Quantitative analysis of polyvinyl alcohol on the surface of poly(D, L-lactide-co-glycolide) microparticles prepared by solvent evaporation method: effect of particle size and PVA concentration

One-Step Precise Characterization of Drug Delivery Systems by PULCON Magnetic Resonance Spectroscopy

Polymers are extensively used for the realization of drug delivery systems across multiple scales, from nanomedicines to microparticles and macroscopic implantable devices, for their favorable biodegradation profiles and tunable physicochemical features. The accurate quantification of the polymer content is key to finely controlling drug loading and release and ensuring reproducibility, yet it continues to be a major challenge in the design and development of delivery systems. In this study, we introduce a novel protocol based on the PULCON technique to quantify, with a routine NMR spectroscopy analysis, the precise concentration of polymers in various delivery systems. Specifically, the PULCON protocol is applied to characterize the physicochemical and pharmaceutical properties of nanoparticles, microparticles, and implantable devices realized by combining three extensively used polymers, namely, poly(lactic-co-glycolic acid) (PLGA), poly(vinyl alcohol) (PVA), and poly(ethylene glycol) (PEG). Without using internal calibration procedures, in a single step, the PULCON protocol precisely quantifies the concentration of each polymer and the drug content. This approach can be readily implemented on standard NMR spectrometers, enabling accurate characterization of drug delivery systems and facilitating their effective development.

Surface Functionalization of Polymer Particles for Cell Targeting by Modifying Emulsifier Chemistry

The oil in water emulsion/solvent extraction method is used to fabricate many FDA approved, polymer particle formulations for drug delivery. However, these formulations do not benefit from surface functionalization that can be achieved through tuning particle surface chemistry. Poly(vinyl alcohol) (PVA) is the emulsifier used for many FDA approved formulations and remains associated with the particle surface after fabrication. We hypothesized that the hydroxyl groups in PVA could be conjugated with biomolecules using isothiocyanate chemistry and that these modifications would endow the particle surface with additional functionality. We demonstrate that fluorescein isothiocyanate and an isothiocyanate derivatized mannose molecule can be covalently attached to PVA in a one-step reaction. The modified PVA polymers perform as well as unmodified PVA in acting as an emulsifier for fabrication of poly(lactide-co-glycolide) particles. Particles made with the fluorescein modified PVA exhibit fluorescence confined to the particle surface, while particles made with mannose modified PVA bind concanavalin A. In addition, mannose modified PVA increases particle association with primary macrophages by three-fold. Taken together, we present a facile method for modifying the surface reactivity of polymer particles widely used for drug delivery in basic research and clinical practice. Given that methods are established for conjugating the isothiocyanate functional group to a wide range of biomolecules, our approach may enable PVA based biomaterials to engage a multitude of biological systems.

Controlled Delivery of Pan-PAD-Inhibitor Cl-Amidine Using Poly(3-Hydroxybutyrate) Microspheres

This study deals with the process of optimization and synthesis of Poly(3-hydroxybutyrate) microspheres with encapsulated Cl-amidine. Cl-amidine is an inhibitor of peptidylarginine deiminases (PADs), a group of calcium-dependent enzymes, which play critical roles in a number of pathologies, including autoimmune and neurodegenerative diseases, as well as cancer. While Cl-amidine application has been assessed in a number of in vitro and in vivo models; methods of controlled release delivery remain to be investigated. P(3HB) microspheres have proven to be an effective delivery system for several compounds applied in antimicrobial, wound healing, cancer, and cardiovascular and regenerative disease models. In the current study, P(3HB) microspheres with encapsulated Cl-amidine were produced in a size ranging from ~4–5 µm and characterized for surface morphology, porosity, hydrophobicity and protein adsorption, in comparison with empty P(3HB) microspheres. Cl-amidine encapsulation in P(3HB) microspheres was optimized, and these were found to be less hydrophobic, compared with the empty microspheres, and subsequently adsorbed a lower amount of protein on their surface. The release kinetics of Cl-amidine from the microspheres were assessed in vitro and expressed as a function of encapsulation efficiency. There was a burst release of ~50% Cl-amidine in the first 24 h and a zero order release from that point up to 16 days, at which time point ~93% of the drug had been released. As Cl-amidine has been associated with anti-cancer effects, the Cl-amidine encapsulated microspheres were assessed for the inhibition of vascular endothelial growth factor (VEGF) expression in the mammalian breast cancer cell line SK-BR-3, including in the presence of the anti-proliferative drug rapamycin. The cytotoxicity of the combinatorial effect of rapamycin with Cl-amidine encapsulated P(3HB) microspheres was found to be 3.5% more effective within a 24 h period. The cells treated with Cl-amidine encapsulated microspheres alone, were found to have 36.5% reduction in VEGF expression when compared with untreated SK-BR-3 cells. This indicates that controlled release of Cl-amidine from P(3HB) microspheres may be effective in anti-cancer treatment, including in synergy with chemotherapeutic agents. Using controlled drug-delivery of Cl-amidine encapsulated in Poly(3-hydroxybutyrate) microspheres may be a promising novel strategy for application in PAD-associated pathologies.

The Synthesis, Characterization and Applications of Polyhydroxyalkanoates (PHAs) and PHA-Based Nanoparticles

Polyhydroxyalkanoates (PHAs) are storage granules found in bacteria that are essentially hydroxy fatty acid polyesters. PHA molecules appear in variety of structures, and amongst all types of PHAs, polyhydroxybutyrate (PHB) is used in versatile fields as it is a biodegradable, biocompatible, and ecologically safe thermoplastic. The unique physicochemical characteristics of these PHAs have made them applicable in nanotechnology, tissue engineering, and other biomedical applications. In this review, the optimization, extraction, and characterization of PHAs are described. Their production and application in nanotechnology are also portrayed in this review, and the precise and various production methods of PHA-based nanoparticles, such as emulsion solvent diffusion, nanoprecipitation, and dialysis are discussed. The characterization techniques such as UV-Vis, FTIR, SEM, Zeta Potential, and XRD are also elaborated.

