Remotely Guided Immunobots Engaged in Anti-Tumorigenic Phenotypes for Targeted Cancer Immunotherapy

Building medical microrobots from the body's own cells may circumvent the biocompatibility concern and hence presents more potential in clinical applications to improve the possibility of escaping from the host defense mechanism. More importantly, live cells can enable therapeutically relevant functions with significantly higher efficiency than synthetic systems. Here, live immune cell-derived microrobots from macrophages, i.e., immunobots, which can be remotely steered with externally applied magnetic fields and directed toward anti-tumorigenic (M1) phenotypes, are presented. Macrophages engulf the engineered magnetic decoy bacteria, composed of 0.5 µm diameter silica Janus particles with one side coated with anisotropic FePt magnetic nanofilm and the other side coated with bacterial lipopolysaccharide (LPS). This study demonstrates the torque-based surface rolling locomotion of the immunobots along assigned trajectories inside blood plasma, over a layer of endothelial cells, and under physiologically relevant flow rates. The immunobots secrete signature M1 cytokines, IL-12 p40, TNF-α, and IL-6, and M1 cell markers, CD80 and iNOS, via toll-like receptor 4 (TLR4)-mediated stimulation with bacterial LPS. The immunobots exhibit anticancer activity against urinary bladder cancer cells. This study further demonstrates such immunobots from freshly isolated primary bone marrow-derived macrophages since patient-derivable macrophages may have a strong clinical potential for future cell therapies in cancer.

Environmental impact assesment regulation applications and their analysis in Turkey

Since the 1970s, the environmental impact assessment (EIA) has been employed as an environmental management tool to minimize or prevent the potential environmental impacts caused. Its use in Turkey was mandated from February 7, 1993. An EIA, which is of particular concern to the mining sector, is implemented in many sectors. In this study, after providing brief information about the EIA regulation, an analysis has been done by determining the status of mining activities in EIA applications. In conclusion, mining has comprised 31% share of EIA-required activities since 1993, when EIA regulation took effect in Turkey. In addition, it was learned that 16% of the applications related to mining activities were unable to get an EIA permit and could not launch their operation.

3D printed personalized magnetic micromachines from patient blood-derived biomaterials

While recent wireless micromachines have shown increasing potential for medical use, their potential safety risks concerning biocompatibility need to be mitigated. They are typically constructed from materials that are not intrinsically compatible with physiological environments. Here, we propose a personalized approach by using patient blood–derivable biomaterials as the main construction fabric of wireless medical micromachines to alleviate safety risks from biocompatibility. We demonstrate 3D printed multiresponsive microswimmers and microrollers made from magnetic nanocomposites of blood plasma, serum albumin protein, and platelet lysate. These micromachines respond to time-variant magnetic fields for torque-driven steerable motion and exhibit multiple cycles of pH-responsive two-way shape memory behavior for controlled cargo delivery and release applications. Their proteinaceous fabrics enable enzymatic degradability with proteinases, thereby lowering risks of long-term toxicity. The personalized micromachine fabrication strategy we conceptualize here can affect various future medical robots and devices made of autologous biomaterials to improve biocompatibility and smart functionality.

Magnetic soft micromachines made of linked microactuator networks

Soft untethered micromachines with overall sizes less than 100 μm enable diverse programmed shape transformations and functions for future biomedical and organ-on-a-chip applications. However, fabrication of such machines has been hampered by the lack of control of microactuator's programmability. To address such challenge, we use two-photon polymerization to selectively link Janus microparticle-based magnetic microactuators by three-dimensional (3D) printing of soft or rigid polymer microstructures or links. Sequentially, we position each microactuator at a desired location by surface rolling and rotation to a desired position and orientation by applying magnetic field-based torques, and then 3D printing soft or rigid links to connect with other temporarily fixed microactuators. The linked 2D microactuator networks exhibit programmed 2D and 3D shape transformations, and untethered limbless and limbed micromachine prototypes exhibit various robotic gaits for surface locomotion. The fabrication strategy presented here can enable soft micromachine designs and applications at the cellular scales.

