Symptom clusters of subjective cognitive decline amongst cognitively normal older persons and their utilities in predicting objective cognitive performance: structural equation modelling.

BACKGROUND AND PURPOSE: Prior literature on subjective cognitive decline (SCD) has mostly focused on memory complaints. It is uncertain whether the other non-memory complaints are equally relevant and can be used, alongside memory complaints, to identify populations at high risk of cognitive impairment. How the memory and non-memory complaints of SCD cluster with each other amongst community-dwelling individuals was investigated, and the differential utility of the symptom clusters of SCD in predicting objective cognitive performance was evaluated. METHODS: This study included 736 participants who were ≥60 years and had normal cognition, using the baseline data of an ongoing cohort study. Participants completed baseline assessments which comprised an SCD scale, a global cognitive measure and neuropsychological tests. Symptom clusters of SCD - as identified from exploratory and confirmatory factor analyses - were included in structural equation models to predict baseline changes in neuropsychological tests. RESULTS: The symptoms of SCD were split into two distinct factors, of which factor 1 was reported much more frequently than factor 2. Each standard deviation (SD) increment in factor 1 led to a 0.16-0.50 SD increase in global cognition, immediate memory, visuospatial abilities, language, attention and delayed memory (P < 0.05). In contrast, each SD increment in factor 2 worsened some of the cognitive domains by 0.18-0.37 SD. CONCLUSIONS: The various complaints of SCD can have different implications amongst cognitively normal older persons and may possibly be classified into age-related symptoms and pathological symptoms. The findings highlight the need for caution when selecting SCD measures, and illustrate the potential utility of SCD subtypes to inform on the underlying neurobiology.

Delineation of clinical features in Wiedemann-Steiner syndrome caused by KMT2A mutations.

Wiedemann-Steiner syndrome (WSS) is an autosomal dominant congenital anomaly syndrome characterized by hairy elbows, dysmorphic facial appearances (hypertelorism, thick eyebrows, downslanted and vertically narrow palpebral fissures), pre- and post-natal growth deficiency, and psychomotor delay. WSS is caused by heterozygous mutations in KMT2A (also known as MLL), a gene encoding a histone methyltransferase. Here, we identify six novel KMT2A mutations in six WSS patients, with four mutations occurring de novo. Interestingly, some of the patients were initially diagnosed with atypical Kabuki syndrome, which is caused by mutations in KMT2D or KDM6A, genes also involved in histone methylation. KMT2A mutations and clinical features are summarized in our six patients together with eight previously reported patients. Furthermore, clinical comparison of the two syndromes is discussed in detail.

Bioengineering virus-like particles as vaccines.

Virus-like particle (VLP) technology seeks to harness the optimally tuned immunostimulatory properties of natural viruses while omitting the infectious trait. VLPs that assemble from a single protein have been shown to be safe and highly efficacious in humans, and highly profitable. VLPs emerging from basic research possess varying levels of complexity and comprise single or multiple proteins, with or without a lipid membrane. Complex VLP assembly is traditionally orchestrated within cells using black-box approaches, which are appropriate when knowledge and control over assembly are limited. Recovery challenges including those of adherent and intracellular contaminants must then be addressed. Recent commercial VLPs variously incorporate steps that include VLP in vitro assembly to address these problems robustly, but at the expense of process complexity. Increasing research activity and translation opportunity necessitate bioengineering advances and new bioprocessing modalities for efficient and cost-effective production of VLPs. Emerging approaches are necessarily multi-scale and multi-disciplinary, encompassing diverse fields from computational design of molecules to new macro-scale purification materials. In this review, we highlight historical and emerging VLP vaccine approaches. We overview approaches that seek to specifically engineer a desirable immune response through modular VLP design, and those that seek to improve bioprocess efficiency through inhibition of intracellular assembly to allow optimal use of existing purification technologies prior to cell-free VLP assembly. Greater understanding of VLP assembly and increased interdisciplinary activity will see enormous progress in VLP technology over the coming decade, driven by clear translational opportunity.