Oral Delivery of Encapsulated All-Trans Retinoic Acid Ameliorates Disease in Rodent Models of Colitis

BACKGROUND

All-trans retinoic acid (ATRA) is a biologically active isomer of retinoic acid (RA). Topical ATRA (retin-a, retin-a micro, atralin, renova, and avita) is the active pharmaceutical ingredient for FDA-approved treatments for acne and skin wrinkles. Oral formulations (Vesanoid) treat acute promyelocytic leukemia, but oral dosing can induce severe side effects. Despite benefits in various rodent models of inflammatory bowel disease (IBD), toxicity and controversial clinical observations have diminished enthusiasm for ATRA IBD clinical trials. To circumvent these issues and to use ATRA's key role in maintaining gut tolerance, we developed a poly(lactic-co-glycolic acid) (PLGA) microsphere (MS) encapsulated ATRA formulation aimed at directing ATRA delivery to immune structures of the gut, limiting systemic exposure. Initially, ATRA MS was developed as a component of a combinatorial product (TreXTAM) that also contained encapsulated transforming growth factor (TGF)-β and ATRA in a 1:2 w/w ratio. Although the combination was optimal, benefit was also observed when ATRA MS was given alone in the CD4+ CD25-T-cell adoptive transfer (ACT) colitis model.

METHODS

We used the ACT and DSS-induced murine models of colitis to expand on the dose-dependent effects of oral ATRA MS when given alone. The DSS model was also used to compare the efficacy of ATRA MS and soluble ATRA, while healthy animals were used to compare the pharmacokinetics of the two drugs.

RESULTS

In both the ACT and DSS-induced murine models of colitis, ATRA MS was observed to be effective in ameliorating disease. ATRA MS was also observed to be more effective than soluble ATRA in these models and displayed more favorable pharmacokinetics.

CONCLUSIONS

We suggest ATRA MS, as a standalone product, may attenuate IBD and perhaps limit fibrosis, while limiting systemic side effects.

Effect of Crystallinity on the Properties of Polycaprolactone Nanoparticles Containing the Dual FLAP/mPEGS-1 Inhibitor BRP-187

Seven polycaprolactones (PCL) with constant hydrophobicity but a varying degree of crystallinity prepared from the constitutional isomers ε-caprolactone (εCL) and δ-caprolactone (δCL) were utilized to formulate nanoparticles (NPs). The aim was to investigate the effect of the crystallinity of the bulk polymers on the enzymatic degradation of the particles. Furthermore, their efficiency to encapsulate the hydrophobic anti-inflammatory drug BRP-187 and the final in vitro performance of the resulting NPs were evaluated. Initially, high-throughput nanoprecipitation was employed for the εCL and δCL homopolymers to screen and establish important formulation parameters (organic solvent, polymer and surfactant concentration). Next, BRP-187-loaded PCL nanoparticles were prepared by batch nanoprecipitation and characterized using dynamic light scattering, scanning electron microscopy and UV-Vis spectroscopy to determine and to compare particle size, polydispersity, zeta potential, drug loading as well as the apparent enzymatic degradation as a function of the copolymer composition. Ultimately, NPs were examined for their potency in vitro in human polymorphonuclear leukocytes to inhibit the BRP-187 target 5-lipoxygenase-activating protein (FLAP). It was evident by Tukey's multi-comparison test that the degree of crystallinity of copolymers directly influenced their apparent enzymatic degradation and consequently their efficiency to inhibit the drug target.

Formulation and Evaluation of Linum usitatissimum Mucilage-Based Nanoparticles for Effective Delivery of Ezetimibe

Introduction

The aim of current study was to prepare Linum usitatissimum mucilage (LUM) based nanoparticles, capable of encapsulating hydrophobic drug ezetimibe as nanocarriers.

Methods

Solvent evaporation and nanoprecipitation techniques were used to develop nanoparticles by encapsulating ezetimibe in the articulated matrix of polysaccharide fractions. Developed nanoparticles were characterized to determine the particle size, zeta potential, polydispersibility index (PDI), and entrapment efficiency (EE). Morphology and physicochemical characterization were carried out through SEM, FTIR, PXRD and thermal analysis. Saturation solubility and in vitro release studies were also performed. Safety assessment of ezetimibe loaded nanoparticles was evaluated via oral acute toxicity study.

Results

The mean particle size, zeta potential, PDI and EE for emulsion solvent evaporation were 683.6 nm, -28.3 mV, 0.39, 63.7% and for nanoprecipitation were 637.7 nm, 0.07, -27.1 mV and 80%, respectively. Thermal analysis confirmed enhanced thermal stability, whereas PXRD confirmed amorphous nature of drug. Saturation solubility (p-value <0.05) demonstrated improved solubility of drug when enclosed in linseed nanoparticles. Nanoprecipitation surpasses emulsion solvent evaporation in dissolution test by possessing smaller size. Acute oral toxicity study indicated no significant changes in behavioral, clinical or histopathological parameters of control and experimental groups.

Conclusion

The in vitro release of ezetimibe was augmented by enhancing aqueous solubility through devised nanoparticles. Thus, linseed mucilage could act as biopolymer in the fabrication of nanoparticle formulation. The acute oral toxicological investigations provided evidence that LUMNs were safe after oral administration.

Topical tacrolimus nanocapsules eye drops for therapeutic effect enhancement in both anterior and posterior ocular inflammation models

Tacrolimus has shown efficacy in eye inflammatory diseases. However, due to the drug lability, its formulation into a stable ophthalmic product remains a challenge. Tacrolimus-loaded nanocapsules (NCs) were designed for ocular instillation. Further, the stability and effects of the formulation were analyzed under different experimental conditions. Physicochemical characterization of the NCs revealed suitable homogeneous size and high encapsulation efficiency. Moreover, the lyophilized formulation was stable at ICH long term and accelerated storage conditions, for at least 18 and 3 months, respectively. The tacrolimus NCs did not elicit any eye irritation in rabbits after single- and multiple-dose applications. Additionally, ex vivo penetration assays on isolated porcine cornea and pharmacokinetics analyses in various rabbit eye compartments demonstrated the superiority of the NCs in retention and permeation into the anterior chamber of the eye compared to the free drug dissolved in oil. Moreover, multiple dose ocular instillation of the NCs in rats allowed high tacrolimus levels in the eye with very low plasma concentrations. Finally, the developed delivery system achieved a significant decrease in four typical inflammatory markers in a murine model of keratitis, an anterior chamber inflammation. Furthermore, these NCs, applied as eye drops, displayed clinical and histological efficacy in the mainly posterior chamber inflammation model of murine, experimental auto-immune uveitis.