Mattertronics for programmable manipulation and multiplex storage of pseudo-diamagnetic holes and label-free cells

Manipulating and separating single label-free cells without biomarker conjugation have attracted significant interest in the field of single-cell research, but digital circuitry control and multiplexed individual storage of single label-free cells remain a challenge. Herein, by analogy with the electrical circuitry elements and electronical holes, we develop a pseudo-diamagnetophoresis (PsD) mattertronic approach in the presence of biocompatible ferrofluids for programmable manipulation and local storage of single PsD holes and label-free cells. The PsD holes conduct along linear negative micro-magnetic patterns. Further, eclipse diode patterns similar to the electrical diode can implement directional and selective switching of different PsD holes and label-free cells based on the diode geometry. Different eclipse heights and junction gaps influence the switching efficiency of PsD holes for mattertronic circuitry manipulation and separation. Moreover, single PsD holes are stored at each potential well as in an electrical storage capacitor, preventing multiple occupancies of PsD holes in the array of individual compartments due to magnetic Coulomb-like interaction. This approach may enable the development of large programmable arrays of label-free matters with high throughput, efficiency, and reliability as multiplex cell research platforms.

3D-Printed Multi-Stimuli-Responsive Mobile Micromachines

Magnetically actuated and controlled mobile micromachines have the potential to be a key enabler for various wireless lab-on-a-chip manipulations and minimally invasive targeted therapies. However, their embodied, or physical, task execution capabilities that rely on magnetic programming and control alone can curtail their projected performance and functional diversity. Integration of stimuli-responsive materials with mobile magnetic micromachines can enhance their design toolbox, enabling independently controlled new functional capabilities to be defined. To this end, here, we show three-dimensional (3D) printed size-controllable hydrogel magnetic microscrews and microrollers that respond to changes in magnetic fields, temperature, pH, and divalent cations. We show two-way size-controllable microscrews that can reversibly swell and shrink with temperature, pH, and divalent cations for multiple cycles. We present the spatial adaptation of these microrollers for penetration through narrow channels and their potential for controlled occlusion of small capillaries (30 μm diameter). We further demonstrate one-way size-controllable microscrews that can swell with temperature up to 65% of their initial length. These hydrogel microscrews, once swollen, however, can only be degraded enzymatically for removal. Our results can inspire future applications of 3D- and 4D-printed multifunctional mobile microrobots for precisely targeted obstructive interventions (e.g., embolization) and lab- and organ-on-a-chip manipulations.

High-Yield Production of Biohybrid Microalgae for On-Demand Cargo Delivery

Biohybrid microswimmers exploit the swimming and navigation of a motile microorganism to target and deliver cargo molecules in a wide range of biomedical applications. Medical biohybrid microswimmers suffer from low manufacturing yields, which would significantly limit their potential applications. In the present study, a biohybrid design strategy is reported, where a thin and soft uniform coating layer is noncovalently assembled around a motile microorganism. Chlamydomonas reinhardtii (a single-cell green alga) is used in the design as a biological model microorganism along with polymer-nanoparticle matrix as the synthetic component, reaching a manufacturing efficiency of ≈90%. Natural biopolymer chitosan is used as a binder to efficiently coat the cell wall of the microalgae with nanoparticles. The soft surface coating does not impair the viability and phototactic ability of the microalgae, and allows further engineering to accommodate biomedical cargo molecules. Furthermore, by conjugating the nanoparticles embedded in the thin coating with chemotherapeutic doxorubicin by a photocleavable linker, on-demand delivery of drugs to tumor cells is reported as a proof-of-concept biomedical demonstration. The high-throughput strategy can pave the way for the next-generation generation microrobotic swarms for future medical active cargo delivery tasks.

Elucidating the interaction dynamics between microswimmer body and immune system for medical microrobots

The structural design parameters of a medical microrobot, such as the morphology and surface chemistry, should aim to minimize any physical interactions with the cells of the immune system. However, the same surface-borne design parameters are also critical for the locomotion performance of the microrobots. Understanding the interplay of such parameters targeting high locomotion performance and low immunogenicity at the same time is of paramount importance yet has so far been overlooked. Here, we investigated the interactions of magnetically steerable double-helical microswimmers with mouse macrophage cell lines and splenocytes, freshly harvested from mouse spleens, by systematically changing their helical morphology. We found that the macrophages and splenocytes can recognize and differentially elicit an immune response to helix turn numbers of the microswimmers that otherwise have the same size, bulk physical properties, and surface chemistries. Our findings suggest that the structural optimization of medical microrobots for the locomotion performance and interactions with the immune cells should be considered simultaneously because they are highly entangled and can demand a substantial design compromise from one another. Furthermore, we show that morphology-dependent interactions between macrophages and microswimmers can further present engineering opportunities for biohybrid microrobot designs. We demonstrate immunobots that can combine the steerable mobility of synthetic microswimmers and the immunoregulatory capability of macrophages for potential targeted immunotherapeutic applications.

