Interfacial Polymer Deposition Research Articles

NO-cGMP-K+ Channels Pathways Participate in the Antihypertensive Effects of Attalea phalerata Martius ex Spreng Oil-Loaded Nanocapsules.

Attalea phalerata Martius ex Spreng is a palm tree that is widely distributed in the Central-West region of Brazil. In this study, we investigated whether the oil-loaded nanocapsules of A. phalerata (APON) have acute and long-lasting antihypertensive effects in male spontaneously hypertensive rats (SHR), as well as explored the underlying molecular mechanisms. APON was prepared using the interfacial polymer deposition method. The particle size, polydispersity index, and zeta potential were investigated using dynamic and electrophoretic light scattering. The antihypertensive effects of APON (administered at doses of 1, 3, and 10 mg/kg) were evaluated after acute intraduodenal administration and after 7 days of oral treatment. To investigate the molecular pathways involved, we used pharmacological antagonists and inhibitors that target prostaglandin/cyclic adenosine monophosphate, nitric oxide/cyclic guanosine monophosphate, and potassium channels. Both acute and prolonged administration of APON (at doses of 3 and 10 mg/kg) resulted in a significant reduction in systolic, diastolic, and mean arterial pressure. Prior treatment with a non-selective nitric oxide synthase inhibitor (Nω-nitro-L-arginine methyl ester), guanylyl cyclase inhibitor (methylene blue), or non-selective calcium-sensitive K+ channel blocker (tetraethylammonium) abolished the antihypertensive effects of APON. Our study showed that A. phalerata oil-loaded nanocapsules have a significant antihypertensive effect in SHR after both short-term and long-term (7-day) use. This effect seems to rely on the vascular endothelium function and involves the NO-cGMP-K+ channel pathway. This research suggests a new direction for future studies to definitively prove the therapeutic benefits of APON in treating cardiovascular disease.

Immunomodulatory and Anticancer Effects of Fridericia chica Extract-Loaded Nanocapsules in Myeloid Leukemia.

Nanocapsules provide selective delivery and increase the bioavailability of bioactive compounds. In this study, we examined the anticancer and immunomodulatory potential of Fridericia chica (crajiru) extract encapsulated in nanocapsules targeting myeloid leukemias. Nanocapsules containing crajiru (nanocapsules-CRJ) were prepared via interfacial polymer deposition and solvent displacement. Size and polydispersity were measured by dynamic light scattering. Biological assays were performed on leukemia cell lines HL60 and K562 and on non-cancerous Vero cells and human PBMC. The anticancer activity was evaluated using cytotoxicity and clonogenic assays, while the immunomodulatory activity was evaluated by measuring the levels of pro- and anti-inflammatory cytokines in PBMC supernatants treated with concentrations of nanocapsules-CRJ. Nanocapsules-CRJ exhibited significant cytotoxic activity against HL60 and K562 cells at concentrations ranging from 0.75 to 50 μg/mL, with the greatest reductions in cell viability observed at 50 μg/mL (p < 0.001 for HL60; p < 0.01 for K562), while not affecting non-cancerous Vero cells and human PBMCs. At concentrations of 25 μg/mL and 50 μg/mL, nanocapsules-CRJ reduced the formation of HL60 and K562 colonies by more than 90% (p < 0.0001). Additionally, at a concentration of 12 μg/mL, nanocapsules-CRJ induced the production of the cytokines IL-6 (p = 0.0002), IL-10 (p = 0.0005), IL-12 (p = 0.001), and TNF-α (p = 0.005), indicating their immunomodulatory potential. These findings suggest that nanocapsules-CRJ hold promise as a potential therapeutic agent with both cytotoxic and immunomodulatory properties.

