Carboxyl-terminated Poly Research Articles

Mesoporous nanoplatform integrating photothermal effect and enhanced drug delivery to treat breast cancer bone metastasis.

Bone metastatic breast cancer has severely threatened the survival and life quality of patients. Due to the suboptimal efficacy of anti-metastatic chemotherapeutic drugs and the complicated bone marrow microenvironments, effective treatment of metastatic breast cancer remains challenging for traditional clinical approaches. In this work, we developed a mesoporous nanoplatform (m-CuS-PEG) with the co-loading of CuS nanodots and a chemotherapeutic drug cisplatin for the combined photothermal-chemotherapy of bone-metastasized breast cancer. The CuS nanodots were decorated onto mesoporous silica (m-SiO2) surface with dendritic mesoporous channels, into which the cisplatin was accommodated. The carboxyl-terminated poly (ethylene glycol) (PEG) was further functionalized onto the surface to obtain the functional nanoplatform m-CuS-PEG. The drug release of the loaded cisplatin exhibited pH- and thermal-dual responsive manner. The attached CuS nanodots rendered the mesoporous nanoplatform with high photothermal conversion ability. Upon irradiation with a near-infrared laser in the second near-infrared (NIR-II) window, m-CuS-PEG dispersions exhibited rapid temperature elevation and high photostability. The results revealed that m-CuS-PEG had excellent biocompatibility. The cisplatin-loaded m-CuS-PEG not only showed superior cancer cell-killing effects, but also significantly inhibit the growth of metastatic tumors. The tumor-induced bone destruction was also dramatically attenuated by the mesoporous nanoplatform-mediated combined therapy. Overall, the developed functional nanoplatform integrates photothermal therapy and efficient chemotherapeutic drug delivery to offer an alternative approach for combating breast cancer bone metastasis.

Charged hybrid block copolymer-lipid-cholesterol vesicles: pH, ionic environment, and composition dependence of phase transitions

The impacts of pH, salt concentration (expressed as Debye length), and composition on the phase behavior of hybrid block copolymer-lipid-cholesterol bilayers incorporating carboxyl-terminated poly(butadiene)-block-poly(ethylene oxide) copolymer (PBdPEO1800(−)) or/and non-carboxyl-terminated PBdPEO (PBdPEO1800 or/and PBdPEO950), egg sphingomyelin (egg SM), and cholesterol were examined using fluorescence spectroscopy of laurdan. Laurdan emission spectra were decomposed into three lognormal curves as functions of energy. The ratio of the area of the mid-energy peak to the sum of the areas of all three peaks was evaluated as vesicles were cooled, yielding temperature breakpoint values (Tbreak) expected to be within the range of the phase transition temperature. Tbreak values displayed dependence on pH, Debye length, and vesicle composition consistent with an electrostatic repulsion contribution to vesicle phase behavior. Increased pH and Debye length, for which a greater dissociated fraction of PBdPEO1800(−) and a greater energy of electrostatic repulsion would be expected, resulted in Tbreak values as much as 10 °C less than at low pH or short Debye lengths. Additionally, at Debye lengths comparable to those at physiologically relevant ionic strength, Tbreak at pH 5.9 was observed to be slightly higher than at pH 7.0 for vesicles containing 50 mol% PBdPEO1800(−). Electrostatic effects observed for hybrid vesicles incorporating significant amounts of carboxyl-terminated polymer may have the ability to drive phase separation in response to pH drops—such as those observed after endocytosis—in physiologically relevant conditions, suggesting the utility of such materials for drug delivery.

Polymer Brush Formation Assisted by the Hierarchical Self-Assembly of Topological Supramolecules.

