Evaluating the Efficacy of Polyglycolic Acid-Loading Tetrandrine Nanoparticles in the Treatment of Dry Eye.

INTRODUCTION: Dry eye disease (DED) is a multifactor-induced disease accompanied by increased osmolarity of the tear film and inflammation of the ocular surface. Traditional anti-inflammation agent corticosteroids applied in DED treatment could result in high intraocular pressure, especially in long-term treatment. Therefore, we explored a nano drug that aimed to block the formation pathway of DED which had anti-inflammatory, sustained release, and good biocompatibility characteristics in this study. METHODS: We prepared a novel nanomedicine (Tet-ATS@PLGA) by the thin film dispersion-hydration ultrasonic method and detected its nanostructure, particle size, and zeta potential. Flow cytometry was used to detect the cell survival rate of each group after 24 h of drug treatment on inflammed Statens Seruminstitut Rabbit Corneal (SIRC) cells. Observed and recorded corneal epithelial staining, tear film rupture time, and Schirmer test to detect tear secretion on the ocular surface of rabbits. The corneal epithelial thickness, morphology, and number of bulbar conjunctival goblet cells were recorded by H&E staining. Finally, we detected the expression of VEGF, IL-1ß, PGE2, and TNF-α by cellular immunofluorescence staining and enzyme-linked immunosorbent assay (ELISA). RESULTS: The encapsulation efficiency and drug loading of Tet-ATS@PLGA were 79.85% and 32.47%, respectively. At eye surface temperature, Tet can easily release from Tet-ATS@PLGA while that it was difficult to release at storage temperature and room temperature. After 2 weeks medication, Tet-ATS@PLGA can effectively improve the tear film rupture time and tear secretion time in a DED model (p <0.05). Compared with the normal group (62.34 ± 4.86 mm), the thickness of corneal epithelium in ATS (29.47 ± 3.21 mm), Tet-ATS (46.23 ± 2.87 mm), and Tet-ATS@PLGA (55.76 ± 3.95 mm) gradually increased. Furthermore, the flow cytometry indicated that Tet-ATS@PLGA can effectively promote the apoptosis of inflammatory SIRC cells, and the cellular immunofluorescence and ELISA experiments showed that the expression intensity of inflammatory factors such as VEGF, IL-1ß, PGE2, and TNF-α decreased in this process. Interestingly, Tet also had the effect of reducing intraocular pressure. CONCLUSION: Tet-ATS@PLGA can effectively promote the apoptosis of inflammatory corneal epithelial cells, thus inhibiting the expression of inflammatory factors to block the formation of DED and improve the secretion of tear on the ocular surface.

Distribution of PLGA-modified nanoparticles in 3D cell culture models of hypo-vascularized tumor tissue.

BACKGROUND: Advanced stage cancer treatments are often invasive and painful-typically comprised of surgery, chemotherapy, and/or radiation treatment. Low transport efficiency during systemic chemotherapy may require high chemotherapeutic doses to effectively target cancerous tissue, resulting in systemic toxicity. Nanotherapeutic platforms have been proposed as an alternative to more safely and effectively deliver therapeutic agents directly to tumor sites. However, cellular internalization and tumor penetration are often diametrically opposed, with limited access to tumor regions distal from vasculature, due to irregular tissue morphologies. To address these transport challenges, nanoparticles (NPs) are often surface-modified with ligands to enhance transport and longevity after localized or systemic administration. Here, we evaluate stealth polyethylene-glycol (PEG), cell-penetrating (MPG), and CPP-stealth (MPG/PEG) poly(lactic-co-glycolic-acid) (PLGA) NP co-treatment strategies in 3D cell culture representing hypo-vascularized tissue. RESULTS: Smaller, more regularly-shaped avascular tissue was generated using the hanging drop (HD) method, while more irregularly-shaped masses were formed with the liquid overlay (LO) technique. To compare NP distribution differences within the same type of tissue as a function of different cancer types, we selected HeLa, cervical epithelial adenocarcinoma cells; CaSki, cervical epidermoid carcinoma cells; and SiHa, grade II cervical squamous cell carcinoma cells. In HD tumors, enhanced distribution relative to unmodified NPs was measured for MPG and PEG NPs in HeLa, and for all modified NPs in SiHa spheroids. In LO tumors, the greatest distribution was observed for MPG and MPG/PEG NPs in HeLa, and for PEG and MPG/PEG NPs in SiHa spheroids. CONCLUSIONS: Pre-clinical evaluation of PLGA-modified NP distribution into hypo-vascularized tumor tissue may benefit from considering tissue morphology in addition to cancer type.

