLUSIONES: El empleo de la crioanalgesia toracoscópica bilateral permitió el alta hospitalaria temprana y buen control del dolor postoperatorio en todos los casos, convirtiéndose en el método analgésico de elección en nuestra práctica clínica.

Carbohydrases and phytase with rice bran, effects on amino acid digestibility and energy use in broiler chickens.

Protein sources from cereals are used in broiler diets, usually in order to reduce feeding costs. However, their efficient use in poultry diets is limited by the level of fiber whose compounds are resistant to digestion in the small intestine; due to this sugars are not digested by endogenous poultry enzymes. The aim of this study was to determine the effect of multi-carbohydrase (MC) and phytase (Phy) on the total retention of nutrients, retention of apparent metabolizable energy corrected for nitrogen (AMEN) (trial 1) and apparent and standardized ileal digestibility of amino acids (trial 2) of rice bran (RB). A total of 245-day-old male broilers (Cobb 500) was distributed at 21-day-old in a completely randomized design in a 2 × 2 + 1 (0 and 200 mg/kg MC; 0 and 50 mg/kg Phy, and basal diet - BD) factorial arrangement of treatments, to give seven replicates and seven birds per replicate. The BD based on corn (trial 1) and cornstarch and casein (trial 2) was used only to determine the coefficients of retention of nutrients and energy, and coefficients of digestibility of amino acids of the RB. The test diets were made by mixing BD and RB 7 : 3 wt/wt basis. There was interaction (P<0.05) between MC × Phy for DM, nitrogen and AMEN, retention and no interaction (P>0.05) for ash, calcium, phosphorous and NDF was observed. Enzymes interacted (P<0.05) on standardized ileal digestibility of arginine, histidine, leucine, methionine, phenylalanine, threonine, valine, aspartic acid, glutamic acid, proline and serine. Dietary combination of MC and Phy resulted in higher (P<0.05) standardized digestibility of arginine, histidine, methionine and threonine relative to single enzyme supplementation or control diet without enzymes. Enzyme isolated inclusions in the diets improved (P<0.05) standardized digestibility of methionine. The supplementation of carbohydrases and Phy in RB will improve the nitrogen, energy and amino acids utilization for broiler chickens.

Nutrient and energy balance, and amino acid digestibility in weaned piglets fed wheat bran and an exogenous enzyme combination.

The digestive system of the weaned piglets can be affected by the type of ingredients present in the diet, and a high fibre content in diets can limit the use of other nutrients and energy. The study was conducted to determine the effects of multicarbohydrase (MC) and phytase (Phy) supplementation on the nutritive value of wheat bran (WB) in weaned piglets. Multicarbohydrase preparation had 700 U α-galactosidase, 2200 U galactomannanase, 3000 U xylanase and 22 000 U ß-glucanase per kilogram of diet, and Phy had 500 phytase units - FTU/kg of diet. Twenty-five weaned piglets (6.1 ± 0.63 kg) at 21 days old were fed five diets in a completely randomised experimental design with a 2 × 2 + 1 (0 and 200 mg/kg MC; 0 and 50 mg/kg Phy; and basal diet - BD) factorial arrangement used to determine treatment effects. An additional group of piglets was fed a corn-basal diet during apparent digestibility of nutrients, and fed a 5% casein-corn starch basal diet during apparent and standardised ileal digestibility (SID) of amino acid evaluations. Piglets were individually caged until 38 days old, when Ileal digesta was collected at slaughter. Test diets were made by mixing the basal diets and WB 7 : 3 (w/w), with or without MC, Phy or the combination. There was an interaction trend (P = 0.07) between MC and Phy in the balance of ash, digestible energy (DE) and metabolisable energy (ME). Effects of MC (P < 0.01) on DM, N retention, DE and ME, as well as an effect of Phy (P < 0.05) on ash, DE and ME and a trend in protein digestibility (P = 0.07) also was observed. The enzyme combination showed effect (P < 0.05) on SID of Lys, Pro and Ser; as a trend (P < 0.07) on His, Thr and Val. Isolated, MC also suggested improving (P < 0.07) on SID of His, Lys, Ala (P < 0.05), while Phy improved (P < 0.06) SID of Leu, Lys, Met (P < 0.01), Thr, Val, Ala (P < 0.01), Pro and Ser (P < 0.05). The MC carbohydrate complex was characterised as a viable alternative to increase the apparent nutrients digestibility and SID of amino acids when WB was used in the diet of young pigs and, when combined with Phy, suggested an additive effect on the apparent use of energy.