The development of methods for the polymer brush layer formation on material surfaces to improve the surface properties has been researched for decades. Here, we report a novel approach for the formation of a polymer brush layer on materials and the alteration of the surface properties using a pseudo-polyrotaxane nanosheet (PPRNS). In the PPRNS, β-cyclodextrin (CD) selectively covered the central poly(propylene oxide)29 segment of the carboxyl-terminated poly(ethylene oxide)75-b-poly(propylene oxide)29-b-poly(ethylene oxide)75 (COOH-EO75PO29EO75) triblock copolymer to form columnar crystals. The EO chains of COOH-EO75PO29EO75 then adopt polymer brush conformations and exhibit an oil-repellent property on the material surfaces. Based on the flexibility derived from the nanosheet structure, the PPRNS showed high adhesion to the Blu-ray disk substrate (1D bending), polystyrene spherical beads (2D bending), and random rough surface of pork skin. The PPRNS is expected to become a new method for obtaining polymer brush layers and improving the surface properties irrespective of the material type.

Chemical modification of exfoliated graphite nanoplatelets with CTBN rubber and highly enhanced impact strength of vinyl ester resin by them

In the present study, exfoliated graphite nanoplatelets (EGN) were chemically modified with carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) liquid rubber via carboxylation, acylation, and subsequently esterification. Multiple characterizations by means of attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, X-ray diffraction spectroscopy, thermogravimetric analysis, and scanning electron microscopy demonstrated the chemical modification. For comparison, neat vinyl ester resin (VE), EGN/VE and CTBN-EGN/VE composites were prepared by using a free-standing Teflon mold to avoid pressure during curing. The amounts of EGN and CTBN-grafted EGN containing in EGN/VE and CTBN-EGN/VE composites were 1, 3, and 5 wt%, respectively. The impact strength of EGN/VE and CTBN-EGN/VE composites was strongly dependent upon the CTBN-grafted EGN concentration incorporated into neat VE. It was remarkably enhanced up to 220–240% even with low contents (5 wt%) of CTBN-grafted EGN in comparison to neat VE and unmodified EGN/VE. The result revealed that a small amount of EGN chemically modified with liquid rubber CTBN played an important role in increasing the impact toughness of thermosetting resin.

Effect of chlorhexidine-loaded poly(amido amine) dendrimer on matrix metalloproteinase activities and remineralization in etched human dentin in vitro

To investigate the effect of chlorhexidine (CHX)-loaded carboxyl-terminated poly (amido amine) dendrimer (CHX-PAMAM-COOH) on matrix metalloproteinase (MMP) activities and remineralization in human dentin, CHX-PAMAM-COOH was prepared and characterized by Fourier-transform infrared spectroscopy. The inhibitory effects of CHX, PAMAM-COOH, and CHX-PAMAM-COOH on soluble recombinant human matrix metalloproteinase (rhMMP-2) and dentin-bound endogenous MMP activity were measured using an MMP Activity Assay Kit. In situ zymography was performed to evaluate the gelatinase activity in dentin pretreated with CHX, PAMAM-COOH, and CHX-PAMAM-COOH. The remineralization of etched dentin pretreated with CHX, PAMAM-COOH, and CHX-PAMAM-COOH was evaluated by field emission-scanning electron microscopy (SEM) and energy disperse spectroscopy (EDS) after incubation in artificial saliva for 14 days. The results of the rhMMP-2 activity assay showed that the MMP-2 activity in the CHX-PAMAM-COOH group and the CHX group decreased significantly to 5.58 ± 0.85% (P < 0.05) and 4.86 ± 1.12% (P < 0.05), respectively, but that in the PAMAM-COOH group increased significantly to 213.38 ± 0.11% (P < 0.05). The results of total MMP activity and in situ zymography showed a significant reduction in endogenous gelatinase activity in dentin in the CHX-PAMAM-COOH group and the CHX group. The SEM and EDS results showed that rod-like crystals were formed on the etched dentin surface in the PAMAM-COOH group and the CHX-PAMAM-COOH group, and their Ca/P ratios were 1.73 and 1.71, respectively. In conclusion, CHX-PAMAM-COOH can inhibit dentin-bound endogenous MMPs and induce remineralization in etched dentin simultaneously. However, it is important to note that the catalytic role of PAMAM dendrimers may have an undesired excitatory effect on MMP activity, which cannot be ignored if PAMAM dendrimers were used alone in the oral environment.

