Neutrophil‐Based Drug Delivery Systems

White blood cells (WBCs) are a major component of immunity in response to pathogen invasion. Neutrophils are the most abundant WBCs in humans, playing a central role in acute inflammation induced by pathogens. Adhesion to vasculature and tissue infiltration of neutrophils are key processes in acute inflammation. Many inflammatory/autoimmune disorders and cancer therapies have been found to be involved in activation and tissue infiltration of neutrophils. A promising strategy to develop novel targeted drug delivery systems is the targeting and exploitation of activated neutrophils. Herein, a new drug delivery platform based on neutrophils is reviewed. There are two types of drug delivery systems: neutrophils as carriers and neutrophil‐membrane‐derived nanovesicles. It is discussed how nanoparticles hijack neutrophils in vivo to deliver therapeutics across blood vessel barriers and how neutrophil‐membrane‐derived nanovesicles target inflamed vasculature. Finally, the potential applications of neutrophil‐based drug delivery systems in treating inflammation and cancers are presented.     

Fluorescent liposomes as contrast agents for in vivo optical imaging of edemas in mice

This study assesses if specially designed fluorescent liposomes can be used as contrast agent for near-infrared fluorescence (NIRF) optical imaging of cultured macrophages in vitro and for NIRF imaging of inflammatory processes, like edema, in an in vivo mouse model. Fluorescent liposomes are prepared by the film hydration and extrusion method using cholesterol, L-phosphatidylcholine, and the NIR fluorescent dye DY-676-C(18) ester. Photon correlation spectroscopy and flow cytometry reveal that fluorescent liposomes are structurally stable for up to 133 days. Distinct uptake/labeling of cultured murine J774 macrophages is demonstrated by confocal laser scanning microscopy (CLSM), flow cytometry, and macroscopic NIRF imaging system at wavelengths >670 nm. Moreover, CLSM analysis reveals fluorescence signals within intracellular compartments. Ear edema is induced in mice (n = 16) by subcutaneous injection of zymosan A. Whole-body NIRF imaging is performed after intravenous injection (0-24 h) of fluorescent liposomes (55 nmol dye per kg body weight). Distinctly higher fluorescence intensities (1613.6 +/- 61.7 a.u.) are detected at inflamed areas of diseased mice as compared to controls (892.8 +/- 19.4 a.u.). Furthermore, cell isolated from ear lavage reveals the presence of labeled F4/80 positive tissue macrophages. Taken together, the results indicate both that mouse macrophages labeled with fluorescent liposomes can be detected in vitro with fluoro-optical methods and that in vivo optical imaging of inflammatory processes with fluorescent liposomes as contrast agent is feasible. Possibly, early stages of other inflammatory diseases could also be detected by the proposed diagnostic tool in the long term.     

Orally delivered thioketal nanoparticles loaded with TNF-α-siRNA target inflammation and inhibit gene expression in the intestines

Small interfering RNAs (siRNAs) directed against proinflammatory cytokines have the potential to treat numerous diseases associated with intestinal inflammation; however, the side-effects caused by the systemic depletion of cytokines demands that the delivery of cytokine-targeted siRNAs be localized to diseased intestinal tissues. Although various delivery vehicles have been developed to orally deliver therapeutics to intestinal tissue, none of these strategies has demonstrated the ability to protect siRNA from the harsh environment of the gastrointestinal tract and target its delivery to inflamed intestinal tissue. Here, we present a delivery vehicle for siRNA, termed thioketal nanoparticles (TKNs), that can localize orally delivered siRNA to sites of intestinal inflammation, and thus inhibit gene expression in inflamed intestinal tissue. TKNs are formulated from a polymer, poly-(1,4-phenyleneacetone dimethylene thioketal), that degrades selectively in response to reactive oxygen species (ROS). Therefore, when delivered orally, TKNs release siRNA in response to the abnormally high levels of ROS specific to sites of intestinal inflammation. Using a murine model of ulcerative colitis, we demonstrate that orally administered TKNs loaded with siRNA against the proinflammatory cytokine tumour necrosis factor-alpha (TNF-α) diminish TNF-α messenger RNA levels in the colon and protect mice from ulcerative colitis.     