African swine fever (ASF) diagnosis, an essential tool in the epidemiological investigation.

Since there is no vaccine available, prevention, control, and eradication of African swine fever (ASF) is based on the implementation of appropriated surveillance and strict sanitary measures. Success of surveillance activities depends on the availability of the most appropriate diagnostic tests. Although a number of good validated ASF diagnostic techniques are available, the interpretation of the ASF diagnostic results can be complex. The reasons lie in the complexity of the epidemiology with different scenarios, as well as in the characteristics of the viruses circulating giving rise to a wide range of clinical forms of ASF. This review provides guidance for an accurate interpretation of ASF diagnostic results linked to the different clinical presentations ranging from per-acute to chronic disease, including apparently asymptomatic infections.

[Analysis of the comorbidities and role of laparoscopy in recurrent abdominal pain]. / Análisis de las comorbilidades y papel de la laparoscopia en el dolor abdominal recurrente.

INTRODUCTION AND OBJECTIVES: Recurrent abdominal pain is defined as > 3 episodes of abdominal pain accompanied by affectation of the daily activity, during > 3 months. Our objective is to analyze the role of diagnostic and/or therapeutic laparoscopy. MATERIAL AND METHODS: A descriptive, retrospective study from 2004 to 2016. Patients: <14 years with DAR who underwent laparoscopy. Variables: age, sex, history, surgical findings, histology and follow-up. RESULTS: 55 patients. Mean age: 10.7 years. Female 63, 6%. Probability of allergic comorbidity: 27.27% [16.138-40.962] (CI 95%). Probability of subsequent psychological comorbidity: 12.72% [5.27 -24.48] (95% CI). Histological changes 31/55 (56.36%): lymphoid nodular hyperplasia 10/31, appendicular inflammation 7/31, fecalite 3/31, carcinoid tumor 1/31, appendicular fibrosis 3/31, Meckel diverticulum 1/31, association of several of the above 8/31. Macroscopic alterations 31/55 (56.36%): appendicular pathology 10/31, adhesions 5/31, lymph nodes 2/31, ileitis 2/31, tubal cysts 1/31, Meckel 1/31 diverticulum, several of the previous ones 10/31. Remission of symptoms: 30/55 (54.54%). In some cases, with partial improvement (4/55) or persistence of symptoms (21/55), organic and/ or psychological cause was demonstrated (16/25). CONCLUSIONS: Recurrent abdominal pain seems to have a significant association with an allergic or psychological history. Exploratory laparoscopy is a useful diagnostic and therapeutic technique.

INTRODUCCION Y OBJETIVOS: El dolor abdominal recurrente (DAR) supone > 3 episodios de dolor abdominal acompañados de afectación de la actividad diaria, durante > 3 meses. Nuestro objetivo es analizar el papel de la laparoscopia diagnóstica y/o terapéutica. MATERIAL Y METODOS: Estudio descriptivo, retrospectivo desde 2004 hasta 2016. Pacientes < 14 años con DAR a los que se les practicó laparoscopia. Variables: edad, sexo, antecedentes, hallazgos quirúrgicos, histología y evolución. RESULTADOS: 55 pacientes. Media de edad: 10,7 años. Mujeres 63, 6%. Probabilidad de comorbilidad alérgica: 27,27% [16,138- 40,962] (I.C 95%). Probabilidad de comorbilidad posterior psicológica: 12,72% [5,27 -24,48] (I.C 95%). Alteraciones histológicas 31/55 (56,36%): hiperplasia nodular linfoide 10/35, inflamación apendicular 7/31, fecalito 3/31, tumor carcinoide 1/31, fibrosis apendicular 3/31, divertículo de Meckel 1/31, asociación de varios de los anteriores 8/31. Alteraciones macroscópicas 31/55 (56,36%): patología apendicular 10/31, bridas 5/31, adenopatías 2/31, ileítis 2/31, quistes tubáricos 1/31, divertículo de Meckel 1/31, varios 10/31. Remisión: 30/ 55 (54,54%). En algunos casos con mejoría parcial (sin desaparición completa del dolor) (4/55) o persistencia de síntomas (21/55) se demostró causa orgánica y/o psicológica (16/25). CONCLUSIONES: El dolor abdominal recurrente parece presentar una asociación significativa con antecedentes alérgicos o psicológicos. La laparoscopia exploradora supone una técnica diagnóstica y terapéutica.

