Quinone propionic acid‐based redox‐triggered polymer nanoparticles for drug delivery: Computational analysis and in vitro evaluation

Redox‐responsive polymers with pendant quinone propionic acid groups as a redox trigger were optimized by computational modeling to prepare efficient redox‐triggered polymer nanoparticles (NPs) for drug delivery. Lipophilicities at complete reduction of redox‐responsive polymers (<5000 Da) constructed with adipic acid and glutaric acid were remarkably reduced to range from ?6.29 to ?0.39 compared with nonreduced state (18.87–32.46), suggesting substantial polymer solubility reversal in water. Based on this hypothesis, redox‐responsive NPs were prepared from the synthesized polymers with paclitaxel as model cancer drug. The average size of paclitaxel‐loaded NPs was 249.8 nm and their reconstitutions were stable over eight weeks. In vitro drug release profiles demonstrated the NPs to release >80% of paclitaxel over 24 h at a simulated redox‐state compared with 26.5 to 41.2% release from the control. Cell viability studies revealed that the polymer was nontoxic and the NPs could release paclitaxel to suppress breast cancer cell growth. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40461.     

Micellization of a di‐block copolymer in ethylene glycol and its utilization for suspension of carbonaceous nanostructures

Suspensions of carbonaceous nanoparticles (NPs) in ethylene glycol (EG) can be used as colloidal inks for additive manufacturing and nano‐fluids for heat‐transfer applications. While micellar solutions of surfactants are often used for suspension of the NPs in water, micellization of surfactants in EG is suppressed as compared to aqueous solutions and a well‐defined critical micellization concentration (CMC) is often not observed. Unlike the surfactants, a di‐block copolymer comprising a poly(ethylene glycol) monomethylether methacrylate (PEGMA) segment, 2‐(diethylaminoethyl) methacrylate (DEAEMA) and butyl methacrylate (BMA), poly(O950)‐b‐(DEAEMA‐co‐BMA) was found to assemble into spherical micelles in EG. Surface tension measurements show a well‐defined CMC that depends on the volume fraction of EG. Cryogenic transmission electron microscopy and dynamic light scattering show the presence of spherical micelles with a diameter that reduces with the volume fraction of EG. The micellar solutions were further used for suspending carbonaceous NPs of different geometry and characteristic dimensions: C₆₀ fullerenes, multi‐walled carbon nanotubes, and nanodiamonds. The flow behavior of the suspensions exhibits a relatively low viscosity and mostly Newtonian behavior due to strong interaction between the NPs and the micelles. These suspensions may be used as colloidal inks for two‐dimensional and three‐dimensional printing. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46518.     

Controlled release of biocides in solid wood. II. Efficacy against Trametes versicolor and Gloeophyllum trabeum wood decay fungi

Biocide‐containing nanoparticles were suspended in water to prepare wood treating suspensions able to deliver up to 0.8 kg biocide/m³ of wood. The nanoparticle preparation method was versatile, and three fungicides (tebuconazole, chlorothalonil, and KATHON 930) and one insecticide (chlorpyrifos) were incorporated into the nanoparticles with little customization of the preparative method. Greater customization was required when the polymer matrix was changed, but the method was generally robust; nanoparticles could be prepared from several different polymers, copolymers, and polymer blends. The median nanoparticle size increased as the matrix hydrophobicity increased. Nanoparticles were quantitatively delivered into birch and southern yellow pine (SYP) at low suspension loadings, but the delivery efficiency decreased with increased suspension loading and with increased matrix hydrophobicity. The delivery efficiency was also less for birch than for SYP. Undelivered nanoparticles were found to have undergone aggregation. Greater aggregation occurred in the more hydrophobic formulations than in the hydrophilic formulations. High biological efficacy was found for all the biocides tested. Nanoparticle‐treated birch was exposed to Trametes versicolor for 55 days and some protection was afforded, even at biocide loading levels of only 0.1 kg/m³. At the highest loadings (～0.6 kg/m³) the weight loss after exposure to T. versicolor was generally ～10% for most formulations. The SYP was treated with KATHON 930 in polyvinylpyridine. At levels of 0.1 kg of biocide/m³ of wood less than 5% of the SYP mass was lost after 50 days of exposure to Gloeophyllum trabeum. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 608–614, 2002     

High throughput fiber reactor process for organic nanoparticle production: Poly(N‐isopropylacrylamide), polyacrylamide,and alginate