Microbially synthesized modular virus-like particles and capsomeres displaying group A streptococcus hypervariable antigenic determinants.

Effective and low-cost vaccines are essential to control severe group A streptococcus (GAS) infections prevalent in low-income nations and the Australian aboriginal communities. Highly diverse and endemic circulating GAS strains mandate broad-coverage and customized vaccines. This study describes an approach to deliver cross-reactive antigens from endemic GAS strains using modular virus-like particle (VLP) and capsomere systems. The antigens studied were three heterologous N-terminal peptides (GAS1, GAS2, and GAS3) from the GAS surface M-protein that are specific to endemic strains in Australia Northern Territory Aboriginal communities. In vivo data presented here demonstrated salient characteristics of the modular delivery systems in the context of GAS vaccine design. First, the antigenic peptides, when delivered by unadjuvanted modular VLPs or adjuvanted capsomeres, induced high titers of peptide-specific IgG antibodies (over 1 × 10(4) ). Second, delivery by capsomere was superior to VLP for one of the peptides investigated (GAS3), demonstrating that the delivery system relative effectiveness was antigen-dependant. Third, significant cross-reactivity of GAS2-induced IgG with GAS1 was observed using either VLP or capsomere, showing the possibility of broad-coverage vaccine design using these delivery systems and cross-reactive antigens. Fourth, a formulation containing three pre-mixed modular VLPs, each at a low dose of 5 µg (corresponding to <600 ng of each GAS peptide), induced significant titers of IgGs specific to each peptide, demonstrating that a multivalent, broad-coverage VLP vaccine formulation was possible. In summary, the modular VLPs and capsomeres reported here demonstrate, with promising preliminary data, innovative ways to design GAS vaccines using VLP and capsomere delivery systems amenable to microbial synthesis, potentially adoptable by developing countries.

Virus-like particle formulation optimization by miniaturized high-throughput screening.

Virus-like particles (VLPs) are non-infectious and immunogenic virus-mimicking protein assemblies that are increasingly researched as vaccine candidates. Stability against aggregation is an important determinant dictating the viability of a pipeline VLP product, making multivariable stability data highly desirable especially in early product development stages. However, comprehensive formulation studies are challenging due to low sample availability early in developability assessment. This issue is exacerbated by industry-standard analytical techniques which are low-throughput and/or sample-consuming. This study presents a miniaturized high-throughput screening (MHTS) methodology for VLP formulation by integrating dynamic light scattering (DLS) and asymmetrical flow field-flow fractionation (AF4) in a formulation funnel analysis. Using only 2 µg of sample and 100 s per measurement, a DLS plate reader was deployed to effectively pre-screen a large experimental space, allowing a smaller set of superior formulation conditions to be interrogated at high-resolution with AF4. The stabilizing effects of polysorbate 20, sucrose, trehalose, mannitol and sorbitol were investigated. MHTS data showed that addition of 0.5% w/v polysorbate 20 together with either 40% w/v sucrose or 40% w/v sorbitol could stabilize VLPs at elevated temperatures up to 58 °C. AF4 data further confirmed that the formulation containing 40% w/v sorbitol and 0.5% w/v polysorbate 20 effectively protected VLPs during freeze-thawing and freeze-drying, increasing recoveries from these processes by 80 and 50 percentage points, respectively. The MHTS strategy presented here could be used to rapidly explore a large formulation development space using reduced amounts of sample, without sacrificing the analytical resolution needed for quality control. Such a method paves the way for rapid formulation development and could potentially hasten the commercialization of new VLP vaccines.

Membrane disruption and anti-quorum sensing effects of synergistic interaction between Lavandula angustifolia (lavender oil) in combination with antibiotic against plasmid-conferred multi-drug-resistant Escherichia coli.