Formulation of drug-loaded oligodepsipeptide particles with submicron size

The size of particulate carriers is key to their transport and distribution in biological systems, and needs to be tailored in the higher submicron range to enable follicular uptake for dermal treatment. Oligodepsipeptides are promising nanoparticulate carrier systems as they can be designed to exhibit enhanced interaction with drug molecules. Here, a fabrication scheme for drug-loaded submicron particles from oligo[3-(S)-sec-butylmorpholine-2,5-dione]diol (OBMD) is presented based on an emulsion solvent evaporation method with cosolvent, surfactant, and polymer concentration as variable process parameters. The particle size (300-950 nm) increased with lower surfactant concentration and higher oligomer concentration. The addition of acetone increased the particle size at low surfactant concentration. Particle size remained stable upon the encapsulation of models compounds dexamethasone (DXM) and Nile red (NR), having different physicochemical properties. DXM was released faster compared to NR due to its higher water solubility. Overall, the results indicated that both drug-loading and size control of OBMD submicron particles can be achieved. When applied on porcine ear skin samples, the NR-loaded particles have been shown to allow NR penetration into the hair follicle and the depth reached with the 300 nm particles was comparable to the one reached with the cream formulation. A potential benefit of the particles compared to a cream is their sustained release profile.

Formulation and optimization of sildenafil citrate-loaded PLGA large porous microparticles using spray freeze-drying technique: A factorial design and in-vivo pharmacokinetic study

The oral administration of sildenafil citrate (SC) for the treatment of pulmonary arterial hypertension is associated with several drawbacks. The study aimed to design and formulate SC-loaded inhalable poly (lactic-co-glycolic acid) [PLGA] large porous microparticles (LPMs) for pulmonary delivery. A factorial design was used to study the effect of the composition of LPMs on physicochemical properties. The study also evaluated the effect of glucose and L-leucine concentration on the formulation. The developed LPMs demonstrated an acceptable yield% (≤48%), large geometric particle size (>5µm) with a spherical and porous surface, and sustained drug release (up to 48 h). Increasing the concentration of poly(ethyleneimine) from 0.5% to 1% in SC-loaded LPMs led to an increase in entrapment efficiency from ~3.02% to ~94.48%. The optimum LPMs showed adequate aerodynamic properties with a 97.68 ± 1.07% recovery, 25.33 ± 3.32% fine particle fraction, and low cytotoxicity. Intratracheal administration of LPMs demonstrated significantly higher lung deposition, systemic bioavailability, and longer retention time (p < 0.05) compared to orally administered Viagra® tablets. The study concluded that SC-loaded LPMs could provide better therapeutic efficacy, reduced dosing frequency, and enhanced patient compliance.

Oral encapsulated transforming growth factor β1 reduces endogenous levels: Effect on inflammatory bowel disease

BACKGROUND

TreXTAM^® is a combination of the key regulatory cytokine transforming growth factor beta (TGFβ) and all trans retinoic acid (ATRA) microencapsulated for oral delivery to immune structures of the gut. It is in development as a novel treatment for inflammatory bowel disease (IBD).

AIM

To measure TGFβ levels in blood and tissue after oral administration of encapsulated TGFβ.

METHODS

Animals were orally administered encapsulated TGFβ by gavage. Levels of drug substance in blood and in gut tissues at various times after administration were measured by ELISA.

RESULTS

We made the surprising discovery that oral administration of TreXTAM dramatically (approximately 50%) and significantly (P = 0.025) reduced TGFβ levels in colon, but not small intestine or mesenteric lymph nodes. Similarly, levels in rat serum after 25 d of thrice weekly dosing with either TreXTAM, or microencapsulated TGFβ alone (denoted as TPX6001) were significantly (P < 0.01) reduced from baseline levels. When tested in the SCID mouse CD4+CD25- adoptive cell transfer (ACT) model of IBD, oral TPX6001 alone provided only a transient benefit in terms of reduced weight loss.

CONCLUSION

These observations suggest a negative feedback mechanism in the gut whereby local delivery of TGFβ results in reduced local and systemic levels of the active form of TGFβ. Our findings suggest potential clinical implications for use of encapsulated TGFβ, perhaps in the context of IBD and/or other instances of fibrosis and/or pathological TGFβ signaling.

Encapsulation of the dual FLAP/mPEGS-1 inhibitor BRP-187 into acetalated dextran and PLGA nanoparticles improves its cellular bioactivity

BACKGROUND

Dual inhibitors of the 5-lipoxygenase-activating protein (FLAP) and the microsomal prostaglandin E2 synthase-1 (mPGES-1) may exert better anti-inflammatory efficacy and lower risks of adverse effects versus non-steroidal anti-inflammatory drugs. Despite these advantages, many dual FLAP/mPGES-1 inhibitors are acidic lipophilic molecules with low solubility and strong tendency for plasma protein binding that limit their bioavailability and bioactivity. Here, we present the encapsulation of the dual FLAP/mPGES-1 inhibitor BRP-187 into the biocompatible polymers acetalated dextran (Acdex) and poly(lactic-co-glycolic acid) (PLGA) via nanoprecipitation.

RESULTS

The nanoparticles containing BRP-187 were prepared by the nanoprecipitation method and analyzed by dynamic light scattering regarding their hydrodynamic diameter, by scanning electron microscopy for morphology properties, and by UV-VIS spectroscopy for determination of the encapsulation efficiency of the drug. Moreover, we designed fluorescent BRP-187 particles, which showed high cellular uptake by leukocytes, as analyzed by flow cytometry. Finally, BRP-187 nanoparticles were tested in human polymorphonuclear leukocytes and macrophages to determine drug uptake, cytotoxicity, and efficiency to inhibit FLAP and mPGES-1.

CONCLUSION

Our results demonstrate that encapsulation of BRP-187 into Acdex and PLGA is feasible, and both PLGA- and Acdex-based particles loaded with BRP-187 are more efficient in suppressing 5-lipoxygenase product formation and prostaglandin E2 biosynthesis in intact cells as compared to the free compound, particularly after prolonged preincubation periods.

