Corneal endothelium damage with intraocular lenses: contact adhesion between surgical materials and tissue.

Intraocular lenses destroy corneal endothelial cells by contact adhesion between the acrylic lens and endothelial surfaces during cataract surgery. Glass and rubber surgical glove surfaces produce similar cell damage. This phenomenon may be important in many surgical procedures and appears to be preventable if a hydrophilic polymer interface is interposed between contacting tissue and the surfaces of materials used.

HPLC determination of dexamethasone in human plasma and its application to an in vitro release study from endovascular stents.

A simple, accurate and precise HPLC assay was developed and validated for determination of dexamethasone in human plasma. Triamcinolone acetonide was used as internal standard (I.S.) and plasma samples were extracted using liquid-liquid extraction with ethyl acetate. Chromatography was performed on a C-18 column with acetonitrile-triple distilled water (28:72% v/v, pH adjusted to 2.3 with phosphoric acid) at a flow rate of 1.2 mL/min and detection wavelength 254 nm. The assay was linear at a concentration range of 0.25-6 microg/mL with recoveries >77%. Precision and accuracy were within the acceptable limits. The method was used to determine dexamethasone release from different material coated endoluminal vascular stents in in vitro human plasma experiments. The results were useful in identifying a good coating material for the stents.

Intratumor chemoimmunotherapy with mitomycin C and components from mycobacteria in regression of line 10 tumors in guinea pigs.

Intratumor chemotherapy with the use of mitomycin C and/or immunotherapy caused regression of line 10 carcinomas in strain 2 guinea pigs and resulted in development of tumor-specific immunity. The immunotherapeutic preparation consisted of oil-in-water emulsions containing Mycobacterium cell walls or residues of cell walls termed cell wall skeletons. The latter preparations were combined with trehalose dimycolate, which was isolated by microparticulate chromatography from whole cells of mycobacteria. Reducing mitomycin C to a single intratumor injection of 50 microgram produced little necrotizing effect and a mean tumor regression rate of 17%. Intratumor immunotherapy 1 day after treatment with 50 microgram of mitomycin C resulted in regression of 90% of the treated tumors as compared to mean regression rates of 30 to 50% for immunotherapy alone. In addition, chemoimmunotherapy was more effective than either chemotherapy or immunotherapy alone in producing regression of relatively large, as well as smaller, tumors.

Hydrophilic albumin microspheres.

A method has been developed for preparing unique hydrophilic HSA/MS. Important aspects of this synthesis include addition of the cross-linking agent (glutaraldehyde) in the organic phase and use of concentrated polymer solutions as dispersion media. The polymer solutions afford excellent steric stabilization of aqueous albumin microdispersions for microsphere synthesis. Steric stabilization of dispersions by polymer solutions was shown to be a function of polymer concentration and molecular weight. The HSA/MS prepared by this method are hydrophilic and easily dispersed in a variety of aqueous media without surfactants. Chemical modifications are easily accomplished using available reactive aldehyde groups remaining after cross-linking. Although hydrophilicity of the microspheres is advantageous for many drug delivery applications, in some instances (such as the use of MS in adjuvant immunotherapy or vaccine preparations) some hydrophobicity may be desirable. For this purpose, surface modifications to produce controlled hydrophobicity is easily achieved by covalent coupling with appropriate reagents (e.g., fatty amines). Adriamycin was bound to HSA/MS by both physical association (to 18 wt%) and covalent binding (also to 18 wt%). In vitro release of drug was measured for the MS using a dynamic flow method. Two distinct release mechanisms could be achieved depending on the type of drug bonding used: slow by hydrolytic degradation of covalent bonds and fast by release of physically adsorbed drug. This new and versatile synthesis of hydrophilic HSA/MS opens up many new opportunities for producing chemically modified MS containing high concentrations of therapeutic agents. Use for immunodiagnostic and adjuvant compositions is also suggested.(ABSTRACT TRUNCATED AT 250 WORDS)

Peritoneal adhesions: prevention with the use of hydrophilic polymer coatings.

Postoperative adhesions, especially peritoneal adhesions, pose an increasingly serious surgical problem. Modern surgical studies have generally attempted to deal with the problem after extensive surgical tissue damage has already occurred. This report focuses on our preliminary findings from exploratory laparotomies with canine and rat animal models, which suggest (1) that inadvertent and generally unappreciated serosal trauma may occur by contact adhesion as well as abrasion and drying mechanisms and (2) that hydrophilic polymer coatings, such as providone (polyvinylpyrrolidone), may be effective in protecting the peritoneal surface from damage. This opens up an important new approach to dealing with the problem: application of adhesive and lubricating tissue and surgical material coatings prior to surgical manipulations to limit tissue damage and thereby minimize postoperative complications. The implications of this study to many other surgical procedures may also be of considerable consequence.