AIM: The aim of this study was to investigate the mode of action of the lavender essential oil (LV) on antimicrobial activity against multi-drug-resistant Escherichia coli J53 R1 when used singly and in combination with piperacillin. METHOD AND RESULTS: In the time-kill analysis, a complete killing of bacteria was observed based on colony counts within 4 h when LV was combined with piperacillin during exposure at determined FIC concentrations. Analysis of the membrane permeabilizing effects of LV on treated cultures through their stability against sodium dodecyl sulphate revealed that the LV played a role in disrupting the bacterial cell membrane. The finding is further supported by scanning electron microscopy analysis and zeta potential measurement. In addition, reduction in light production expression of E. coli [pSB1075] by the LV showed the presence of potential quorum sensing (QS) inhibitors. CONCLUSIONS: These results indicated that the LV has the potential to reverse bacterial resistance to piperacillin in E. coli J53 R1. It may operate via two mechanisms: alteration of outer membrane permeability and inhibition of bacterial QS. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings offer a novel approach to develop a new option of phytopharmaceuticals against multi-drug-resistant E. coli.

Effects of pre-existing anti-carrier immunity and antigenic element multiplicity on efficacy of a modular virus-like particle vaccine.

Modularization of a peptide antigen for presentation on a microbially synthesized murine polyomavirus (MuPyV) virus-like particle (VLP) offers a new alternative for rapid and low-cost vaccine delivery at a global scale. In this approach, heterologous modules containing peptide antigenic elements are fused to and displayed on the VLP carrier, allowing enhancement of peptide immunogenicity via ordered and densely repeated presentation of the modules. This study addresses two key engineering questions pertaining to this platform, exploring the effects of (i) pre-existing carrier-specific immunity on modular VLP vaccine effectiveness and (ii) increase in the antigenic element number per VLP on peptide-specific immune response. These effects were studied in a mouse model and with modular MuPyV VLPs presenting a group A streptococcus (GAS) peptide antigen, J8i. The data presented here demonstrate that immunization with a modular VLP could induce high levels of J8i-specific antibodies despite a strong pre-existing anti-carrier immune response. Doubling of the J8i antigenic element number per VLP did not enhance J8i immunogenicity at a constant peptide dose. However, the strategy, when used in conjunction with increased VLP dose, could effectively increase the peptide dose up to 10-fold, leading to a significantly higher J8i-specific antibody titer. This study further supports feasibility of the MuPyV modular VLP vaccine platform by showing that, in the absence of adjuvant, modularized GAS antigenic peptide at a dose as low as 150 ng was sufficient to raise a high level of peptide-specific IgGs indicative of bactericidal activity.

The impact of neuropsychiatric symptoms on caregiver distress and quality of life in persons with dementia in an Asian tertiary hospital memory clinic.

BACKGROUND: This study aims to determine the prevalence, profile, and severity of neuropsychiatric symptoms (NPS) across the dementia continuum and their relative impact on caregiver distress and quality of life (QoL) in persons with dementia (PWD). METHOD: Six hundred and sixty-seven PWD and their family caregivers presented to a memory clinic in a tertiary hospital across a 60-month period. Clinicians determined the dementia diagnosis and severity using the Diagnostic and Statistical Manual of Mental Disorders, 4th Edition and the Clinical Dementia Rating scale, respectively. The Neuropsychiatric Inventory Questionnaire was administered to assess NPS in PWD and the corresponding distress experienced by the caregiver. QoL for PWD (PWD-QoL) was assessed by the Quality of Life-Alzheimer's Disease scale. RESULTS: Ninety-six percent of PWD presented with at least one NPS, 18% experiencing mild, 31% moderate, and 47% severe symptoms, respectively. While agitation (63.1%), apathy (61.8%), depression (55.5%), and irritability (55.5%) were the most common NPS; disinhibition (35.2%), hallucination (25.5%), and elation (14.2%) were the least common. NPS increased generally but differentially as dementia progressed and significantly predicted caregiver distress (ηp 2 = 0.732, p < 0.0001) and PWD-QoL (ηp 2 = 0.066, p < 0.0001). Factor analysis revealed two NPS clusters, disruptive and affective; the former exerting greater impact on caregiver distress and the latter on PWD-QoL. CONCLUSION: The results show a high prevalence of NPS which increase caregiver distress and negatively impact PWD-QoL. The differential profile of NPS across the dementia stages warrants stage-specific interventions and due consideration in resource planning and service design for PWD and their caregivers.