Computational simulation on the study of Tacrolimus and its improved dermal retention using Poly(Ԑ-caprolactone) nanocapsules

Tacrolimus (TAC) is a drug from natural origin that can be used for topical application to control autoimmune skin diseases such as atopic dermatitis, psoriasis, and vitiligo. Computational simulation based on quantum mechanics theory by solving Schrödinger Equation for n-body problem may allow the theoretical calculation of drug geometry, charge distribution and dipole moment, electronic levels and molecular orbitals, electronic transitions, and vibrational transitions. Additionally, the development of novel nanotechnology-based delivery systems containing TAC can be an approach for reducing the dose applied topically, increasing dermal retention, and reducing the reported side effects due to the controlled release pattern. Firstly, this paper was devoted to obtaining the molecular, electronic, and vibrational data for TAC by using five semi-empirical (SE) methods and one Density Functional Theory (DFT) method in order to expand the knowledge about the drug properties by computational simulation. Then, this study was carried out to prepare TAC-loaded poly(ԑ-caprolactone) nanocapsules by interfacial polymer deposition following solvent displacement and investigate the in vitro drug permeation using the Franz diffusion cell and the photoacoustic spectroscopy. Computational simulations were compared in the three schemes SE/SE, SE/DFT, and DFT/DFT, where the first method represented the procedure used for geometry optimization and the second one was performed to extract electronic and vibrational properties. Computational data showed correspondence with TAC geometry description and electronic properties, with few differences in HOMO – LUMO gap (Δ) and dipole values. The SE/DFT and DFT/DFT methods presented a better drug description for the UV–Vis, Infrared, and Raman spectra with low deviation from experimental values. Franz cell model demonstrated that TAC was more delivered across the Strat-M® membrane from the solution than the drug-loaded poly(ԑ-caprolactone) nanocapsules. Photoacoustic spectroscopy assay revealed that these nanocapsules remained more retained into the Strat-M® membranes, which is desirable for the topical application.

Positively charged polymeric nanoparticles improve ocular penetration of tacrolimus after topical administration

Tacrolimus (TAC) is an immunosuppressant with potential use in ophthalmology, especially as a steroid sparing agent. The efficacy of TAC has been investigated in the treatment of different anterior segment inflammatory disorders. However, its use is limited by its poor corneal penetration, which has led to the development of different nanocarriers. In order to overcome this limitation, we prepared positively charged polymeric nanoparticles loaded with tacrolimus (TAC-NPs) for topical ocular application. TAC-NPs were prepared by interfacial polymer deposition following solvent displacement method, using Eudragit® RL100, a cationic polymer. The formulation was characterized and the ocular safety was assessed in vivo by Draize eye test and histopathological analysis. TAC was quantified in aqueous humor to determine the in vivo release of the nanoparticles. TAC-NPs presented suitable physical-chemical characteristics for ocular application, including monomodal size distribution with a mean diameter of 104 ± 1 nm, positive zeta potential and mucoadhesive properties. The monitoring of the physical-chemical characteristics and the multiple light scattering analysis of TAC-NPs suggested their long-term stability. The in vivo safety investigation of TAC-NPs and blank-NPs showed no signs of ocular irritation on the ophthalmological examination and histopathological study, indicating the biocompatibility of this carrier. The nanoparticles were able to deliver TAC for over 36 h with a better performance than the drug suspension. The in vivo release profile of TAC-NPs indicated slower elimination with 1.7-fold higher maximum concentration of TAC and 5.3-fold higher AUC, suggesting increased ocular penetration and bioavailability in addition to extended delivery. TAC-NPs improved the ocular delivery of tacrolimus after topical administration, without causing any ocular irritation. It shows the potential of this carrier as an alternative for ocular delivery of tacrolimus in the treatment of anterior segment inflammatory conditions.