Improved procedure for surface analysis of explanted intraocular lenses by combined light microscopy and scanning electron microscopy.

An improved surface characterization procedure for evaluating explanted intraocular lens (IOL) biocompatibility was developed. The technique combines aqueous hematoxylin-eosin staining for characterizing adherent cells and tissue with subsequent scanning electron microscopy of the same IOL.

Polycarbonate intraocular lenses.

Bisphenol-A polycarbonate has been investigated as an improved polymer for ocular implants, especially for intraocular lenses (IOLs). Polycarbonate properties afford special opportunities for development of tougher, stronger, one-piece IOLs. Autoclave or gamma sterilizability and a higher refractive index may provide additional IOL advantages over polymethylmethacrylate. Implant studies in rabbits have shown polycarbonate IOLs to be well tolerated in the anterior chamber for 2.5 years. Polycarbonate appears promising for new IOLs and other ocular implant applications.

Preparation of hydrophilic albumin microspheres using polymeric dispersing agents.

A new method for preparing glutaraldehyde cross-linked human serum albumin microspheres has been developed. Important aspects of this method include addition of glutaraldehyde in the organic phase and use of concentrated solutions of hydrophobic polymers (polymethylmethacrylate) or hydrophilic polymers (polyoxyethylene-polyoxypropylene block copolymer) as dispersion media. Uniform, round, solid, 3-150-microns hydrophilic microspheres were readily prepared by this process. The average size of microspheres was a function of dispersion time and energy input. Surface properties were altered by chemical modification using either 2-aminoethanol or aminoacetic acid to quench residual aldehyde groups. Optical and scanning electron microscopy and electronic particle size characterization indicate that the process is versatile in producing solid microspheres in a wide size range. Albumin microspheres of this type are readily dispersed in aqueous media for injection, without the need for surfactants.

Synthesis, properties, and intratumoral evaluation of mitoxantrone-loaded casein microspheres in Lewis lung carcinoma.

Smooth, round, uniform bovine casein microspheres of 1-5 and 10-20 microns size were readily prepared by a steric stabilization technique previously developed in this laboratory for synthesis of albumin microspheres. The avid phagocytic uptake of casein and albumin microspheres was demonstrated with fluorescein-labelled microspheres using a macrophage-like mouse myelomonocytic leukaemia cell line. Post-synthesis loading of 25% mitoxantrone was achieved for casein microspheres containing 20% polyglutamic acid. Preliminary intratumoural chemotherapy experiments with a mouse Lewis lung carcinoma indicated that mitoxantrone and mitoxantrone-loaded casein-polyglutamic acid microspheres exhibited lower toxicity when administered intratumorally.

Effect of Ringer's lactate irrigation on the formation of postoperative abdominal adhesions.

Intraabdominal adhesions continue to pose a potentially serious postoperative clinical problem. Reported here is an experiment designed to study any effect that balanced Ringer's lactate (RL) solution may have on intraabdominal adhesion formation. Surgical trauma was induced in mice by controlled gauze abrasion of one side of the abdominal wall; the opposite side was used as a control. RL irrigation was compared with no irrigation. Adhesions were scored on the basis of incidence (%) and severity (on a 0-10 scale). The abraded right peritoneum exhibited 100% adhesions for both the RL group and the nonirrigated group. However, on the side that was not abraded, the nonirrigated group showed only 30% incidence of adhesions and 1.7 +/- 3.3 severity as compared with 100% adhesions and 7.7 +/- 2.2 severity for the RL group. These results suggest the need for further studies to establish the extent to which irrigation with solutions such as Ringer's lactate or saline may enhance formation of postoperative adhesions.

Evaluation of CMC and HA solutions for adhesiolysis.

Aqueous hyaluronic acid (HA) and carboxymethylcellulose (CMC) solutions were tested as tissue-protective coatings during lysis of surgical adhesions by blunt dissection or electrocautery in a rat cecal abrasion model. Phosphate-buffered saline (PBS) was used as a tissue coating solution in 200 female Sprague-Dawley rats prior to controlled cecal abrasion with a surgical gauze-tipped rotary abrader (four 1.5-cm-diameter areas; 70 g weight/60 revolutions/130 rpm). One-week after this initial cecal abrasion, rats were operated on again and adhesions were scored and lysed. The rats were randomly assigned to receive experimental tissue coating solutions either before (prelysis; n = 160) or after (postlysis; n = 40) adhesiolysis. Animals with prelysis coatings were further divided into blunt dissection or electrocautery adhesiolysis groups and were tested with 2 mL cecal coating of PBS, 0.4% HA, 0.5% CMC, or 1.0% CMC tissue coating solutions (n = 20/group). Rats treated postlysis received 2 mL cecal coating plus 2 mL intraperitoneal instillation of PBS, 1.8, 1.9, or 2.0% CMC. One week after adhesiolysis, rats were operated on again for final adhesion scoring. Prelysis tissue coating with 0.5 or 1.0% CMC solution appeared to inhibit adhesion reformation after blunt dissection, whereas 0.4% HA was not effective in this model. Solutions applied before electrocautery dissection or after blunt dissection were ineffective.