New trends to support independence in persons with mild dementia: a mini-review.

Our research was motivated by the growing aging population worldwide and the need to concentrate research efforts on a specific target group; it focuses on elderly persons with physical and cognitive deficiencies. The primary goal is to enable persons with mild dementia to maximize their physical and mental functions through assistive technologies in order to be able to continue to participate in social networks and lead independent and purposeful lives. Persons with mild dementia usually have problems in performing activities of daily living due to episodic memory decline. These can include simple activities, such as bathing, changing clothes and preparing meals. Through extended field test trials involving end users, we have demonstrated that assistive technology that provides timely prompts, alarms and reminders can enable them to preserve their abilities and improve their quality of life. Understanding the user context, especially when targeting demented individuals, and providing the required personalized assistive services is the objective of our research work. Finding the appropriate user interface to interact with the provided services is often a barrier. Thus, we have adopted the approach of a multimodal interactive system with the living environment including a TV set, iPad-like tablets, sensors/actuators, and wireless speakers connected to a reasoning engine that is able to consider the complexity of the users' profile defined by his/her cognitive abilities. In this paper we will mainly focus on the interaction level with the system as well as on the validation stages performed to meet the users' requirements. This is the result of several years' work since 2006 in the frame of two projects (IST-FP6 COGKNOW European completed project and AMUPADH ongoing project in Singapore).

Lactic acid bacteria waste infusion as a source of attraction and oviposition stimulation of gravid female Aedes albopictus mosquitoes.

Aedes albopictus poses a public health risk in tropical countries and temperate countries in recent decades due to its capability to transmit various human arboviruses including dengue, yellow fever, and chikungunya. Vector control is the key for preventing transmission of these pathogenic viruses. Improving the effectiveness of currently utilized collection methods, such as ovitraps, is important for best species abundance monitoring, assessment of the threat of arbovirus transmission, and optimizing control activities. Therefore, this study aimed to assess the potential use of lactic acid bacteria (LAB) waste as an infusion-baited ovitrap for Aedes collection. The performance of overnight tap water, grass hay infusion and LAB waste infusion were compared for their ability in attracting gravid female Ae. albopictus. In this study, the LAB waste infusion was substantially more alluring to Ae. albopictus mosquitoes than the two controls grass hay infusion and tap water.

Nutritional Status and Risks of Cognitive Decline and Incident Neurocognitive Disorders: Singapore Longitudinal Ageing Studies.

BACKGROUND: Studies suggest that nutritional interventions using the whole diet approach such as the Mediterranean diet may delay cognitive decline and dementia onset. However, substantial numbers of older adults are non-adherent to any ideally healthy dietary pattern and are at risk of malnutrition. OBJECTIVE: The present study investigated the relationship between global malnutrition risk and onsets of cognitive decline and neurocognitive disorders (NCD), including mild cognitive impairment (MCI) or dementia in community-dwelling older adults. METHODS: Participants aged ≥ 55 years in the Singapore Longitudinal Ageing Studies (SLAS) were assessed at baseline using the Elderly Nutritional Indicators for Geriatric Malnutrition Assessment (ENIGMA) and followed up 3-5 years subsequently on cognitive decline (MMSE drop ≥ 2) among 3128 dementia-free individuals, and incident neurocognitive disorders (NCD) among 2640 cognitive normal individuals. RESULTS: Individuals at high nutritional risk score (≥ 3) were more likely to develop cognitive decline (OR=1.42, 95%CI=1.01-1.99) and incident MCI-or-dementia (OR=1.64, 95%CI=1.03-2.59), controlling for age, sex, ethnicity, low education, APOE-e4, hearing loss, physical, social, and mental activities, depressive symptoms, smoking, alcohol, central obesity, hypertension, diabetes, low HDL, high triglyceride, cardiac disease, and stroke. Among ENIGMA component indicators, low albumin at baseline was associated with cognitive decline and incident NCD, and 5 or more drugs used, few fruits/vegetables/milk products daily, and low total cholesterol were associated with incident NCD. CONCLUSION: The ENIGMA measure of global malnutrition risk predicts cognitive decline and incident neurocognitive disorders, suggesting the feasibility of identifying vulnerable subpopulations of older adults for correction of malnutrition risk to prevent neurocognitive disorders.