Rapid delivery of drug carriers propelled and navigated by catalytic nanoshuttles

This paper reports the first proof-of-concept of using catalytic nanoshuttles to pick up, transport, and release common drug carriers including biocompatible and biodegradable polymeric particles and liposomes. The rapid transport of a wide size range of drug-loaded particles (100 nm-3.0 μm) with a speed approximately three orders of magnitude faster than that of the particles transported by Brownian motion demonstrates the high propulsion power of the nanoshuttles. The nanoshuttles' navigation ability is illustrated by the transport of the drug carriers through a microchannel from the pick-up to the release microwell. Such ability of nanomotors to rapidly deliver drug-loaded polymeric particles and liposomes to their target destination represents a novel approach towards transporting drug carriers in a target-specific manner. This also potentially addresses the obstacles of current nanoparticle drug delivery, such as off-targeting of particles. While an initial concept of actively transporting therapeutic particles is demonstrated in vitro in this paper, future efforts will focus on practical in vivo motor-based targeted drug delivery in connection to fuel-free nanovehicles.     

Sustained release of a p38 inhibitor from non-inflammatory microspheres inhibits cardiac dysfunction

Cardiac dysfunction following acute myocardial infarction is a major cause of death in the world and there is a compelling need for new therapeutic strategies. In this report we demonstrate that a direct cardiac injection of drug-loaded microparticles, formulated from the polymer poly(cyclohexane-1,4-diylacetone dimethylene ketal) (PCADK), improves cardiac function following myocardial infarction. Drug-delivery vehicles have great potential to improve the treatment of cardiac dysfunction by sustaining high concentrations of therapeutics within the damaged myocardium. PCADK is unique among currently used polymers in drug delivery in that its hydrolysis generates neutral degradation products. We show here that PCADK causes minimal tissue inflammatory response, thus enabling PCADK for the treatment of inflammatory diseases, such as cardiac dysfunction. PCADK holds great promise for treating myocardial infarction and other inflammatory diseases given its neutral, biocompatible degradation products and its ability to deliver a wide range of therapeutics.     

Modification of the soft tissue response to implanted materials through the use of an anti-inflammatory drug

The soft tissue response of adult rats to a drug-loaded copolymer hydrogel was studied histologically by using monoclonal antibodies specific for certain inflammatory cell types. A hydrogel was loaded with Diclofenac sodium, a non-steroidal anti-inflammatory drug, and designed to release the drug at a constant rate after implantation into muscle tissue. The sites of antibody binding were analysed automatically, by using an image analysis system, providing information on the number of inflammatory cells and their distribution relative to the hydrogel implant. The ability to measure these and other parameters is considered to be of major importance in the assessment of biocompatibility. The experiments demonstrate that Diclofenac sodium (25–30 µg ml^–1) reduced the number of macrophages and neutrophils found at the implant site compared with a PBS control. Diclofenac sodium did not have any effect on the T cell response.     

Liposomal Encapsulation of a Near‐Infrared Fluorophore Enhances Fluorescence Quenching and Reliable Whole Body Optical Imaging Upon Activation In Vivo

In the past decade, there has been significant progress in the development of water soluble near‐infrared fluorochromes for use in a wide range of imaging applications. Fluorochromes with high photo and thermal stability, sensitivity, adequate pharmacological properties and absorption/emission maxima within the near infrared window (650–900 nm) are highly desired for in vivo imaging, since biological tissues show very low absorption and auto‐fluorescence at this spectrum window. Taking these properties into consideration, a myriad of promising near infrared fluorescent probes has been developed recently. However, a hallmark of most of these probes is a rapid clearance in vivo, which hampers their application. It is hypothesized that encapsulation of the near infrared fluorescent dye DY‐676‐COOH, which undergoes fluorescence quenching at high concentrations, in the aqueous interior of liposomes will result in protection and fluorescence quenching, which upon degradation by phagocytes in vivo will lead to fluorescence activation and enable imaging of inflammation. Liposomes prepared with high concentrations of DY‐676‐COOH reveal strong fluorescence quenching. It is demonstrated that the non‐targeted PEGylated fluorescence‐activatable liposomes are taken up predominantly by phagocytosis and degraded in lysosomes. Furthermore, in zymosan‐induced edema models in mice, the liposomes are taken up by monocytes and macrophages which migrate to the sites of inflammation. Opposed to free DY‐676‐COOH, prolonged stability and retention of liposomal‐DY‐676‐COOH is reflected in a significant increase in fluorescence intensity of edema. Thus, protected delivery and fluorescence quenching make the DY‐676‐COOH‐loaded liposomes a highly promising contrast agent for in vivo optical imaging of inflammatory diseases.     

