Slower Release Rate Research Articles

Sodium alginate/poly (ethylene oxide) blend hydrogel membranes for controlled release of valganciclovir hydrochloride

Sodium alginate (SA) and poly (ethylene oxide) PEO blend membranes were prepared by solvent casting method for the controlled release of valganciclovir hydrochloride, an antiHIV drug. The prepared membranes were thin, flexible, smooth, and characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC), X-ray diffraction (X-RD), scanning electron microscopy (SEM), and tensile strength measurement. FTIR was used to understand the formation of hydrogen bonding between SA and PEO. The DSC and X-RD studies were performed to understand the crystalline nature of drug after encapsulation into the membranes. SEM was used to study the surface morphology of the membranes. Tensile strength measurements revealed the mechanical strength of the membranes. In vitro release studies indicated a dependence of release rate on the extent of crosslinking, amount of drug loading, and the amount of PEO, but slow release rates was extended up to 12 h. Cumulative release data were fitted onto to an empirical equation to compute diffusional exponent (n), which indicated the nonFickian trend for drug release.

Utilization of environmental waste cyanobacteria as a pesticide carrier: Studies on controlled release and photostability of avermectin

Cyanobacteria (Cyb), an environment waste, was first utilized as a carrier for controlled release of avermectin (Av) and improvement of pesticide photostability. Microalgae powder prepared from Cyb blooms was characterized by elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), optical microscopy, and scanning electron microscopy (SEM). The globular morphology and the size (∼3.5μm) of Cyb do not change significantly, with increase of roughness, after Av adsorption and Carbopol coating. Av manifests considerable binding affinity to Cyb in isopropanol and adsorption decreases in more polar solvents at 25°C. An extended release of Av from Cyb-Av in ethanol/water (v/v, 4:1) mixture was obtained and the release was further controlled by the Carbopol resin coated on Cyb-Av. Thicker Carbopol coating results in larger lag time (t0), slower release rate, and less total release amount. The release process was found to be controlled by a diffusion mechanism, but was strongly affected by polymer matrix–Av interaction and polymer relaxation. Finally, adsorbed Av on Cyb exhibits much greater UV-stability than free Av.

Preparation and characterization and release properties of Eudragit RS based ibuprofen pellets prepared by extrusion spheronization: effect of binder type and concentration

Objective: The effects of type and concentration of binding agent on properties of Eudragit RS based pellets were studied.Materials and methods: Pellets containing ibuprofen (60%), Eudragit RS (30%), Avicel (10%) were prepared by extrusion spheronization. PVP K30, PVP K90, HPMC 6cp, HPMC K100LV or HPMC K4M were used as binders in concentrations of 2, 4 or 6% based on the total weight of formulation. The process efficiency, pellet shape, size distribution, crushing strength, elastic modulus and drug release were examined. The effect of curing on pellet properties was also investigated.Results: The process of extrusion spheronization became difficult with increase in binder viscosity and/or concentration. An increase in binder viscosity and/or concentration resulted in reduction in the yield of pellets, wider particle size distribution and departure from spherical shape especially in the case of HPMC binder. The crushing strength and elastic modulus of pellets decreased with increase in PVPs concentration. However this was not the case for pellets containing HPMCs. Drug release rate increased as the concentration of binder increased. Pellets containing 2%w/w of PVP K30 showed the slowest release rate. For those pellets with brittle nature, curing changed the behavior of pellet under mechanical test to plastic deformation. Yield point and elastic modulus of all formulations decreased after curing. Curing decreased the drug release rate.Conclusion: Binder type and concentration significantly affected the properties of pellets. For production of sustained release ibuprofen Eudragit RS based pellets lower viscosity binders (PVP K30) with concentrations less than 4%w/w was optimum.