Development, Validation and Field Evaluation of the Singapore Longitudinal Ageing Study (SLAS) Risk Index for Prediction of Mild Cognitive Impairment and Dementia.

BACKGROUND: Mild cognitive impairment (MCI) is a critical pre-dementia target for preventive interventions. There are few brief screening tools based on self-reported personal lifestyle and health-related information for predicting MCI that have been validated for their generalizability and utility in primary care and community settings. OBJECTIVE: To develop and validate a MCI risk prediction index, and evaluate its field application in a pilot community intervention trial project. DESIGN: Two independent population-based cohorts in the Singapore Longitudinal Ageing Study (SLAS). We used SLAS1 as a development cohort to construct the risk assessment instrument, and SLA2 as a validation cohort to verify its generalizability. SETTING: community-based screening and lifestyle intervention Participants: (1) SLAS1 cognitively normal (CN) aged ≥55 years with average 3 years (N=1601); (2) SLAS2 cohort (N=3051) with average 4 years of follow up. (3) 437 participants in a pilot community intervention project. MEASUREMENTS: The risk index indicators included age, female sex, years of schooling, hearing loss, depression, life satisfaction, number of cardio-metabolic risk factors (wide waist circumference, pre-diabetes or diabetes, hypertension, dyslipidemia). Weighted summed scores predicted probabilities of MCI or dementia. A self-administered questionnaire field version of the risk index was deployed in the pilot community project and evaluated using pre-intervention baseline cognitive function of participants. RESULTS: Risk scores were associated with increasing probabilities of progression to MCI-or-dementia in the development cohort (AUC=0.73) and with increased prevalence and incidence of MCI-or-dementia in the validation cohort (AUC=0.74). The field questionnaire risk index identified high risk individuals with strong correlation with RBANS cognitive scores in the community program (p<0.001). CONCLUSIONS: The SLAS risk index is accurate and replicable in predicting MCI, and is applicable in community interventions for dementia prevention.

Diagnostic performance of the Chinese Frontal Assessment Battery in early cognitive impairment in an Asian population.

BACKGROUND: The Frontal Assessment Battery (FAB) has been shown to be useful in evaluating frontal dysfunction. There is a paucity of studies validating cutoffs in the early cognitive impairment. We aim to validate the Chinese FAB in Asian subjects with mild cognitive impairment (MCI) and early dementia. METHODS: Eighty subjects with MCI and mild dementia and 100 cognitively healthy community subjects were studied. ROC analysis was done to determine the Chinese FAB's optimal cutoff scores for age- and education-adjusted subgroups. RESULTS: Chinese FAB scores were significantly lower in early cognitive impairment compared with cognitively normal controls. The optimal cutoff score was 12/13 (sensitivity 92%, specificity 78.7%). A similar cutoff score was obtained following age-adjustment and for subjects with <6 years' education. Of note, the optimal cutoff for subjects with ≥6 years' education was 13/14 (sensitivity 91.8%, specificity 70.3%), an improved diagnostic performance compared to the earlier reported 11/12 cutoff. In comparison, the Mini-Mental Status Examination (MMSE) had lower rule-out accuracy (77% sensitivity, 91.2% specificity). The combination of the Chinese FAB and MMSE was superior to either test in isolation. CONCLUSION: The education-adjusted Chinese FAB has good diagnostic performance, which can supplement the MMSE in early cognitive impairment evaluation with construct differences observed between the Chinese FAB and MMSE.

The Changing Profile of Patients in a Geriatric Medicine Led Memory Clinic over 12 Years.