Photoacoustic tomography of joints aided by an Etanercept-conjugated gold nanoparticle contrast agent-an ex vivo preliminary rat study

Monitoring of anti-rheumatic drug delivery in experimental models and in human diseases would undoubtedly be very helpful for both basic research and clinical management of inflammatory diseases. In this study, we have investigated the potential of an emerging hybrid imaging technology-photoacoustic tomography-in noninvasive monitoring of anti-TNF drug delivery. After the contrast agent composed of gold nanorods conjugated with Etanercept molecules was produced, ELISA experiments were performed to prove the conjugation and to show that the conjugated anti-TNF-α drug was biologically active. PAT of ex vivo rat tail joints with the joint connective tissue enhanced by intra-articularly injected contrast agent was conducted to examine the performance of PAT in visualizing the distribution of the gold-nanorod-conjugated drug in articular tissues. By using the described system, gold nanorods with a concentration down to 1?pM in phantoms or 10?pM in biological tissues can be imaged with good signal-to-noise ratio and high spatial resolution. This study demonstrates the feasibility of conjugating TNF antagonist pharmaceutical preparations with gold nanorods, preservation of the mechanism of action of TNF antagonist along with preliminary evaluation of novel PAT technology in imaging optical contrast agents conjugated with anti-rheumatic drugs. Further in vivo studies on animals are warranted to test the specific binding between such conjugates and targeted antigen in joint tissues affected by inflammation.     

Disease‐Triggered Drug Release Effectively Prevents Acute Inflammatory Flare‐Ups,Achieving Reduced Dosing

For conditions with inflammatory flare‐ups, fast drug‐release from a depot is crucial to reduce cell infiltration and prevent long‐term tissue destruction. While this concept has been explored for chronic diseases, preventing acute inflammatory flares has not been explored. To address this issue, a preventative inflammation‐sensitive system is developed and applied to acute gout, a condition where millions of inflammatory cells are recruited rapidly, causing excruciating and debilitating pain. Rapid drug release is first demonstrated from a pH‐responsive acetalated dextran particle loaded with dexamethasone (AcDex‐DXM), reducing proinflammatory cytokines in vitro as efficiently as free drug. Then, using the air pouch model of gout, mice are pretreated 24 h before inducing inflammation. AcDex‐DXM reduces overall cell infiltration with decreased neutrophils, increases monocytes, and diminishes cytokines and chemokines. In a more extended prophylaxis model, murine joints are pretreated eight days before initiating inflammation. After quantifying cell infiltration, only AcDex‐DXM reduces the overall joint inflammation, where neither free drug nor a conventional drug‐depot achieves adequate anti‐inflammatory effects. Here, the superior efficacy of disease‐triggered drug‐delivery to prevent acute inflammation is demonstrated over free drug and slow‐release depots. This approach and results promise exciting treatment opportunities for multiple inflammatory conditions suffering from acute flares.     

Engineering nanoparticles for targeting rheumatoid arthritis: Past,present, and future trends

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by synovial joint inflammation and cartilage and bone tissue destruction. Although there exist some treatment strategies for RA, they are not completely safe and effective. Therefore, it is important to develop and test new drugs for RA that specifically target inflamed/swollen joints and simultaneously attenuate other possible damages to healthy tissues. Nanotechnology can be a good alternative to consider when envisioning precise medication for treating RA. Through the use of nanoparticles, it is possible to increase bioavailability and bioactivity of therapeutics and enable selective targeting to damaged joints. Herein, recent studies using nanoparticles for the treatment of RA, namely with liposomes, polymeric nanoparticles, dendrimers, and metallic nanoparticles, have been reviewed. These therapeutic strategies have shown great promise in improving the treatment over that by traditional drugs. The results of these studies confirm that feasibility of the use of nanoparticles is mainly due to their biocompatibility, low toxicity, controlled release, and selective drug delivery to inflamed tissues in animal RA models. Therefore, it is possible to claim that nanotechnology will, in the near future, play a crucial role in advanced treatments and patient-specific therapies for human diseases such as RA.