Immobilization of poly(lactide-co-glycolide) microspheres on bone implant materials for antibiotic release and the binding mechanisms

Bone implants are susceptible to postoperative infections. Immobilization of antibiotic-loaded microparticles on implants is an effective approach to addressing this problem. Immobilization methods reported in earlier studies frequently used special or potentially harmful conditions. Therefore, the present study explored a new method to immobilize poly(lactide-co-glycolide) (PLGA) microspheres on bone implant materials. PLGA microspheres were prepared by an emulsion method using polyvinyl alcohol (PVA) as an emulsifier. The microspheres were immobilized on two commonly used orthopaedic biomaterials [hydroxyapatite-coated titanium (HA-Ti) and poly(methyl methacrylate) (PMMA)] by dispersing on the surface followed by vacuum drying. Microspheres were retained stably on both materials even after immersion in phosphate-buffered saline for 12 d. Pretreatment of microspheres with sodium borate (i.e., an eliminator of hydroxyl groups of PVA) substantially reduced their retention on HA-Ti, but only moderately reduced their retention on PMMA. This suggested that the binding of the residual PVA on the microspheres to the HA coating is the dominant contributor to their immobilization on HA-Ti, whereas other forces contributed substantially to their immobilization on PMMA. Microspheres containing ciprofloxacin (a water-soluble antibiotic) and triclosan (an oil-soluble antibiotic) were immobilized on HA-Ti and PMMA, respectively. They effectively killed adjacent bacteria. These results offer a simple and versatile method for immobilizing drug-release microspheres on some important bone implant surfaces.

Nonspherical Nanoparticle Shape Stability Is Affected by Complex Manufacturing Aspects: Its Implications for Drug Delivery and Targeting

The shape of nanoparticles is known recently as an important design parameter influencing considerably the fate of nanoparticles with and in biological systems. Several manufacturing techniques to generate nonspherical nanoparticles as well as studies on in vitro and in vivo effects thereof have been described. However, nonspherical nanoparticle shape stability in physiological-related conditions and the impact of formulation parameters on nonspherical nanoparticle resistance still need to be investigated. To address these issues, different nanoparticle fabrication methods using biodegradable polymers are explored to produce nonspherical nanoparticles via the prevailing film-stretching method. In addition, systematic comparisons to other nanoparticle systems prepared by different manufacturing techniques and less biodegradable materials (but still commonly utilized for drug delivery and targeting) are conducted. The study evinces that the strong interplay from multiple nanoparticle properties (i.e., internal structure, Young's modulus, surface roughness, liquefaction temperature [glass transition (T_g ) or melting (T_m )], porosity, and surface hydrophobicity) is present. It is not possible to predict the nonsphericity longevity by merely one or two factor(s). The most influential features in preserving the nonsphericity of nanoparticles are existence of internal structure and low surface hydrophobicity (i.e., surface-free energy (SFE) > ≈55 mN m^-1 , material-water interfacial tension <6 mN m^-1 ), especially if the nanoparticles are soft (<1 GPa), rough (R_rms > 10 nm), porous (>1 m² g^-1 ), and in possession of low bulk liquefaction temperature (<100 °C). Interestingly, low surface hydrophobicity of nanoparticles can be obtained indirectly by the significant presence of residual stabilizers. Therefore, it is strongly suggested that nonsphericity of particle systems is highly dependent on surface chemistry but cannot be appraised separately from other factors. These results and reviews allot valuable guidelines for the design and manufacturing of nonspherical nanoparticles having adequate shape stability, thereby appropriate with their usage purposes. Furthermore, they can assist in understanding and explaining the possible mechanisms of nonspherical nanoparticles effectivity loss and distinctive material behavior at the nanoscale.

PLGA-PEG nanoparticles containing gallium phthalocyanine: Preparation, optimization and analysis of its photodynamic efficiency on red blood cell and Hepa-1C1C7

Poly(lactide-co-glycolide) (PLGA) has been used for the encapsulation of phthalocyanine motived by its biocompatibility and biodegradability. Many studies have already been done to evaluate the influence of parameters used in the PLGA nanoparticle synthesis but without the evaluation of the combinatory interaction between these parameters on the nanoparticulate properties. Ga(III)-phthalocyanine (GaPc) was encapsulated into the PEGlated PLGA-nanoparticles and the individual and combinatory effects of the emulsification time, the method used for the nanoparticle synthesis and the temperature of the aqueous phase was evaluated on the size, entrapment efficiency, efficacy of nanoparticle recovery, residual PVA and zeta potential value using a 2³ factorial design (FD). Mathematical models were adjustable to the data and evolutionary operations were performed to optimize the nanoparticle size. The ability of the optimized nanoparticle to decrease the viability of the Hepa-1C1C7 cell and the blood red cell was also evaluated. The FD disclosed the emulsification-diffusion method decreased the residual PVA and the size of PLGA-PEG nanoparticle, but also decreased the entrapment efficiency of GaPc, the zeta potential absolute value and the recovery efficacy of nanoparticles. The combinatory effect between the method used in the nanoparticle preparation and the temperature of aqueous phase influenced four of the five evaluated properties. The viability of Hepa-1C1C7 cells was reduced until 13× when the cells were irradiated in the presence of encapsulated GaPc while it was decreased until 4.7× when the experiment was carried out with the free GaPc. The encapsulated GaPc was also more efficient to cause the haemolysis of the RBC than it was the free GaPc. The optimization of the nanoparticles synthesis increased the efficiency of the GaPc to oxidize the evaluated cells.

Application of statistical design to evaluate critical process parameters and optimize formulation technique of polymeric nanoparticles

In advanced medication, drug-loaded polymeric nanoparticles (NPs) appeared as a novel drug delivery system with lots of advantages over conventional medicines. Despite all the advantages, NPs do not gain popularity for manufacturing hurdles. The study focused on the formulation difficulties and implementation of statistical design to establish an effective model for manufacturing NPs. In this study, physico-chemical properties of the drug and polymer (PLGA) were incorporated to understand the mechanistic insights of nanoformulations. Primarily, the process controlling parameters were screened by Plackett-Burman design and the critical process parameters (Cpp) were further fabricated by Box-Behnken design (BBD). The TLM-PLGA-NPs (telmisartan loaded PLGA NPs) exhibited particle size, encapsulation efficiency and zeta potential of 232.4 nm, 79.21% and -9.92 mV respectively. The NPs represented drug loading of 76.31%. Korsmeyer-Peppas model (R 2 = 0.925) appeared to be the best fitted model for in vitro release kinetics of NPs. The model identified Fickian diffusion of TLM from the polymeric nanoparticles. The ANOVA results of variables indicate that BBD is a suitable model for the development of polymeric NPs. The study successfully identified and evaluated the correlation of significant parameters that were directly or indirectly influencing the formulations which deliberately produce desired nanoparticles with the help of statistical design.