3D-Printed Biodegradable Microswimmer for Theranostic Cargo Delivery and Release

Untethered mobile microrobots have the potential to leverage minimally invasive theranostic functions precisely and efficiently in hard-to-reach, confined, and delicate inner body sites. However, such a complex task requires an integrated design and engineering, where powering, control, environmental sensing, medical functionality, and biodegradability need to be considered altogether. The present study reports a hydrogel-based, magnetically powered and controlled, enzymatically degradable microswimmer, which is responsive to the pathological markers in its microenvironment for theranostic cargo delivery and release tasks. We design a double-helical architecture enabling volumetric cargo loading and swimming capabilities under rotational magnetic fields and a 3D-printed optimized 3D microswimmer (length = 20 μm and diameter = 6 μm) using two-photon polymerization from a magnetic precursor suspension composed from gelatin methacryloyl and biofunctionalized superparamagnetic iron oxide nanoparticles. At normal physiological concentrations, we show that matrix metalloproteinase-2 (MMP-2) enzyme could entirely degrade the microswimmer in 118 h to solubilized nontoxic products. The microswimmer rapidly responds to the pathological concentrations of MMP-2 by swelling and thereby boosting the release of the embedded cargo molecules. In addition to delivery of the drug type of therapeutic cargo molecules completely to the given microenvironment after full degradation, microswimmers can also release other functional cargos. As an example demonstration, anti-ErbB 2 antibody-tagged magnetic nanoparticles are released from the fully degraded microswimmers for targeted labeling of SKBR3 breast cancer cells in vitro toward a potential future scenario of medical imaging of remaining cancer tissue sites after a microswimmer-based therapeutic delivery operation.

Light-Triggered Drug Release from 3D-Printed Magnetic Chitosan Microswimmers

Advances in design and fabrication of functional micro/nanomaterials have sparked growing interest in creating new mobile microswimmers for various healthcare applications, including local drug and other cargo ( e. g., gene, stem cell, and imaging agent) delivery. Such microswimmer-based cargo delivery is typically passive by diffusion of the cargo material from the swimmer body; however, controlled active release of the cargo material is essential for on-demand, precise, and effective delivery. Here, we propose a magnetically powered, double-helical microswimmer of 6 μm diameter and 20 μm length that can on-demand actively release a chemotherapeutic drug, doxorubicin, using an external light stimulus. We fabricate the microswimmers by two-photon-based 3D printing of a natural polymer derivative of chitosan in the form of a magnetic polymer nanocomposite. Amino groups presented on the microswimmers are modified with doxorubicin by means of a photocleavable linker. Chitosan imparts the microswimmers with biocompatibility and biodegradability for use in a biological setting. Controlled steerability of the microswimmers is shown under a 10 mT rotating magnetic field. With light induction at 365 nm wavelength and 3.4 × 10^-1 W/cm² intensity, 60% of doxorubicin is released from the microswimmers within 5 min. Drug release is ceased by controlled patterns of light induction, so as to adjust the desired release doses in the temporal domain. Under physiologically relevant conditions, substantial degradation of the microswimmers is shown in 204 h to nontoxic degradation products. This study presents the combination of light-triggered drug delivery with magnetically powered microswimmer mobility. This approach could be extended to similar systems where multiple control schemes are needed for on-demand medical tasks with high precision and efficiency.

3D Nanoprinted Plastic Kinoform X-Ray Optics

High-performance focusing of X-rays requires the realization of very challenging 3D geometries with nanoscale features, sub-millimeter-scale apertures, and high aspect ratios. A particularly difficult structure is the profile of an ideal zone plate called a kinoform, which is manufactured in nonideal approximated patterns, nonetheless requires complicated multistep fabrication processes. Here, 3D fabrication of high-performance kinoforms with unprecedented aspect ratios out of low-loss plastics using femtosecond two-photon 3D nanoprinting is presented. A thorough characterization of the 3D-printed kinoforms using direct soft X-ray imaging and ptychography demonstrates superior performance with an efficiency reaching up to 20%. An extended concept is proposed for on-chip integration of various X-ray optics toward high-fidelity control of X-ray wavefronts and ultimate efficiencies even for harder X-rays. Initial results establish new, advanced focusing optics for both synchrotron and laboratory sources for a large variety of X-ray techniques and applications ranging from materials science to medicine.