Comparative Studies of Lamivudine-zidovudine Nanoparticles for the Selective Uptake by Macrophages

The present study investigates the specific drug targeting of anti retroviral drugs, such as lamivudine and zidovudine, after intraperitoneal (i.p) injection by incorporation into polymeric nanoparticles (PNs) and solid lipid nanoparticles (SLNs). Our results showed that Glyceryl Monosterate-Poloxamer 188 SLNs (average diameter of 522.466 nm) showed slow drug release rates (63.18% of lamivudine and 62.37% of zidovudine were released in 12 hrs) among all the SLN formulations. For Poly lactic-co-glycolic acid (PLGA)-Poloxamer 188 PNs (average diameter of 70.348 nm), there were faster release rates of both lamivudine and zidovudine (97% and 94.06%, respectively, in 12 hrs). Tissue distribution studies were carried out in mice and concentrations of drugs in different organs were determined using high performance liquid chromatography (HPLC) after i.p. administration. Glyceryl Monosterate-Poloxamer 188 SLNs and PLGA-Poloxamer 188 PNs showed increase in the distribution of lamivudine and zidovudine to liver and spleen when compared to the drugs in solution. Also, Glyceryl Monosterate-P 188 SLNs showed higher concentration of drugs in RES organs than PLGA-P 188 PNs.

Controlled drug release on amine functionalized spherical MCM-41

MCM-41 silica with spherical morphology and small particle sizes (100nm) was synthesized and modified by post-synthesis method with different amounts of 3-aminopropyltriethoxysilane (APTES). A comparative study of the adsorption and release of a model drug, ibuprofen, was carried out. The modified and drug loaded mesoporous materials were characterized by XRD, TEM, N2 physisorption, elemental analysis, thermal analysis and FT-IR spectroscopy. A new method was developed for the quantitative determination of amino groups in surface modified mesoporous materials by the ninhydrin reaction. Good correlation was found between the amino content of the MCM-41 materials determined by the ninhydrin method and their ibuprofen adsorption capacity. Amino modification resulted in high degree of ibuprofen loading and slow release rate in comparison to the parent non-modified MCM-41.

Effect of light on toxicity of nanosilver to Tetrahymena pyriformis

More and more silver nanoparticles (AgNPs) have been released into the aquatic environment due to their widespread use, which may result in harmful effects on aquatic organisms. Environmental risk assessments of AgNPs on aquatic organisms in the natural environment (including light, sound, etc.) are indispensable. The aim of the present study was to elucidate the influence of light on the toxicity of AgNPs to Tetrahymena pyriformis. Silver nanoparticles, which were synthesized by reduction of silver nitrate with sodium borohydride, ranged in size from 5 to 20 nm with most particles approximately 10 nm. The authors performed AgNPs toxicity assays under a simulated natural environment with sunlight. The results indicated that the toxicity of AgNPs is higher than silver ion in the environment without light, but under the light condition, the toxicity of AgNPs decreased greatly. After 24 h of incubation with AgNPs, the inhibition ratio was 69.2 ± 7% in the dark and 35.5 ± 2% in the light, and the degree of inhibition was reduced by 33.7%. However, the effect of light on Ag(+) could be negligible. Further investigation indicated that the light irradiation could induce the growth of AgNPs and sequentially form bulk agglomeration. This decreased the surface area and the number of bare Ag atoms, resulting in a slower release rate and less Ag(+) ions released from AgNPs. At the same time, bulk agglomeration induced the deposition of part of the AgNPs to the aquatic bottom, which decreased the amount of AgNPs existing in water. All these phenomena led to the weakened toxicity of AgNPs in a light irradiation environment.

Preparation of Mesoporous Nano-Hydroxyapatite Using a Surfactant Template Method for Protein Delivery