A thermosensitive textile-based drug delivery system for treating UVB-induced damage

Ultraviolet radiation is one of the most dangerous sources of damage to skin and causes sunburn, erythema, photoaging, and photocarcinogenesis. Some passive drug delivery systems (DDSs) have been developed to treat skin damage. Nevertheless, there have been few studies on the application of intelligent DDSs to enhance the treatment of sunburn. In this paper, thermosensitive microgels were prepared by porous CaCO3 infiltrated by a thermoresponsive polymer, which was synthesized by grafting carboxyl-terminated poly (N-vinylcaprolactam) (PVCL-COOH) onto hydrolyzed chitosan. By means of the pad-dry-cure method, microgels were attached to cotton fabrics to develop a medical textile for drug delivery. The results indicated that the microgels were deposited both on the fiber surface and in the space between the fibers. The loaded drug presented a thermoresponsive release profile, and the release mechanism also varied with temperature. After being treated with the medical textile, human keratinocyte HaCaT cells could be protected by inhibiting UVB-induced lactate dehydrogenase leakage and increasing the levels of superoxide dismutase and glutathione peroxidase (GSH-Px). Our study suggested that this thermosensitive microgel-finished cotton fabric can be used as an effective device for the treatment of UVB-induced damage.

The Effect of PAMAM Dendrimer on the Dentin Remineralization and Matrix Metalloproteinases Activity

The purpose of this study was to investigate the effect of G4.5 carboxyl-terminated poly dendrimer (PAMAM-COOH) on the dentin remineralization and the matrix metalloproteinases (MMPs) activity. The dentine samples were averagely divided into four groups: 100 mg/mL PAMAM-COOH group (A group), 10 mg/mL PAMAM-COOH group (B group), 2% (wt) chlorhexidine (CHX) group (C group) and deionized water group (Control group). MMP Activity Assay Kit was used to detect the activity of dentin endogenous MMPs in the four groups. The loss of dry mass of dentin after 30 d were measured. In situ zymography analysis was performed to detect the effects of PAMAM dendrimer in each group (except A group) on gelatinase activity in dentin. After incubation in artificial saliva for 7 and 14 d incubated, the remineralization of each group (except A group) in dentin surfaces were examined using a field emission-scanning electron microscope (FESEM). Compared with the control group, the dentin endogenous MMPs activity in A, B and C groups were all decreased ( P<0.05). The activity of endogenous MMPs in C group was lower than that of A and B groups ( P<0.001), but the difference between A and B groups was not statistically significant. The loss of dry mass in A, B and C groups were lower than that in control group ( P<0.05), but there were no significant difference in A, B and C groups. The in situzymography analysis showed that 48 h later, the dentin gelatinase activity in B group was inhibited compared with the control group, but the inhibitory effect was weaker than that of CHX. After 7 d and 14 d, there were no obvious mineralization in the control group, while distinct mineralization were observed in B group. The mineralization effect in group B was better than group C. G4.5 PAMAM-COOH could introduce remineralizationin and demineralizeddentin by effectively inhibiting endogenous MMPs and gelatinase, thus contributes as novel material to enhancing durability of adhesion.