Accelerated blood clearance of PEGylated PLGA nanoparticles following repeated injections: effects of polymer dose, PEG coating, and encapsulated anticancer drug.

PURPOSE: To investigate accelerated blood clearance (ABC) induction upon repeated injections of PLGA-PEG nanoparticles as a commonly used polymeric drug carrier. METHODS: Etoposide-loaded PLGA-PEG NPs were developed and administered as the test dose to rats pre-injected with various NP treatments at certain time intervals. Pharmacokinetic parameters of etoposide and production of anti-PEG IgM antibody were evaluated. RESULTS: A notable ABC effect was induced by a wide range of polymer doses (0.1 to 20 mg) of empty NPs, accompanied by IgM secretion. However, a further increase in polymer dose resulted not only in the abrogation of the observed ABC induction but also in distinctly a higher value for AUC of the NPs relative to the control. The data from the PEG-negative group verified the fundamental role of PEG for ABC induction. The first injection of etoposide-containing PEGylated nanoparticles (a cell cycle phase-specific drug) produced a strong ABC phenomenon. Three sequential administrations of etoposide-loaded NPs abolished ABC, although a high level of IgM was still detected, which suggests saturation with insignificant poisoning of immune cells. CONCLUSION: The presented results demonstrate the importance of clinical evaluations for PLGA-PEG nanocarriers that consider the administration schedule in multiple drug delivery, particularly in cancer chemotherapy.

Engineered andrographolide nanoparticles mitigate paracetamol hepatotoxicity in mice.

PURPOSE: Paracetamol (acetaminophen, APAP) overdose is often fatal due to progressive and irreversible hepatic necrosis. The aim of this work was to design Andrographolide (AG) loaded nanoparticles to prevent similar hepatic necrosis. METHODS: Functionalized AG-loaded PLGA nanoparticles carrying different densities of heparin were prepared following a facile emulsion solvent evaporation technique. Nanoparticle morphology, loading and release kinetics were studied. Hepatic localization of the nanoparticles was investigated in both normal and APAP damaged conditions using FITC fluorescent probe. Different serum parameters and liver histopathology were further examined as indicators of hepatic condition before and after treatment. RESULT: A collection of heparin functionalized AG-loaded PLGA nanoparticles were designed. Low amount of heparin on the particle surface could rapidly localize the nanoparticles up to the liver. The new functionalized AG nanoparticles affect efficient hepatoprotection in experimental mouse APAP overdose conditions. AG nanoparticle hepatoprotection was due to the rapid regeneration of antioxidant capacity and hepatic GSH store. CONCLUSIONS: Engineered nanoparticles loaded with AG provided a fast protection in APAP induced acute liver failure.

Modification of TiO(2) nanotube surfaces by electro-spray deposition of amoxicillin combined with PLGA for bactericidal effects at surgical implantation sites.

OBJECTIVE: To fabricate the antibiotic-releasing coatings on TiO(2) nanotube surfaces for wide applications of implant and bone plate in medical and dental surgery, the optimal deposition time of amoxicillin/PLGA solution simultaneously performing non-toxicity and a high bactericidal effect for preventing early implant failures was found. MATERIALS AND METHODS: FE-SEM, ESD and FT-IR were used for confirming deposition of amoxicillin/PLGA on the TiO(2) surface. Also, the elution of amoxicillin/PLGA in a TiO(2) nanotube surface was measured by a UV-VIS spectrophotometer. The bactericidal effect of amoxicillin on the TiO(2) nanotube surface was evaluated by using Staphylococcus aureus (S. aureus). The cytotoxicity and cell proliferation were observed by WST assay using MC3T3-E1 osteoblast cells. RESULTS: The results indicated that the TiO(2) nanotube surface controlled by electro-spray deposition time with amoxicillin/PLGA solution could provide a high bactericidal effect against S. aureus by the bactericidal effect of amoxicillin, as well as good osteoblast cell proliferation at the TiO(2) nanotube surface without toxicity. CONCLUSIONS: This study used electro-spray deposition (ESD) methodology to obtain amoxicillin deposition in nanotube structures of TiO(2) and found the optimal deposition time of amoxicillin/PLGA solution simultaneously performing non-toxicity and a high bactericidal effect for preventing early implant failures.