Mesoporous nano-hydroxyapatite (n-HA) has gained more and more attention as drug storage and release hosts. The aim of this study is to observe the effect of the ratio of surfactant to the theoretical yield of HA on the mesoporous n-HA, then to reveal the effect of the mesoporous nanostructure on protein delivery. The mesoporous n-HA was synthesized using the wet precipitation in the presence of cetyltrimethylammonium bromide (CTAB) at ambient temperature and normal atmospheric pressure. The morphology, size, crystalline phase, chemical composition and textural characteristics of the product were well characterized by X-ray Powder Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) and N2 adsorption/desorption, respectively. The protein adsorption/release studies were also carried out by using Bovine Serum Albumin (BSA) as a model protein. The results reveal that the mesoporous n-HA synthesized with CTAB exhibits high pure phase, low crystallinity and the typical characteristics of the mesostructure. The BSA loading increases with the specific surface area and the pore volume of n-HA, and the release rates of BSA are different due to their different pore sizes and pore structures. n-HA synthesized with 0.5% CTAB has the highest BSA loading and the slowest release rate because of its highest surface area and smaller pore size. These mesoporous n-HA materials demonstrate a potential application in the field of protein delivery due to their bioactive, biocompatible and mesoporous properties.

Novel erythropoietin-loaded nanoparticles with prolonged in vivo response

The aim of this study was to incorporate human recombinant erythropoietin (EPO) in biodegradable polymeric nanoparticles targeting a prolonged-release effect. EPO-loaded poly(DL-lactide-co-glycolide) nanoparticles were prepared using double emulsion method (w/o/w) with least process-related stress on the encapsulated drug. The nanoparticles have been fully characterized including in vitro release profile. The biological activity was assessed in vivo using BALB-c mice. The produced particles appeared spherical in shape with smooth regular surfaces and had an average particle size of 225.9 ± 3.8 nm. The entrapment efficiency was 33.3%. The in vitro release profile exhibited a biphasic mode with a burst of 50% cumulative drug release, followed by a slow rate of release over 24 h, reaching a maximum of 82%. The bioassay results showed that EPO-loaded nanoparticles were able to maintain the physiological activity of EPO for 14 days after single subcutaneous injection compared with pure and marketed EPO formulae (EPREX®).

A Novel Lanreotide-Encoded Micelle System Targets Paclitaxel to the Tumors with Overexpression of Somatostatin Receptors

Many tumor cells specifically overexpress somatostatin receptors, in particular, subtype 2 (SSTR2). Lanreotide, a somatostatin analogue with high affinity for SSTR2, can be exploited as a ligand for tumor targeted therapy. In this study, lanreotide was first conjugated to poly(ethylene glycol)-b-poly(ε-caprolactone) (PEG-b-PCL) copolymer, and the active targeting micelles with paclitaxel (lanreotide-PM-PTX) or fluorescent agent were constructed and characterized with various analytical methods. Lanreotide-PM-PTX micelles were spherical in shape with a hydrodynamic diameter of 43.2 ± 0.4 nm, high drug encapsulation (87.1 ± 2.8%) and slow drug release rate. Two cancer cell lines (human lung cancer H446 and human breast cancer MCF-7 cells) with different expression levels of SSTR2 were used in this study. As observed by flow cytometry, confocal microscopy and cytotoxicity studies, lanreotide-encoded PEG-b-PCL micelles demonstrated more specific cell uptake and cytotoxicity in SSTR2-positive tumor cells via a receptor-mediated mechanism over the passive targeting micelles. The active targeting micelles showed higher accumulation in tumor tissue and tumor cells in tumor-bearing mice in vivo by near-infrared fluorescence (NIRF) imaging, high-performance liquid chromatography and confocal microscopy, respectively. Furthermore, treatment with lanreotide-PM-PTX micelles resulted in stronger tumor inhibition, increased life span and enhanced tumor cell apoptosis in SSTR2-overexpressing tumor model in athymic nude mice. The in vivo efficacy test with both H446 and MCF-7 tumor models further demonstrated the involvement of receptor-mediated interaction. Finally, the active targeting micelles exhibited less body weight loss, lower hemolysis and lower myelosuppression, as compared with the control groups. In conclusion, lanreotide can serve as an effective homing peptide, and the lanreotide-modified PEG-b-PCL micelles hold considerable promise in the treatment of SSTR2-overexpressing solid tumors.