Epoxidized soybean oil grafted with CTBN as a novel toughener for improving the fracture toughness and mechanical properties of epoxy resin

We prepared epoxidized soybean oil (ESO) grafted with carboxyl-terminated poly(acrylonitrile-co-butadiene) (CTBN) (ESO-g-CTBN) by a ring-opening reaction between the epoxide group and the carboxyl group. The structural features of the resulting product were determined using modern analytical techniques, such as Fourier transform infrared (FTIR) spectroscopy, proton nuclear magnetic resonance (1H NMR) spectroscopy, and gel permeation chromatography (GPC). The ESO-g-CTBN was applied as a toughener for an epoxy resin-based composite that was fabricated by blending the epoxy resin with diethylenetriamine (DETA) as the curing agent. The main aim of this procedure is to simultaneously improve the mechanical properties and fracture toughness of a bisphenol A-based epoxy resin. When 15 phr of ESO-g-CTBN was added to the EP/DETA mixture, the resin fracture toughness (KIC) and tensile strength increased from 0.65 to 1.09 MPa m1/2 and from 34.42 to 42.55 MPa, respectively. The ESO-g-CTBN existed in the EP matrix as a separate phase and induced an increase in the KIC via stopping crack growth or changing the crack direction. The epoxydized soybean oil grafted with CTBN (ESO-g-CTBN) was synthesized from ring opening reaction between epoxide group and carboxyl group. The ESO-g-CTBN help to improve the fracture toughness of epoxy resin by the mechanism as shown in the figure.

Influence of CTBN content on fracture toughness of PF particleboard

The study investigated whether the single-edge-notch bending method could be used in quantitative determinating the fracture toughness of the particleboard. Also, carbo xyl-terminated poly (butadiene-co-acrylonitrile) liquid rubber was chosen to improve the fracture toughness of the particleboard. Critical energy release rate GIC and critical stress intensity factor KIC were measured in different directions with sandwich structure and common specimens. The study shows that it is a feasible method to compare the fracture performance of different particleboard by the single-edge-notch bending. The liquid rubber can toughen the particleboard when the addition amount is less than 12% when PF resin was used. More addition can lead to dispersion problem which will decrease the ductibility of particleboard.

Controlled release of corticosteroid with biodegradable nanoparticles for treating experimental autoimmune uveitis

Noninfectious uveitis is a potentially blinding ocular condition that often requires treatment with corticosteroids to prevent inflammation-related ocular complications. Severe forms of uveitis such as panuveitis that affects the whole eye often require a combination of topical and either regional or systemic corticosteroid. Regional corticosteroids are currently delivered inside the eye by intravitreal injection (e.g. Ozurdex®, an intravitreal dexamethasone implant). Intravitreal injection is associated with rare but potentially serious side effects, including endophthalmitis, retinal and vitreous hemorrhage, and retinal detachment. Subconjunctival (SCT) injection is a less invasive option that is a common route used for post-surgical drug administration and treatment of infection and severe inflammation. However, it is the water soluble form of dexamethasone, dexamethasone sodium phosphate (DSP), that has been demonstrated to achieve high intraocular penetration with subconjunctival injection. It is difficult to load highly water soluble drugs, such as DSP, and achieve sustained drug release using conventional encapsulation methods. We found that use of carboxyl-terminated poly(lactic-co-glycolic acid) (PLGA) allowed encapsulation of DSP into biodegradable nanoparticles (NP) with relatively high drug content (6% w/w) if divalent zinc ions were used as an ionic “bridge” between the PLGA and DSP. DSP-Zn-NP had an average diameter of 210 nm, narrow particle size distribution (polydispersity index ~0.1), and near neutral surface charge (−9 mV). DSP-Zn-NP administered by SCT injection provided detectable DSP levels in both the anterior chamber and vitreous chamber of the eye for at least 3 weeks. In a rat model of experimental autoimmune uveitis (EAU), inflammation was significantly reduced in both the front and back of the eye in animals that received a single SCT injection of DSP-Zn-NP as compared to animals that received either aqueous DSP solution or phosphate buffered saline (PBS). DSP-Zn-NP efficacy was evidenced by a reduced clinical disease score, decreased expression of various inflammatory cytokines, and preserved retinal structure and function. Furthermore, SCT DSP-Zn-NP significantly reduced microglia cell density in the retina, a hallmark of EAU in rats. DSP-Zn-NP hold promise as a new strategy to treat noninfectious uveitis and potentially other ocular inflammatory disorders.