The goal of the present research was to scale microfluidic technology to a high throughput system using a fiber reactor platform. The nanoparticles studied are used in nanomedicine as drug delivery devices or “cages.” This process complements new research into skid‐based pharmaceutical production. Alginate nanoparticles were successfully generated in this process ranging in size from 23 to 151 nm with 424 g/day throughput. Polyacrylamide (PAm) nanoparticles were also formed and crosslinked with sizes ranging from 79 to 117 nm with 662 g/day throughput. Poly(N‐isopropylacrylamide) (PNIPAm) nanoparticles with a size range of 12 to 63 nm and 650 g/day were produced as well. Both one‐ and two‐phase flows were demonstrated. The effects of changes in various process parameters on the formed nanoparticle morphology are documented. Tunable process control is demonstrated to reliably manipulate the PNIPAm nanoparticle lower critical solution temperature. Process temperature affected the mean diameter and size dispersity of all the nanoparticles. This was postulated to be due to a shearing effect arising from carrier viscosity changes. Flow rate affected the average particle diameter by 10%–30%, and temperature could be used to tune the NP diameter by 50% across a moderate process temperature range of 5 to 25 °C. The PDI was very responsive to process temperature as well, decreasing by almost 50% across the same temperature range. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45524.     

Influence of Pluronic coating formulation on iron oxide nanoparticle transport in natural and oil-impacted sandy aquifer media

Targeted delivery of nanoparticles has the potential to enhance remediation and characterization of sites contaminated with non-aqueous phase liquids (NAPLs) by ensuring delivery of treatment or contrast agents to the NAPL/water interface. For a targeted delivery technique to be successful, nanoparticles must be capable of transporting through porous media and binding to NAPLs under relevant geological conditions. In this study, successful targeted delivery of nanoparticles to sandy aquifer material mixed with crude oil was achieved using an active targeting technique based on an amphiphilic polymer coating. It was determined that the molecular structure and concentration of the nanoparticle coating greatly influenced the recovery of nanoparticles injected into saturated columns. Coatings with longer polymer molecules and lower polymer concentrations reduced recovery, and the nanoparticle coating formulation could be adjusted to improve transport while maintaining targeted binding behaviour. This study demonstrated that nanoparticle retention in oil-impacted sand exceeded that of clean sand in flow through experiments, indicating that a nanoparticle targeted delivery strategy for soil contaminated with LNAPLs such as crude oil is possible under the experimental conditions explored.     

A combinatorial polymer library approach yields insight into nonviral gene delivery

The potential of gene therapy to benefit human health is tremendous because almost all human diseases have a genetic component, from untreatable monogenic disorders to cancer and heart disease. Unfortunately, a method for gene therapy that is both effective and safe has remained elusive. It has been said that "there are only three problems in gene therapy - delivery, delivery, and delivery." (quote from I. M. Verma in Jaroff, L. TIME, 1999; Jan 11). This Account describes an alternative strategy to viral gene delivery: the design of biodegradable polymers that are able to deliver DNA like a synthetic virus. Using high-throughput synthesis and screening techniques, we have created libraries of over 2000 structurally unique poly(β-amino esters) (PBAEs). PBAEs are formed by the conjugate addition of amines to diacrylates. These biomaterials are promising for nonviral gene delivery due to their ability to condense plasmid DNA into small and stable nanoparticles and their ability to promote cellular uptake and endosomal escape. Our laboratory has iteratively improved PBAE nanoparticles through polymer end modifications and nanoparticle coatings. Lead PBAEs have high gene delivery efficacy and low cytotoxicity both in vitro and in vivo. Certain polymer structural characteristics are important for effective gene delivery. The best PBAEs are linear polymers of ~10 kDa that contain hydroxyl side chains and primary amine end groups. These polymers bind DNA to form nanoparticles that are small (<200 nm) and stable and have near-neutral ζ potential in the presence of serum-containing media. Lead PBAEs also contain tertiary amines that can buffer the low pH environment of endosomes and facilitate escape of polymer/DNA particles into the cytoplasm. Diamine end-modified 1,4-butanediol diacrylate-co-5-amino-1-pentanol polymers (C32) bind DNA more tightly and form smaller nanoparticles than other PBAEs. These nanoparticles also have higher cellular uptake and the best gene expression of all gene delivery polymers in the library. These polymers are more effective for gene delivery than top commercially available nonviral vectors including jet-PEI and Lipofectamine 2000 and are comparable to adenovirus for in vitro gene delivery to human primary cells. In vivo, these PBAE/DNA particles are promising as cancer therapeutics. This Account summarizes the results of our laboratory in using a combinatorial polymer library approach to elucidate polymer structure/function relationships and enable the development of polymeric gene delivery nanoparticles with viral-like efficacy.     