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Bubble-Based Microrobots with Rapid Circular Motions for Epithelial Pinning and Drug Delivery

Remotely powered microrobots are proposed as next-generation vehicles for drug delivery. However, most microrobots swim with linear trajectories and lack the capacity to robustly adhere to soft tissues. This limits their ability to navigate complex biological environments and sustainably release drugs at target sites. In this work, bubble-based microrobots with complex geometries are shown to efficiently swim with non-linear trajectories in a mouse bladder, robustly pin to the epithelium, and slowly release therapeutic drugs. The asymmetric fins on the exterior bodies of the microrobots induce a rapid rotational component to their swimming motions of up to ≈150 body lengths per second. Due to their fast speeds and sharp fins, the microrobots can mechanically pin themselves to the bladder epithelium and endure shear stresses commensurate with urination. Dexamethasone, a small molecule drug used for inflammatory diseases, is encapsulated within the polymeric bodies of the microrobots. The sustained release of the drug is shown to temper inflammation in a manner that surpasses the performance of free drug controls. This system provides a potential strategy to use microrobots to efficiently navigate large volumes, pin at soft tissue boundaries, and release drugs over several days for a range of diseases.     

Stimuli responsive co-delivery of celecoxib and BMP2 from micro-scaffold for periodontal disease treatment

Controlling inflammation meanwhile facilitating tissue regeneration has been considered as a promis-ing strategy to treat inflammatory bone defect.Herein,we describe the synthesis of a bio-sensitive poly(lactic-co-glycolic acid)/mesoporous silica nanocarriers core-shell porous microsphere(PLGA/MSNs-PMS)encapsulated poly(L-lactic acid)(PLLA)spongy nanofibrous micro-scaffold as a new generation of therapeutic platform for effective reconstruction of bone defects caused by periodontal diseases.The PLGA/MSNs-PMS were designed as stimuli-responsive carriers for on-demand co-delivery of mul-tiple biomolecules to provide proper physiological environment,while the multi-level(from macro-,micro-to nanometers)nanofibrous and porous structures in PLLA micro-scaffold were in charge of the reconstruction of ECM,which synergistically contribute to the enhancement of new tissue formation under inflammatory condition.After local injection into periodontal tissue,this construct could sequen-tially release bone growth factor(BMP-2)as well as anti-inflammatory drug(celecoxib)loaded MSNs in response to the over-expressed matrix metalloproteinases(MMP)in periodontal region.During alveolar bone regeneration induced by BMP-2 and ECM like structure,the MSNs would further deliver celecoxib in target cells to achieve inflammation inhibition,resulting in effective treatment of periodontal disease.     

Self-Assemble Silk Fibroin Microcapsules for Cartilage Regeneration through Gene Delivery and Immune Regulation

Effective treatments for cartilage defects are currently lacking. Gene delivery using proper delivery systems has shown great potential in cartilage regeneration. However, the inflammatory microenvironment generated by the defected cartilage severely affects the system's delivery efficiency. Therefore, this study reports a silk fibroin microcapsule (SFM) structure based on layer-by-layer self-assembly, in which interleukin-4 (IL-4) is modified on silk by click chemistry and loaded with lysyl oxidase plasmid DNA (LOX pDNA). The silk microcapsules display good biocompatibility and the release rate of genes can be adjusted by controlling the number of self-assembled layers. Moreover, the functionalized SFMs mixed with methacrylated gelatin (GelMA) exhibit good injectability. The IL-4 on the outer layer of the SFM can regulate macrophages to polarize toward the M2 type, thereby promoting cartilage matrix repair and inhibiting inflammation. The LOX pDNA loaded inside can be effectively delivered into cells to promote extracellular matrix generation, significantly promoting cartilage regeneration. The results of this study provide a promising biomaterial for cartilage repair, and this novel silk-based microcapsule delivery system can also provide strategies for the treatment of other diseases.     

