Enzymatically-triggered, isothermally responsive polymers: re-programming poly(oligoethylene glycols) to respond to phosphatase

Polymers which can respond to externally applied stimuli have found much application in the biomedical field due to their (reversible) coil–globule transitions. Polymers displaying a lower critical solution temperature are the most commonly used, but for blood-borne (i.e., soluble) biomedical applications the application of heat is not always possible, nor practical. Here we report the design and synthesis of poly(oligoethylene glycol methacrylate)-based polymers whose cloud points are easily varied by alkaline phosphatase-mediated dephosphorylation. By fine-tuning the density of phosphate groups on the backbone, it was possible to induce an isothermal transition: A change in solubility triggered by removal of a small number of phosphate esters from the side chains activating the LCST-type response. As there was no temperature change involved, this serves as a model of a cell-instructed polymer response. Finally, it was found that both polymers were non cytotoxic against MCF-7 cells (at 1 mg·mL–1), which confirms promise for biomedical applications

Biophysical studies in polymer therapeutics: the interactions of anionic and cationic PAMAM dendrimers with lipid monolayers

Understanding how polymers interact with biological membranes is important for the development of polymer based therapeutics and wider biomedical applications. Here, biophysical methods (surface pressure measurements, external reflection FTIR) have been used to investigate the interaction between PAMAM dendrimers (Generation 5 or 4.5) and anionic (DPPG) or zwitterionic (DPPC) model membranes. We observed a concentration-dependent binding behaviour of both PAMAM species to both model membranes; however, equivalent levels of penetration into DPPC monolayers required approximately 10-fold higher dendrimer concentrations than for penetration into DPPG monolayers. Overall, the anionic PAMAM G4.5 showed a slightly better penetration ability which could be caused by repulsive forces towards the lipid layers. In comparison, increasing concentration of cationic PAMAM G5 leads to saturation of adsorption at the anionic lipid surface before penetration into the lipid layer likely driven by electrostatic attraction. Our studies also showed that physiologically relevant concentrations of sodium chloride (144 mM) decreased PAMAM penetration into DPPG monolayers but did not significantly affect the dendrimer-DPPC interaction. These results provide an insight into the mechanism of interaction between charged dendritic polymers with a lipid interface and show that the nature of such interactions are affected by lipid headgroup, dendrimer charge and solution salinity

Effects of PAMAM dendrimers on model and biological membranes

Poly(amidoamine) (PAMAM) dendrimers are nanosized, highly defined, hyperbranched polymeric vehicles designed for targeted delivery of drugs or bioactive molecules. Whilst heavily researched, their mechanism of interaction with biological systems is barely understood. Here, medium-generation PAMAMs (-COOH-terminus (G4.5); -NH2-terminus (G5)) were characterized by UV-Vis and fluorescence, small-angle X-ray scattering and computational simulations. Biophysical (surface pressure measurements, neutron reflectometry) and microbiological techniques were used to assess modulating factors (i.e. solvent pH, residual methanol) of dendrimer-membrane interactions and related toxicity. PAMAM surface groups are charged at pH 7, and in phosphate buffer solution the dendrimers assumed a compact, near-globular shape (radius ≈2.5 – 3 nm). PAMAM G5 penetrated anionic phosphatidylglycerol (DPPG, model bacterial lipid) monolayers rapidly but showed lesser membrane-activity on supported bilayers. Electrostatic effects could be potential drivers but also hinder PAMAM G4.5 penetration into DPPG monolayers. Across techniques, it was shown that solvent pH influenced dendrimer core (tertiary amines) and surface charge, with higher impact on structural characteristics of zwitterionic PAMAM G4.5 than of G5. At pH 4, the charge effect led to higher penetration levels into DPPG monolayers and bilayers for both dendrimers (G5 > G4.5) compared to pH 7. Methanol as co-solvent affected PAMAM radii and spectroscopic properties across the pH range tested. Additionally, it increased DPPG monolayer penetration compared to the methanol-free buffer environment, which could be explained by both, the impact on PAMAMs and on lipid layer organization. Anti-bacterial efficacy was studied on gram-negative and gram-positive bacteria. Amine-terminated PAMAMs led to growth-inhibition of most strains, but specifically gram-positive Staphylococcus spp. which are rich in anionic membrane lipids (i.e. PG lipids). Whilst overall less inhibitory than G5, PAMAM G4.5 was bactericidal against Staphylococcus saprophyticus. Taken together, our findings highlight the significance of the PAMAM characteristics and the solvent-PAMAM-lipid interplay and explain, at least partially, potential drivers of PAMAM membrane-toxicity