Single-Emulsion P(HB-HV) Microsphere Preparation Tuned by Copolymer Molar Mass and Additive Interaction

Herein, we describe the production of poly(hydroxybutyrate-co-hydroxyvalerate) [P(HB-HV)]-based microspheres containing coumarin-6 (C6) or pyrene (Py) fluorophores as additives and models for hydrophobic and hydrophilic drug encapsulation. Their photophysical and morphological properties, as well as encapsulation efficiencies, are studied as this work aims to describe the influence of additive hydrophobicity/hydrophilicity on microparticle formation. These properties were studied by scanning electron microscopy, fluorescence confocal laser scanning microscopy (FCLSM), and steady-state fluorescence spectroscopy. The results show that the surfactant concentration, polymer molar mass, emulsification stirring rate, and the presence of the fluorophore and its nature are determinants of the P(HB-HV) microsphere properties. Also, encapsulation efficiency is shown to be governed by synergic effects of these parameters on the formation of microspheres. Moreover, size distribution is proved to be strongly influenced by the surfactant poly(vinyl alcohol) content. FCLSM showed that the fluorophores were efficiently encapsulated in P(HB-HV) microspheres at distinct distributions within the copolymer matrix. Surprisingly, nanospheres were observed in the microsphere surface, suggesting that microspheres are formed from nanosphere coalescence.

Polymeric Nanoparticles for Increasing Oral Bioavailability of Curcumin

Despite the promising biological and antioxidant properties of curcumin, its medical applications are limited due to poor solubility in water and low bioavailability. Polymeric nanoparticles (NPs) adapted to oral delivery may overcome these drawbacks. Properties such as particle size, zeta potential, morphology and encapsulation efficiency were assessed. Then, the possibility of storing these NPs in a solid-state form obtained by freeze-drying, in vitro curcumin dissolution and cytocompatibility towards intestinal cells were evaluated. Curcumin-loaded Eudragit^® RLPO (ERL) NPs showed smaller particle diameters (245 ± 2 nm) and better redispersibility after freeze-drying than either poly(lactic-co-glycolic acid) (PLGA) or polycaprolactone (PCL) NPs. The former NPs showed lower curcumin encapsulation efficiency (62%) than either PLGA or PCL NPs (90% and 99%, respectively). Nevertheless, ERL NPs showed rapid curcumin release with 91 ± 5% released over 1 h. The three curcumin-loaded NPs proposed in this work were also compatible with intestinal cells. Overall, ERL NPs are the most promising vehicles for increasing the oral bioavailability of curcumin.

Insights into maleimide-thiol conjugation chemistry: Conditions for efficient surface functionalization of nanoparticles for receptor targeting

Maleimide-thiol chemistry is widely used for the design and preparation of ligand-decorated drug delivery systems such as poly(lactide-co-glycolide) (PLGA) based nanoparticles (NPs). While many publications on nanocarriers functionalized exploiting this strategy are available in the literature, the conditions at which this reaction takes place vary among publications. This paper presents a comprehensive study on the conjugation of the peptide cRGDfK and the nanobody 11A4 (both containing a free thiol group) to maleimide functionalized PLGA NPs by means of the maleimide-thiol click reaction. The influence of different parameters, such as the nanoparticles preparation method and storage conditions as well as the molar ratio of maleimide to ligand used for conjugation, on the reaction efficiency has been evaluated. The NPs were prepared by a single or double emulsion method using different types and concentrations of surfactants and stored at 4 or 20 °C before reaction with the targeting moieties. Several maleimide to ligand molar ratios and different reaction times were studied and the conjugation efficiency was determined by quantification of the not-bound ligand by liquid chromatography. The kind of emulsion used to prepare the NPs as well as the type and concentration of surfactant used had no effect on the conjugation efficiency. Reaction between the maleimide groups present in the NPs and cRGDfK was optimal at a maleimide to thiol molar ratio of 2:1, reaching a conjugation efficiency of 84 ± 4% after 30 min at room temperature in 10 mM HEPES pH 7.0. For 11A4 nanobody the optimal reaction efficiency, 58 ± 12%, was achieved after 2 h of incubation at room temperature in PBS pH 7.4 using a 5:1 maleimide to protein molar ratio. Storage of the NPs at 4 °C for 7 days prior to their exposure to the ligands resulted in approximately 10% decrease in the reactivity of maleimide in contrast to storage at 20 °C which led to almost 40% of the maleimide being unreactive after the same storage time. Our findings demonstrate that optimization of this reaction, particularly in terms of reactant ratios, can represent a significant increase in the conjugation efficiency and prevent considerable waste of resources.

Paradigm shift in theranostics of neuroendocrine tumors: conceptual horizons of nanotechnology in nuclear medicine

We present a comprehensive review of Neuroendocrine Tumors (NET) and the current and developing imaging and therapeutic modalities for NET with emphasis on Nuclear Medicine modalities. Subsequently, nanotechnology and its emerging role in cancer management, especially NET, are discussed. The article is both educative and informative. The objective is to provide an insight into the developments made in nuclear medicine and nanotechnology towards management of NET, individually as well as combined together.