PLGA Nanoparticles for Peptide Receptor Radionuclide Therapy of Neuroendocrine Tumors: A Novel Approach towards Reduction of Renal Radiation Dose

BackgroundPeptide receptor radionuclide therapy (PRRT), employed for treatment of neuroendocrine tumors (NETs) is based on over-expression of Somatostatin Receptors (SSTRs) on NETs. It is, however, limited by high uptake and retention of radiolabeled peptide in kidneys resulting in unnecessary radiation exposure thus causing nephrotoxicity. Employing a nanocarrier to deliver PRRT drugs specifically to the tumor can reduce the associated nephrotoxicity. Based on this, 177Lu-DOTATATE loaded PLGA nanoparticles (NPs) were formulated in the present study, as a potential therapeutic model for NETs.Methodology and FindingsDOTATATE was labeled with Lutetium-177 (177Lu) (labeling efficiency 98%; Rf∼0.8). Polyethylene Glycol (PEG) coated 177Lu-DOTATATE-PLGA NPs (50∶50 and 75∶25) formulated, were spherical with mean size of 304.5±80.8 and 733.4±101.3 nm (uncoated) and 303.8±67.2 and 494.3±71.8 nm (coated) for PLGA(50∶50) and PLGA(75∶25) respectively. Encapsulation efficiency (EE) and In-vitro release kinetics for uncoated and coated NPs of PLGA (50∶50 & 75∶25) were assessed and compared. Mean EE was 77.375±4.98% & 67.885±5.12% (uncoated) and 65.385±5.67% & 58.495±5.35% (coated). NPs showed initial burst release between 16.64–21.65% with total 42.83–44.79% over 21days. The release increased with coating to 20.4–23.95% initially and 60.97–69.12% over 21days. In-vivo studies were done in rats injected with 177Lu-DOTATATE and 177Lu-DOTATATE-NP (uncoated and PEG-coated) by imaging and organ counting after sacrificing rats at different time points over 24 hr post-injection. With 177Lu-DOTATATE, renal uptake of 37.89±10.2%ID/g was observed, which reduced to 4.6±1.97% and 5.27±1.66%ID/g with uncoated and coated 177Lu-DOTATATE-NP. The high liver uptake with uncoated 177Lu-DOTATATE-NP (13.68±3.08% ID/g), reduced to 7.20±2.04%ID/g (p = 0.02) with PEG coating.ConclusionPLGA NPs were easily formulated and modified for desired release properties. PLGA 50∶50 NPs were a more suitable delivery vehicle for 177Lu-DOTATATE than PLGA 75∶25 because of higher EE and slower release rate. Reduced renal retention of 177Lu-DOTATATE and reduced opsonisation strongly advocate the potential of 177Lu-DOTATATE-PLGA-PEG NPs to reduce radiation dose in PRRT.

Enhanced payload and photo-protection for pesticides using nanostructured lipid carriers with corn oil as liquid lipid

With the aim to establish a novel nanocarrier system with higher payload and higher photo-protection for deltamethrin (active ingredient) compared to solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC) were prepared by combining hot homogenization and sonication with different ratios of corn oil (liquid lipid) and beeswax (solid lipid). Compared to SLN, the incorporation of corn oil gave a higher payload, slower release rate and higher photo-protection for deltamethrin. Particularly, compared to beeswax solid lipid nanoparticles (BSLN), NLC gave a higher payload (approximately 1.79 times) with a high encapsulation efficiency (83.6%), higher photo-protection in direct photolysis (1.8 times) after 12 h exposure of ultraviolet light (UV) and in indirect photolysis (1.37 times) after 2 h exposure of UV in 2% (v/v) acetone solution used as a photosensitizer. This study demonstrated that novel nanocarrier possesses a wide range of applicability in protecting photo-labile compounds for the crop, food and pharmaceutical industries.