Chitosan-g-poly(N-isopropylacrylamide) copolymers as delivery carriers for intracameral pilocarpine administration

This study reports, for the first time, the development of a chitosan-g-poly(N-isopropylacrylamide) (Chi-PN) biodegradable in situ gelling delivery system for ocular pilocarpine administration through intracameral injection. The number of thermo-responsive polymer segments grafted onto the chitosan via carbodiimide-mediated formation of amide linkages was greatly affected by varying the feeding amount of carboxyl-terminated poly(N-isopropylacrylamide) in the synthesis, thereby determining the phase transition temperature and enzymatic degradability of Chi-PN materials. The increase in grafting ratio facilitated temperature triggered gelation and drug encapsulation at physiological conditions. Additionally, the slow biodegradation process of delivery carriers was responsible for the delayed pilocarpine release, which allowed that the drug concentration could reach minimum therapeutic level for treating glaucoma during 42days of the study. All of the synthesized Chi-PN carriers demonstrated good ocular biocompatibility with lens epithelial cell cultures. In a rabbit model of experimental glaucoma, the intraocular pressure-lowering and miotic as well as corneal endothelial preservation responses to pilocarpine strongly depended on the drug release profiles. It is concluded that injectable biodegradable chitosan-based thermogels can be potentially utilized as intracameral biomaterials for extended release of antiglaucoma medications and improved performance of delivery carriers.

Conjugation to Poly(amidoamine) Dendrimers and Pulmonary Delivery Reduce Cardiac Accumulation and Enhance Antitumor Activity of Doxorubicin in Lung Metastasis.

Lung is one of the most common sites to which almost all other primary tumors metastasize. The major challenges in the chemotherapy of lung metastases include the low drug concentration found in the tumors and high systemic toxicity upon systemic administration. In this study, we combine local lung delivery and the use of nanocarrier-based systems for improving pharmacokinetics and biodistribution of the therapeutics to fight lung metastases. We investigate the impact of the conjugation of doxorubicin (DOX) to carboxyl-terminated poly(amidoamine) dendrimers (PAMAM) through a bond that allows for intracellular-triggered release, and the effect of pulmonary delivery of the dendrimer-DOX conjugate in decreasing tumor burden in a lung metastasis model. The results show a dramatic increase in efficacy of DOX treatment of the melanoma (B16-F10) lung metastasis mouse model upon pulmonary administration of the drug, as indicated by decreased tumor burden (lung weight) and increased survival rates of the animals (male C57BL/6) when compared to iv delivery. Conjugation of DOX further increased the therapeutic efficacy upon lung delivery as indicated by the smaller number of nodules observed in the lungs when compared to free DOX. These results are in agreement with the biodistribution characteristics of the DOX upon pulmonary delivery, which showed a longer lung accumulation/retention compared to iv administration. The distribution of DOX to the heart tissue is also significantly decreased upon pulmonary administration, and further decreased upon conjugation. The results show, therefore, that pulmonary administration of DOX combined to conjugation to PAMAM dendrimer through an intracellular labile bond is a potential strategy to enhance the therapeutic efficacy and decrease systemic toxicity of DOX.

Layer-by-layer surface decoration of electrospun nanofibrous meshes for air–liquid interface cultivation of epidermal cells

PEG multilayered nanofibrous mat for air–liquid interface cell cultivation.

