Evaluation of Biopolymer Materials and Synthesis Techniques to Develop a Rod-Shaped Biopolymer Surrogate for Legionella pneumophila

Biopolymer microparticles have been developed for applications that require biocompatibility and biodegradability, such as drug delivery. In this study, we assessed the production of microparticles using carnauba wax, κ-carrageenan, alginate, and poly (lactic-co-glycolic acid) (PLGA) with the aim of developing a novel, DNA-tracer-loaded, biopolymer surrogate with a size, shape, surface charge, and relative hydrophobicity similar to stationary-phase Legionella pneumophila to mimic the bacteria’s mobility and persistence in engineered water systems. We found that the type and concentration of biopolymer, reaction conditions, and synthesis methods affected the morphology, surface charge, relative hydrophobicity, and DNA tracer loading efficiency of the biopolymer microparticles produced. Carnauba wax, κ-carrageenan, and alginate (Protanal^®, and low and medium viscosity) produced highly polydisperse microspheres. In contrast, PLGA and alginate-CaCO₃ produced uniform microspheres and rod-shaped microparticles, respectively, with high DNA tracer loading efficiencies (PLGA 70% and alginate-CaCO₃ 95.2 ± 5.7%) and high reproducibilities. Their synthesis reproducibility was relatively high. The relative hydrophobicity of PLGA microspheres closely matched the cell surface hydrophobicity of L. pneumophila but not the bacterial morphology, whereas the polyelectrolyte layer-by-layer assembly was required to enhance the relative hydrophobicity of alginate-CaCO₃ microparticles. Following this surface modification, alginate-CaCO₃ microparticles represented the best match to L. pneumophila in size, morphology, surface charge, and relative hydrophobicity. This new biopolymer surrogate has the potential to be used as a mimic to study the mobility and persistence of L. pneumophila in water systems where the use of the pathogen is impractical and unsafe.

Frequency of Hereditary Hemochromatosis Gene (HFE) Variants in Sri Lankan Transfusion-Dependent Beta-Thalassemia Patients and Their Association With the Serum Ferritin Level

INTRODUCTION

Co-inheritance of hereditary hemochromatosis (HFE) gene variants p. C282Y and p.H63D worsen iron overload in transfusion-dependent thalassemia. Data on the HFE gene variants in Sri Lankan patients with thalassemia have not been extensively studied. This study aimed to analyze the p.C282Y and p.H63D variants in transfusion-dependent beta (β) and HbE/β-thalassemia patients and establish an association between these variants and their serum ferritin levels.

MATERIALS AND METHODS

A total of 125 transfusion-dependent β-thalassemia major and HbE/β thalassemia patients were tested for the c.845G>A (p.C282Y) and c.187C>G (p.H63D) HFE gene variants using the multiplex Amplification Refractory Mutation System Polymerase Chain Reaction method. For phenotype-genotype correlation, serum ferritin levels, the erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) levels were measured. The standard descriptive statistics were used for data analysis.

RESULTS

The study cohort consisted of transfusion-dependent 123 β-thalassemia and 2 HbE/β-thalassemia patients. The p.C282Y variant was not detected in any patient; allele frequency for the wild type (c.845GG) was 100%. Twenty-three patients were heterozygous for the p.H63D variant allele, and the allele frequencies were c.187CC 91.8%, c.187CG 9.2%, and c.187GG 0%. The mean serum ferritin level was relatively higher (mean level 4,987 ng/ml) in the p.H63D heterozygous (c.187CG) group compared to the wild type (c.187CC) group (mean level 4,571 ng/ml), but the difference was statistically not significant (p = 0.865). Among the total study population, CRP, ESR, and serum glutamine aspartate transaminase (SGPT) were elevated in 9 (7.2%), 65 (52%), and 82 (65.6%) patients, respectively. Among the p.H63D c.187CG group, elevated CRP, ESR, and SGPT were present in 5 (5%), 15 (12%), and 18 (14.4%) patients, respectively. The detected sample number was low to correlate with the confounding effect of inflammatory disorders and liver damage on the serum ferritin levels.

CONCLUSIONS

The HFE gene variant p.C282Y is unlikely to cause iron overload in the Asian β-thalassemia patients; the rarity of this variant in the study cohort replicates the findings of other South Asian population studies of this variant. The presence of the p.H63D variant could be a potential risk factor for iron overload in the β-thalassemia patients. A more extensive cohort study is required to validate this finding.

