Pharmacokinetics, biodistribution, and in vivo toxicity of 7-nitroindazole loaded in pegylated and non-pegylated nanoemulsions in rats.

Sepsis is a life-threatening condition caused by a dysregulated host response to infection. The development of sepsis is associated with excessive nitric oxide (NO) production, which plays an important role in controlling vascular homeostasis. 7-nitroindazole (7-NI) is a selective inhibitor of neuronal nitric oxide synthase (NOS-1) with potential application for treating NO imbalance conditions. However, 7-NI exhibits a low aqueous solubility and a short plasma half-life. To circumvent these biopharmaceutical limitations, pegylated (NEPEG7NI) and non-pegylated nanoemulsions (NENPEG7NI) containing 7-NI were developed. This study evaluates the pharmacokinetic profiles and toxicological properties of 7-NI loaded into the nanoemulsions. After a single intravenous administration of the free drug and the nanoemulsions at a dose of 10 mg.kg-1 in Wistar rats, 7-NI was widely distributed in the organs. The pharmacokinetic parameters of Cmax, t1/2, and AUC0-t were significantly increased after administration of the NEPEG7NI, compared to both free 7-NI and NENPEG7NI (p < 0.05). No observable adverse effects were observed after administering the free 7-NI, NEPEG7NI, or NENPEG7NI in the animals after a single dose of up to 3.0 mg.kg-1. The results indicated that 7-NI-loaded nanoemulsions are safe, constituting a promising approach to treating sepsis.

The nanotechnological approach for nasal delivery of peptide drugs: a comprehensive review.

This review gathers recent studies, patents, and clinical trials involving the nasal administration of peptide drugs to supply a panorama of developing nanomedicine advances in this field. Peptide drugs have been featured in the pharmaceutical market, due to their high efficacy, biological activity, and low immunogenicity. Pharmaceutical industries need technology to circumvent issues relating to peptide stability and bioavailability. The oral route offers very harsh and unfavourable conditions for peptide administration, while the parenteral route is inconvenient and risky for patients. Nasal administration is an attractive alternative, mainly when associated with nanotechnological approaches. Nanomedicines may improve the nasal administration of peptide drugs by providing protection for the macromolecules from enzymes while also increasing their time of retention and permeability in the nasal mucosa. Nanomedicines for nasal administration containing peptide drugs have been acclaimed for both prevention, and treatment, of infections, including the pandemic COVID-19, cancers, metabolic and neurodegenerative diseases.

Protection of bovine mammary epithelial cells by a nanoemulsion of the medicinal herb Achyrocline satureioides (Lam.) DC and its capacity of permeation through mammary epithelium.

The low levels of toxicity and cytoprotective effect attributed to Achyrocline satureioides (Lam.) DC, a medicinal plant native to South America, are of interest for bovine mastitis therapy. This research paper reports the hypothesis that a nanoemulsion of macela extract (Achyrocline satureioides) exerts protective effects on bovine mammary alveolar cells -T (MAC-T) and increases the permeation of flavonoid compounds through mammary epithelium. Extract-loaded nanoemulsions (2.5 mg/ml) (NE-ML) (n = 4) were prepared using high-pressure homogenization with varying concentrations of flaxseed oil and Tween 80. Permeation and retention of free and nanoencapsulated quercetin, 3-O-methylquercetin and luteolin were performed on mammary glandular epithelium using Franz diffusion cells. The cell viability was evaluated on mammary epithelial cells (MAC-T lineage) using the MTT method (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) after exposure to loaded and blank nanoemulsions (NE-ML and NE-BL). Necrotic or apoptotic cell death was evaluated by flow cytometry after exposure to nanoemulsions (NE-ML and NE-BL). Subsequently, the cell death was assessed by previously treating MAC-T cells with NE-ML for 23 h, followed by exposure to H2O2 (2 mM) for 1 h. Higher permeation of quercetin and 3-O-methylquercetin in NE-ML was found compared to that of free extract with a final permeated amount of 50.7 ± 3.2 and 111.2 ± 0.6 µg/cm2 compared to 35.0 ± 0.6 and 48.9 ± 1.2, respectively. For NE-BL, the IC50 was at least 1.3% (v/v), while for the NE-ML, it was at least 2.6% (v/v). After exposure to NE-ML (5 and 1.2%, v/v), the percentage of apoptotic cells was reduced (±30%). For the H2O2 assay, the percentage of cells in necrosis was reduced by 40% after exposure to NE-ML1% (v/v) + H2O2 2 mM. The protective effects and increased permeation of macela nanoemulsion make this a promising new candidate for bovine mastitis therapy.