OBJECTIVES: Memory clinics play an important role in enabling early dementia diagnosis and intervention. Few studies have investigated the changing patient profiles at memory clinics over time. We studied the trend of patient characteristics in a geriatric medicine-led memory clinic over 12 years to improve services and care to meet their needs. SETTING AND PARTICIPANTS: Data from 2340 first-visit patients seen at a memory clinic from 2005-2017 were extracted from a registered database and analysed. DESIGN: ANOVA, Pearson chi-square and non-parametric tests were used to describe and compare between patients with dementia (PWD) and patients with no dementia (PND). MEASUREMENTS: Data included diagnoses of dementia and mild cognitive impairment, age, education, MMSE scores and comorbidities. RESULTS: Patients averaged 77.2 ± 8.3 years of age with mean MMSE score of 16.2 ± 6.7. Those diagnosed with dementia were older (78.3 ± 7.9 years) and almost half (48.4%) had moderate or moderately severe dementia (FAST 5-6). Over time, there was a growing proportion of patients with mild cognitive impairment (MCI) and mild Alzheimer's dementia. Many PWD had co-morbidities of hypertension (65.9%), hyperlipidemia (55.1%), diabetes (33.5%) and 28.4% were frail. CONCLUSIONS: The findings call for services to better diagnose and manage patients at the earlier stages of cognitive impairment and provide holistic interventions for those with frailty and other co-morbidities. The continued rise in number of patients presenting to memory clinics provides impetus to expedite integration of tertiary-based memory clinics with primary and community care providers to better support PWD and their families.

Author Correction: Sculpting nanoparticle dynamics for single-bacteria-level screening and direct binding-efficiency measurement.

The original version of this Article omitted the author Kuan Wang, who is from the 'College of Biomedical Engineering, Taipei Medical University, Taipei 11031, Taiwan' and 'Nanyang Environment & Water Research Institute, Nanyang Technological University, Singapore 637141, Singapore.'Also, the author S.H. Lim was incorrectly given as L.S. Hoi and A. Larsson was incorrectly given as A. Larson.The "Author contributions" was amended to reflect the authorship changes. It previously read 'Y.Z.S., C.-W.Q., and A.Q.L. jointly conceived the idea. Y.Z.S., S.X., Y.Z., J.B.Z., W.S., J.H.W., T.N.C., Z.C.Y., Y.L.H., B.L., P.H.Y., D.P.T., and C.-W.Q. performed the numerical simulations and theoretical analysis. Y.Z.S., S.X., and L.K.C. did the fabrication and experiments of particle hopping, biomolecule binding and flow cytometry. A.L. and L.S.H. did the SPR experiments. S.X., Y.Z.S., Y.Z., C.-W.Q., Y.-Y.C., L.K.C., T.H.Z., and A.Q.L. prepared the manuscript. S.X., Y.Z., C.-W.Q., and A.Q.L. supervised and coordinated all the work. All authors commented on the manuscript.' The correct version states 'B.L., K. W., P.H.Y.' instead of 'B.L., P.H.Y.' and 'S.H.L.' in place of 'L.S.H.'This has been corrected in both the PDF and HTML versions of the Article.

Chimeric Murine Polyomavirus Virus-Like Particles Induce Plasmodium Antigen-Specific CD8+ T Cell and Antibody Responses.

An effective vaccine against the Plasmodium parasite is likely to require the induction of robust antibody and T cell responses. Chimeric virus-like particles are an effective vaccine platform for induction of antibody responses, but their capacity to induce robust cellular responses and cell-mediated protection against pathogen challenge has not been established. To evaluate this, we produced chimeric constructs using the murine polyomavirus structural protein with surface-exposed CD8+ or CD4+ T cell or B cell repeat epitopes derived from the Plasmodium yoelii circumsporozoite protein, and assessed immunogenicity and protective capacity in a murine model. Robust CD8+ T cell responses were induced by immunization with the chimeric CD8+ T cell epitope virus-like particles, however CD4+ T cell responses were very low. The B cell chimeric construct induced robust antibody responses but there was no apparent synergy when T cell and B cell constructs were administered as a pool. A heterologous prime/boost regimen using plasmid DNA priming followed by a VLP boost was more effective than homologous VLP immunization for cellular immunity and protection. These data show that chimeric murine polyomavirus virus-like particles are a good platform for induction of CD8+ T cell responses as well as antibody responses.