Synthesis of novel copper nanoparticles/ternary polymer blend nanocomposites and their structural,thermal and rheological properties and AC impedance

Copper nanoparticles (Cu NPs)/ternary polymer blend nanocomposites were synthesized via a solution‐casting technique. The nanocomposites were studied for their structural, thermal, rheological and electric properties. Scanning electron micrographs and atomic force micrographs showed no phase separation between the polymers, a narrow size distribution of Cu NPs (in the range 25–43 nm) and good dispersion of Cu NPs in the polymer matrix. Energy‐dispersive X‐ray analysis confirmed the presences of Cu in the matrix. X‐ray diffraction data showed a characteristic face‐centred cubic architecture for Cu unit cell and interaction of the Cu NPs with oxygen‐carrying polymers. Thermogravimetric analysis showed an increase in the degradation temperature (from 254 to 268 °C) and three‐step degradation of the nanocomposites. Rheological analysis showed an increase in the complex viscosities and storage modulus for the nanocomposites. AC impedance studies showed increased ionic conductivities and decreased bulk resistance for the nanocomposites. All these studies suggested interactions between Cu NPs and polymer matrix and the formation of a network structure. © 2017 Society of Chemical Industry     

The nanocomposites of zinc oxide/L‐amino acid‐based chiral poly(ester‐imide) via an ultrasonic route: Synthesis,characterization, and thermal properties

In this investigation, a chiral poly) ester‐imide) (PEI) via direct polyesterification of N,N′‐(pyromellitoyl)‐bis‐(L ‐tyrosine dimethyl ester) and N‐trimellitylimido‐L ‐methionine was prepared using the tosyl chloride/pyridine/N,N′‐dimethylformamide system as a condensing agent. This approach allows the insertion of two natural amino acids into the polymer backbone and the creation of a bioactive polymer. From the chemical point of view, the ester groups impart to the polymer's main and side chain increased sensibility to hydrolysis that can cause chain breaking. Therefore, this polymer is expected to be biodegradable and could be classified as an eco‐friendly polymer. The polymer also had a useful level of thermal stability associated with excellent solubility. PEI/zinc oxide bionanocomposites were subsequently prepared by an ultrasonic method as a simple and inexpensive route, using ZnO nanoparticles (ZnO‐NPs) modified by 3‐aminopropyltriethoxylsilane (KH550) as a coupling agent. The structure and properties of the obtained BNC polymers were confirmed by Fourier transform infrared spectroscopy, X‐ray diffraction, field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The direct proofs for the formation of the true BNC polymers were provided by TEM. Also, the morphology study of the synthesized polymer‐based BNCs showed well‐dispersed ZnO‐NPs in the polymer matrix by FE‐SEM analysis. TGA studies indicated that an increase of the NP content led to an enhancement of the thermal stability of the new BNC polymers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Water‐soluble fluorescent nanoparticles without distinct aggregation of conjugated polymer chains

In a previous study, we reported water‐soluble light‐emitting nanoparticles with distinct interchain aggregation states of the constituent conjugated polymers. These interchain states usually result in strong self‐quenching, dramatically reducing the quantum efficiency of fluorescence. In the work reported in the present study, we developed new water‐soluble fluorescent nanoparticles without distinct aggregation of the conjugated polymer chains, which demonstrated distinctive morphologies and optical properties. ‘Strawberry’ morphologies of the nanoparticles were directly observed using transmission electron microscopy. The conjugated polymers were dispersed in the individual cores of the nanoparticles and the majority of the core diameters were in the range 8–12 nm. The primary optical properties of the conjugated polymers in tetrahydrofuran still remained in the nanoparticles. The results suggest that the conjugated polymer chains formed a possible unimolecular structure without distinct aggregation in the nanoparticles. Copyright © 2010 Society of Chemical Industry     

Morphology,structure, and properties of metal oxide/polymer nanocomposite electrospun mats

Adding nanoparticles into polymer solutions before electrospinning creates unique hierarchical morphologies dispersed throughout small diameter nanoparticle‐polymeric fibers. Effects of polymer composition, nanoparticle (NP) type, loading, and electrospinning voltage conditions were studied. As examples, indium, iron, and titanium oxide engineered nanoparticles (NPs) were dispersed into polyvinylpyrrolidone or polystyrene and electrospun. NP loadings below 5 wt % did not affect critical voltage required for Taylor cone formation, whereas higher NP loadings require higher critical voltages. Polymeric fiber thickness and macroscopic morphology is not impacted by up to 5 wt % NP loadings, and NP dispersion throughout the fibers were similar to their dispersion in initial polymer suspension. NP loadings above 5 wt % increased viscosity, which decrease subsequent fiber diameter. Experiments in water containing inorganic and organic pollutants in water demonstrate that the polymer is largely nonporous. This work enables design of multifunctional nanomaterial‐polymer composite fibers for wide‐ranging applications such as water and air treatment. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43811.     