Development and in vivo evaluation of lipid-based nanocarriers containing Jatropha isabellei dry extract from the dichloromethane fraction intended for oral treatment of arthritic diseases

In this study, a dichloromethane fraction dry extract from the underground parts of Jatropha isabellei (DFJi) was used to prepare lipid nanocarriers (LNCJi) aimed at providing the oral delivery of terpenic compounds in the treatment of arthritis. The lipid nanocarriers were prepared by the spontaneous emulsification method. The lipid nanocarriers displayed sizes ranging from 180 to 200 nm and zeta potential values of around -18 mV. A high value of entrapment efficiency (> 90%) was obtained for jatrophone, which was used as the chemical marker of DFJi. LNCJi stored at 4°C were demonstrated to be stable through measurements of transmitted light after analytical centrifugation of the samples. In vitro drug release studies conducted in biorelevant dissolution media demonstrated that jatrophone release was faster from LNCJi than from free DFJi. When tested in an acute arthritis model, the LNCJi exhibited antinociceptive properties after oral administration of a 50 mg/kg dose, unlike the free DFJi, although no reduction in articular diameter was observed. These results suggest that an increase in the oral absorption of DFJi constituents may have occurred through the carrying of this fraction in LNCJi, thus improving the antinociceptive activity of this compound

Fluorescence properties of curcumin-loaded nanoparticles for cell tracking.

BACKGROUND: Posttransplant cell tracking, via stem cell labeling, is a crucial strategy for monitoring and maximizing benefits of cell-based therapies. The structures and functionalities of polysaccharides, proteins, and lipids allow their utilization in nanotechnology systems. MATERIALS AND METHODS: In the present study, we analyzed the potential benefit of curcumin-loaded nanoparticles (NPC) using Vero cells (in vitro) and NPC-labeled adipose-derived mesenchymal stem cells (NPC-ADMSCs) (in vivo) in myocardial infarction and sciatic nerve crush preclinical models. Thereafter, transplantation, histological examination, real time imaging, and assessment of tissue regeneration were done. RESULTS: Transplanted NPC-ADMSCs were clearly identified and revealed potential benefit when used in cell tracking. CONCLUSION: This approach may have broad applications in modeling labeled transplanted cells and in developing improved stem cell therapeutic strategies.

7-nitroindazol-loaded nanoemulsions: Preparation, characterization and its improved inhibitory effect on nitric oxide synthase-1.

Nitric oxide (NO) participates in several physiological processes such as maintenance of blood pressure, host defense, neurotransmission, inhibition of platelet aggregation and learning and memory. NO is also involved in several diseases or dysfunctions in the cardiovascular, central nervous and musculoskeletal systems. NO also has been shown to be a major player in sepsis. NOS-1-derived NO has been shown to be a relevant species in physiology but also is an important element in pathology. There exist some NOS-1 inhibitors and among of them, 7-nitroindazole has been used for its in vivo selectivity. However, 7-NI has a very short half-life (∼2 h) and a poor water solubility. In this study, we describe the preparation and characterization of 7-NI-loaded nanoemulsions (NE7-NI). The chemical stability of 7-NI was greatly increased and the drug release rate could be controlled after nanoemulsification. NE7-NI reduced NO production in a long-lasting manner in vascular smooth muscle cells and skeletal muscle, without cytotoxicity. Our results evidenced that nanoemulsification approach increases the effective action time of 7-NI, rendering a suitable dosage form, which may be an interesting tool to study the role of NOS-1 in physiology and disease.

Chitosan microencapsulation of the dispersed phase of an O/W nanoemulsion to hydrochlorothiazide delivery.