Local Immunomodulation Using an Adhesive Hydrogel Loaded with miRNA‐Laden Nanoparticles Promotes Wound Healing

Chronic wounds are characterized by impaired healing and uncontrolled inflammation, which compromise the protective role of the immune system and may lead to bacterial infection. Upregulation of miR‐223 microRNAs (miRNAs) shows driving of the polarization of macrophages toward the anti‐inflammatory (M2) phenotype, which could aid in the acceleration of wound healing. However, local‐targeted delivery of microRNAs is still challenging, due to their low stability. Here, adhesive hydrogels containing miR‐223 5p mimic (miR‐223*) loaded hyaluronic acid nanoparticles are developed to control tissue macrophages polarization during wound healing processes. In vitro upregulation of miR‐223* in J774A.1 macrophages demonstrates increased expression of the anti‐inflammatory gene Arg‐1 and a decrease in proinflammatory markers, including TNF‐α, IL‐1β, and IL‐6. The therapeutic potential of miR‐223* loaded adhesive hydrogels is also evaluated in vivo. The adhesive hydrogels could adhere to and cover the wounds during the healing process in an acute excisional wound model. Histological evaluation and quantitative polymerase chain reaction (qPCR) analysis show that local delivery of miR‐223* efficiently promotes the formation of uniform vascularized skin at the wound site, which is mainly due to the polarization of macrophages to the M2 phenotype. Overall, this study demonstrates the potential of nanoparticle‐laden hydrogels conveying miRNA‐223* to accelerate wound healing.     

Adhesive interactions between cells and biotinylated phospholipid vesicles in alginate: towards new responsive biomaterials

Creating tissue-mimetic biomaterials able to deliver bioactive compounds after receipt of a remote and non-invasive trigger has so far proved to be challenging. The possible applications of such “smart” biomaterials are vast, ranging from subcutaneous drug delivery to tissue engineering. Self-assembled phospholipid vesicles (liposomes) have the ability to deliver both hydrophilic and hydrophobic drugs, and controlling interactions between functionalized vesicles and cells within biomaterials is an important step for targeted drug delivery to cells. We report an investigation of the interactions between thermally-sensitive and biotin-coated dipalmitoyl phosphatidylcholine vesicles and 3T3 fibroblast cells. The stability of these vesicles under physiological conditions was assessed and their interaction with the cell membranes of fibroblasts in media and alginate/fibronectin mixtures was studied. Stable vesicle-cell aggregates were formed in fluid matrices, and could be a model system for improving the delivery of remotely released drugs within vesicle-containing biomaterials.     

Core/shell nanoparticles for pH-sensitive delivery of doxorubicin

Core/shell nanoparticles with lipid core were prepared and characterized as pH-sensitive delivery system of anticancer drug. The lipid core is composed of drug-loaded lecithin and the polymeric shell is composed of Pluronics (poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) tri-block copolymer, F-127). Based on the preparation method in the previous report by us, the freeze-drying of drug-loaded lecithin was performed in the F-127 aqueous solution containing trehalose used as a cryoprotectant to form stabilized core/shell nanoparticles. For the application of core/shell nanoparticles as a pH-sensitive drug delivery system for anticancer drug, doxorubicin was loaded into the core/shell nanoparticles and the drug loading amount and drug release behavior in response to pH change were observed.     

Chitosan surface-modified hydroxycamptothecin loaded nanoparticles with enhanced transport across Caco-2 cell monolayer

This study explored the feasibility of using surface-modified nanoparticulate drug delivery system to enhance the transepithelial transport of antitumor drugs. An antitumor drug, 10-hydroxycamptothecin, was encapsulated into nanoparticles made of biodegradable poly(caprolactone-co-lactide)-PEG-poly(caprolactone-co-lactide) by a novel two-step nano-precipitation method. The obtained nanoparticles had a drug loading content of 10.4% and a size of 256.3 nm, exhibiting a steady and sustained in vitro release profile. By incubation in chitosan containing medium, the drug-loaded nanoparticles could be subsequently surface-modified with chitosan. The surface modification was monitored by dynamic light scattering method, zeta potential observation, and transmission electron microscopy, and its degree could be easily adjusted by varying the concentration of chitosan in the incubation medium. Caco-2 cell monolayer was used as an in vitro model to evaluate the intestinal 10-hydroxycamptothecin absorption. The absorptive transport of 10-hydroxycamptothecin could be improved to some extent by drug loaded nanoparticles and could be further enhanced in the case of surface-modified nanoparticles, suggesting that chitosan surface-modified nanoparticles may be a promising oral delivery system for antitumor drugs.     