Preparation of doubly responsive polymer functionalized silica hybrid nanoparticles via a one‐pot thiol‐isocyanate click reaction at room temperature

Well‐defined poly(N‐isopropylacrylamide) and poly(2‐(diethylamino) ethyl methacrylate) were synthesized first by a reversible addition‐fragmentation chain transfer process. These polymers were then reduced to generate an end thiol group to react with isocyanate groups on the surface of silica nanoparticles, which were pretreated with toluene‐2,4‐diisocyanate, by a one‐pot “click” reaction to prepare temperature and pH responsive polymer functionalized hybrid silica nanoparticles. The polymer functionalized silica hybrid nanoparticles were characterized by a range of techniques such as Fourier transform infrared spectroscopy and dynamic light scattering. The doubly responsive polymer functionalized silica hybrid nanoparticles show both temperature and pH responsive behavior and their solution properties were dependent on the ratio of the two polymers on the surface of silica. Covalent functionalization of the silica nanoparticle with well‐defined temperature and pH responsive polymers was accomplished via a one‐pot thiol‐isocyanate click reaction. This reaction was found to be extremely efficient in producing doubly responsive polymer functionalized silica hybrid nanoparticle, even at relatively low reaction temperature and short reaction time. Thermogravimetric analysis indicated that the same ratio of poly(N‐isopropylacrylamide) and poly(2‐(diethylamino)ethyl methacrylate) functionalized silica hybrid nanoparticle consisted of 42.46 wt% polymer. POLYM. COMPOS., 38:1454–1461, 2017. © 2015 Society of Plastics Engineers     

Poly(9‐vinylcarbazole)/silver composite nanotubes and networks formed at the air–water interface

Silver‐nanoparticle‐doped poly(9‐vinylcarbazole) (PVK) nanocomposites were prepared via the reduction of Ag⁺ ions and the self‐assembly of PVK on AgNO₃ aqueous solution surfaces. The formed composite nanostructures depended strongly on the experimental temperature. Thick round disks of PVK surrounded by discrete Ag nanoparticles and/or with irregular holes formed at room temperature; nanotubes and micronetworks doped with Ag nanoparticles formed at about 30–40°C, and networks formed at higher temperature. Further investigation revealed that the nanotubes were transformed from thin round disks. The length of the PVK/Ag composite nanotubes were longer than 10 μm, and the average size of the embedded Ag nanoparticles was found to be about 3.5 nm. The composite networks were composed of round pores with diameters of several hundred nanometers and fine silver nanoparticles embedded in the thin polymer films that covered the pores. The formation of the nanotubes was a very interesting self‐assembly phenomenon of the polymer at the air–water interface that has not been reported before. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel copolymer for SiO2 nanoparticles dispersion

High performance polymers exhibiting multifunctional characteristics can be achieved by the introduction of inorganic nanoparticles like SiO₂ into the functional polymers. In the present work a copolymer epoxy poly(dimethylacrylamide) was synthesized to disperse the SiO₂ nanoparticles. The aim of the work is to develop a new method/process/material for the dispersion of nanoparticles and evaluating the performance of these composites. FT‐IR studies of the polymer adsorbed SiO₂ nanoparticles confirmed that the polymer molecules chain was anchored on the surface of the SiO₂ nanoparticles. The improved interfacial interaction between the particles and polymer enhanced the thermal properties of the composites. The results also show the newly synthesized polymer disperse the nanoparticles well as evidenced by SEM analysis, the uniformly dispersed SiO₂ nanoparticles in the polymer matrix and the particles almost remained in their original shape and size even after incorporation in to the polymer matrix. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Protein Interactions with Nanoparticle Surfaces: Highlighting Solution NMR Techniques