The Permeability of Poly(lactic-co-glycolic acid) Nanoparticles Loaded with Psoralen to Human Skin in Medical Chemotherapy

Objective: In order to improve the clinical efficacy and reduce the side effects, PLGA nanoparticles loaded with psoralen for external use were prepared, and the permeation, distribution and influencing factors of PLGA nanoparticles delivered via microneedles in human skin were investigated. Methods: The psoralen nanoparticles were prepared by solvent replacement and interfacial polymer deposition. The percutaneous process of PLGA nanoparticles loaded with psoralen was observed with Franz diffusion cell and laser confocal microscope. The distribution of the nanoparticles in each cortex was quantified by HPLC. Results: The retention of PLGA nanoparticles delivered via microneedles in the skin was significantly increased (P &lt; 0.01), and the retention in the epidermis was greater than that in the dermis (P &lt; 0.01); the release rate in vitro was 75.58% after 24 hours, and less than 0.5% after 48 hours. Conclusion: PLGA nanoparticles loaded with psoralen can effectively promote the penetration and distribution of PLGA nanoparticles in human skin after being delivered to human skin through microneedles. With the increase of depth, the amount of PLGA nanoparticles gradually decreases, and with the extension of time, the penetration promotion effect of microneedles is more obvious. PLGA nanoparticles loaded with psoralen may become one of the clinical methods to improve the photochemotherapy of psoralen and develop a new transdermal drug delivery system to reduce its toxic and side effects.

An Alternative Approach for Improved Entrapment Efficiency of Hydrophilic Drug Substance in PLGA Nanoparticles by Interfacial Polymer Deposition Following Solvent Displacement

Background: Alzheimer’s disease (AD) is an age-related and irreversible neurological disorder. The low efficacy of current therapeutic strategies is related to both poor drug potency and the presence of various obstacles in the delivery routes, such as blood-brain barrier (BBB) that limits the uptake of most drugs by the brain. Rivastigmine hydrogen tartrate (RHT) is used in mild to moderate forms of AD therapy. Objectives: The present study described the use of Poly-lactic-co-glycolic acid (PLGA) nanoparticles (NPs), as effective delivery vehicles, to improve the therapeutic efficiency of RHT. Methods: RHT-loaded PLGA NPs were prepared using interfacial polymer deposition, following solvent displacement method with different ratios of polymer: Drug. The NPs were studied for entrapment efficiency, particle size, and surface morphology, using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). In vitro drug release from NPs was also assessed by a modified dissolution method. Results: The entrapment efficiency of RHT in NPs was found to be between 27.71 ± 6.86 and 45.70 ± 11.06 and the average size was about 75.14 to 173 nm. The zeta potential was negative (-2.28 to -10.5 mV), as determined by dynamic light scattering (DLS). The drug released from NP formulations was between 69.98% and 89% upon 24 hours, which indicated improved sustained drug release characteristics. Conclusions: These results suggested the potential usefulness of PLGA NPs for the delivery of RHT in a sustained and controlled manner.

Efficient Praziquantel Encapsulation into Polymer Microcapsules and Taste Masking Evaluation Using an Electronic Tongue

Abstract Taste masking is an important strategy for improving adherence of patients, especially children, who have to take pharmaceutical drugs with a bitter taste, as is the case of praziquantel (PZQ) used to treat schistosomiasis. In this work, a modified interfacial polymer deposition method was used to prepare polymer microcapsules and microspheres to encapsulate PZQ, where formulations were optimized to fulfill the stringent requirements for controlled drug release. In vitro release tests confirmed the suitability of the formulation with microcapsules of the anionic copolymer L30D, in which the loading of PZQ was larger than 90% in solutions that were stable at low pH but released PZQ under enteric conditions. We also show that the encapsulation was effective in terms of masking PZQ taste through the analysis with an electronic tongue.

Reduced cardiotoxicity and increased oral efficacy of artemether polymeric nanocapsules in Plasmodium berghei-infected mice.