Mobile microrobots for bioengineering applications

Untethered micron-scale mobile robots can navigate and non-invasively perform specific tasks inside unprecedented and hard-to-reach inner human body sites and inside enclosed organ-on-a-chip microfluidic devices with live cells. They are aimed to operate robustly and safely in complex physiological environments where they will have a transforming impact in bioengineering and healthcare. Research along this line has already demonstrated significant progress, increasing attention, and high promise over the past several years. The first-generation microrobots, which could deliver therapeutics and other cargo to targeted specific body sites, have just been started to be tested inside small animals toward clinical use. Here, we review frontline advances in design, fabrication, and testing of untethered mobile microrobots for bioengineering applications. We convey the most impactful and recent strategies in actuation, mobility, sensing, and other functional capabilities of mobile microrobots, and discuss their potential advantages and drawbacks to operate inside complex, enclosed and physiologically relevant environments. We lastly draw an outlook to provide directions in the veins of more sophisticated designs and applications, considering biodegradability, immunogenicity, mobility, sensing, and possible medical interventions in complex microenvironments.

3D Chemical Patterning of Micromaterials for Encoded Functionality

Programming local chemical properties of microscale soft materials with 3D complex shapes is indispensable for creating sophisticated functionalities, which has not yet been possible with existing methods. Precise spatiotemporal control of two-photon crosslinking is employed as an enabling tool for 3D patterning of microprinted structures for encoding versatile chemical moieties.

A simple technique for small-diameter urethrocutaneous fistula repair: Ligation

OBJECTIVE

To describe a simple and effective technique for repairing a small-diameter urethrocutaneous fistula.

METHODS AND TECHNIQUE

A total of 13 patients with a solitary and small-diameter (≤2 mm) urethrocutaneous fistula underwent repair with a ligation technique.

RESULTS

None of the patients had voiding difficulties. One recurrent urethrocutaneous fistula occurred and it was successfully repaired with the same technique.

CONCLUSION

This is a simple, quick and useful technique, particularly for small-diameter (≤2 mm) urethrocutaneous fistulas.

Removal of Some Heavy Metal Cations from Aqueous Solution by Adsorption onto Natural Kaolin

The adsorption removal of some heavy metal cations such as Cu(II), Zn(II) and Co(II) from aqueous solution onto kaolin has been studied using the batch method with initial metal ion concentrations within the range 15–70 mg/l. The percentage adsorption and equilibrium concentrations were determined by means of atomic absorption flame photometry as a function of adsorbate concentration, pH and temperature.

Ion-exchange studies showed that over the complete concentration range studied the adsorption ratios for metal cations adsorbed onto kaolin correlated with the linear forms of the Langmuir, Freundlich and Dubinin—Kaganer—Radushkevich (DKR) adsorption isotherms. The cationexchange capacity of kaolin towards each metal ion studied was evaluated. It was found that the adsorption phenomena depended on the charge density and diameter of the hydrated ion. The equilibrium studies demonstrated that the selectivity of the ions followed the sequence Zn(II) > Cu(II) > Co(II) at pH 7.0. Calculation of thermodynamic parameters such as the standard enthalpy (ΔH0), Gibbs free energy (ΔG0) and entropy (ΔS0) showed that the adsorption of the heavy metal ions studied onto kaolin was an endothermic process which was favoured at higher temperatures.

These results show that natural kaolin has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.

Multi-domain short peptide molecules for in situ synthesis and biofunctionalization of gold nanoparticles for integrin-targeted cell uptake

We describe design and synthesis model of multidomain (modular) peptides (MDPs), which direct a reaction cascade coupling the synthesis and surface functionalization of gold nanoparticles (AuNPs) in a single step. The synthesis is achieved via simple mixing of the aqueous solutions of auric acid and MDPs at room temperature without the addition of any surfactants or toxic intermediate reagents. This method allows facile control over the nanoparticle size between ∼2-15 nm, which opens a practical window for biomedical applications. In contrast to the conventional citrate-mediated methods, peptide-mediated synthesis and stabilization provide increased colloidal stability to AuNPs. As a proof of this concept, we demonstrate active targeting of human breast adenocarcinoma cell line (MCF7) using the one-step-prepared engineered AuNPs. Overall, we propose a single-step, chemically greener, biologically safer method for the synthesis and surface functionalization of gold nanoparticles in a size-controlled manner. The chemical versatility of the MDP design broadens the applicability of this strategy, thereby emerging as a successful alternative for the currently available nanoparticle preparation technologies.