Biodegradable rifampicin-releasing coating of surgical meshes for the prevention of bacterial infections

Polypropylene mesh implants are routinely used to repair abdominal wall defects or incisional hernia. However, complications associated with mesh implantation, such as mesh-related infections, can cause serious problems and may require complete surgical removal. Hence, the aim of the present study was the development of a safe and efficient coating to reduce postoperative mesh infections. Biodegradable poly(lactide-co-glycolide acid) microspheres loaded with rifampicin as an antibacterial agent were prepared through single emulsion evaporation method. The particle size distribution (67.93±3.39 μm for rifampicin-loaded microspheres and 64.43±3.61 μm for unloaded microspheres) was measured by laser diffraction. Furthermore, the encapsulation efficiency of rifampicin (61.5%±2.58%) was detected via ultraviolet–visible (UV/Vis) spectroscopy. The drug release of rifampicin-loaded microspheres was detected by UV/Vis spectroscopy over a period of 60 days. After 60 days, 92.40%±3.54% of the encapsulated rifampicin has been continuously released. The viability of BJ fibroblasts after incubation with unloaded and rifampicin-loaded microspheres was investigated using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, which showed no adverse effects on the cells. Furthermore, the antibacterial impact of rifampicin-loaded microspheres and mesh implants, coated with the antibacterial microspheres, was investigated using an agar diffusion model with Staphylococcus aureus. The coated mesh implants were also tested in an in vivo mouse model of staphylococcal infection and resulted in a 100% protection against mesh implant infections or biofilm formation shown by macroscopic imaging, scanning electron microscopy, and histological examinations. This effective antibacterial mesh coating combining the benefit of a controlled drug delivery system and a potent antibacterial agent possesses the ability to significantly reduce postoperative implant infections.

Solvent effect in the synthesis of hydrophobic drug-loaded polymer nanoparticles

Quercetin is an abundant flavonoid in fruits, vegetables such as onion, tea leaves, cranberry, radish leaves etc. with numerous biological activities and widely used as an effective antioxidant. Its low solubility in water and chemical decomposition in intestinal environment are predicaments in delivery through dietary or oral intake. Noble polymeric nanoparticles are of particular interest today because of their applications in many areas. Polymer nanoparticles have attracted the interest of many research groups and have been utilised in an increasing number of fields such as site targeted drug delivery in cancer research during the last decades. Various techniques can be used to produce polymer nanoparticles, such as solvent evaporation, salting-out, dialysis, supercritical fluid technology etc. The choice of method depends on a number of factors, such as, particle size, particle size distribution, area of application, etc. In the present study, single emulsion-solvent evaporation technique has been utilised with two different organic solvents: acetone and chloroform/methanol to prepare quercetin loaded poly(D,L-lactide-co-glycolide) nanoparticles. According to the authors' observations acetone is a better solvent for encapsulating quercetin in polymer nanoparticles owing to its physical and chemical properties.

Formulation and In vitro Interaction of Rhodamine-B Loaded PLGA Nanoparticles with Cardiac Myocytes

This study aims to characterize rhodamine B (Rh B) loaded poly(D,L-lactide-co-glycolide; PLGA) nanoparticles (NPs) and their interactions with cardiac myocytes. PLGA NPs were formulated using single emulsion solvent evaporation technique. The influence of varying parameters such as the stabilizer concentration, the sonication time, and the organic to aqueous ratio were investigated. The diameter, the dispersity, the encapsulation efficiency and the zeta potential of the optimized NPs were about 184 nm, 0.19, 40% and -21.7 mV, respectively. In vitro release showed that 29% of the Rh B was released within the first 8 h. Scanning electron microscopy measurements performed on the optimized NPs showed smooth surface and spherical shapes. No significant cytotoxic or apoptotic effects were observed on cardiac myocytes after 24 and 48 h of exposure with concentrations up to 200 μg/mL. The kinetic of the intracellular uptake was confirmed by confocal microscopy and cells took up PLGA NPs within the 1st hours. Interestingly, our data show an increase in the NPs' uptake with time of exposure. Taken together, we demonstrate for the first time that the designed NPs can be used as potential probes for drug delivery in cardiac myocytes.

Development, characterization and in vitro evaluation of biodegradable rhein-loaded microparticles for treatment of osteoarthritis

Rhein is an active metabolite of the drug diacerein, whose anti-inflammatory properties have been demonstrated in both in vitro and in vivo models. However, the low oral bioavailability of rhein has limited its utility as a potential treatment of osteoarthritis (OA), a chronic inflammatory disease. In order to overcome this limitation, the aim of this work was the development of a drug delivery system intended for intra-articular administration of rhein, based on polymeric biodegradable PLGA microparticles (MPs) loaded with the drug. The MPs, prepared by the emulsion-solvent evaporation technique were characterized in terms of several parameters including morphology, encapsulation efficiency, molecular interactions between components of the formulation and in vitro release profiling. Furthermore, cell-based in vitro studies were performed to evaluate the cytotoxicity of the formulations and their effect on the release of inflammatory markers including pro-inflammatory cytokines and reactive oxygen species (ROS). Scanning electron microscopy demonstrated that the prepared MPs exhibited an almost spherical shape with smooth surface. The size distribution of the prepared MPs ranged between 1.9 and 7.9μm, with mean diameter of 4.23±0.87μm. The optimal encapsulation efficiency of rhein was 63.8±3.0%. The results of powder X-ray diffraction and differential scanning calorimetry studies demonstrated that the active ingredient is partially the crystalline state, dispersed in the polymer matrix. This outcome is somewhat reflected in the release kinetics of rhein from the MPs. The cytotoxicity evaluation, carried out in macrophages derived from THP-1 cells, showed that both rhein-loaded MPs and unloaded MPs did not significantly affect the cell viability at MP concentrations up to 13.8μM. In lipopolysaccharide-activated macrophages, the rhein-loaded MPs significantly decreased the production of interleukin-1β (IL-1β) and (ROS), when compared to the unloaded MPs. In conclusion, the results of this preliminary study suggest that an MP-based formulation of rhein could be tested in animal models of inflammation, aiming for an injectable commercial product capable of providing a therapeutic solution to patients suffering from chronic joint diseases.