Identification of psoralen loaded PLGA microspheres in rat skin by light microscopy.

Drug delivery systems involving the use of polymers are widely studied and discovery of biocompatible polymers has become the focus of research in this area. Psoralen loaded poly(DL-lactide-co-glycolide) (PLGA) microspheres to be used in PUVA therapy (psoralen and UVA irradiation (ultraviolet A, 320-400 nm) of psoriasis were identified in paraffin sections by histological analysis. The psoralen loaded PLGA microspheres were prepared using the solvent evaporation technique. They were spherical and possessed an external smooth surface as observed by scanning electron microscopy (SEM) analysis. This study describes a modification in the routine preparation of microsphere samples for examination by light microscopy. The changes involved fixative agents and/or stains allowing the identification of microspheres containing a non-fluorescent material. The preservation and identification of microspheres in tissues for histological processing in paraffin was greatly improved by these modifications as proven by our results.

Pharmaceutical analysis of synthetic lipid A-based vaccine adjuvants in poly (D,L-lactic-co-glycolic acid) nanoparticle formulations.

The present study had two main objectives. First, was to compare the immune stimulatory effect of two synthetic lipid A analogues (7-acyl lipid A and pentaerythritol-based lipid A (PET lipid A)) on maturation/stimulation of bone marrow derived dendritic cells (DCs). Our second objective was to develop a liquid chromatography/mass spectrometry (LC-MS) method for the quantitative analysis of lipid A-based vaccine adjuvants. Treatment of immature DCs with 7-acyl lipid A and PET lipid A up regulated the surface expression of CD86 and CD40 molecules, and also induced similar profile of pro-inflammatory cytokine secretion. LC-MS analyses were performed using a Waters Micromass ZQ 4000 spectrometer, coupled to a Waters 2795 separations module with an autosampler. Calibration curves with R(2)>0.999 were constructed over the concentration range of 1.25-20 microg/ml for the solution of 7-acyl lipid A and PET lipid A. The method was tested in a 3 day validation protocol. The accuracy of the assay at different concentrations tested ranged from 89 to 108% and from 92 to 107% for 7-acyl lipid A and PET lipid A, respectively. The limit of quantification for both 7-acyl lipid A and PET lipid A was 1.25 microg/ml (signal/noise (S/N)) ratio >15:1. The sensitivity of the method (the limit of detection) was 0.35 and 0.15 ng for 7-acyl lipid A and PET lipid A, respectively (S/N ratio between 4:1 or 3:1). As a preliminary application, this method has been successfully applied to the determination of 7-acyl lipid A and PET lipid A content in poly (D,L-lactic-co-glycolic acid) nanoparticles (PLGA-NP).

Relationships between mechanical properties and drug release from electrospun fibers of PCL and PLGA blends.

Electrospun nanofibers have the potential to achieve high drug loading and the ability to sustain drug release. Mechanical properties of the drug-incorporated fibers suggest the importance of drug-polymer interactions. In this study, we investigated the mechanical properties of electrospun polycaprolactone (PCL) and poly (D,L-lactic-co-glycolic) acid (PLGA) fibers at various blend ratios in the presence and absence of a small molecule hydrophilic drug, tenofovir (TFV). Young׳s modulus of the blend fibers showed dependence on PLGA content and the addition of the drug. At a PCL/PLGA (20/80) composition, Young׳s modulus and tensile strength were independent of drug loading up to 40wt% due to offsetting effects from drug-polymer interactions. In vitro drug release studies suggested that release of TFV significantly decreased fiber mechanical properties. In addition, mechanically stretched fibers displayed a faster release rate as compared to the non-stretched fibers. Finally, drug partition in the blend fibers was estimated using a mechanical model and then experimentally confirmed with a composite of individually stacked fiber meshes. This work provides scientific understanding on the dependence of drug release and drug loading on the mechanical properties of drug-eluting fibers.

Mechanical properties and state of miscibility in poly(racD,L-lactide-co-glycolide)/(L-lactide-co-ε-caprolactone) blends.