Cross-linking of carboxyl-terminated nitrile rubber with polyhedral oligomeric silsesquioxane

Glycidyl polyhedral oligomeric silsesquioxane (POSS) was used as a cross-linking agent to prepare a new organic–inorganic hybrid material from carboxyl-terminated poly(acrylonitrile-co-butadiene) (CTBN). The structure of the reacted material was characterized by Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) at different heating rates in the presence and absence of catalyst, triphenyl phosphine (TPP), was conducted to investigate the curing kinetics. The reaction is catalyzed by the addition of TPP, and rate is maximum at higher catalyst concentrations. Different kinetic models were used to analyze the kinetic parameters. The effect of catalyst on curing process was determined by calculating the activation energy (Ea) using Kissinger method. Dependency of Ea with extent of conversion was monitored by different isoconversional methods. The curing mechanism of POSS–CTBN system followed autocatalytic model. Moreover, the predicted curves from the kinetic models fit well with the non-isothermal DSC curve. The Ea of gelation obtained from rheological studies matched with that from DSC study, in league with the Flory’s theory of cross-linking.

Volume Shrinkage and Cure Kinetics in Carboxyl-Terminated Poly(butadiene-co-acrylonitrile) (CTBN) Modified Epoxy/Clay Nanocomposites

The role of carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) liquid rubber and reactive surfactant modified nanoclay on the volume shrinkage during cure reaction and cure kinetics of epoxy/anhydride system in the presence of a catalyst was studied using Pressure-Volume-Temperature (PVT) measurements and real time FTIR spectroscopic analysis, respectively. The dilution effect of CTBN and catalytic effect of clay modifier on the epoxy/anhydride reaction reflected in the volume shrinkage behavior of CTBN modified epoxy/clay nanocomposites (epoxy/clay/CTBN hybrid) during cure. The kinetics of cure was studied based on the conversions derived from PVT data assuming a linear relation between network formation and volume shrinkage. The consumption of epoxy band (913 cm−1) during cure obtained from the real time FTIR spectroscopic analysis was employed to compare the effect of both CTBN and nanoclay on the cure kinetics. In epoxy/clay/CTBN hybrid, during the initial stage of cure the catalytic activity of the clay modifier controls the cure rate, and at the final stage the phase separated CTBN obstruct the diffusion of reactive sites to slows down the conversion rate. The Tg obtained from DSC analysis of the cured samples confirmed the observed shrinkage and cure behavior.

Liquid-rubber-modified epoxy/clay nanocomposites: effect of dispersion methods on morphology and ultimate properties

Epoxy/clay nanocomposites modified with carboxyl-terminated poly(butadiene-co-acrylonitrile) (CTBN) liquid rubber (epoxy/clay/CTBN nanocomposites) are synthesized using two different pre-mixing techniques: mechanical high shear mixer (homogenizer) and ultrasonication using tip sonicator. The observations suggest that low molecular weight CTBN easily diffuses into clay galleries, thereby increasing the d-spacing in epoxy/clay/CTBN nanocomposites, regardless of pre-mixing method. High shear mixing causes breaking of clay platelets in epoxy/clay/CTBN nanocomposites, leading to a reduction in the aspect ratio. Epoxy/clay/CTBN nanocomposites prepared via sonication have achieved a uniform and stable morphology, in which the clay platelets are dispersed in epoxy matrix in such a way that most of them try to localize near the phase-separated CTBN domains. Thermal and mechanical properties of the resulting nanocomposites are correlated with morphological findings.

Dendrimer nanofluids in the concentrated regime: from polymer melts to soft spheres.

Understanding dendrimer structures and their interactions in concentrated solutions is important to a wide range of applications, such as drug delivery and lubrication. However, controversy has persisted concerning whether, when confined to proximity, dendrimers would entangle as observed for polymer systems, or act as deformable spheres. Furthermore, how such behavior may be related to their size-dependent molecular architecture remains unclear. Using small-angle X-ray scattering (SAXS), the intermolecular interactions and structures in aqueous nanofluids containing three generations of carboxyl-terminated poly(amidoamine) (PAMAM) dendrimers (G0.5, Rg = 9.3 Å; G3.5, Rg = 22.6 Å; G5.5, Rg = 39.9 Å, where Rg is the radius of gyration) over a mass fraction range 0.005 ≤ x ≤ 0.316 have been studied. In the highly concentrated regime (x ≥ 0.157), we observe that the solution properties depend on the dendrimer generation. Our results suggest that the smaller G0.5 dendrimers form a highly entangled polymer melt, while the larger dendrimers, G3.5 and G5.5, form densely packed and ordered structures, in which the individual dendrimers exhibit some degree of mutual overlap or deformation. Our results demonstrate the tunability of interdendrimer interactions via their molecular architecture, which in turn may be harnessed to control and tailor the physical properties of dendrimer nanofluids.