EFFECT OF ALENDRONATE-CONTAINING COATINGS ON OSTEOINTEGRATION INTO POROUS TANTALUM IN A CORTICAL BONE MODEL

Hip replacement is extensively performed in hips with serious damages. The clinical outcomes of hip implants remain to be improved. Local delivery of bisphosphonates may improve implant fixation by positively affecting local bone modeling. In this study, two alendronate-containing coatings were prepared on porous tantalum by electrolytic deposition. Calcium phosphate coating was deposited and adsorbed with alendronate; the resulting coating had a low drug dose and slow release rate. Solid calcium alendronate coating was also deposited on tantalum; the resulting coating had high drug dose and faster release rate. The effects of the two coatings on new bone formation and implant fixation were studied in the rabbit tibial cortex. Four weeks after implantation, the implants with adsorbed alendronate showed the highest total new bone formation and mechanical fixation, whereas the implants with solid drug coating showed slightly lower fixation and total new bone formation than control bare implants. The improvement by the alendronate-adsorbed calcium phosphate coating provides potentials of enhancing early fixation of porous implants. The solid drug coating warranted further studies to exploit its high drug dose for inhibiting future osteolysis.

Controlled drug delivery through a novel PEG hydrogel encapsulated silica aerogel system

A novel composite material consisting of a silica aerogel core coated by a poly(ethylene) glycol (PEG) hydrogel was developed. The potential of this novel composite as a drug delivery system was tested with ketoprofen as a model drug due to its solubility in supercritical carbon dioxide. The results indicated that both drug loading capacity and drug release profiles could be tuned by changing hydrophobicity of aerogels, and that drug loading capacity increased with decreased hydrophobicity, while slower release rates were achieved with increased hydrophobicity. Furthermore, higher concentration of PEG diacrylate in the prepolymer solution of the hydrogel coating delayed the release of the drug which can be attributed to the lower permeability at higher PEG diacrylate concentrations. The novel composite developed in this study can be easily implemented to achieve the controlled delivery of various drugs and/or proteins for specific applications.

Molecularly imprinted nanoparticles prepared by miniemulsion polymerization as selective receptors and new carriers for the sustained release of carbamazepine

Water-compatible imprinted nanoparticles were prepared for carbamazepine as a template and used for the selective extraction and controlled release of carbamazepine. Assay materials and drug delivery carriers were typically used in aqueous environments, so it is generally preferable to prepare solvent-free molecularly imprinted nanoparticles in water using the miniemulsion polymerization method. The present work investigates a bio-analytical strategy generically applicable to imprinted materials for molecular recognition studies, including equilibrium and non-equilibrium binding, and release experiments, increasing the knowledge of the molecular interactions between the template molecules and imprinted nanoparticles. The results showed that the imprinted nanoparticles exhibited a higher binding level and slower release rate than non-imprinted nanoparticles. The selectivity of imprinted nanoparticles for carbamazepine studied in comparison with an analogue compound, oxcarbazepine, the main metabolite of carbamazepine. The recovery and selectivity of carbamazepine in human serum was determined to be 100%, 1.7 times that of oxcarbazepine. The results indicated that carbamazepine-imprinted nanoparticles are appropriate for serum level determination of the drug in therapeutic range. The template to functional monomer ratio as a key factor controlling the recognition and release kinetic mechanism of imprinted nanoparticles is discussed. The imprinted nanoparticles prepared at the appropriate template to functional monomer mole ratio (2:8) exhibited the best drug affinity (5.1 times higher) and a slower drug release rate due to the interaction of carbamazepine with the imprinted cavities within the nanoparticles. Loaded imprinted nanoparticles as drug reservoirs were able to prolong carbamazepine release, in 1% wt sodium dodecyl sulfate aqueous solution, for more than 8 days.

Liposomal topotecan formulation with a low polyethylene glycol grafting density: pharmacokinetics and antitumour activity