Artemether (ATM) cardiotoxicity, its short half-life and low oral bioavailability are the major limiting factors for its use to treat malaria. The purposes of this work were to study free-ATM and ATM-loaded poly-ε-caprolactone nanocapules (ATM-NC) cardiotoxicity and oral efficacy on Plasmodium berghei-infected mice. ATM-NC was obtained by interfacial polymer deposition and ATM was associated with polymeric NC oily core. For cardiotoxicity evaluation, male black C57BL6 uninfected or P. berghei-infected mice received, by oral route twice daily/4 days, vehicle (sorbitol/carboxymethylcellulose), blank-NC, free-ATM or ATM-NC at doses 40, 80 or 120 mg kg-1. Electrocardiogram (ECG) lead II signal was obtained before and after treatment. For ATM efficacy evaluation, female P. berghei-infected mice were treated the same way. ATM-NC improved antimalarial in vivo efficacy and reduced mice mortality. Free-ATM induced significantly QT and QTc intervals prolongation. ATM-NC (120 mg kg-1) given to uninfected mice reduced QT and QTc intervals prolongation 34 and 30%, respectively, compared with free-ATM. ATM-NC given to infected mice also reduced QT and QTc intervals prolongation, 28 and 27%, respectively. For the first time, the study showed a nanocarrier reducing cardiotoxicity of ATM given by oral route and it was more effective against P. berghei than free-ATM as monotherapy.

Chlorhexidine Nanocapsule Drug Delivery Approach to the Resin-Dentin Interface

In this study, we are introducing a new drug-delivery approach to demineralized dentin substrates through microsized dentinal tubules in the form of drug-loaded nanocapsules. Chlorhexidine (CHX) is widely used in adhesive dentistry due to its nonspecific matrix metalloproteinase inhibitory effect and antibacterial activities. Poly(ε-caprolactone) nanocapsules (nano-PCL) loaded with CHX were fabricated by interfacial polymer deposition at PCL/CHX ratios of 125:10, 125:25, and 125:50. Unloaded nanocapsules (blank) were fabricated as control. The fabricated nanocapsules were characterized in vitro in terms of particle size, surface charges, particle recovery, encapsulation efficiency, and drug loading. Nanocapsule morphology, drug inclusion, structural properties, and crystallinity were investigated by scanning and transmission electron microscopes (SEM/TEM), energy-dispersive x-ray analysis, Fourier transform infrared spectroscopy, and x-ray diffraction. Initial screening of the antibacterial activities and the cytotoxicity of the nanocapsules were also conducted. Nanocapsules, as carried on ethanol/water solution, were delivered to demineralized dentin specimens connected to an ex vivo model setup simulating the pulpal pressure to study their infiltration, penetration depth, and retention inside the dentinal tubules by SEM/TEM. Nanocapsules were Ag labeled and delivered to demineralized dentin, followed by the application of a 2-step etch-and-rinse dentin adhesive. CHX-release profiles were characterized in vitro and ex vivo up to 25 d. Spherical nanocapsules were fabricated with a CHX core coated with a thin PCL shell. The blank nanocapsules exhibited the largest z-average diameter with negatively charged ζ-potential. With CHX incorporation, the nanocapsule size was decreased with a positive shift in ζ-potential. Nano-PCL/CHX at 125:50 showed the highest drug loading, antibacterial effect, and CHX release both in vitro and ex vivo. SEM and TEM revealed the deep penetration and retention of the CHX-loaded nanocapsules inside dentinal tubules and their ability to be gradually degraded to release CHX in vitro and ex vivo. Ag-labeled nanocapsules revealed the close association and even distribution of nanocapsules throughout the resin tag structure. This study demonstrated the potential of introducing this novel drug-delivery approach to demineralized dentin substrates and the resin-dentin interface with nanosized CHX-loaded nanocapsules through the microsized dentinal tubules.

The analytic network process for the pharmaceutical sector: Multi criteria decision making to select the suitable method for the preparation of nanoparticles