Biomedical Applications of Untethered Mobile Milli/Microrobots

Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size goes down to the order of a single cell, previously inaccessible body sites would become available for high-resolution in situ and in vivo manipulations. This unprecedented direct access would enable an extensive range of minimally invasive medical operations. Here, we provide a comprehensive review of the current advances in biome dical untethered mobile milli/microrobots. We put a special emphasis on the potential impacts of biomedical microrobots in the near future. Finally, we discuss the existing challenges and emerging concepts associated with designing such a miniaturized robot for operation inside a biological environment for biomedical applications.

Size-controlled conformal nanofabrication of biotemplated three-dimensional TiO₂ and ZnO nanonetworks

A solvent-free fabrication of TiO₂ and ZnO nanonetworks is demonstrated by using supramolecular nanotemplates with high coating conformity, uniformity, and atomic scale size control. Deposition of TiO₂ and ZnO on three-dimensional nanofibrous network template is accomplished. Ultrafine control over nanotube diameter allows robust and systematic evaluation of the electrochemical properties of TiO₂ and ZnO nanonetworks in terms of size-function relationship. We observe hypsochromic shift in UV absorbance maxima correlated with decrease in wall thickness of the nanotubes. Photocatalytic activities of anatase TiO₂ and hexagonal wurtzite ZnO nanonetworks are found to be dependent on both the wall thickness and total surface area per unit of mass. Wall thickness has effect on photoexcitation properties of both TiO₂ and ZnO due to band gap energies and total surface area per unit of mass. The present work is a successful example that concentrates on nanofabrication of intact three-dimensional semiconductor nanonetworks with controlled band gap energies.

Glycosaminoglycan mimetic peptide nanofibers promote mineralization by osteogenic cells

Bone tissue regeneration is accomplished by concerted regulation of protein-based extracellular matrix components, glycosaminoglycans (GAGs) and inductive growth factors. GAGs constitute a significant portion of the extracellular matrix and have a significant impact on regulating cellular behavior, either directly or through encapsulation and presentation of growth factors to the cells. In this study we utilized a supramolecular peptide nanofiber system that can emulate both the nanofibrous architecture of collagenous extracellular matrix and the major chemical composition found on GAGs. GAGs and collagen mimetic peptide nanofibers were designed and synthesized with sulfonate and carboxylate groups on the peptide scaffold. The GAG mimetic peptide nanofibers interact with bone morphogenetic protein-2 (BMP-2), which is a critical growth factor for osteogenic activity. The GAG mimicking ability of the peptide nanofibers and their interaction with BMP-2 promoted osteogenic activity and mineralization by osteoblastic cells. Alkaline phosphatase activity, Alizarin red staining and energy dispersive X-ray analysis spectroscopy indicated the efficacy of the peptide nanofibers in inducing mineralization. The multifunctional and bioactive microenvironment presented here provides osteoblastic cells with osteogenic stimuli similar to those observed in native bone tissue.

Amyloid inspired self-assembled peptide nanofibers

Amyloid peptides are important components in many degenerative diseases as well as in maintaining cellular metabolism. Their unique stable structure provides new insights in developing new materials. Designing bioinspired self-assembling peptides is essential to generate new forms of hierarchical nanostructures. Here we present oppositely charged amyloid inspired peptides (AIPs), which rapidly self-assemble into nanofibers at pH 7 upon mixing in water caused by noncovalent interactions. Mechanical properties of the gels formed by self-assembled AIP nanofibers were analyzed with oscillatory rheology. AIP gels exhibited strong mechanical characteristics superior to gels formed by self-assembly of previously reported synthetic short peptides. Rheological studies of gels composed of oppositely charged mixed AIP molecules (AIP-1 + 2) revealed superior mechanical stability compared to individual peptide networks (AIP-1 and AIP-2) formed by neutralization of net charges through pH change. Adhesion and elasticity properties of AIP mixed nanofibers and charge neutralized AIP-1, AIP-2 nanofibers were analyzed by high resolution force-distance mapping using atomic force microscopy (AFM). Nanomechanical characterization of self-assembled AIP-1 + 2, AIP-1, and AIP-2 nanofibers also confirmed macroscopic rheology results, and mechanical stability of AIP mixed nanofibers was higher compared to individual AIP-1 and AIP-2 nanofibers self-assembled at acidic and basic pH, respectively. Experimental results were supported with molecular dynamics simulations by considering potential noncovalent interactions between the amino acid residues and possible aggregate forms. In addition, HUVEC cells were cultured on AIP mixed nanofibers at pH 7 and biocompatibility and collagen mimetic scaffold properties of the nanofibrous system were observed. Encapsulation of a zwitterionic dye (rhodamine B) within AIP nanofiber network was accomplished at physiological conditions to demonstrate that this network can be utilized for inclusion of soluble factors as a scaffold for cell culture studies.