Quantitative analysis of virus-like particle size and distribution by field-flow fractionation.

Asymmetric flow field-flow fractionation (AFFFF) coupled with multiple-angle light scattering (MALS) is a powerful technique showing potential for the analysis of pharmaceutically-relevant virus-like particles (VLPs). A lack of published methods, and concerns that membrane adsorption during sample fractionation may cause sample aggregation, have limited widespread acceptance. Here we report a reliable optimized method for VLP analysis using AFFFF-MALS, and benchmark it against dynamic light scattering (DLS) and transmission electron microscopy (TEM). By comparing chemically identical VLPs having very different quaternary structure, sourced from both bacteria and insect cells, we show that optimized AFFFF analysis does not cause significant aggregation, and that accurate size and distribution information can be obtained for heterogeneous samples in a way not possible with TEM and DLS. Optimized AFFFF thus provides a quantitative way to monitor batch consistency for new vaccine products, and rapidly provides unique information on the whole population of particles within a sample.

High-level expression of soluble viral structural protein in Escherichia coli.

Pharmaceutically relevant virus-like particles (VLPs) can potentially be manufactured cheaply and efficiently through in vitro assembly of viral structural protein in cell-free reactors, but a bottleneck for this processing route is the currently low-level expression of soluble viral protein in efficient cell factories such as Escherichia coli (E. coli). Here, we report expression levels of up to 180 mg L(-1) that are achievable from low-cell-density E. coli cultures using a simple and low cost strategy. We investigated effects of host strain, plasmid, inducer concentration, pre-induction temperature and cell density at induction with design of experiment (DOE). The statistical approach successfully identified significant effects and their interactions, and provided insights into the role of codon-usage effects in expression of viral structural protein. In particular, our results support the notion that full codon optimization may be unnecessary to improve expression of viral genes rich in E. coli rare codons; using a strategically modified host cell could provide a simpler and cheaper alternative.

Sculpting nanoparticle dynamics for single-bacteria-level screening and direct binding-efficiency measurement.

Particle trapping and binding in optical potential wells provide a versatile platform for various biomedical applications. However, implementation systems to study multi-particle contact interactions in an optical lattice remain rare. By configuring an optofluidic lattice, we demonstrate the precise control of particle interactions and functions such as controlling aggregation and multi-hopping. The mean residence time of a single particle is found considerably reduced from 7 s, as predicted by Kramer's theory, to 0.6 s, owing to the mechanical interactions among aggregated particles. The optofluidic lattice also enables single-bacteria-level screening of biological binding agents such as antibodies through particle-enabled bacteria hopping. The binding efficiency of antibodies could be determined directly, selectively, quantitatively and efficiently. This work enriches the fundamental mechanisms of particle kinetics and offers new possibilities for probing and utilising unprecedented biomolecule interactions at single-bacteria level.

High-resolution and multi-range particle separation by microscopic vibration in an optofluidic chip.

An optofluidic chip is demonstrated in experiments for high-resolution and multi-range particle separation through the optically-induced microscopic vibration effect, where nanoparticles are trapped in loosely overdamped optical potential wells created with combined optical and fluidic constraints. It is the first demonstration of separating single nanoparticles with diameters ranging from 60 to 100 nm with a resolution of 10 nm. Nanoparticles vibrate with an amplitude of 3-7 µm in the loosely overdamped potential wells in the microchannel. The proposed optofluidic device is capable of high-resolution particle separation at both nanoscale and microscale without reconfiguring the device. The separation of bacteria from other larger cells is accomplished using the same chip and operation conditions. The unique trapping mechanism and the superb performance in high-resolution and multi-range particle separation of the proposed optofluidic chip promise great potential for a diverse range of biomedical applications.