Physical and biological characterization of sericin-loaded copolymer liposomes stabilized by polyvinyl alcohol

Sericin protein (SP) is widely used as a nutrient biomaterial for biomedical and cosmeceutical applications although it shows low stability to heat and light. To overcome these problems and add value to wastewater from the silk industry, sericin protein was recovered as sericin-loaded copolymer-liposomes (SP-PVA-LP), prepared through thin film hydration. The size and morphology of the liposomes were investigated using dynamic light scattering (DLS), and electron microscopy (SEM and TEM). The particle size, liposome surface morphology and encapsulation efficiency of SP were dependent on PVA concentration. The hydrodynamic size of the nanoparticles was between 200 and 400nm, with the degree of negative charge contingent on sericin loading. SEM and TEM images confirmed the mono-dispersity, and spherical nature of the particles, with FTIR measurements confirming the presence of surface bound PVA. Exposure of liposomes to 500ppm sericin highlighted a dependence of encapsulation efficiency on PVA content; 2% surface PVA proved the optimal level for sericin loading. Cytotoxicity and viability assays revealed that SP-loaded surface modified liposomes promote cellular attachment and proliferation of human skin fibroblasts without adverse toxic effects. Surface modified copolymer liposomes show high performance in maintaining structural stability, and promoting enhancements in the solubility and bio-viability of sericin. Taken together, these biocompatible constructs allow for effective controlled release, augmenting sericin activity and resulting in effective drug delivery systems.

Development and in vitro characterization of poly(lactide-co-glycolide) microspheres loaded with an antibacterial natural drug for the treatment of long-term bacterial infections

Biodegradable polymers, especially poly(lactide-co-glycolide) (PLGA), have good biocompatibility and toxicological properties. In combination with active ingredients, a specialized drug delivery system can be generated. The aim of the present study was to develop a drug delivery system consisting of PLGA microspheres loaded with the natural active ingredient totarol, which has several antimicrobial mechanisms. Totarol, isolated from the Podocarpus totara tree, was purified using column chromatography, and the eluate was checked for purity using thin layer chromatography. The spherically shaped microspheres with mean diameters of 147.21±3.45 µm and 131.14±3.69 µm (totarol-loaded and -unloaded microspheres, respectively) were created using the single emulsion evaporation method. Furthermore, the encapsulation efficiency, in a range of 84.72%±6.68% to 92.36%±0.99%, was measured via UV/vis spectroscopy. In a 90-day in vitro drug release study, the release of totarol was investigated by UV/vis spectroscopy as well, showing a release of 53.76%. The toxicity on cells was determined using BJ fibroblasts or Human Embryonic Kidney cells and an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, which showed no influence on the cell growth. The minimal inhibitory concentration was ascertained. A totarol concentration between 64 µg/mL and 128 µg/mL was necessary to inhibit the bacterial growth over a period of 24 hours. Biofilm formation on the surface of totarol-loaded microspheres was determined using transmission electron microscopy. No biofilm formation could be detected, even if the totarol concentration was below the minimal inhibitory concentration. The hemocompatibility investigations on various markers with fresh heparinized blood (1.5 IU/mL) showed that totarol and totarol-loaded microspheres have no influence on different blood parameters. The PLGA microspheres characterized by slow release of totarol and great entrapment efficiency represent a novel drug delivery system, which may be highly beneficial for the long-term therapy of bacterial infections.

Development of bicalutamide-loaded PLGA nanoparticles: preparation, characterization and in-vitro evaluation for the treatment of prostate cancer

In this study we report the development and optimization of poly (D, L-lactide-co-glycolide) (PLGA) polymer encapsulated poorly aqueous soluble nonsteroidal antiandrogen drug bicalutamide, to develop a sustained release formulation for the treatment of prostate cancer. The bicalutamide-loaded PLGA nanoparticles were prepared by single emulsion (O/W) solvent evaporation method, and different process parameters like polymer concentration in the organic phase, surfactant concentration in aqueous phase and centrifugation speed for separation of nanoparticles were evaluated to optimize the drug-loaded nanoparticles. The optimum formulation of bicalutamide-loaded PLGA nanoparticles characterized extensively by different analytical techniques like laser light scattering to determine average particle size and size distribution, scanning electron microscopy (SEM) for surface morphology, powder X-ray diffraction (PXRD) for surface chemistry and differential scanning calorimetry (DSC) for thermogram properties. Significant decrease of crystallinity of bicalutamide confirms entrapment of the drug within the PLGA polymer matrix. Further, the drug encapsulation efficiency (EE) and in vitro drug release profile were measured by high-performance liquid chromatography and UV-spectrophotometry. In vitro drug release exhibited biphasic pattern with initial burst release followed by slow and continuous release up to 5 days. Optimum formulation of bicalutamide-loaded PLGA nanoparticles shows significant anti-tumor activity over prostate cancer cell lines (DU 145). The newly developed optimum formulation nanoparticles could be useful for sustained release delivery of bicalutamide.

Microparticle of drug and nanoparticle: a biosynthetic route

Microparticles (MPs) have great potentiality in material science- based applications. Their use in biology is however limited to clinics and has rarely been exploited in the pharmaceutical context. Unlike nanoparticles (NPs), they are amenable to routine detection by flow cytometry and confocal microscopy. Though MPs can constitute a wide variety of materials, including ceramics, glass, polymers, and metals and can be synthesized by chemical process but wet processes for the preparation of microparticles have rarely been attemped. In this paper, a thrombotic route is shown to successfully generate biocompatible MP of a model anticancer drug (doxorubicin hydrochloride). Synthesis of MPs from platelets and drug loading in to these MPs was confirmed by flow cytometry and confocal microscopy. Human cervical cancer cell line (HeLa) was treated with these drug-loaded MPs to investigate whether the loaded MPs have the capacity to deliver drug to the cancer cells. In addition, Magnetic force microscopy was used to detect the preparation of MPs loaded with magnetic NPs. The efficiency of the drug-loaded MPs in inducing cytotoxicity in cancer cell line, shown to be significantly higher than the free drug itself. The drug-loaded MP is shown to have a much higher cytotoxic propensity than the free drug applied at comparable doses. The thrombotic approach can also be applied to synthesize MP containing NPs which in turn can lead to generate a wide variety of new biocompatible materials.

pH dependent chemical stability and release of methotrexate from a novel nanoceramic carrier

The study reveals maximum chemical stability of methotrexate in LDH–MTX at pH 7.00 and controlled release profile of PLGA–LDH–MTX.

Optimization of the process parameters for the fabrication of a polymer coated layered double hydroxide-methotrexate nanohybrid for the possible treatment of osteosarcoma

The study demonstrates the method of optimization for the development of PLGA encapsulated LDH-MTX, MTX and their in vitro and in vivo evaluation.