In view of biopharmaceutical limitations of hydrochlorothiazide (HCTZ), Trojan-type mucoadhesive systems were proposed, aiming to improve HCTZ pharmacological properties by modulating its release. Nanoemulsions were formed spontaneously by combining medium-chain triglycerides (Lipoid® S75 and Pluronic® F68) and high encapsulation efficiency was obtained. The mucoadhesive properties were provided by chitosan and microencapsulation of nanoemulsions in spray-dryer was successfully achieved by using Aerosil® as wall material. The rapid redispersion of nanoemulsion in simulated fluids led to a fast and complete release of HCTZ in gastric medium. The pharmacodynamics of HCTZ was improved, extending the diuretic activity. Once a simple and low-energy method contributed to obtain stable mucoadhesive nanoemulsions, advantages in terms of production could also be achieved, allowing easy scaling up. This novel mucoadhesive Trojan particulate system of HCTZ showed to be a promising approach to overcome limitations in terms of absorption and consequently improve the therapeutic efficacy.

Potential Application of Nanoemulsions for Skin Delivery of Pomegranate Peel Polyphenols.

Pomegranate peel and seeds have demonstrated to possess antioxidant compounds with potential application to protect the skin against the ultraviolet radiation damage. However, the photoprotection activity is dependent on the amount of these compounds that reach the viable skin layers. In this paper, we describe the in vitro skin permeation and retention of the major pomegranate peel polyphenols using Franz diffusion cells, after entrapping a ethyl acetate fraction (EAF) from Punica granatum peel extract into nanoemulsions (NEs) prepared with pomegranate seed oil (PSO) or medium chain triglyceride oil (MCT). The in vitro skin permeation of gallic acid (GA), ellagic acid (EA), and punicalagin (PC) was evaluated using a HPLC-DAD validated method. After 8 h of skin permeation, all polyphenol compounds were mostly retained in the skin and did not reach the receptor compartment. However, a 2.2-fold enhancement of the retained amount of gallic acid in the stratum corneum was verified after EAF-loaded NEs are applied, when compared with the free EAF. GA and EA were delivered to the viable epidermis and dermis only when nanoemulsions were applied onto the skin. The mean retained amounts of GA and EA in the EP and DE after applying the EAF-loaded PSO-NE were 1.78 and 1.36 µg cm-2 and 1.10 and 0.97 µg cm-2, respectively. Similar values were obtained after applying the EAF-loaded MCT-NE. The skin permeation results were supported by the confocal microscopy images. These results evidenced the promising application of nanoemulsions to deliver the pomegranate polyphenols into the deeper skin layers.

Antinociceptive and anti-inflammatory activities of the Jatropha isabellei dichloromethane fraction and isolation and quantitative determination of jatrophone by UFLC-DAD.

CONTEXT: Jatropha isabellei Müll. Arg. (Euphorbiaceae) has been used in the traditional medicine to treat arthritis. OBJECTIVE: To evaluate the anti-inflammatory and antinociceptive activities of the dichloromethane fraction (DFJi) from underground parts of J. isabellei, and to develop an analytical method to quantify the diterpene jatrophone. MATERIALS AND METHODS: Anti-inflammatory and antinociceptive activities of the DFji were determined by an acute arthritis model through assessment of the paw elevation time (PET) and articular diameter (AD) of Wistar rats treated orally (50, 100 or 200 mg/kg in a single-dose), and intravenously (0.1, 1, 10, 25 or 50 mg/kg in a bolus administration). The isolation of jatrophone from the DFji was carried out and confirmed by spectroscopic techniques. A UFLC-DAD method was developed and validated. RESULTS: When orally administered, the highest dose (200 mg/kg) of DFJi was able to significantly reduce the PET to 24.8 ± 1.4 s (p < 0.01), when compared with the control group (33.7 ± 1.8 s). The administration of the intravenous dose of 10 mg/kg reduced the PET to 14.8 ± 0.3 s (p < 0.001). The oral and intravenous administration of the DFJi at dose of 200 and 10 mg/kg significantly prevented the formation of edema, reducing the AD in 25.3% and 32.5% (p < 0.01), respectively. The UFLC-DAD method allowed the quantification of jatrophone, which was found to be around 90 µg/mg of fraction. DISCUSSION AND CONCLUSION: The DFJi displayed antinociceptive and antiedematogenic activities, representing a promising plant product for the arthritis treatment.

Self-Nanoemulsified Drug Delivery System of Hydrochlorothiazide for Increasing Dissolution Rate and Diuretic Activity.