Analysis of smoking cessation beliefs in pregnant smokers and ex-smokers using the theory of planned behavior

Aim: To analyze the association between smoking cessation beliefs and smoking status, and between smoking cessations beliefs and intention to quit, using the Theory of Planned Behavior (TPB). Subjects and methods: An observational study using a questionnaire was performed; data were collected from 264 Flemish pregnant smokers and ex-smokers before week 16 of pregnancy. Results: There was a significant difference in the behavioral beliefs of the TPB between smokers and ex-smokers, after controlling for education and age. All respondents experienced more support from their non-smoking partners to maintain abstinence during pregnancy. We found no significant difference in the behavioral beliefs of the TPB between respondents with low and high intention to quit smoking. Conclusion: Our results suggest that attitude, subjective norms, support especially from the partner, and perceived behavioral control are associated with actual smoking behavior in pregnant women and not with intention to quit smoking. It is important to engage the partner and/or significant others in smoking cessation counselling so that they can support the pregnant woman in an attempt to quit or to maintain abstinence

Which role do midwives and gynecologists have in smoking cessation in pregnant women? - A study in Flanders, Belgium

Objectives: The objectives of our study were (1) to explore knowledge, beliefs and practice among midwives and gynecologists concerning a smoking cessation policy for pregnant women and their partners and (2) to examine if midwives and gynecologists do have a role in smoking cessation in pregnant women. Method: We performed a qualitative study using semi-structured interviews with nine midwives and eight gynecologists. Data were analyzed using deductive content analysis, based on the 5 A\u27s framework (Ask-Advise-Assess-Assist-Arrange). Results: The national smoking cessation policy seemed to be insufficiently known. Ask and Advise were part of a standard prenatal consultation, the next three steps were rarely implemented. Participants had a negative image of the smoking pregnant woman : a low educated woman with a smoking partner and bad examples in their history. Reported barriers were fear of provoking resistance and lack of time and communication skills regarding smoking cessation. Conclusions: These findings suggest that training in communication skills and dealing with resistance should be offered, i.e. by using motivational interviewing. It could be considered that a trained midwife or tobaccologist is part of an obstetrical team or that the AAR-method (Ask-Advise-Refer) is used instead of the 5 A\u27s framework

Smoking patterns, depression and socio-demographic variables among Flemish Women during Pregnancy and the Postpartum period

Background - Feelings of depression may contribute to persistent smoking during pregnancy. Relationships between feelings of depression, smoking behavior and educational level during pregnancy have been documented. So far, however, there have been no longitudinal studies assessing feelings of depression in women with different smoking patterns antepartum and postpartum. Objectives – The aim of this study was to determine relationships between depressive symptoms, socio-demographic characteristics and smoking pattern during and after pregnancy. Methods – We conducted an observational, prospective, non-interventional study. Data were collected during two stages of pregnancy (T0: 6 weeks) in 523 respondents. Feelings of depression (according to the Beck Depression Inventory - BDI), smoking behavior and socio-demographic variables were registered and analyzed using generalized linear mixed models (SAS 9.2). Results - At all sampling points smokers and initial smokers reported significantly more depressive symptoms compared to recent ex-smokers, non-smokers and initial non-smokers (F(4,486) = 12.06; p < .001). The three-way interaction between time point, smoking pattern and educational level (F(8,619) = 2.29; p = 0.02) was significant. The evolution of the mean BDI over time differed between the educational level classes of the smokers. Within respondents with a secondary school certificate or less differences were observed between smokers and non-smokers, recent ex-smokers and initial non-smokers, and non-smokers and initial non-smokers. Within the respondents with a college or university degree no differences were observed. Discussion – Paying attention to depressive symptoms and offering adapted stop-smoking 3 advice to lower educated pregnant women and their smoking partners might reduce the prevalence of smoking among pregnant and postpartum women.status: publishe