Growth phase-dependent surface properties of Legionella pneumophila and their role in adhesion to stainless steel coated QCM-D sensors

Legionella pneumophila cell surface hydrophobicity and charge are important determinants of their mobility and persistence in engineered water systems (EWS). These surface properties may differ depending on the growth phase of L. pneumophila resulting in variable adhesion and persistence within EWS. We describe the growth-dependent variations in L. pneumophila cell surface hydrophobicity and surface charge using the microbial adhesion to hydrocarbon assay and microelectrophoresis, respectively, and their role in cell adhesion to stainless steel using a quartz crystal microbalance with dissipation (QCM-D) monitoring instrument. We observed a steady increase in L. pneumophila hydrophobicity during their lifecycle in culture media. Cell surfaces of stationary phase L. pneumophila were significantly more hydrophobic than their lag and midexponential counterparts. No significant changes in L. pneumophila cell surface charge were noted. Morphology of L. pneumophila remained relatively constant throughout their lifecycle. In the QCM-D study, lag and exponential phase L. pneumophila weakly adhered to stainless steel surfaces resulting in viscoelastic layers. In contrast, stationary phase bacteria were tightly and irreversibly bound to the surfaces, forming rigid layers. Our results suggest that the stationary phase of L. pneumophila would highly favour their adhesion to plumbing surfaces and persistence in EWS.

Water tracking in surface water, groundwater and soils using free and alginate-chitosan encapsulated synthetic DNA tracers

Investigating contamination pathways and hydraulic connections in complex hydrological systems will benefit greatly from multi-tracer approaches. The use of non-toxic synthetic DNA tracers is promising, because unlimited numbers of tracers, each with a unique DNA identifier, could be used concurrently and detected at extremely low concentrations. This study aimed to develop multiple synthetic DNA tracers as free molecules and encapsulated within microparticles of biocompatible and biodegradable alginate and chitosan, and to validate their field utility in different systems. Experiments encompassing a wide range of conditions and flow rates (19 cm/day-39 km/day) were conducted in a stream, an alluvial gravel aquifer, a fine coastal sand aquifer, and in lysimeters containing undisturbed silt loam over gravels. The DNA tracers were identifiable in all field conditions investigated, and they were directly detectable in the stream at a distance of at least 1 km. The DNA tracers showed promise at tracking fast-flowing water in the stream, gravel aquifer and permeable soils, but were unsatisfactory at tracking slow-moving groundwater in the fine sand aquifer. In the surface water experiments, the microencapsulated DNA tracers' concentrations and mass recoveries were 1-3 orders of magnitude greater than those of the free DNA tracers, because encapsulation protected them from environmental stressors and they were more negatively charged. The opposite was observed in the gravel aquifer, probably due to microparticle filtration by the aquifer media. Although these new DNA tracers showed promise in proof-of-concept field validations, further work is needed before they can be used for large-scale investigations.

The spectrum of deletions and duplications in the dystrophin (DMD) gene in a cohort of patients with Duchenne muscular dystrophy in Sri Lanka

Background

Duchenne muscular dystrophy (DMD), which affects 1 in 3500 newborn males, is the most common fatal neurodegenerative disorder in children. Deletions and duplications in the DMD gene are the most common underlying etiological factors.

Materials and Methods

Fifty consecutive children with DMD were screened for deletions and duplications in the DMD gene using Multiple Ligation-binding Probe Amplification (MLPA).

Results

Forty (80%) children had deletions and 4 (8%) had duplications. Single exon involvement was seen in 8 (16%), two exon involvement was seen in 3 (6%), three exon involvement was seen in 6 (12%) children, and four exon involvement in 1 (2%) child. More than four exon involvement were seen in 26 (52%) children. The most common deletion was the deletion spanning from exon 45 to exon 52, which was seen in 6 (12%) children. The next common exon deletion was single exon 45 deletion seen in 4 (8%) children. The most frequent mutant region fell within exons 45 to 55 (52%) followed by within exons 21 to 44 (26%) and exons 1 to 20 (26%). The least common region fell within exons 56 to 79 (4%).

Conclusion

The deletion/duplication pattern seen in this cohort of children with DMD was similar to that reported among other global populations.