HPMA copolymer-phospholipase C and dextrin-phospholipase A2 as model triggers for polymer enzyme liposome therapy (PELT)

‘Polymer Enzyme Liposome Therapy’ (PELT) is a two-step anticancer approach in which a liposomal drug and polymer-phospholipase conjugate are administered sequentially to target the tumour interstitium by the enhanced permeability and retention effect, and trigger rapid, local, drug release. To date, however, the concept has only been described theoretically. We synthesised two polymer conjugates of phospholipase C (PLC) and A2 (PLA2) and evaluated their ability to trigger anthracycline release from the clinically used liposomes, Caelyx® and DaunoXome®. N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymer–PLC and a dextrin-PLA2 were synthesised and their enzymatic activity characterised. Doxorubicin release from polyethyleneglycol-coated (PEGylated) Caelyx® was relatively slow (<20%, 60 min), whereas daunomycin was rapidly released from non-PEGylated DaunoXome® (∼87%) by both enzymes. Incubation with dextrin–PLA2 triggered significantly less daunomycin release than HPMA copolymer-PLC, but when dextrin-PLA2 was pre-incubated with α-amylase, the rate of daunomycin release increased. DaunoXome®’s diameter increased in the presence of PLA2, while Caelyx®’s diameter was unaffected by free or conjugated PLA2. Dextrin–PLA2 potentiated the cytotoxicity of DaunoXome® to MCF-7 cells to a greater extent than free PLA2, while combining dextrin–PLA2 with Caelyx® resulted in antagonism, even in the presence of α-amylase, presumably due to steric hindrance by PEG. Our findings suggest that in vivo studies to evaluate PELT combinations should be further evaluated

Linear programming can help identify practical solutions to improve the nutritional quality of food aid.

OBJECTIVES: To assess the nutritional quality of food aid delivered by food banks in France and to identify practical modifications to improve it. DESIGN: National-level data were collected for all food aid distributed by French food banks in 2004, and its nutrient content per 2000 kcal was estimated and compared with French recommendations for adults. Starting with the actual donation and allowing new foods into the food aid donation, linear programming was used to identify the minimum changes required in the actual donation to achieve the French recommendations. RESULTS: French food-bank-delivered food aid does not achieve the French recommendations for dietary fibre, ascorbic acid, vitamin D, folate, magnesium, docosahexaenoic acid, alpha-linolenic acid and the percentage of energy from saturated fatty acids. Linear programming analysis showed that these recommendations are achievable if more fruits, vegetables, legumes and fish were collected and less cheese, refined cereals and foods rich in fat, sugar and/or salt. In addition, new foods not previously collected are needed, particularly nuts, wholemeal bread and rapeseed oil. These changes increased the total edible weight (42%) and economic value (55%) of the food aid donation, with one-third of its edible weight coming from fruits and vegetables, one-third from staples, one-quarter from dairy products and approximately a tenth from meat/fish/eggs. CONCLUSIONS: Important changes in the types and amounts of food collected will improve the nutritional quality of food-bank-delivered food aid in France. Such changes are recommended to improve the diets of deprived French populations

Exploratory Analysis of Nutritional Quality and Metrics of Snack Consumption among Nepali Children during the Complementary Feeding Period.

The World Health Organization recommends feeding snacks between meals to young children. This study explored nutritional quality of snacks consumed between meals and consumption metrics (% total energy intakes (%TEI) and amount of kcal from snacks) to understand correlations with dietary outcomes (total energy intakes and dietary adequacy) and body-mass-index-for-age z-scores (BMIZ). Data used were 24-h dietary recalls and anthropometric measurements among a representative sample (n = 679) of one-year-olds in Nepal. Nepali meal patterns for young children were identified through formative research and all foods/beverages consumed outside of meals were categorized as snacks. A nutrient profiling model was used to categorize snacks as healthy or unhealthy, based on positive and negative nutrient content. Snacks consumed between meals provided half of all energy consumed, and were associated with increased energy and nutrient intakes. The positive effect of snacks between meals on dietary adequacy was greater when these snacks were healthy, while increasing %TEI from unhealthy snacks consumed between meals was negatively associated with dietary adequacy. Consumption of snacks between meals was not associated with mean BMIZ among the children. These findings indicate that the provision of and nutritional quality of snacks are important considerations to communicate to caregivers. Discouragement of unhealthy, nutrient-poor snacks is critical for complementary feeding dietary guidelines in contexts experiencing nutrition transition

Context-specific complementary feeding recommendations developed using Optifood could improve the diets of breast-fed infants and young children from diverse livelihood groups in northern Kenya.