Gaps in African swine fever: Analysis and priorities.

African swine fever (ASF) causes greater sanitary, social and economic impacts on swine herds than many other swine diseases. Although ASF was first described in 1921 and it has affected more than fifty countries in Africa, Europe and South America, several key issues about its pathogenesis, immune evasion and epidemiology remain uncertain. This article reviews the main characteristics of the causative virus, its molecular epidemiology, natural hosts, clinical features, epidemiology and control worldwide. It also identifies and prioritizes gaps in ASF from a horizontal point of view encompassing fields including molecular biology, epidemiology, prevention, diagnosis and vaccine development. The purpose of this review is to promote ASF research and enhance its control.

Effects of multi-carbohydrase and phytase on standardized ileal digestibility of amino acids and apparent metabolizable energy in canola meal fed to broiler chicks.

Two assays were conducted to evaluate nutritive value of canola meal (CM) fed to broiler chicks without or with a multi-carbohydrase (MC) preparation (700 U α-galactosidase, 2,200 U galactomannanase, 30,000 U xylanase, and 22,000 U ß-glucanase per kg of diet) and phytase (Phy, 500 FTU per kg of diet). Assay 1 determined apparent total tract digestibility (ATTD) of nutrients and metabolizable energy (AME) by the difference method. Assay 2 determined apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of amino acids by the index method. Two reference diets (RD) - an 85% corn based and a 5% casein-cornstarch diet fortified with vitamins and minerals - were made for assays 1 and 2, respectively. For each assay, the test diets were made by mixing RD and CM 7:3 wt/wt basis and fed without or with MC or Phy or combination. A total of 245 day-old male broilers (Cobb 500) was allocated to 5 treatments to give 7 replicates (7 birds/cage). The birds were fed a commercial diet from day zero to 10 followed by assay 1 fed from d 11 to 18 and assay 2 fed from d 19 to 21. Excreta samples were collected on d 15 to18, and all birds were slaughtered on d 21 for ileal digesta. There was an interaction (P < 0.05) between MC and Phy on ATTD of DM, N, and P. There was no interaction (P > 0.05) between MC and Phy on AMEn; however, MC and Phy individually improved AMEn retention. Enzymes interacted (P < 0.05) on SID of Arg, His, Leu, Met, Thr, Ala, Asp, Gln, and Gly. In this context, feeding a combination of MC and Phy resulted in higher (P < 0.05) SID of Arg, His, Met, and Thr relative to single activity or control. Both enzymes improved (P < 0.05) SID of Lys independently. The combination of carbohydrase and Phy may be an effective strategy to improve amino acid utilization in CM for poultry.

Experimental Infection of Domestic Pigs with African Swine Fever Virus Lithuania 2014 Genotype II Field Isolate.

An experimental infection was conducted to evaluate horizontal transmission, clinical, virological and humoral response induced in domestic pigs infected with African swine fever (ASF) genotype II virus circulating in 2014 into the European Union (EU). Ten naive pigs were placed in contact with eight pigs experimentally inoculated with the Lithuanian LT14/1490 ASF virus (ASFV) responsible for the first ASF case detected in wild boar in Lithuania in January 2014. Clinical examination and rectal temperature were recorded each day. Blood sampling from every animal was carried out twice weekly. Blood samples were examined for presence of ASF virus-specific antibodies and for determining the ASFV viral load. From the obtained results, it was concluded that the Lithuanian ASFV induced an acute disease which resulted in 94, 5% mortality. The disease was easily detected by real-time PCR prior to the onset of clinical signs and 33% of the animals seroconverted. All findings were in accordance with observations previously made in domestic pigs and wild boar when infected with ASF genotype II viruses characterized by a high virulence. One in-contact pig remained asymptomatic and survived the infection. The role of such animals in virus transmission would need further investigation.

Identification of a New Genotype of African Swine Fever Virus in Domestic Pigs from Ethiopia.