PEGylated liposomes could evade recognition by the reticulo-endothelial system and prolong the circulation time of vesicles, resulting in enhanced targeting efficiency and antitumour effect. Typically, vesicles are modified with distearoylphosphatidylethanolamine (DSPE)-polyethylene glycol (PEG) at a high PEG grafting density. However, long circulation time and slow drug release rate might induce severe hand-foot syndrome in clinical practice. In this study, a liposomal topotecan formulation with a low PEG grafting density was prepared and its pharmacokinetics, acute toxicity and antitumour effect were investigated. Topotecan was loaded into liposomes using an ammonium sulfate gradient. The resulting formulation was injected to healthy Wistar rats at different dose levels to investigate whether its clearance followed linear kinetics. Biodistribution was performed in Lewis lung cancer-bearing mice. The acute toxicity was evaluated in healthy mice and beagle dogs. To compare the antitumour effects of different formulations and dose schedule, RM-1 prostate, Lewis lung, H446 and L1210 cancer models were used. Topotecan could be encapsulated into low DSPE-PEG liposomes with ∼100% loading efficiency. The clearance of the liposomal formulation followed linear kinetics at a dose level ranging from 0.5 to 4 mg/kg despite the fact that the vesicles were coated at a low PEG density. Compared with free topotecan the liposomal formulation preferentially accumulated into tumour zones instead of normal tissues. Both formulations could rapidly accumulate into liver and tumour, but the liposomal formulation was cleared from tissues at a slow rate relative to the conventional formulation. In rats and beagle dogs, liposomal formulations could not induce skin toxicity. In all the tumour models, smaller split doses were more therapeutically active than larger doses when the overall dose intensity was equivalent. This has been the first report that plasma kinetics of a liposomal formulation with a low PEG density followed linear kinetics. Moreover, due to its short circulation half-life, the formulation did not induce skin toxicity. Our data revealed that the dose schedule of liposomal drugs should be adjusted in accordance with the biophysical and biological properties of the formulations to achieve the optimal therapeutic efficacy.

Development and evaluation of sustained-release Compritol® 888 ATO matrix mini-tablets

Context: Sustained-release mini-tablets are a potentially suitable for paediatric drug delivery or as multi-particulate dosage forms.Objective: To evaluate the potential for developing lipophilic matrix mini-tablets and to assess the effects of Compritol® 888 ATO concentration on drug release from differently sized mini-tablets prepared by direct compression.Methods: A formulation comprising theophylline as a model soluble drug, 15% w/w Compritol® 888 ATO as the inert matrix-forming agent, with dibasic dicalcium phosphate anhydrous and lactose as diluents was evaluated by producing 12 mm tablets at a range of compression speeds and forces. The same formulation and further formulations with 25, 35 or 45% w/w Compritol® 888 ATO were evaluated by producing 2, 3 and 4 mm mini-tablets.Results and Discussion: Drug release from matrix tablets was sustained over a period of 12 hours and release rate varied according to the compression force and speed employed. The rate of drug release from matrix mini-tablets was more rapid and increasing Compritol® 888 ATO concentration resulted in slower release rates. The rate of drug release from matrix mini-tablets was inversely proportional to mini-tablet size (2 mm > 3 mm > 4 mm). Drug release from the matrix tablets and mini-tablets followed square-root of time kinetics.Conclusion: Tailored drug release from matrix mini-tablets may achieved by altering the size of mini-tablet or level of Compritol® 888 ATO in the formulation and this may have potential in the development of paediatric formulations or multi-particulate dosage forms.

Antimicrobial acrylic materials with in situ generated silver nanoparticles

Polymethyl methacrylate (PMMA) is widely used to treat traumatic head injuries (cranioplasty) and orthopedic injuries (bone cement), but there is a problem with implant-centered infections. With organisms such as Acinetobacter baumannii and methicillin-resistant staphylococcus aureus developing resistance to antibiotics, there is a need for novel antimicrobial delivery mechanisms without risk of developing resistant organisms. To develop a novel antimicrobial implant material by generating silver nanoparticles (AgNP) in situ in PMMA. All PMMA samples with AgNP's (AgNP-PMMA) released Ag(+) ions in vitro for over 28 days. In vitro antimicrobial assays revealed that these samples (even samples with the slowest release rate) inhibited 99.9% of bacteria against four different strains of bacteria. Long-term antimicrobial assay showed a continued antibacterial effect past 28 days. Some AgNP-loaded PMMA groups had comparable Durometer-D hardness (a measure of degree of cure) and modulus to control PMMA, but all experimental groups had slightly lower ultimate transverse strengths. AgNP-PMMA demonstrated a tremendously broad-spectrum and long-intermediate-term antimicrobial effect with comparable mechanical properties to control PMMA. Current efforts are focused on further improving mechanical properties by reducing AgNP loading and assessing fatigue properties.