Selective adhesion and growth of vascular endothelial cells on bioactive peptide nanofiber functionalized stainless steel surface

Metal-based scaffolds such as stents are the most preferred treatment methods for coronary artery disease. However, impaired endothelialization on the luminal surface of the stents is a major limitation occasionally leading to catastrophic consequences in the long term. Coating the stent surface with relevant bioactive molecules is considered to aid in recovery of endothelium around the wound site. However, this strategy remains challenging due to restrictions in availability of proper bioactive signals that will selectively promote growth of endothelium and the lack of convenience for immobilization of such signaling molecules on the metal surface. In this study, we developed self-assembled peptide nanofibers that mimic the native endothelium extracellular matrix and that are securely immobilized on stainless steel surface through mussel-inspired adhesion mechanism. We synthesized Dopa-conjugated peptide amphiphile and REDV-conjugated peptide amphiphile that are self-assembled at physiological pH. We report that Dopa conjugation enabled nanofiber coating on stainless steel surface, which is the most widely used backbone of the current stents. REDV functionalization provided selective growth of endothelial cells on the stainless steel surface. Our results revealed that adhesion, spreading, viability and proliferation rate of vascular endothelial cells are remarkably enhanced on peptide nanofiber coated stainless steel surface compared to uncoated surface. On the other hand, although vascular smooth muscle cells exhibited comparable adhesion and spreading profile on peptide nanofibers, their viability and proliferation significantly decreased. Our design strategy for surface bio-functionalization created a favorable microenvironment to promote endothelial cell growth on stainless steel surface, thereby providing an efficient platform for bioactive stent development for long term treatment of cardiovascular diseases.

Pediatric gastric outlet obstruction following corrosive ingestion

PURPOSE

Corrosive substance ingestion is still a major medical and social problem for children. Gastric injury after corrosive ingestion is relatively uncommon as compared with esophageal injury. Gastric outlet obstruction (GOO) is a significant complication of corrosive ingestion.

METHODS

Medical records of 20 consecutive patients with GOO due to corrosive ingestion during an 8-year period between 2002 and 2009 were retrospectively reviewed.

RESULTS

There were 10 boys and 10 girls with a mean age of 5.1 years (1.5-15 years). Ingested material was acid in all the patients. Two patients had associated esophageal stricture. The mean time between the ingestion and the development of GOO was 27.8 days (range 21-45 days) and all the patients presented with postprandial epigastric distension, nonbilious vomiting and weight loss. Surgical treatment included gastroduodenostomy (n = 8), Billroth I (n = 7), pyloroplasty (n = 5), and gastrojejunostomy (n = 2) procedures for GOO. Anastomotic stricture requiring a second operation developed in two patients. There was no surgical mortality. The mean follow-up is 3.3 years and all patients are free of symptoms.

CONCLUSION

GOO is one of the most common gastric complications of corrosive ingestion that may require surgical treatment. Prevention of corrosive ingestion has great importance to avoid such complications.

Effects of whole-body hypoxic preconditioning on hypoxia/reoxygenation-induced intestinal injury in newborn rats

PURPOSE

The precise cause of necrotizing enterocolitis (NEC) is elusive. Ischemia and reperfusion injury of the intestine has been considered to be a major contributing factor for NEC. Ischemic preconditioning is defined as one or more brief periods of ischemia with intermittent reperfusion that protects tissues against a sustained period of subsequent ischemia. Contribution of preconditioning to hypoxia/reoxygenation-induced intestinal injury in newborn rats has not been evaluated previously.