African swine fever (ASF) is an important emerging transboundary animal disease (TAD), which currently has an impact on many countries in Africa, Eastern Europe, the Caucasus and the Russian Federation. The current situation in Europe shows the ability of the virus to rapidly spread, which stands to threaten the global swine industry. At present, there is no viable vaccine to minimize spread of the disease and stamping out is the main source of control. In February 2011, Ethiopia had reported its first suspected outbreaks of ASF. Genomic analyses of the collected ASF virus (ASFV) strains were undertaken using 23 tissue samples collected from domestic swine in Ethiopia from 2011 to 2014. The analysis of Ethiopian ASFVs partial p72 gene sequence showed the identification of a new genotype, genotype XXIII, that shares a common ancestor with genotypes IX and X, which comprise isolates circulating in Eastern African countries and the Republic of Congo. Analysis of the p54 gene also followed the p72 pattern and the deduced amino acid sequence of the central variable region (CVR) of the B602L gene showed novel tetramer repeats not previously characterized.

Development of a novel lateral flow assay for detection of African swine fever in blood.

BACKGROUND: African swine fever (ASF) is a viral infectious disease of domestic and wild suids of all breeds and ages, causing a wide range of hemorrhagic syndromes and frequently characterized by high mortality. The disease is endemic in Sub-Saharan Africa and Sardinia. Since 2007, it has also been present in different countries of Eastern Europe, where control measures have not been effective so far. The continued spread poses a serious threat to the swine industry worldwide. In the absence of vaccine, early detection of infected animals is of paramount importance for control of the outbreak, to prevent the transmission of the virus to healthy animals and subsequent spreading of the disease. Current laboratory diagnosis is mainly based on virological methods (antigen and genome detection) and serodiagnosis. RESULTS: In the present work, a Lateral Flow Assay (LFA) for antigen detection has been developed and evaluated. The test is based on the use of a MAb against VP72 protein of ASFV, the major viral capsid protein and highly immunogenic. First experiments using VP72 viral and recombinant protein or inactivated culture virus showed promising results with a sensitivity similar to that of a commercially available Antigen-ELISA. Moreover, these strips were tested with blood from experimentally infected pigs and field animals and the results compared with those of PCR and Antigen-ELISA. For the experimentally infected samples, there was an excellent correlation between the LFA and the ELISA, while the PCR always showed to be more sensitive (38 % positive samples by PCR versus 27 % by LFA). The LFA was demonstrated to be positive for animals with circulating virus levels exceeding 10(4) HAU. With the field samples, once again, the PCR detected more positives than either the Antigen-ELISA or LFA, although here the number of positive samples scored by the LFA exceeded the values obtained with the Antigen-ELISA, showing 60 % positivity vs 48 % for the ELISA. For the two groups of sera, the specificity was close to 100 % indicating that hardly any false positive samples were found. CONCLUSIONS: The newly developed LFA allows rapid and reliable detection of ASFV, at field and laboratory level, providing a new useful tool for control programs and in situations where laboratory support and skilled personnel are limited.

Biological synthesis of fluorescent nanoparticles by cadmium and tellurite resistant Antarctic bacteria: exploring novel natural nanofactories.

BACKGROUND: Fluorescent nanoparticles or quantum dots (QDs) have been intensely studied for basic and applied research due to their unique size-dependent properties. There is an increasing interest in developing ecofriendly methods to synthesize these nanoparticles since they improve biocompatibility and avoid the generation of toxic byproducts. The use of biological systems, particularly prokaryotes, has emerged as a promising alternative. Recent studies indicate that QDs biosynthesis is related to factors such as cellular redox status and antioxidant defenses. Based on this, the mixture of extreme conditions of Antarctica would allow the development of natural QDs producing bacteria. RESULTS: In this study we isolated and characterized cadmium and tellurite resistant Antarctic bacteria capable of synthesizing CdS and CdTe QDs when exposed to these oxidizing heavy metals. A time dependent change in fluorescence emission color, moving from green to red, was determined on bacterial cells exposed to metals. Biosynthesis was observed in cells grown at different temperatures and high metal concentrations. Electron microscopy analysis of treated cells revealed nanometric electron-dense elements and structures resembling membrane vesicles mostly associated to periplasmic space. Purified biosynthesized QDs displayed broad absorption and emission spectra characteristic of biogenic Cd nanoparticles. CONCLUSIONS: Our work presents a novel and simple biological approach to produce QDs at room temperature by using heavy metal resistant Antarctic bacteria, highlighting the unique properties of these microorganisms as potent natural producers of nano-scale materials and promising candidates for bioremediation purposes.