Liquid rubber and silicon carbide nanofiber modified epoxy nanocomposites: Volume shrinkage, cure kinetics and properties

A cyclic anhydride cured epoxy modified with carboxyl-terminated poly (butadiene-co-acrylonitrile) liquid rubber (CTBN) and SiC nanofibers was developed by two different mixing strategies. In mixing method 1, SiC nanofibers were sonicated in epoxy/CTBN mixture, while in mixing method 2 the sonicated epoxy/SiC mixture was mechanically mixed with CTBN. The effects of liquid rubber, SiC nanofiber and their mixing methods on the cure shrinkage and cure kinetics of an epoxy/nadic methyl anhydride system were studied using pressure–volume–temperature (PVT) analysis. The influence of SiC nanofiber and mixing method on cross-linking induced phase separation were investigated by means of optical microscopy. The glass transition temperature (Tg) and the thermal stability of nanocomposites were evaluated. The epoxy/SiC/CTBN nanocomposite prepared by method 2 exhibited enhanced Tg and thermal stability compared with neat epoxy and epoxy/CTBN blend. Moreover, improved impact strength was shown by epoxy/SiC/CTBN nanocomposites prepared by both methods, in comparison with epoxy/CTBN blend and epoxy/SiC nanocomposite. Additionally, fractographic analysis was carried out using scanning electron microscopy and a toughening mechanism for epoxy/SiC/CTBN nanocomposites was proposed.

Triclosan-loaded poly(amido amine) dendrimer for simultaneous treatment and remineralization of human dentine

In order to treat dental caries of damaged dentine, triclosan-loaded carboxyl-terminated poly(amido amine) dendrimer (PAMAM-COOH) is prepared and characterized. While being incubated in artificial saliva, triclosan-loaded PAMAM-COOH formulation can induce in situ remineralization of hydroxyapatite (HA) on etched dentine, and the regenerated HA has a similar crystal structure with natural dentine. It can also release the encapsulated triclosan for a long period. The interesting drug release profiles are controlled by both dendrimer encapsulation capability and the mineralization degree, which are ideal to obtain multifunctional properties of long-term release of anti-bacterial drug for local treatment during the remineralization process. The triclosan-loaded G4-COOH provides a general strategy to cure dental caries and repair damaged dentine at the same time, which forms a potential restorative material for dental repair.

Carboxyl-terminated PAMAM dendrimer interaction with 1-palmitoyl-2-oleoyl phosphocholine bilayers

Polyanionic polymers and liposomes have a great potential use as individual drug delivery systems and greater potential as a combined drug delivery system. Thus, it is important to better understand the interactions of polymers with phospholipid bilayers. A mechanistic study of the interaction between carboxyl-terminated poly(amidoamine) (PAMAM) dendrimers with 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) bilayer using fluorescence leakage and quartz crystal microbalance with dissipation monitoring (QCMD) was conducted. Fluorescence leakage experiments demonstrated that carboxyl-terminated generation 2 (G2-COOH) dendrimers caused increased liposome leakage with increasing dendrimer concentration over a 0 to 20μM range. Generation 5 (G5-COOH), on the other hand, reduced leakage over the same concentration range, presumably by increasing lipid packing. QCMD and atomic force microscopy (AFM) measurements demonstrated that G2-COOH interacting with supported bilayers resulted in small defects with some mass loss and no adsorption. In contrast, G5-COOH interaction with a bilayer resulted in adsorption and local bilayer swelling.