Stimuli-responsive polyelectrolyte multilayer films and microcapsules.

Polyelectrolyte multilayer (PEM) films and particularly hollow capsules composed of PEM shells have gained significant interest since their introduction. Their compositional versatility and easiness of preparation via so-called layer-by-layer assembly led to the development of numerous systems containing also stimuli-responsive components. This paper reviews the achievements related to the formation, determination of structure, and properties of PEM films and capsules responding to major physical, chemical, and biological stimuli. Their applications as e.g., microcarriers for controlled delivery release of active components, substrates for controlled cells' growth, coatings for enhanced surface adhesion, or self-healing anticorrosive systems are shown and discussed. The influence of various stimuli on integrity, permeability of the films or capsules shell are presented together with related applications in biomedicine for controlled drug release as well as in biotechnology and industrial protective coatings.

Structural evolution of supported lipid bilayers intercalated with quantum dots.

HYPOTHESIS: Supported lipid bilayers (SLBs) embedded with hydrophobic quantum dots (QDs) undergo temporal structural rearrangement. EXPERIMENTS: Synchrotron X-ray reflectivity (XRR) was applied to monitor the temporal structural changes over a period of 24 h of mixed SLBs of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) / 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-ethanolamine (POPE) intercalated with 4.9 nm hydrophobic cadmium sulphide quantum dots (CdS QDs). The QD-embedded SLBs (QD-SLBs) were formed via rupture of the mixed liposomes on a positively charged polyethylene imine (PEI) monolayer. Atomic force microscopy (AFM) imaging provided complementary characterization of the bilayer morphology. FINDINGS: Our results show time-dependent perturbations in the SLB structure due to the interaction upon QD incorporation. Compared to the SLB without QDs, at 3 h incubation time, there was a measurable decrease in the bilayer thickness and a concurrent increase in the scattering length density (SLD) of the QD-SLB. The QD-SLB then became progressively thicker with increasing incubation time, which - along with the fitted SLD profile - was attributed to the structural rearrangement due to the QDs being expelled from the inner leaflet to the outer leaflet of the bilayer. Our results give unprecedented mechanistic insights into the structural evolution of QD-SLBs on a polymer cushion, important to their potential biomedical and biosensing applications.

Supported lipid bilayers with encapsulated quantum dots (QDs) via liposome fusion: effect of QD size on bilayer formation and structure.

Understanding interactions between functional nanoparticles and lipid bilayers is important to many emerging biomedical and bioanalytical applications. In this paper, we report incorporation of hydrophobic cadmium sulphide quantum dots (CdS QDs) into mixed 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) liposomes, and into their supported bilayers (SLBs). The QDs were found embedded in the hydrophobic regions of the liposomes and the supported bilayers, which retained the QD fluorescent properties. In particular, we studied the effect of the QD size (2.7-5.4 nm in diameter) on the formation kinetics and structure of the supported POPC/POPE bilayers, monitored in situ using quartz crystal microbalance with dissipation monitoring (QCM-D), as the liposomes ruptured onto the substrate. The morphology of the obtained QD-lipid hybrid bilayers was studied using atomic force microscopy (AFM), and their structure by synchrotron X-ray reflectivity (XRR). It was shown that the incorporation of hydrophobic QDs promoted bilayer formation on the PEI cushion, evident from the rupture and fusion of the QD-endowed liposomes at a lower surface coverage compared to the liposomes without QDs. Furthermore, the degree of disruption in the supported bilayer structure caused by the QDs was found to be correlated with the QD size. Our results provide mechanistic insights into the kinetics of the rupturing and formation process of QD-endowed supported lipid bilayers via liposome fusion on polymer cushions.

Properties of POPC/POPE supported lipid bilayers modified with hydrophobic quantum dots on polyelectrolyte cushions.

The formation and properties of supported lipid bilayers (SLB) containing hydrophobic nanoparticles (NP) was studied in relation to underlying cushion obtained from selected polyelectrolyte multilayers. Lipid vesicles were formed from zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) in phosphate buffer (PBS). As hydrophobic nanoparticles - quantum dots (QD) with size of 3.8nm (emission wavelength of 420nm) were used. Polyelectrolyte multilayers (PEM) were constructed by the sequential, i.e., layer-by-layer (LbL) adsorption of alternately charged polyelectrolytes from their solutions. Liposomes and Liposome-QDs complexes were studied with Transmission Cryo-Electron Microscopy (Cryo-TEM) to verify the quality of vesicles and the position of QD within lipid bilayer. Deposition of liposomes and liposomes with quantum dots on polyelectrolyte films was studied in situ using quartz crystal microbalance with dissipation (QCM-D) technique. The fluorescence emission spectra were analyzed for both: suspension of liposomes with nanoparticles and for supported lipid bilayers containing QD on PEM. It was demonstrated that quantum dots are located in the hydrophobic part of lipid bilayer. Moreover, we proved that such QD-modified liposomes formed supported lipid bilayers and their final structure depended on the type of underlying cushion.

Effect of Supporting Polyelectrolyte Multilayers and Deposition Conditions on the Formation of 1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-Palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine Lipid Bilayers.

The formation of complete supported lipid bilayers by vesicle adsorption and rupture was studied in relation to deposition conditions of vesicles and underlying cushion formed from various polyelectrolytes. Lipid vesicles were formed from zwitterionic 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and negatively charged 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) in phosphate buffer of various pH with or without NaCl addition. Polyelectrolyte multilayer films (PEM) were constructed by sequential adsorption of alternately charged polyelectrolytes from their solutions-layer-by-layer deposition (LBL). The mechanism of the formation of supported lipid bilayer on polyelectrolyte films was studied by quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM). QCM-D allowed following the adsorption kinetics while AFM measurements verified the morphology of lipid vesicles and isolated bilayer patches on the PEM cushions providing local topological images in terms of lateral organization. Additionally, polyelectrolyte cushions were characterized with ellipsometry to find thickness and swelling properties, and their roughness was determined using AFM. It has been demonstrated that the pH value and an addition of NaCl in the buffer solution as well as the type of the polyelectrolyte cushion influence the kinetics of bilayer formation and the quality of formed bilayer patches.