METHODS

The study was carried out on 1-day-old Wistar albino rat pups. Whole-body hypoxia and reoxygenation (H/R) was achieved by 10 min hypoxia using 95 % N (2) + 5 % CO (2) followed by 10 min reoxygenation with 100 % oxygen. Whole body hypoxic preconditioning (HP) cycles were performed with 3 min hypoxia and 5 min reoxygenation. Thirty-three pups were randomly allocated into 4 groups. Group 1 served as untreated controls. The pups in group 2 were subjected to H/R only. In groups 3 and 4, 1 cycle and 3 cycles of HP were performed prior to H/R, respectively. Animals were killed at the end of the protocols. Intestine specimens were obtained to determine the histological changes, as well as to measure the tissue malondialdehyde (MDA) and nitric oxide (NO) levels, and xanthine oxidase (XO) and myeloperoxidase (MPO) activities.

RESULTS

The microscopic lesions in H/R rat pups were virtually the same as those seen in neonatal NEC, with severe destruction of villi and crypts, in some cases extending to the muscularis. In both HP groups, the lesions were found to be milder. H/R resulted in a marked elevation in MDA and NO levels, and XO and MPO activities compared to the untreated controls. Both 1 cycle and 3 cycles of HP prior to H/R resulted in an obvious decrease in all biochemical parameters. Differences of the biochemical results between both HP groups were not statistically significant.

CONCLUSION

This study revealed that whole-body hypoxic preconditioning is beneficial for hypoxia/reoxygenation-induced intestinal injury in newborn rats.

Conservative management of intrahepatic perforation of the gallbladder secondary to acalculous cholecystitis

Gallbladder (GB) perforation is a rare complication of acute acalculous cholecystitis. This complication mostly manifests as acute free perforation into the peritoneal cavity, subacute pericholecystic abscess, or chronic perforation with cholecystoenteric fistula. Perforation of the GB into the liver is extremely rare, and was reported only in adults, of whom all were treated surgically. The authors present an intrahepatic GB perforation secondary to acute acalculous cholecystitis, and its successful conservative management in a 13-year-old boy.

Paraurethral cyst: is conservative management always appropriate?

Paraurethral cyst, arising from cystic dilatation of a paraurethral gland in a girl, is rarely reported in infancy. Although the lesion has a reported incidence of between 1 in 2000 and 1 in 7000 live female births, only 41 examples have been reported previously in the English literature. The management of this lesion is controversial. Surgical excision has been advocated, but spontaneous rupture has also been reported. The latter has prompted some authors to recommend non-operative treatment. We report a female infant whose paraurethral cyst failed to resolve despite a 6-month observation period. She eventually required surgery. The management of our case and the experience in the literature is discussed.

Laparoscopic management of malfunctioning peritoneal dialysis catheters

BACKGROUND

Continuous ambulatory peritoneal dialysis (CAPD) is an established alternative method to hemodialysis for treating end-stage renal disease patients. However, this method is associated with a significant number of complications, such as catheter malposition, omental wrapping, and infection. The purpose of this study was to determine the efficacy of laparoscopy in the treatment of malfunctioning CAPD catheters.

METHODS

Between November 1994 and June 1999, a total of 16 patients with CAPD underwent laparoscopy for the evaluation and management of CAPD catheter dysfunction. Two trocars (10-mm and 5-mm) were used. Recorded data included patient demographics, catheter implantation method, date of malfunction, cause of dysfunction, procedure performed, complications, and catheter outcome.

RESULTS

The primary etiology of dysfunction was omentum and/or small bowel wrapping with adhesions in eight cases, malpositioning in five cases, and infection in the remaining three cases. Adhesiolysis was performed in the eight cases with adhesions. In the five cases with malpositioning but no adhesions, the catheters were repositioned in the pelvic cavity. Two catheters had to be withdrawn because of infection. In one case with tunnel infection, the catheters were exchanged simultaneously. There was only one perioperative complication, consisting of temporary dialysate leakage. There were no mechanical or infection problems. The overall success rate of catheter function (>30 days after laparoscopy) was 100%, except for two cases in which the catheters had to be removed.

CONCLUSION

Laparoscopy is a highly effective and successful method for the evaluation and management of peritoneal dialysis catheter dysfunction.

Segmental dilatation of the jejunum

A 6 months old girl with segmental dilatation of the jejunum is described. Clinical findings were intermittent colic, severe pain and bilious vomiting, mimicking intussusception. At laparatomy dilated jejunal segment was encountered and resection performed. Histological examination showed normal ganglion cells with normal bowel structures. Postoperative course was uneventful.