Praful U. Jani

NANOPARTICLE UPTAKE BY THE RAT GASTROINTESTINAL MUCOSA : QUANTITATION AND PARTICLE SIZE DEPENDENCY

Abstract— Polystyrene microspheres in the size range 50 nm to 3 μm were fed by gavage to female Sprague Dawley rats daily for 10 days at a dose of 1.25 mg kg−1. Previous histological evidence of the uptake of these particles and their absorption across the gastrointestinal tract and passage via the mesentery lymph supply and lymph nodes to the liver and spleen was confirmed by analysis of tissues for the presence of polystyrene by gel permeation chromatography. Measurement of radioactivity of tissues following administration of 100 nm and 1 μm I125‐labelled polystyrene latex particles for 8 days was corroborative although less secure because of the potential lability of the labelled particles. The extent of absorption of 50 nm particles under the conditions of these experiments was 34% and of the 100 nm particles 26% (as measured by determination of polystyrene content), of which total, about 7% (50 nm) and 4% (100 nm), was in the liver, spleen, blood and bone marrow. Particles larger than 100 nm did not reach the bone marrow, and those larger than 300 nm were absent from blood. No particles were detected in heart or lung tissue.

The Uptake and Translocation of Latex Nanospheres and Microspheres after Oral Administration to Rats

Abstract— Non‐ionic and carboxylated fluorescent polystyrene microspheres (100, 500 nm, 1 and 3 μm in diameter), were fed by gavage (2·5% w/v; 1·25 mg kg−1) daily for 10 days to female Sprague Dawley rats. Peyers patches, villi, liver, lymph nodes and spleen of animals fed the non‐ionic microspheres from 100 nm to 1 μm showed unequivocal evidence of uptake and translocation of the particles. Heart, kidney and lung showed no evidence of the presence of microspheres. Carboxylated microspheres were taken up to a lesser degree than the non‐ionised particles. Experiments with 125I radiolabeled 100 nm and 1 μm particles showed a higher uptake of the smaller particles, which were concentrated in GI tissue and liver. Particles were not distributed randomly in the tissues, but were concentrated at the serosal side of the Peyers patches and could be seen traversing the mesentery lymph vessels towards the lymph nodes. The results demonstrate a need to re‐examine the possibilities of particulate oral delivery, as well as the potential toxicity of ingested particulates.

Enhanced oral uptake of tomato lectin-conjugated nanoparticles in the rat

AbstractPurpose. To investigate the usefulness of a surface-conjugated, bioadhesive molecule, tomato lectin, to augment intestinal uptake of orally administered inert nanoparticles. Methods. Fluorescent 500 nm polystyrene nanoparticles with tomato lectin covalently surface coupled using a carbodiimide reaction were administered to female Wistar rats by oral gavage daily for 5 days. Results. Analysis of tissue extracted polymer by gel permeation chromatography revealed a 23% systemic uptake of tomato lectin conjugated nanoparticles compared to < 0.5% of TL nanoparticles blocked with N-acetylchitotetraose thus representing an increase of almost 50 fold across the intestine. Intestinal uptake of tomato lectin-conjugated nanoparticles via the villous tissue was 15 times higher than uptake by the gut-associated lymphoid tissue. Conclusions. The application of tomato lectin as a bioadhesive agent in vivo has been demonstrated to enhance subsequent intestinal transcytosis of colloidal particulates to which it is bound.

Titanium dioxide (rutile) particle uptake from the rat GI tract and translocation to systemic organs after oral administration

Titanium dioxide (rutile) particles of nominal size 500 nm were administered as a 0.1 ml dose of a 2.5% w/v suspension (12.5 mg kg−1) to female Sprague Dawley rats, by oral gavage daily for 10 days. Organs and tissues such as Peyers patches, small intestine, colon, mesentery network and nodes, peritoneal tissue, liver, spleen, heart and kidney were removed for histology, scanning electron microscopy, and spectroscopic analysis for titanium using the technique of inductively coupled plasma atomic emission spectroscopy. Histological and chemical analysis proved the presence of titanium dioxide particles in all the major tissues of the gut associated lymphoid tissue (GALT), and demonstrated that 500 nm tianium dioxide particles were translocated to systemic organs such as the liver and the spleen. Titanium dioxide particles were also found in the lung and perioneal tissues, but were not detected in the heart or the kidney. The uptake of inert particulate matter, such as titanium dioxide, used in pharmaceuticals and food poses the question whether insolubility and inertness necessarily guarantess their innocuous nature.