OBJECTIVE: To formulate age- and context-specific complementary feeding recommendations (CFR) for infants and young children (IYC) and to compare the potential of filling population-level nutrient gaps using common sets of CFR across age groups. DESIGN: Linear programming was used to develop CFR using locally available and acceptable foods based on livelihood- and age-group-specific dietary patterns observed through 24 h dietary recalls. Within each livelihood group, the nutrient potential of age-group-specific v. consolidated CFR across the three age groups was tested. SETTING: Three food-insecure counties in northern Kenya; namely, settled communities from Isiolo (n 300), pastoralist communities from Marsabit (n 283) and agro-pastoralist communities from Turkana (n 299). SUBJECTS: Breast-fed IYC aged 6-23 months (n 882). RESULTS: Age-specific CFR could achieve adequacy for seven to nine of eleven modelled micronutrients, except among 12-23-month-old children in agro-pastoralist communities. Contribution of Fe, Zn and niacin remained low for most groups, and thiamin, vitamin B6 and folate for some groups. Age-group-consolidated CFR could not reach the same level of nutrient adequacy as age-specific sets among the settled and pastoralist communities. CONCLUSIONS: Context- and age-specific CFR could ensure adequate levels of more modelled nutrients among settled and pastoralist IYC than among agro-pastoralist communities where use of nutrient-dense foods was limited. Adequacy of all eleven modelled micronutrients was not achievable and additional approaches to ensure adequate diets are required. Consolidated messages should be easier to implement as part of a behaviour change strategy; however, they would likely not achieve the same improvements in population-level dietary adequacy as age-specific CFR

Local food-based complementary feeding recommendations developed by the linear programming approach to improve the intake of problem nutrients among 12-23-month-old Myanmar children.

Poor feeding practices result in inadequate nutrient intakes in young children in developing countries. To improve practices, local food-based complementary feeding recommendations (CFR) are needed. This cross-sectional survey aimed to describe current food consumption patterns of 12-23-month-old Myanmar children (n 106) from Ayeyarwady region in order to identify nutrient requirements that are difficult to achieve using local foods and to formulate affordable and realistic CFR to improve dietary adequacy. Weekly food consumption patterns were assessed using a 12-h weighed dietary record, single 24-h recall and a 5-d food record. Food costs were estimated by market surveys. CFR were formulated by linear programming analysis using WHO Optifood software and evaluated among mothers (n 20) using trial of improved practices (TIP). Findings showed that Ca, Zn, niacin, folate and Fe were 'problem nutrients': nutrients that did not achieve 100 % recommended nutrient intake even when the diet was optimised. Chicken liver, anchovy and roselle leaves were locally available nutrient-dense foods that would fill these nutrient gaps. The final set of six CFR would ensure dietary adequacy for five of twelve nutrients at a minimal cost of 271 kyats/d (based on the exchange rate of 900 kyats/USD at the time of data collection: 3rd quarter of 2012), but inadequacies remained for niacin, folate, thiamin, Fe, Zn, Ca and vitamin B6. TIP showed that mothers believed liver and vegetables would cause worms and diarrhoea, but these beliefs could be overcome to successfully promote liver consumption. Therefore, an acceptable set of CFR were developed to improve the dietary practices of 12-23-month-old Myanmar children using locally available foods. Alternative interventions such as fortification, however, are still needed to ensure dietary adequacy of all nutrients

In vitro evaluation of the interaction of dextrin-colistin conjugates with bacterial lipopolysaccharide.

Dextrin-colistin conjugates have been developed with the aim of reducing clinical toxicity associated with colistin and improving targeting to sites of bacterial infection. This study investigated the in vitro ability of these dextrin-colistin conjugates to bind and modulate bacterial lipopolysaccharide (LPS), and how this binding affects its biological activity. These results showed that colistin, and ‘amylase-activated’ dextrin-colistin conjugate to a lesser extent, bound to LPS and induced significant conformational changes to its structure. In biological studies, both colistin and dextrin-colistin conjugate effectively inhibited LPS-induced hemolysis and TNFα secretion in a concentration-dependent manner, but only dextrin-colistin conjugate did not cause additive toxicity at higher concentrations. This study provides the first direct structural experimental evidence for the binding of dextrin-colistin conjugates and LPS, providing insight into the mode of action of dextrin-colistin conjugates

Rates of common communicable illnesses in non-anaemic 12-24 month old South Island, New Zealand children