BackgroundThis paper presents the methodology for assessing and selecting the most appropriate procedure for the preparation of nanoparticles by implementing the analytical network process. The commonly utilized nanoparticle preparation methods are Polymer Precipitation, Interfacial polymer deposition, Complex Coacervation, Cross linking, Emulsion solvent diffusion, Homogenization and Polymerization method. There are numerous parameters to be considered in groundwork of nanoparticles that departs the conclusion manufacturer in bias. One has to address a number of components in alignment to determine and choose the optimum conclusion choices, because an unsuitable conclusion could lead to the eventual merchandise having to be formulated and developed again. For this cause in this paper, we study selecting the most appropriate procedure for the preparation of nanoparticles utilizing one of the multi criteria-decision making techniques, Analytic Network Process.MethodologyThe main goal was determined. The criteria and sub-criteria that affect the main goal were determined. The alternatives for the problem were determined. The interactions between criteria, sub-criteria, and alternatives respect to the main goal were determined. The super matrixes according to the network were assembled and then weighted super matrix and limit super matrix were then constructed. The values of this limit matrix are the desired priorities of the elements with respect to the goal. The alterative with the highest priority was finally chosen as the best alternative.ResultsThe emulsion solvent diffusion technique (M-5) has the highest value (0.434379) among the alternative methods that are applicable to the preparation of the nanoparticles. The second highest is Polymer Precipitation (M-1) with a value of 0.178798, and the lowest value or last choice is Cross Linking (M-4) with a value of only 0.024516. The alternative with the highest priority would achieve the goal, i.e., the best method for the preparation of the nanoparticles.ConclusionThe alternative M5 emulsion solvent diffusion technique, scoring 0.434379 was the one with largest main concern amidst all the other alternatives and thereby judged to be the most apt procedure for the preparation of nanoparticles.

Potentiation of the bactericidal activity of Harungana madagascariensis Lam. ex Poir. (Hypericaceae) leaf extract against oral bacteria using poly (D, L-lactide-co-glycolide) nanoparticles: in vitro study

Harungana madagascariensis Lam. ex Poir. (Hypericaceae) is known to have biological properties with mainly antibacterial, antifungal, and antiviral effects. The objective of this study was to investigate the in vitro bactericidal activity of the ethyl acetate H. madagascariensis leaf extract (HLE) on the main oral bacterial strains largely implicated in dental caries and gingivitis infections, and the possibility of potentialization of HLE antibacterial effects using the poly (D,L-lactide-co-glycolide) nanoparticles (PLG-NP). The microdilution technique and the interfacial polymer deposition following the solvent diffusion method were used to investigate the in vitro bactericidal activity of ethyl acetate HLE and to prepare nanoparticles, respectively. HLE showed significant bactericidal effects against the bacterial strains tested, with minimal bactericidal concentration (MBC) to 5×102 mg/l or less, except for Lactobacillus casei with 7.5×102 mg/l. With the HLE incorporated into PLG nanoparticles (HLE-PLG-NP), we observed diminution of the bactericidal concentration compared to HLE, the upper MBC being of 1.875×102 mg/l. Incorporation of the HLE into a colloidal carrier optimized its antibacterial performance.

Enhanced Ascorbyl Palmitate Stability by Polymeric Nanoparticles

Ascorbyl palmitate (AP) loaded poly(D.L-lactide) (PLA) and poly(D.L-lactide-co-glycolide) (PLGA) nanoparticles (NP) were prepared by interfacial polymer deposition according to the solvent displacement method. The particle size varied from 115 to 150 nm (polydispersity index around 0.10) while the zeta potential was around - 30 mV for all formulations. In general. NP formulations exhibited a high AP encapsulation efficiency. Low temperature and pHs around neutrality increased the AP stability in both PLA and PLC A NP. However. PLA NP was more stable in distilled water than in diverse phosphate buffer systems elucidating an important effect of the ionic strength on the stability of AP. Additional degassing of the distilled water led to the best AP protection in PLA NP even when stored under atmospheric condition. The degassing step and the polymer type were found to be essential for stabilization purposes. PLA NP demonstrated their potential as a promising formulation for increased AP stabilization.

Effect of nanoprecipitation on the physicochemical properties of low molecular weight poly( l-lactic acid) nanoparticles loaded with salbutamol sulphate and beclomethasone dipropionate

A modified nanoprecipitation (interfacial polymer deposition following solvent displacement) method was used to produce nanoparticles from low molecular weight poly( l-lactic acid). Model drugs, either salbutamol sulphate or beclomethasone dipropionate, were encapsulated in the particles. The influence of the preparation method on the physicochemical state of the polymer and the drugs as well as on the drug–polymer interactions were studied by electron microscopy, X-ray diffractometry, thermal analysis and infrared spectroscopy. Nanoprecipitation lowered the crystallinity of the PLA polymer. The crystallinity of the polymer was higher in the particles containing salbutamol sulphate then those containing beclomethasone dipropionate. The crystal form of beclomethasone dipropionate was changed from an anhydrate to a monohydrate as a result of nanoprecipitation. Although changes in the crystallinity of the polymer and the model drugs were seen, no clear interactions between the polymer and the drug were detected.