Factors Affecting the Oral Uptake and Translocation of Polystyrene Nanoparticles: Histological and Analytical Evidence

Quantitative and qualitative evidence from our laboratories on the absorption and translocation of polystyrene latex nanoparticles both by histological (qualitative) and analytical measurement of levels of polystyrene (quantitative) is briefly reviewed in this paper. We have previously compared the uptake of nonionized polystyrene latex ranging in size from 50nm to 3 microns, and made some comparisons of uptake between carboxylated microspheres and nonionic systems, showing the lower uptake of the former through the lymphoid tissue of the gastrointestinal tract. Size is a key parameter, uptake increasing with decreasing particle diameter. Early evidence suggested that uptake is by way of the Peyers patches and other elements of the gut associated lymphoid tissue (GALT). Adsorption of hydrophilic block-copolymers onto polystyrene markedly reduces the uptake by intestinal GALT. Modification of the surface with specific ligands such as by covalent attachment of tomato lectin molecules has indicated widespread uptake by non-GALT tissues, following their binding to and internalisation by enterocytes. The ability to decrease and increase uptake is clear evidence of a phenomenon which has the potential for further control to allow it to be exploited fully for drug or vaccine delivery. The evidence to date with nanoparticles as carriers systems for labile drugs such as proteins by the oral route remains to be substantiated.

Nanosphere and microsphere uptake via Peyer's patches: observation of the rate of uptake in the rat after a single oral dose

Abstract Polystyrene latex particles of diameter 50 nm, 500 nm and 1 μm were fed by oral gavage as a single dose to female Sprague-Dawley rats. At intervals following administration, histological examination of tissues allowed the uptake and movement of the particles to be monitored, at least semiquantitatively. Uptake is relatively rapid. At 6 h, 50 nm particles were seen in considerable numbers in Peyers patches. The rate of uptake is particle-size dependent, smaller particles gaining access to all tissues more rapidly. At 6 h, 50 nm particles can also be detected in the mesentery, while 1 μm particles cannot be observed until about 12 h after administration. Peak concentrations of 500 nm and 1 μm particles occur in the Peyers patches at 18 h and in the lymph nodes at 12 and 24 h, respectively. Particles of 500 nm and 1 μm appear in the liver after 18 h, 50 nm particles reaching this organ in small quantities in 12 h.

Comparative, quantitative study of lymphoid and non-lymphoid uptake of 60 nm polystyrene particles.

Uptake by gut epithelial tissue of 60 nm polystyrene particles was studied in female Sprague-Dawley rats (180 g, 9 weeks old) after 5 days oral dosing by gavage (14 mg/kg). The gut was divided into lymphoid and non-lymphoid tissue of the small and large intestine, prior to analysis for polystyrene by gel permeation chromatography (GPC). Approximately 10% of the administered dose was recovered from the entire gastrointestinal tract. The total percentage of the administered dose taken up through lymphoid tissue was statistically much greater than through non-lymphoid tissue. It was estimated that 60% of the uptake in the small intestine occurred through the Peyers patches, even though the patches comprised a small percentage of the total surface area of the small intestinal tissue. A significant amount of the total uptake was shown to occur in the large intestine, particularly in the lymphoid sections of this tissue. These results were confirmed by fluorescence microscopy.

Further histological evidence of the gastrointestinal absorption of polystyrene nanospheres in the rat

Further histological evidence of the oral absorption of fluorescent polystyrene nanospheres is presented. Fluorescent polystyrene microspheres of diameter ranging from 50 nm to 3 μm were administered daily for 10 days by oral gavage (2.5% w/v; 12.5 mg kg−1) to female Sprague Dawley rats. All except the 3 μm non-ionic fluorescent polystyrene nanospheres and microspheres were concentrated in the serosal layer of Peyers patches and could be seen thereafter traversing the mesentery lymph vessels. The migrating particles were subsequently found in the lymph nodes and liver tissues. No particles were found in the lung or heart. We have previously shown that uptake and translocation is size dependent, increasing with decreasing size. Special emphasis is placed on the fate of the smallest particles investigated — 50 nm non-ionic polystyrene microspheres — which were seen in kidney and were also present in the villi and GI crypts.