In the last decade, nanoparticles (NPs) have become a key tool in medicine and biotechnology as drug delivery systems, biosensors and diagnostic devices. The composition and surface chemistry of NPs vary based on the materials used: typically organic polymers, inorganic materials, or lipids. Nanoparticle classes can be further divided into sub‐categories depending on the surface modification and functionalization. These surface properties matter when NPs are introduced into a physiological environment, as they will influence how nucleic acids, lipids, and proteins will interact with the NP surface. While small‐molecule interactions are easily probed using NMR spectroscopy, studying protein‐NP interactions using NMR introduces several challenges. For example, globular proteins may have a perturbed conformation when attached to a foreign surface, and the size of NP‐protein conjugates can lead to excessive line broadening. Many of these challenges have been addressed, and NMR spectroscopy is becoming a mature technique for in situ analysis of NP binding behavior. It is therefore not surprising that NMR has been applied to NP systems and has been used to study biomolecules on NP surfaces. Important considerations include corona composition, protein behavior, and ligand architecture. These features are difficult to resolve using classical surface and material characterization strategies, and NMR provides a complementary avenue of characterization. In this review, we examine how solution NMR can be combined with other analytical techniques to investigate protein behavior on NP surfaces.     

Semiconductor‐assisted self‐cleaning polymeric fibers based on zinc oxide nanoparticles

Self‐cleaning polymeric fibers have been successfully prepared by depositing ZnO nanoparticle onto wool and polyacrylonitrile (PAN) fibers with good compatibility and significant photocatalytic self‐cleaning activity using the sol‐gel process at ambient temperature. scanning electron microscopy, energy dispersive spectroscopy, transmission electron microscopy, diffuse reflectance spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area analysis, and thermogravimetric analysis have been adopted as the characterization techniques. Transmission electron microscopy studies revealed presence of zinc oxide nanoparticles with 10–15 nm in size. Brunauer‐Emmett‐Teller measurement showed surface area of 48 m²/g for the ZnO nanoparticles. Photocatalytic activity of the self‐cleaning materials were tested by measuring the photo‐assisted degradation of methylene blue (MB) and eosin yellowish (EY) under ultraviolet‐visible illumination. The results indicate that both of the ZnO‐coated polyacrylonitrile and ZnO‐coated wool fibers acquire photocatalytic activity toward dyes degradation. The photocatalytic activity of the treated fibers is maintained upon several numbers of photodegradation cycles. This facile and cheap preparation technique can be also applied to new polymeric fabrics to produce self‐cleaning materials for industrial application. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Semitransparent poly(styrene‐r‐maleic anhydride)/alumina nanocomposites for optical applications

This article presents the development and characterization of transparent poly(styrene‐r‐maleic anhydride) (SMA)/alumina nanocomposites for potential use in optical applications. Chemically treated spherical alumina nanoparticles were dispersed in an SMA matrix polymer via the solution and melt‐compounding methods to produce 2 wt % nanocomposites. Field emission scanning electron microscopy was used to examine the nanoparticle dispersion. When the solution method was used, nanoparticle reagglomeration occurred, despite the fairly good polymer wetting. However, through the coating of the alumina nanoparticles with a thin layer (ca. 20 nm) of low‐molecular‐weight SMA, reagglomeration was absent in the melt‐compounded samples, and this resulted in excellent nanoparticle dispersion. The resultant nanocomposites were semitransparent to visible light at a 2‐mm thickness with improved UV‐barrier properties. Their impact strengths, tensile strengths, and strains at break were slightly reduced compared with those of their neat resin counterpart, whereas a small enhancement in their moduli was achieved. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

New fluorinated hybrid organic/inorganic water soluble polymeric network

This work presents the elaboration of nanoparticle networks from HASE (hydrophobically alkali-soluble emulsion) thickeners grafted with silica nanoparticles. Three HASE were realized by copolymerization in emulsion of methacrylic acid and ethyl acrylate or trifluoroethyl methacrylate and a hydrocarbon or fluorocarbon macromonomer. The macromonomer contains a hydrophobic pendant group separated from the backbone by a polyethylene glycol spacer chain. The free acid functions of the copolymer were coupled with amine functionalized silica nanoparticles. In basic aqueous solutions, the suspensions containing 1 wt.% of this polymer/SiO₂ nanocomposite characterized by DLS (size analysis) and Cryo-SEM are stable, translucent, and gel-like at pH = 7.5. Rheological measurements demonstrated that the grafting of silica nanoparticles did not affect the thickening effect of precursor co-polymers. Coating of glass plates was realized with these hybrid networks and characterized by AFM, indicating that the silica nanoparticles were more homogeneously dispersed when a fluorocarbon co-polymer was used.     