Hydrochlorothiazide (HCTZ) is a class IV drug according to the Biopharmaceutical Classification System. This study aimed the development of self-nanoemulsifying drug delivery system (SNEDDS) for HCTZ as an approach to overcome the biopharmaceutical limitations. Pre-formulation screening and ternary phase diagrams were carried out to select the oil phase, the surfactant, and the co-surfactant as the amount of each constituent. The optimized formulations, with reduced amount of surfactant, and composed of medium chain triglycerides, Cremophor EL and Transcutol P did not affect the pH or show drug incompatibilities. The SNEDDS were stabilized by the nanoscale globules and high negative zeta potential. All the physicochemical characterization assays were performed in biorelevant media to better predict the in vivo performance. The enhanced dissolution rate of the SNEDDS reflected in the in vivo diuretic activity, presenting a natriuresis, kaliuresis, and chloriuresis at early stages and an increased volume of total urine compared with HCTZ alone. The designed SNEDDS produced an improvement in the pharmacodynamics due to high dissolution and probable inhibition of intestinal efflux protein by Cremophor EL. The use of SNEDDS demonstrated to be an efficient approach to modulate the absorption of HCTZ and drug therapeutics.

Oral Delivery of a High Quercetin Payload Nanosized Emulsion: In Vitro and In Vivo Activity Against B16-F10 Melanoma.

Quercetin is a natural compound that has several biological activities including anticancer activity. However, the use of this drug has been limited mostly because of its poor water solubility and low bioavailability. Therefore, the development of quercetin-loaded nanocarrier systems may be considered a promising advance to exploit its therapeutic properties in clinical setting including cancer treatment. This study evaluates the effect of orally administered nanosized emulsion containing quercetin (QU-NE) on the cytotoxicity activity against B16-F10 cells in vitro, and on subcutaneous melanoma in mice inoculated with B16-F1O cells. In vivo experiments, also evaluate the co-administration of quercetin with cisplatin in order to predict synergic effects and the renal and hepatic toxicity. The nanocarriers were prepared through the hot solvent diffusion associated with the phase inversion temperature methods. In vitro study showed reduction of cell viability in a concentration-depend manner for free quercetin and QU-NE. In vivo study, quercetin either as a free drug or colloidal dispersion was administrated at a dose of 5 mg kg(-1) twice a week for 17 days via oral route. Cisplatin was administrated at dose of 1 mg kg(-1) once a week intraperitoneally. Free quercetin and QU-NE reduced tumor growth, however, the reduction observed for QU-NE (P < 0.001 vs. control) was significantly higher than free quercetin (P < 0.05 vs. control). The association of both drugs did not show synergic effect. Besides, no renal or hepatic toxicities were observed after administration of free quercetin and QU-NE. These results suggest that an improvement in the oral bioavailability of quercetin occurred when this compound was dissolved in the oily phase of a nanosized emulsion, indicating that it might have a potential application in the treatment of melanoma.

Development of low density azithromycin-loaded polycaprolactone microparticles for pulmonary delivery.

CONTEXT: The development of low-density polymeric microparticles may be a useful approach to deliver antibiotics such as azithromycin into the lung. OBJECTIVE: The aim of this study was to develop azithromycin-loaded low density polycaprolactone microparticles by the double emulsion/solvent evaporation method. MATERIALS AND METHODS: Microparticles were prepared and characterized according to their physicochemical properties, drug loading, and drug release profiles. A full 23 factorial design was used to evaluate the effect of some independent variables on the drug loading and aerodynamic diameter of the particles. An in silico pulmonary deposition model was used to predict the lung deposition profiles for the formulations. RESULTS AND DISCUSSION: The resulting particles presented drug loading up to 23.1% (wt%) and mean geometric diameters varying from 4.0 µm to 15.4 µm. Bulk and tapped densities were low, resulting in good or excellent flow properties. SEM images showed spherical particles with a smooth surface. However, hollow inner structures were observed, which may explain the low values of bulk density. The estimated aerodynamic diameters ranged from 2.3 µm to 8.9 µm. The in silico pulmonary deposition profiles indicated, for some formulations, that a significant fraction of the particles would be deposited in the deeper lung regions. CONCLUSIONS: Statistical analysis demonstrated that not only drug loading but also the aerodynamic diameter of the microparticles is greatly affected by the preparation conditions. Overall, the results indicated that the low-density azithromycin-loaded microparticles with a relatively high respirable fraction may be obtained for the local treatment of lung infections.