Externally controlled triggered-release of drug from PLGA micro and nanoparticles

Biofilm infections are extremely hard to eradicate and controlled, triggered and controlled drug release properties may prolong drug release time. In this study, the ability to externally control drug release from micro and nanoparticles was investigated. We prepared micro/nanoparticles containing ciprofloxacin (CIP) and magnetic nanoparticles encapsulated in poly (lactic-co-glycolic acid) PLGA. Both micro/nanoparticles were observed to have narrow size distributions. We investigated and compared their passive and externally triggered drug release properties based on their different encapsulation structures for the nano and micro systems. In passive release studies, CIP demonstrated a fast rate of release in first 2 days which then slowed and sustained release for approximately 4 weeks. Significantly, magnetic nanoparticles containing systems all showed ability to have triggered drug release when exposed to an external oscillating magnetic field (OMF). An experiment where the OMF was turned on and off also confirmed the ability to control the drug release in a pulsatile manner. The magnetically triggered release resulted in a 2-fold drug release increase compared with normal passive release. To confirm drug integrity following release, the antibacterial activity of released drug was evaluated in Pseudomonas aeruginosa biofilms in vitro. CIP maintained its antimicrobial activity after encapsulation and triggered release.

Preparation and evaluation of tilmicosin-loaded hydrogenated castor oil nanoparticle suspensions of different particle sizes

Three tilmicosin-loaded hydrogenated castor oil nanoparticle (TMS-HCO-NP) suspensions of different particle sizes were prepared with different polyvinyl alcohol surfactant concentrations using a hot homogenization and ultrasonic technique. The in vitro release, in vitro antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability study were conducted to evaluate the characteristics of the suspensions. The in vitro tilmicosin release rate, antibacterial activity, mammalian cytotoxicity, acute toxicity in mice, and stability of the suspensions were evaluated. When prepared with polyvinyl alcohol concentrations of 0.2%, 1%, and 5%, the mean diameters of the nanoparticles in the three suspensions were 920±35 nm, 452±10 nm, and 151±4 nm, respectively. The three suspensions displayed biphasic release profiles similar to that of freeze-dried TMS-HCO-NP powders, with the exception of having a faster initial release. Moreover, suspensions of smaller-sized particles showed faster initial release, and lower minimum inhibitory concentrations and minimum bactericidal concentrations. Time-kill curves showed that within 12 hours, the suspension with the 151 nm particles had the most potent bactericidal activity, but later, the suspensions with larger-sized particles showed increased antibacterial activity. None of the three suspensions were cytotoxic at clinical dosage levels. At higher drug concentrations, all three suspensions showed similar concentration-dependent cytotoxicity. The suspension with the smallest-sized particle showed significantly more acute toxicity in mice, perhaps due to faster drug release. All three suspensions exhibited good stability at 4°C and at room temperature for at least 6 months. These results demonstrate that TMS-HCO-NP suspensions can be a promising formulation for tilmicosin, and that nanoparticle size can be an important consideration for formulation development.

Biosurfactant stabilized anticancer biomolecule-loaded poly (D,L-lactide) nanoparticles

PLA nanoparticles (NPs) were prepared via green route using turmeric (Curcuma longa) extract (TE) as biostabiliser/biosurfactant. Of the 29 formulations, two formulations of TE synthesized PLA NPs were evaluated for encapsulation and controlled release of well known antioxidant and less bioavailable molecules curcumin and quercetin. Size of curcumin loaded PLA NPs synthesized using 0.8 mg/ml PLA (C-En-D) and 0.1 mg/ml PLA (C-En-P) were 203±77 and 110±44 nm, respectively. However, quercetin loaded PLA NPs synthesized at 0.8 mg/ml (Q-En-D) and 0.1mg/ml (Q-En-P) PLA concentrations were 170±95 and 102±31 nm, respectively. The encapsulation efficiency of curcumin loaded PLA (C-En-D and C-En-P) NPs as well as quercetin loaded PLA (Q-En-D and Q-En-P) NPs was found ∼95%. In vitro release study of C-En-D, C-En-P, Q-En-D and Q-En-P NPs showed initial burst release followed by slow and sustained release. C-En-D NPs and Q-En-D NPs showing maximum in vitro release (∼100%) were evaluated for cytotoxicity. Blank PLA NPs, C-En-D and Q-En-D NPs were found to be safe against normal human leukocytes up to 2 mg/ml dose. Both C-En-D and Q-En-D NPs showed anticancer activity against A549 cell line. But Q-En-D NPs showed better anticancer activity than C-En-D NPS on A549 cells. While blank PLA NPs did not possess anticancer activity. TE extract stabilized PLA NPs were non-toxic, biocompatible and safe to normal human leukocytes. Such technology will be better, effective and safer in use for anticancer as well as other biological application.

THE EFFECT OF RESIDUAL POLY(VINYL ALCOHOL) ON BIOPHYSICAL INTERACTION OF NANOPARTICLES WITH ENDOTHELIAL CELL MODEL MEMBRANE

Poly(vinyl alcohol) (PVA) is commonly used as an emulsifier in the formulation of nanoparticles (NPs) comprising poly DL-lactide co-glycolide and polylactide-based biodegradable polymers for drug and gene delivery applications. A fraction of PVA remains associated with the NPs at the interface despite their repeated washing (residual PVA). We hypothesize that this residual PVA influences the interfacial properties of NPs and hence their biophysical interactions with membrane lipids. In this study, we formulated NPs using PVA of different molecular weights to determine the effects of the residual PVA on biophysical interactions of the formulated NPs with the endothelial cell model membrane using a Langmuir balance. Despite similar physical properties (particle size and zeta potential), NPs formulated with different PVA demonstrated significant variations in their intrinsic surface properties and biophysical interactions with the model membrane. This was evident from the difference in the surface pressure–area (π–A) isotherms prepared in the presence of different formulations of NPs and the change in surface pressure of the model membrane following interaction with NPs. The variation in the biophysical properties was observed even with the NPs formulated using the same molecular weight PVA but obtained from different lots. Since the interfacial properties of NPs can significantly influence NP interactions with cells and tissue, their biophysical characterization could prove to be an important parameter not only to obtain consistent results with NPs but also to optimize their properties for drug/gene delivery applications.