Preparation and evaluation of vitamin C and folic acid-coloaded antioxidant liposomes

Vitamin C (VC) and folic acid (FA) are the important nutrients and antioxidants in human body. To protect them from pro-oxidant elements and reveal their co-operation effects, VC-loaded liposomes (VC-Lip), FA-loaded liposomes (FA-Lip), and their coloaded liposomes (VCFA-Lip) are prepared using the modified ethanol injection method in this study. The properties of the prepared liposomes including morphology, encapsulation efficiency, DPPH radical scavenging activity, hydrogen peroxide scavenging activity, and stability are determined and discussed in detail. The experimental results show that the vesicle size of the prepared liposomes are about 100–150?nm. The encapsulation efficiency of VC- and FA-coloaded liposomes is higher than that of the individual loaded ones. In vitro antioxidant activity study shows that the prepared liposomes have excellent antioxidant activity and the co-operation of VC and FA are better than the individual ones. Furthermore, the stability experiment reveals that the coloaded liposomes have a good stability in the relatively low temperature. These results indicate that VC- and FA-coloaded liposomes could be used as an effective antioxidant and it could be applied as a promising delivery system for the antioxidant defense system to food industry.     

A Smart Responsive Dual Aptamers‐Targeted Bubble‐Generating Nanosystem for Cancer Triplex Therapy and Ultrasound Imaging

The absence of targeted, single treatment methods produces low therapeutic value for treating cancers. To increase the accumulation of drugs in tumors and improve the treatment effectiveness, near‐infrared 808 nm photothermal responsive dual aptamers‐targeted docetaxel (DTX)‐containing nanoparticles is proposed. In this system, DTX and NH₄HCO₃ are loaded in thermosensitive liposomes. The surface of liposomes is coated with gold nanoshells and connected with sulfydryl (SH? ) modified AS1411 and S2.2 aptamers. The nanosystem has good biocompatibility and uniform size (diameter about 200 nm). The drug is rapidly released, reaching a maximum amount (84%) at 4 h under 808 nm laser irradiation. The experiments conducted in vitro and in vivo demonstrate the nanosystem can synergistically inhibit tumor growth by combination of chemotherapy, photothermal therapy, and biological therapy. Dual ligand functionalization significantly increases cellular uptake on breast cancer cell line (MCF‐7) cells and achieves ultrasound imaging (USI) at tumor site. The results indicate that this drug delivery system is a promising theranostic agent involving light‐thermal response at tumor sites, dual ligand targeted triplex therapy, and USI.     

Design and development of SMEDDS for colon-specific drug delivery

Abstract

Context: Lipoidal systems have particularly shown potential for specific accumulation in areas with inflamed tissue increasing the selectivity of local drug delivery.

Objective: Formulation and evaluation of self-microemulsifying drug delivery system (SMEDDS) for colon-specific drug delivery for effective treatment of colonic diseases.

Method: Ternary phase diagram was used to optimize level of oil, surfactant and co-surfactant to optimize SMEDDS and were evaluated for percent transmittance, emulsification time, in vitro release, myeloperoxidase (MPO) activity and intestinal accumulation. The spray dried SMEDDS were filled in capsules which were enteric coated with Eudragit S-100 at 10% weight gain to ensure SMEDDS delivery at colon. The spray dried SMEDDS were also evaluated for IR, DSC, XRD, SEM and stability study.

Result: In ternary phase diagram, Capmul MCM C8 and Capmul PG12 NF with surfactant (Tween 20) and co-surfactant (PG) in ratio 2:1 and 3:1, respectively, showed maximum emulsification area. These liquid SMEDDS show maximum transmittance, globule size of 90–30?nm. The spray-dried SMEDDS with diluents show good flow property. The units of MPO activity show lower level as compared to pure drug and control group, histopathology results supports better healing with SMEDDS. This was attributed to accumulation of SMEDDS in inflammatory area as compared to drug which was further proved by accumulation study. Enteric-coated capsule containing SMEDDS are able to deliver drug, specifically at the colonic region.

Conclusion: Higher accumulation of lipoidal drug in inflammatory area and specific release of liposomes by enteric-coated capsules provide better option for the treatment of colonic disease.