Development of low density azithromycin-loaded polycaprolactone microparticles for pulmonary delivery.

CONTEXT: The development of low-density polymeric microparticles may be a useful approach to deliver antibiotics such as azithromycin into the lung. OBJECTIVE: The aim of this study was to develop azithromycin-loaded low density polycaprolactone microparticles by the double emulsion/solvent evaporation method. MATERIALS AND METHODS: Microparticles were prepared and characterized according to their physicochemical properties, drug loading, and drug release profiles. A full 2(3) factorial design was used to evaluate the effect of some independent variables on the drug loading and aerodynamic diameter of the particles. An in silico pulmonary deposition model was used to predict the lung deposition profiles for the formulations. RESULTS AND DISCUSSION: The resulting particles presented drug loading up to 23.1% (wt%) and mean geometric diameters varying from 4.0 µm to 15.4 µm. Bulk and tapped densities were low, resulting in good or excellent flow properties. SEM images showed spherical particles with a smooth surface. However, hollow inner structures were observed, which may explain the low values of bulk density. The estimated aerodynamic diameters ranged from 2.3 µm to 8.9 µm. The in silico pulmonary deposition profiles indicated, for some formulations, that a significant fraction of the particles would be deposited in the deeper lung regions. CONCLUSIONS: Statistical analysis demonstrated that not only drug loading but also the aerodynamic diameter of the microparticles is greatly affected by the preparation conditions. Overall, the results indicated that the low-density azithromycin-loaded microparticles with a relatively high respirable fraction may be obtained for the local treatment of lung infections.

Curcumin-Loaded Chitosan-Coated Nanoparticles as a New Approach for the Local Treatment of Oral Cavity Cancer.

Mucoadhesive nanoparticles loaded with curcumin were developed as a new approach to deliver curcumin for the local treatment of oral cancer. PCL nanoparticles coated with chitosan displaying different molar masses were prepared by using the nanoprecipitation technique. The mucoadhesive properties of nanoparticle suspensions were demonstrated by their strong ability to interact with the glycoprotein mucin through electrostatic interactions. Similar permeation profiles of curcumin loaded in uncoated and chitosan-coated nanoparticles across porcine esophageal mucosa were verified. Curcumin concentrations retained in the mucosa suggest the possibility of a local effect of the drug. In vitro studies demonstrated that free curcumin.and curcumin loaded into nanoparticles coated with chitosan caused significant reduction of SCC-9 human oral cancer cell viability in a concentration and time-dependent manner. However, no significant cell death was observed after 24 h of treatment with unloaded nanoparticles coated with chitosan. In addition, curcumin-loaded nanoparticles showed reduced cytotoxicity, when compared with the free drug. Therefore, chitosan-coated PCL nanoparticles may be considered a promising strategy to deliver curcumin directly into the oral cavity for the treatment of oral cancer.

Photoprotection by Punica granatum seed oil nanoemulsion entrapping polyphenol-rich ethyl acetate fraction against UVB-induced DNA damage in human keratinocyte (HaCaT) cell line.

There has been an increase in the use of botanicals as skin photoprotective agents. Pomegranate (Punica granatum L.) is well known for its high concentration of polyphenolic compounds and for its antioxidant and anti-inflammatory properties. The aim of this study was to analyze the photoprotection provided by P. granatum seed oil nanoemulsion entrapping the polyphenol-rich ethyl acetate fraction against UVB-induced DNA damage in the keratinocyte HaCaT cell line. For this purpose, HaCaT cells were pretreated for 1h with nanoemulsions in a serum-free medium and then irradiated with UVB (90-200 mJ/cm(2)) rays. Fluorescence microscopy analysis provided information about the cellular internalization of the nanodroplets. We also determined the in vitro SPF of the nanoemulsions and evaluated their phototoxicity using the 3T3 Neutral Red Uptake Phototoxicity Test. The nanoemulsions were able to protect the cells' DNA against UVB-induced damage in a concentration dependent manner. Nanodroplets were internalized by the cells but a higher proportion was detected along the cell membrane. The SPF obtained (~25) depended on the concentration of the ethyl acetate fraction and pomegranate seed oil in the nanoemulsion. The photoprotective formulations were classified as non-phototoxic. In conclusion, nanoemulsions entrapping the polyphenol-rich ethyl acetate fraction show potential for use as a sunscreen product.