Sustained ex vivo skin antiseptic activity of chlorhexidine in poly(ϵ-caprolactone) nanocapsule encapsulated form and as a digluconate

In this work, the sustained bactericidal activity of chlorhexidine base loaded poly(ϵ-caprolactone), PCL, nanocapsules against Staphylococcus epidermidis inoculated onto porcine ear skin was investigated. Drug loaded nanocapsules were prepared by the interfacial polymer deposition following solvent displacement method, then characterized by photon correlation spectroscopy, electrophoretic measurements, transmission and scanning electron microscopy. Antimicrobial activity of these colloidal carriers was evaluated (i) in vitro against eight strains of bacteria, and (ii) ex vivo against Staphylococcus epidermidis inoculated for 12 h onto porcine ear skin surface treated for 3 min either with 0.6% chlorhexidine base loaded or unloaded nanocapsules suspended in hydrogel, or 1% chlorhexidine digluconate aqueous solution. Chlorhexidine absorption into the stratum corneum (SC) was evaluated by the tape-stripping method. The results showed that chlorhexidine nanocapsules in aqueous suspension having a 200–300 nm size and a positive charge exhibited similar minimum inhibitory concentrations against several bacteria with chlorhexidine digluconate aqueous solution. Ex vivo, there was a significant reduction in the number of colony forming units (CFUs) from 3-min treated skin with chlorhexidine nanocapsule suspension (5 to <1 log 10) compared to chlorhexidine digluconate solution (5 to 2.02 log 10) after a 8-h artificial contamination. After a 12-h artificial contamination, both formulations failed to achieve a 5 log 10 reduction. Furthermore, from a 3-min treatment with an identical applied dose and a subsequent 12-h artificial contamination, a residual chlorhexidine concentration in the SC was found to be three-fold higher with chlorhexidine nanocapsule suspension than with chlorhexidine digluconate solution. Interestingly, nanocapsules were shown in porcine skin follicles. Consequently, a topical application of chlorhexidine base-loaded positively charged nanocapsules in an aqueous gel achieved a sustained release of bactericide against Staphylococcus epidermidis for at least 8 h. Enhancement of drug delivery by mediating a more direct and prolonged contact between the carrier and (i) bacteria, (ii) skin surface, and (iii) skin follicles was assumed.

Poly(lactic acid)−Poly(ethylene oxide) (PLA−PEG) Nanoparticles: NMR Studies of the Central Solidlike PLA Core and the Liquid PEG Corona

NMR studies on a series of poly(lactic acid)−poly(ethylene oxide) (PLA−PEG) diblock copolymers have been carried out in d6-acetone and in D2O. Nanoparticles of the PLA−PEG copolymers were obtained using a modified interfacial polymer deposition−solvent evaporation technique (Fessi, H.; Devissaguet, J. P.; Puisieux, F.; Thies, C. French Patent 2 608 988, 1986). In D2O, the PLA block forms a central hydrophobic core, while the PEG block forms an hydrophilic corona layer. In D2O, the hydrophobic core of the nanoparticle is generally not seen, while the PEG corona is observed. Only the PLA methyl protons at the interface between the two regions are observed, and these are seen as a double doublet structure. For nanoparticles with a low molecular weight PLA block length, an additional methyl multiplet signal is seen suggesting that PLA methyl groups are in more than one chemical environment. This is not seen for nanoparticles with a high molecular weight PLA block length indicating more uniform structure in th...