Potentiation of infections by biomaterials: a comparison of three materials.

Biomaterial implants frequently potentiate infections in patients, yet rarely have we considered the interactions between bacteria and biomaterials responsible for this. There is extensive literature concerning suture materials of various types and a few studies comparing porous and solid implants. We have developed a simple, relatively atraumatic model for comparing rates of infection surrounding a biomaterial implant in paired single animal observations. Statistically significant differences between silicone and fluorocarbon implants and between silicone and bioglass implants are demonstrated. The relatively greater rate of infection with silicones is consistent with a previous clinical study. The further use of this model for evaluation of material-surface interfacial effects is proposed.

Management of malignant pleural effusion by suicide gene therapy in advanced stage lung cancer: a case series and literature review.

Gene therapy can be defined as the transfer of genetic material into a cell for therapeutic purposes. Cytosine deaminase (CD) transferred into tumor cells by an adenoviral vector (Ad.CD), can convert the antifungal drug fluorocytosine (5-FC) to the antimetabolite 5-fluorouracil (5-FU), which kills not only the transfected tumor cells but also their neighbors by the so-called 'bystander effect'. After testing a protocol for Ad.CD transfer and lung tumor burden control in a Lewis mouse model, we used this technique in the management of lung cancer patients with malignant pleural effusion (MPE): two cases are presented investigating the possible enhancement of anticancer effect in both non-small-cell lung cancer (NSCLC) and small-cell lung cancer (SCLC) by local activation of the pro-drug 5-FC. Results were discussed in parallel to a literature review on the topic. 5-FC and Ad.CD were administered intratumorally to Lewis mouse lung carcinoma and the effect was monitored by tumor size and electromicroscopy. Two patients with advanced stage lung cancer (1SCLC, 1NSCLC), which developed MPE during first-line treatment were administered 10(12) plaque-forming unit (pfu) Ad.CD by intrapleural instillation, in two doses (day 1 and day 7). Instillation was performed when the pleural fluid was ≤200 ml. In addition, they received 5-FC 500 mg four times daily for 14 days. Lung tumor regression and successful transfer of adenoviral particles were observed in treated animals. Patients presented complete regression of pleural effusion as monitored by computerized tomography scan. Neutrapenia and anemia were the most severe adverse effect presented (grade III/grade IV 100%). The increased toxicity followed by the intrapleural gene therapy indicates the augmentation of anticancer effect of transformed pro-drug 5-FC to active 5-FU. The obtained data indicate that intrapleural gene therapy may be a useful tool, adjunct to chemotherapy, in the management of MPE related to lung cancer.

EphrinA1 inhibits malignant mesothelioma tumor growth via let-7 microRNA-mediated repression of the RAS oncogene.

EphrinA1 binding with receptor EphA2 suppresses malignant mesothelioma (MM) growth. The mechanisms whereby EphrinA1 attenuates the MM cell (MMC) growth are not clear. In this study, we report that the activation of MMCs with EphrinA1 leads to an induction of let-7 microRNA (miRNA) expression, repression of RAS proto-oncogene and the attenuation of MM tumor growth. The expression of miRNAs was determined by reverse transcription-quantitative polymerase chain reaction and in situ hybridization. RAS expression was determined by q-PCR, western blotting and immunofluorescence. MMC proliferation and tumor growth were determined by WST-1 and Matrigel assay, respectively. EphrinA1 activation induced several fold increases in let-7a1, let-7a3, let-7f1 and let-7f2 miRNA expression in MMCs. In contrast, EphrinA1 activation significantly downregulated H-RAS, K-RAS and N-RAS expression and inhibited MMC proliferation and tumor growth. In MMCs transfected with 2'-O-methyl antisense oligonucleotides to let-7 miRNA, EphrinA1 activation failed to inhibit the proliferative response and tumor growth. In mismatch antisense oligonucleotide-treated MMCs, the proliferation and tumor growth were comparable to untreated proliferating cells. Furthermore, the transfection of MMCs with let-7a miRNA precursor inhibited RAS expression and attenuated MMC tumor growth. Our data revealed that EphrinA1 signaling induces let-7 miRNA expression and attenuates MM tumor growth by targeting RAS proto-oncogene in MMCs.