Aims : To describe the incidence of parentally reported illness in otherwise healthy South Island toddlers; characterise the predictors of illness; and determine whether there was a relationship between teething and illness in this population.Methods : A 20-week randomised controlled trial was conducted on 1-year-old children (n=225) from Otago and Southland between February 2004 and December 2005. Information on symptoms of morbidity, occurrence of teething, and childcare attendance were recorded daily throughout the intervention period. Morbidity symptoms were categorised into respiratory illness (RI), gastrointestinal illness (GII), ear infection, and total illness, and the number and duration of events were determined.Results : The mean (SD) number of total illnesses was 3.4 (2.3) per 20 weeks, with an average duration of 4.5 days. Episodes of RI were most common (50% of total illness events), and tended to be the longest in duration (mean of 3.7 days). Having siblings aged less than 5 years (23% increase, 95%CI 6%&ndash;42%, p=0.007) and attending childcare (72% increase, 95%CI 38%&ndash;113%, p&lt;0.001)), were positively associated with the number of total illness events but not duration. In addition, teething was positively associated with total events (OR 1.94, 95%CI 1.45&ndash;2.60, p&lt;0.001), RI events (OR 2.03, 95%CI 1.41&ndash;2.93, p&lt;0.001) and GII events (OR 1.90, 95%CI 1.36&ndash;2.67, p&lt;0.001). Conclusion : This study has shown that illness (particularly RI) is common in the second year of life. It has also confirmed that attending childcare and having siblings aged under 5 years increases the number of illness events. An association between teething and the occurrence of illness was also seen but the exact nature of this relationship requires verification. <br /

Controlled release of Dextrin-conjugated growth factors to support growth and differentation of neural stem cells

An essential aspect of stem cell in vitro culture and in vivo therapy is achieving sustained levels of growth factors to support stem cell survival and expansion, while maintaining their multipotency and differentiation potential. This study investigated the ability of dextrin (~74,000 g/mol; 27.8 mol% succinoylation) conjugated to epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF; or FGF-2) (3.9 and 6.7% w/w protein loading, respectively) to support the expansion and differentiation of stem cells in vitro via sustained, controllable growth factor release. Supplementation of mouse neural stem cells (mNSCs) with dextrin-growth factor conjugates led to greater and prolonged proliferation compared to unbound EGF/bFGF controls, with no detectable apoptosis after 7 days of treatment. Immunocytochemical detection of neural precursor (nestin) and differentiation (Olig2, MAP2, GFAP) markers verified that controlled release of dextrin-conjugated growth factors preserves stem cell properties of mNSCs for up to 7 days. These results show the potential of dextrin-growth factor conjugates for localized delivery of bioactive therapeutic agents to support stem cell expansion and differentiation, and as an adjunct to direct neuronal repair

A physicochemical assessment of the thermal stability of dextrin–colistin conjugates

Attachment of polysaccharide carriers is increasingly being used to achieve precision delivery and improved effectiveness of protein and peptide drugs. Although it is clear that their clinical effectiveness relies on the purity and integrity of the conjugate in storage, as well as following administration, instability of polysaccharide-based conjugates can reduce the protective efficacy of the polymer, which may adversely affect the bioactive’s potency. As a model, these studies used dextrin–colistin conjugates, with varying degrees of polymer modification (1, 2.5 and 7.5 mol% succinoylation) to assess the effect of storage temperature (− 20, 4, 21 and 37 °C) and duration (up to 12 months) on saccharide and colistin release and antimicrobial activity. Estimation of the proportion of saccharide release (by comparison of area under the curve from size exclusion chromatograms) was more pronounced at higher temperatures (up to 3 and 35% at − 20 °C and 37 °C, respectively after 12 months), however, repeated freeze–thaw did not produce any measurable release of saccharides, while addition of amylase (20, 100, 500 IU/L) caused rapid release of saccharides (> 70% total within 24 h). At all temperatures, conjugates containing the lowest degree of succinoylation released the highest proportion of free colistin, which increased with storage temperature, however no trend in saccharide release was observed. Despite the clear physical effects of prolonged storage, antimicrobial activity of all samples was only altered after storage at 37 °C for 12 months (> threefold decreased activity). These results demonstrate significant release of saccharides from dextrin–colistin conjugates during prolonged storage in buffered solution, especially at elevated temperature, which, in most cases, did not affect antimicrobial activity. These findings provide vital information about the structure–activity relationship of dextrin–colistin conjugates, prior to full-scale commercial development, which can subsequently be applied to other polysaccharide-protein and -peptide conjugates

Two-step polymer- and liposome- enzyme prodrug therapies for cancer: PDEPT and PELT concepts and future perspectives

Polymer-directed enzyme prodrug therapy (PDEPT) and polymer enzyme liposome therapy (PELT) are two-step therapies developed to provide anticancer drugs site-selective intratumoral accumulation and release. Nanomedicines, such as polymer-drug conjugates and liposomal drugs, accumulate in the tumor site due to extravasation-dependent mechanism (enhanced permeability and retention – EPR – effect), and further need to cross the cellular membrane and release their payload in the intracellular compartment. The subsequent administration of a polymer-enzyme conjugate able to accumulate in the tumor tissue and to trigger the extracellular release of the active drug showed promising preclinical results. The development of polymer-enzyme, polymer-drug conjugates and liposomal drugs had undergone a vast advancement over the past decades. Several examples of enzyme mimics for in vivo therapy can be found in the literature. Moreover, polymer therapeutics often present an enzyme-sensitive mechanism of drug release. These nanomedicines can thus be optimal substrates for PDEPT and this review aims to provide new insights and stimuli toward the future perspectives of this promising combination