Novel oral drug formulations : their potential in modulating adverse effects

SummaryThe rationale for specialised oral formulations of drugs include prolongation of effect for increased patient convenience and reduction of adverse effects through lowered peak plasma concentrations. Local and systemic adverse effects due to high concentrations of drug can be minimised by the use of controlled release delivery systems. Local effects in the gastrointestinal (GI) tract from the release of irritant drug molecules can also be reduced, but the gastric damage caused by nonsteroidal anti-inflammatory drugs (NSAIDs) is only partially relieved by formulation approaches because of the involvement of systemic factors in the aetiology of GI adverse events. The advantages for each drug class must be examined. Newer dosage forms include: (i) osmotic pumps and zero order kinetics systems to control the release rate of the drug; (ii) bioadhesive systems and gastric retention devices to control GI transit; (iii) bioerodible hydrogels; (iv) molecular carrier systems (e.g. cyclodextrin-encapsulated drugs) to modulate local toxicity in the GI tract; (v) externally activated systems; and (vi) colloidal systems such as liposomes and microspheres.There is evidence for improved tolerability for a variety of drugs administered in novel delivery systems. However, the evidence for improved tolerability is complicated by the potential bias in adverse reaction reporting systems, and a lack of studies directly comparing conventional and modified release preparations. The technology now available to produce delivery systems which not only release drugs in a controlled and predetermined fashion, but which can also target to regions of the GI tract such as the colon, should allow greater control of therapy and potentially might minimise patient variables. However, the problem of variable GI transit times still eludes solution. Systems which rely on time to release drug might be more vulnerable to patient-to-patient variability than those which respond to local environments. The effect of food intake is more apparent on single-unit, nondisintegrating dosage forms, although of course none so far are immune from influence. The risk of new adverse effects resulting from such positional therapy with novel delivery devices must be considered.Understanding the mechanisms of induction of individual adverse effects can lead to advances in modes of delivery to decrease the potential for adverse reactions and events while maintaining therapeutic efficacy. Increased compliance can lead to increased therapeutic control and hence safety. Each system has to be considered on its merits. No generalisations can be made, although invariably the modulation of high peak plasma concentrations diminishes adverse effects due to rapid absorption.

Oral Uptake and Translocation of Nanoparticles: A Real but Useful Phenomenon?

Peptide and proteins represent an increasingly important group of drugs which frequently require specialized modes of delivery. A great challenge is now presented to deliver these substances by the oral route. While the wall of the mammalian gastrointestinal tract has been commonly assumed to be a largely impenetrable barrier to the passage of particulate matter, work carried out in several laboratories (Florence and Jani 1993., Jani et al., 1989, 1992a, Le Fevre et al. 1978a, b, 1980, 1989., Eldridge et al., 1990) has shown that the uptake of microspheres through specialised regions of the GI tract (eg Peyer’s patches) is possible. Experimental evidence in animal models has confirmed that sub-micron particulates can be taken up into the intestinal Peyer’s patches following oral administration, and transported, if below a critical size, via the lymphatics to organs such as the liver and spleen. This phenomenon could be exploited such that these particles could serve as drug carriers to deliver therapeutic peptides and proteins to the systemic circulation, following the oral uptake of the intact drug-carrier complex. But, in spite of the evidence there is controversy over the nature and extent of the phenomenon. With peptide and protein antigens it is clearer that the oral route holds promise for oral immunisation as immune responses are not subject to conventional dose response relationships. Since the Peyer’s patches are the sites of induction of the secretory immune response (Bjerke et al. 1993., McStecky and McGhee 1989), antigens have been encapsulated in microparticles and delivered orally to induce enhanced secretory immunity in attempts to develop effective oral vaccines. Additional targeting of the antigen loaded particles to mesentery lymph nodes following translocation from Peyer’s patches, should boost the induction of systemic immunity.