Microstructural matrix-crystal interactions in calcium oxalate monohydrate kidney stones.

The role of the proteinaceous matrix in the formation of calcium oxalate kidney stones is still not well understood. Simple scanning electron microscopy (SEM) has been of somewhat limited value in visualizing the organic and inorganic microstructure due to difficulties in obtaining detailed structural information for cut or fractured surfaces. To help clarify matrix-crystal microstructure, serial sections from 10-20 mm calcium oxalate calculi were partially demineralized with ethylenediamine tetraacetic acid (EDTA) and examined by SEM. Sections etched by EDTA showed a radial crystal structure composed of "microcrystal" subunits. Sections simultaneously EDTA etched and fixed with glutaraldehyde to insolubilize all matrix mucoprotein showed interesting forms of matrix structure: an amorphous sometimes membrane-like material, and a fibrous material that exhibited an apparent affinity for the inorganic crystalline phase. These observations give evidence for a more important etiological and structural role for the matrix than may be suggested by the relatively low matrix concentration in stones (2-6 wt. %).

Prevention of postoperative adhesions by precoating tissues with dilute sodium hyaluronate solutions.

Postoperative adhesions (POA), the collagenous connective tissues which form in response to surgical trauma, can be a severe and life threatening surgical complication. However, no generally applicable methods are currently available to mitigate this often serious problem. We have investigated the use of dilute aqueous solutions of sodium hyaluronate (HA) as protective tissue coatings applied prior to surgical manipulation. In a random/blind rat cecal adhesions study conducted at three separate research centers, 0.4 wt% HA in buffered saline gave a three center average of 24% significant adhesions (n = 74) versus 87% for phosphate buffered saline (PBS) controls (n = 69). Histological data suggest that hyaluronic acid tissue precoating minimizes surgical trauma thereby inhibiting POA formation. Clinical studies have been initiated to evaluate the efficacy of tissue precoating with HA solutions in human surgery.

Hydrogel contact lens-corneal interactions: a new mechanism for deposit formation and corneal injury.

PURPOSE: In this study, we examined the interactions between hydrogel contact lenses and the cornea, and the role of these interactions in the pathogenesis of interfacial debris formation and the complications of contact lens use. METHODS: We used a corneal abrasion device to simulate the motion of contact lenses on the cornea and the ensuing abrasive interactions. We examined lens and corneal surfaces by Atomic Force Microscopy (AFM), Low Voltage Scanning Electron Microscopy (LVSEM), and optical microscopy (with vital staining of corneas) for unused hydrogel contact lenses, lenses tested in the corneal abrasion device, and worn contact lenses. Young's modulus of hydrogel contact lenses was also measured and compared with the modulus of the human cornea, as reported in the literature. RESULTS: We observed patterns of abrasive damage to the rabbit cornea in vitro caused by corneal interaction with hydrogel contact lenses. Comparison of AFM and SEM of unused lens surfaces with the surfaces of lenses tested in the abrasion device showed dramatic alterations of the contact lens surfaces. Damage to the lenses was also evident by AFM for lenses worn by volunteers. The modulus of hydrogel contact lenses was lower than the modulus of the human cornea. CONCLUSIONS: The surface morphology of hydrogel contact lenses is significantly altered during use. The Young's modulus of the cornea is higher than the modulus of hydrogel contact lenses. These observations suggest a new mechanism for contact lens complications; namely, damage to the contact lens by the cornea as an initial event that produces lens particles and deposits at the lens-cornea interface, followed by corneal abrasion and the onset of other complications.

Examination of contact lens surfaces by Atomic Force Microscope (AFM).

PURPOSE: We evaluated the use of Atomic Force Microscopy (AFM) in examining the surfaces of unused and worn hydrogel contact lenses under natural, fully hydrated conditions. METHODS: Using the AFM contact mode, we examined hydrogel lenses (Acuvue, Surevue, NewVues, CSI Clarity, SeeQuence) that were hydrated. RESULTS: Surface morphologies characteristics of each lens type and wear history were readily observed. The surfaces of worn lenses showed evidence of abrasion and altered morphology. These changes varied with type of contact lens and conditions of use and by site on the lens. CONCLUSIONS: AFM is a very powerful tool for high resolution examination of hydrated contact lens surface structure. The method avoids artifacts due to dehydration and coating which can occur even with low voltage Scanning Electron Microscopy. Significant differences in contact lens surface morphology were observed before and after wear. These observations may be of importance in helping develop improved new lens polymers and ocular solutions.