In vitro cell interaction and in vivo biodistribution of poly(lactide-co-glycolide) nanospheres surface modified by poloxamer and poloxamine copolymers

Biodegradable poly(lactide-co-glycolide) (PLGA) nanospheres in the size range 80–150 nm have been produced, using an interfacial polymer deposition (nanoprecipitation) method. The nanospheres have been surface modified with poly(ethylene glycol) (PEG) either by adsorption of polypropylene oxide-polyethylene oxide (PPO-PEO) block copolymers of the poloxamer and poloxamine series (poloxamer 407, poloxamine 904 and poloxamine 908) or by incorporation of the same copolymers into the nanospheres during the production. The nanospheres were radiolabelled by incorporation of indium-111-oxine during nanosphere production. The biological behaviour of the PLGA nanosphere systems is discussed in terms of the in vitro cell interaction with isolated non-parenchymal liver cells and the in vivo biodistribution in the rat and rabbit models after intravenous injection. The results are compared to those for model polystyrene nanospheres surface modified in the same manner. It is shown that PLGA nanospheres coated with poloxamer 407 or poloxamine 908 exhibit prolonged blood circulation times accompanied by a combined reduction in liver and spleen accumulation after intravenous injection to the rat. Three hours post intravenous injection, 39% and 28% of the administered dose of poloxamer 407- and poloxamine 908-coated PLGA nanospheres remains in the blood circulation.

Lymph node localisation of biodegradable nanospheres surface modified with poloxamer and poloxamine block co-polymers

Studies were performed to develop a sub-100 nm biodegradable colloidal system for the efficient delivery of drugs and diagnostic agents to the lymphatic system. Nanospheres of poly(lactide-co-glycolide) were prepared by interfacial polymer deposition. The nanospheres were coated with block co-polymers in order to modify their surface characteristics. Radiolabelling of the nanospheres for in vivo tracing was achieved by the incorporation of the lipophilic complex 111In-oxine during nanosphere preparation. In vitro stability of the radiolabelled nanospheres was determined in rat serum at 37°C. The lymphatic distribution of the nanospheres was determined after subcutaneous administration to the rat. Lymphatic uptake of all coated systems was enhanced compared to the uncoated nanospheres, and a maximal uptake of 17% of the administered dose in the regional lymph nodes was achieved. These observations suggest that the nanospheres are suitable for diagnostic and therapeutic applications in clinical and experimental medicine.

Nanocapsule formation by interfacial polymer deposition following solvent displacement

Indomethacin-loaded nanocapsules were prepared by deposition of poly-( D,L-lactide) polymer at the o/w interface following acetone displacement from the oily nanodroplets. An attempt was made to elucidate the mechanisms of formation in terms of interfacial turbulence between two unequilibrated liquid phases involving flow, diffusion and surface tension decrease (Marangoni effect).

Structure of hollow polystyrene microspheres: an SEM study.

Hollow polystyrene microspheres have been prepared by a modified interfacial polymer deposition technique. The hollow microspheres were characterized using scanning electron microscopy. The effects of polymer concentration and the quantity of the internal phase material (methanol) used on the microsphere size and their wall thickness were studied. Increase in polymer concentration causes increase in wall thickness while increasing internal phase material increases microsphere size and deforms them from a spherical shape.

Preparation of ethylcellulose/polystyrene composite microcapsules of two-phase structure and permeability of the microcapsule membranes towards phenobarbital

Water-loaded ethylcellulose/polystyrene composite microcapsules with a two-phase structure were prepared by interfacial polymer deposition using mixed solutions of the two polymers in dichloromethane, which exhibit phase separation. Inward diffusion of phenobarbital, a sparingly water-soluble drug, through the composite microcapsule membranes from the surrounding medium into the interior of the microcapsules was investigated by measuring the change with time of drug concentration in the surroudning medium. The drug concentration changed in a periodic fashion, with an overall declining trend, which was interpreted as showing that the drug is periodically accumulated in the polystyrene-rich part of the microcapsule membranes due to fluctuations of its chemical potential, causing oscillatory changes in drug concentration in the surrounding medium.