Functional dendrimer–gold nanoparticle hybrids for biomedical applications

Dendrimers are a class of nano‐sized synthetic polymers with a well‐defined composition and regularly branched tree‐like structure produced by stepwise growth. The uniform size, globular shape and tunable surface chemistry make dendrimers versatile nanoscaffolds to encapsulate or stabilize various inorganic (metal, metal oxide, semiconductor) nanoparticles. In the past decade, research interest in dendrimer–inorganic nanoparticle hybrids has evolved from the development of interesting properties to the exploitation of advanced and useful functions. In particular, because gold nanoparticles with controlled morphology and optical properties have been demonstrated to be promising and versatile candidates for a diverse field of biomedical applications including sensing, in vitro and in vivo imaging, drug delivery, diagnostics and therapies, dendrimer–gold nanoparticle hybrids with biocompatibility have recently been intensively investigated for promising biomedical applications due to their controllable structures and dimensions, as well as their desirable internal and/or external functionalities. In this review, we discuss the recent progress regarding the development of functional dendrimer–gold nanoparticle hybrids for biomedical applications. The strategies for the fabrication of various structures of dendrimer–gold nanoparticle hybrids will first be summarized, followed by their biomedical applications in drug and gene delivery, photothermal therapy and combined therapies. © 2018 Society of Chemical Industry     

Suspensions of Iron Oxide Nanoparticles Stabilized by Anionic Surfactants

Two common anionic surfactants, sodium oleate (SO) and sodium dodecyl benzene sulfonate (SDBS) were used to re‐suspend iron oxide nanoparticles in aqueous solutions. At certain SO concentrations, the SO formulations produced highly stable suspensions. In contrast, SDBS‐stabilized nanoparticles exhibited poor stability at all concentrations. The adsorption isotherm of SO on iron oxide nanoparticles revealed that stable suspensions were obtained when the equilibrium SO concentration (after adsorption) reached its critical micelle concentration (CMC). At this “optimal” condition, the maximum SO adsorption was reached, and the zeta‐potential of the particles was highly negative (～ ?50 mV). According to the SO isotherm, this optimal formulation coincided with the formation of a highly compact SO bilayer. The SDBS isotherm, on the other hand, revealed that SDBS is not strongly adsorbed on the surface of iron oxide nanoparticles and that is likely that a patchy, loosely packed bilayer, is formed on the surface of the iron oxide nanoparticles when the equilibrium SDBS concentration reaches its CMC. The DLVO theory confirmed the connection between formulation conditions and the corresponding stability. This works confirmed that the formation of a surfactant bilayer is an important element in producing stable nanoparticle suspensions with anionic surfactants. It was also confirmed that for anionic surfactants, electrostatic repulsions are an important factor in establishing an energy barrier against flocculation. This work also introduced two more elements into the design of nanoparticle suspensions. The first element is that, in order to ensure the best possible dispersion, the surfactant concentration in solution at equilibrium with the adsorbed surfactant should be close or slightly above its CMC. The second element is that the molecular structure of the surfactant should facilitate the formation of closely packed bilayers.     

Fabrication, modeling and characterization of multi-crosslinked methacrylate copolymeric nanoparticles for oral drug delivery

Nanotechnology remains the field to explore in the quest to enhance therapeutic efficacies of existing drugs. Fabrication of a methacrylate copolymer-lipid nanoparticulate (MCN) system was explored in this study for oral drug delivery of levodopa. The nanoparticles were fabricated employing multicrosslinking technology and characterized for particle size, zeta potential, morphology, structural modification, drug entrapment efficiency and in vitro drug release. Chemometric Computational (CC) modeling was conducted to deduce the mechanism of nanoparticle synthesis as well as to corroborate the experimental findings. The CC modeling deduced that the nanoparticles synthesis may have followed the mixed triangular formations or the mixed patterns. They were found to be hollow nanocapsules with a size ranging from 152 nm (methacrylate copolymer) to 321 nm (methacrylate copolymer blend) and a zeta potential range of 15.8-43.3 mV. The nanoparticles were directly compressible and it was found that the desired rate of drug release could be achieved by formulating the nanoparticles as a nanosuspension, and then directly compressing them into tablet matrices or incorporating the nanoparticles directly into polymer tablet matrices. However, sustained release of MCNs was achieved only when it was incorporated into a polymer matrix. The experimental results were well corroborated by the CC modeling. The developed technology may be potentially useful for the fabrication of multi-crosslinked polymer blend nanoparticles for oral drug delivery.