Protection against oxidative damage in human erythrocytes and preliminary photosafety assessment of Punica granatum seed oil nanoemulsions entrapping polyphenol-rich ethyl acetate fraction.

The main purpose of the present study is to evaluate the ability of nanoemulsion entrapping pomegranate peel polyphenol-rich ethyl acetate fraction (EAF) prepared from pomegranate seed oil and medium chain triglyceride to protect human erythrocyte membrane from oxidative damage and to assess preliminary in vitro photosafety. In order to evaluate the phototoxic effect of nanoemulsions, human red blood cells (RBCs) are used as a biological model and the rate of haemolysis and photohaemolysis (5 J cm(-2) UVA) is assessed in vitro. The level of protection against oxidative damage caused by the peroxyl radical generator AAPH in human RBCs as well as its effects on bilayer membrane characteristics such as fluidity, protein profile and RBCs morphology are determined. EAF-loaded nanoemulsions do not promote haemolysis or photohaemolysis. Anisotropy measurements show that nanoemulsions significantly retrain the increase in membrane fluidity caused by AAPH. SDS-PAGE analysis reveals that AAPH induced degradation of membrane proteins, but that nanoemulsions reduce the extension of degradation. Scanning electron microscopy examinations corroborate the interaction between AAPH, nanoemulsions and the RBC membrane bilayer. Our work demonstrates that Punica granatum nanoemulsions are photosafe and protect RBCs against oxidative damage and possible disturbance of the lipid bilayer of biomembranes. Moreover it suggests that these nanoemulsions could be promising new topical products to reduce the effects of sunlight on skin.

Orally Administered Chitosan-Coated Polycaprolactone Nanoparticles Containing Curcumin Attenuate Metastatic Melanoma in the Lungs.

The study was aimed to evaluate the effect of orally administered chitosan-coated nanoparticles containing curcumin on metastatic melanoma. Chitosan-coated nanoparticles containing curcumin were prepared, and their antimetastatic activity was investigated both in vitro and in vivo. Curcumin decreased cell viability and induced apoptosis of B16F10 melanoma cells. We observed that curcumin significantly decreased the expression of metalloproteinases, which are known to be associated with migration and proliferation of cancer cells. Importantly, treatment with chitosan-coated nanoparticles containing curcumin decreased pulmonary tumor formation in a murine model of experimental metastasis. Histological analyses confirmed the macroscopic results in which lungs of mice treated with curcumin-loaded chitosan-coated polycaprolactone nanoparticles had only a few small nodules and most of them were free of melanoma. Our findings indicate that nanoparticles coated with the mucoadhesive polymer chitosan containing curcumin may be a promising approach and/or intervention for the treatment of malignant melanoma.

Nanoparticles Made From Xyloglucan-Block-Polycaprolactone Copolymers: Safety Assessment for Drug Delivery.

Xyloglucan-block-polycaprolactone (XGO-PCL) copolymer nanoparticles have been proposed as nanocarriers for drug delivery. However, the possible harmful effects of exposure to nanoparticles still remain a concern. Therefore, the aim of this study is to evaluate the potential toxicity of XGO-PCL nanoparticles using in vitro and in vivo assays. Cytotoxicity and genotoxicity studies were conducted on MRC-5 human fetal lung fibroblast cells upon exposure to XGO-PCL nanoparticles. No significant reduction in the cell viability and no DNA damage were observed at the different concentrations tested. Erythrocyte toxicity was assessed by the incubation of nanoparticles with human blood. XGO-PCL nanoparticles induced a hemolytic ratio of less than 1%, indicating good blood compatibility. Finally, the subacute toxicity of XGO-PCL nanoparticles (10 mg/kg/day) was evaluated in BALB/c mice when administered orally or intraperitoneally for 14 days. Results of the in vivo toxicity study showed no clinical signs of toxicity, mortality, weight loss, or hematological and biochemical alterations after treatment with nanoparticles. Also, microscopic analysis of the major organs revealed no histopathological abnormalities, corroborating the previous results. Thus, it can be concluded that XGO-PCL nanoparticles induced no effect indicative of toxicity, indicating their potential use as drug delivery systems.