Improved biological effects of uniconazole using porous hollow silica nanoparticles as carriers

The aim of this work is to prepare a controlled-release formulation of uniconazole using porous hollow silica nanoparticles (PHSNs) as carrier, and to investigate the biological effects on rice growth. PHSNs with a shell thickness of ~15 nm and a particle size of 80-100 nm were synthesised through a sol-gel route using nanosized calcium carbonate particles as templates. Simple immersing (SI) and supercritical fluid drug loading (SFDL) technologies were employed to load uniconazole into PHSNs with loading efficiencies of ~22 and ~26% respectively. The prepared uniconazole-loaded PHSNs (UCZ-PHSNs) by SI and SFDL both demonstrated sustained release properties, and the latter showed better controlled release ability with a slower release rate. Compared with free uniconazole, UCZ-PHSNs exhibited a weaker growth retardation effect in the early stage but more significant retardation ability in later stages for agar-cultured rice seedlings. For the rice that grew in clay, UCZ-PHSNs demonstrated a weaker plant height retardation effect than free uniconazole at the early jointing stage by foliar spraying, but exhibited a stronger retardation capacity than free uniconazole by being applied into soil before seedling transplantation. The results indicated that the prepared UCZ-PHSNs possessed good controlled-release properties and had improved retardation effects on rice growth. It is recommended that UCZ-PHSNs be applied into soil before seedling transplantation rather than administered by foliar spraying at the early jointing stage.

Core–Shell Structured Up-Conversion Luminescent and Mesoporous NaYF4:Yb3+/Er3+@nSiO2@mSiO2 Nanospheres as Carriers for Drug Delivery

Core–shell structured up-conversion luminescent and mesoporous NaYF4:Yb3+/Er3+@nSiO2@mSiO2 nanospheres were prepared by coating mesoporous SiO2 layers with different thicknesses on NaYF4:Yb3+/Er3+ nanoparticles via a simple two-step sol–gel process. The obtained sample shows a typical mesoporous structure and well-dispersed spherical morphology with a narrow size distribution. The nanospheres exhibit little cytotoxicity (via MTT assay), and ibuprofen (IBU) was used as a model drug to access the release properties of the system in detail. The amount of IBU adsorbed in mesoporous channels increases with the thickness of the ordered mesoporous silica shell coated on the NaYF4:Yb3+/Er3+ nanoparticles. The in vitro release study of IBU reveals a release profile in two steps: an initial diffusion-controlled release, followed by a slower release rate. Furthermore, upon excitation by a 980 nm near-infrared laser, the nanospheres emit green (2H11/2 and 4S3/2 → 4I15/2) and red (4F9/2 → 4I15/2) fluorescence of Er3+ ...

Development and characterization of molecularly imprinted polymers for controlled release of citalopram

In this work, the use of molecularly imprinted polymers (MIPs) for citalolpram as anti-depressant drug was studied. Imprinted polymers were prepared from methacrylic acid (MAA; functional monomer), ethylene glycol dimethacrylate (EGDMA; cross-linker), and citalopram (as a drug template) using bulk polymerization method. The polymeric devices were further characterized by FT-IR, thermogravimetric analysis, scanning electron microscopy, and binding experiments. The dissolution media employed in controlled release studies were hydrochloric acid at the pH level of 4.3 and phosphate buffers, at pH levels of 7.2 and 10.1, maintained at 37.0 and 25.0±0.5°C. Results showed the ability of MIP polymers to control the release of citalopram. In all cases, the imprinted polymers showed a higher affinity for citalopram and a slower release rate than the nonimprinted polymers. At the pH level of 4.3 and at the temperature of 25°C, slower release of citalopram imprinted polymer occurred.