HIV-1 genetic diversity and transmitted drug resistance mutations among patients from the North, Central and South regions of Angola.

BACKGROUND: Angola presents a very complex HIV-1 epidemic characterized by the co-circulation of several HIV-1 group M subtypes, intersubtype recombinants and unclassified (U) variants. The viral diversity outside the major metropolitan regions (Luanda and Cabinda) and the prevalence of transmitted drug resistance mutations (DRM) since the introduction of HAART in 2004, however, has been barely studied. METHODS: One hundred and one individuals from the Central (n = 44), North (n = 35), and South (n = 22) regions of Angola were diagnosed as HIV-1 positive and had their blood collected between 2008 and 2010, at one of the National Referral Centers for HIV diagnosis, the Kifangondo Medical Center, located in the border between the Luanda and Bengo provinces. Angolan samples were genotyped based on phylogenetic and bootscanning analyses of the pol (PR/RT) gene and their drug resistance profile was analyzed. RESULTS: Among the 101 samples analyzed, 51% clustered within a pure group M subtype, 42% were classified as intersubtype recombinants, and 7% were denoted as U. We observed an important variation in the prevalence of different HIV-1 genetic variants among country regions, with high frequency of subtype F1 in the North (20%), intersubtype recombinants in the Central (42%), and subtype C in the South (45%). Statistically significant difference in HIV-1 clade distribution was only observed in subtype C prevalence between North vs South (p = 0.0005) and Central vs South (p = 0.0012) regions. DRM to NRTI and/or NNRTI were detected in 16.3% of patients analyzed. CONCLUSIONS: These results demonstrate a heterogeneous distribution of HIV-1 genetic variants across different regions in Angola and also revealed an unexpected high frequency of DRM to RT inhibitors in patients that have reported no antiretroviral usage, which may decrease the efficiency of the standard first-line antiretroviral regimens currently used in the country.

[Tumours in newborns and infants up to three months of life. One institution experience]. / Guzy u noworodków i malych niemowlat. Doswiadczenia wlasne.

INTRODUCTION: Newborns and infants up to three months of life are a specific group of population in paediatric oncology due to immaturity of tissues and organs and rarity of neoplastic diseases in this group of patients (pts). There are no strict therapeutic procedures established for these children. THE AIM of our study was to examine distribution of tumours in newborns and infants up to 3 months of age treated in our institution and to present our own experience in the treatment of these patients. MATERIAL AND METHODS: Medical records of 71 pts (37 boys and 34 girls) treated from 1996 to 2004 were reviewed. Distribution of tumour types in newborns and babies from 1 to 3 months of age was analyzed separately. Due to similar growth pattern, response to treatment and it's side effects in newborns and small infants, treatment results were evaluated for the whole group. RESULTS: there were 50 newborns. The most common diagnosis in this group was germ cell tumours (GCT) which constituted 60% of all tumours, amongst them 52% were mature teratomas (MT). The second most common was neuroblastoma (NBL) 22%. There were also 3 cases of soft tissue sarcomas (STS), 2 central nervous system tumours (CNS), 2 retinoblastoma (RB), 2 hepatoblastoma (HB). In the group of 21 babies aged 1-3 months NBL was the commonest (37%) followed by RB, CNS tumours (14% of each) HB and MT (10% of each) and Wilms tumour (WT) and immature teratoma (IT) each 5%. Surgery alone was performed in 48 pts. It concerned pts with MT--28, IT--3 pts, yolk sac tumour (YST)--1 pt and malignant tumours (stage I and II): 8-NBL, 2-CNS tumours, 2 STS, 3-HB, 1-WT. Forty two pts from this group are alive. Six pts died: 2 from surgical complications, 1 from sepsis, 1 of congenital heart defect and 1 from unknown reason at the age of 18 months. It was a patient with severe infantile cerebral palsy. One pt died of disease--relapse of yolk sac tumour, 2 years 4 months after surgery of MT. Eleven pts underwent combined treatment of chemotherapy and surgery: 5 with stage III and IV NBL, 6 with other tumours. One pt with STS at the age of 1 yr 6 months was the tumour bed irradiated after surgery for microscopic tumour residual. Four pts are alive, 4 with NBL and 5 with other tumours. Two pts died from disease: one with NBL and one with IT. Chemotherapy alone was administered to 7 pts in whom local advancement of disease enabled surgery and to pts with RBL. Three out of 7 pts are alive all with RBL. Four pts died: 3 from disease, 1 from infectious complications. Four pts with NBL (2 stage IV and 2 stage IVS) were treated with irradiation to the liver only. Two pts (st. IV) died and 2 (st. IVS) pts are alive. One pt relapsed at age of 2 yrs 3 mths, probably at the primary site which was not visualized at primary diagnosis. One pt, critically ill, died before any treatment. Fifty six out of 70 pts (80%) are alive with a follow up from 1 year to 9 yrs 11 months (median- 4 yrs 4 months). Fourteen pts died (20%), 8 from disease and 6 of other reasons. CONCLUSIONS: 1. GCT and neuroblastoma are the most common tumours in newborns and infants up to 3 months of age. 2. Newborns and small infants with advanced neoplastic disease, similarly to older children can be cured with chemotherapy. 3. Individual approach is warranted in newborns and small infants and treatment should be carried out in specialized centres. 4. All patients who completed treatment of any tumour type should be followed up by a pediatric oncologist.