Polymers based on lactic acid (PLA) are a very promising category of biopolymers. As they are multi-stimuli responsive, can, in many ways, positively interact with the host, stimulating the innate reparative machinery of the human body. Since biopolymers for medical applications are subject to restrictive regulations, blending stands out as an effective method for obtaining tailored properties within a reduced time to market if compared to synthesis. Hence, in this study a set of PDLGA/PLCL blends was obtained by means of thermoplastic techniques and then further characterized. Evaluation techniques include GPC, NMR, DSC, tensile testing and SEM. Although mixtures proved to be immiscible, a full range of tensile properties was achieved. Observation of the surfaces of fracture provided visual evidence of the deformation mechanisms that occurred during the tensile tests which in the end led to failure. Interpretation of the thermal events based on molecular characterization parameters revealed phase separation, crystallization and plasticisation mechanisms that are relevant to any potential applications based on mechanical performance and shape memory behaviour.

Micro-Flow Imaging as a quantitative tool to assess size and agglomeration of PLGA microparticles.

The purpose of this study was to explore the potential of flow imaging microscopy to measure particle size and agglomeration of poly(lactic-co-glycolic acid) (PLGA) microparticles. The particle size distribution of pharmaceutical PLGA microparticle products is routinely determined with laser diffraction. In our study, we performed a unique side-by-side comparison between MFI 5100 (flow imaging microscopy) and Mastersizer 2000 (laser diffraction) for the particle size analysis of two commercial PLGA microparticle products, i.e., Risperdal Consta and Sandostatin LAR. Both techniques gave similar results regarding the number and volume percentage of the main particle population (28-220µm for Risperdal Consta; 16-124µm for Sandostatin LAR). MFI additionally detected a 'fines' population (<28µm for Risperdal Consta; <16µm for Sandostatin LAR), which was overlooked by Mastersizer. Moreover, MFI was able to split the main population into 'monospheres' and 'agglomerates' based on particle morphology, and count the number of particles in each sub-population. Finally, we presented how MFI can be applied in process development of risperidone PLGA microparticles and to monitor the physical stability of Sandostatin LAR. These case studies showed that MFI provides insight into the effect of different process steps on the number, size and morphology of fines, monospheres and agglomerates as well as the extent of microparticle agglomeration after reconstitution. This can be particularly important for the suspendability, injectability and release kinetics of PLGA microparticles.

Combination of a biodegradable three-dimensional (3D) - printed cage for mechanical support and nanofibrous membranes for sustainable release of antimicrobial agents for treating the femoral metaphyseal comminuted fracture.

The aim of this study was to develop a biodegradable three-dimensional-printed polylactide (PLA) cage for promoting bony fixation and an antibiotics-embedded poly(d,l)-lactide-co-glycolide (PLGA) nanofibrous membrane for infectious prophylaxis during treating the comminuted metaphyseal fracture in a rabbit femoral model. The in vitro studies included measuring the mechanical properties of the 3D printed cage and determining release activities of vancomycin and ceftazidime from the nanofibers. The in vivo study included comparisons of rabbits of the femoral metaphyseal comminuted fracture treated with or without the combined biodegradable polymers. The results showed that vancomycin and ceftazidime were sustainably detected above the effective levels in the local tissue fluid around the fracture site for 3 weeks. The animal studies showed that rabbits with the 3D cage implantation possessed better cortical integrity, leg length ratio, and maximal bending strengths. The study results indicate that these combined polymers may promote fracture fixation during treating the rabbit femoral metaphyseal comminuted fracture.

The impact of monomer sequence and stereochemistry on the swelling and erosion of biodegradable poly(lactic-co-glycolic acid) matrices.

Monomer sequence is demonstrated to be a primary factor in determining the hydrolytic degradation profile of poly(lactic-co-glycolic acid)s (PLGAs). Although many approaches have been used to tune the degradation of PLGAs, little effort has been expended in exploring the sequence-control strategy exploited by nature in biopolymers. Cylindrical matrices and films prepared from a series of sequenced and random PLGAs were subjected to hydrolysis in a pH 7.4 buffer at 37 °C. Swelling ranged from 107% for the random racemic PLGA with a 50:50 ratio of lactic (L) to glycolic (G) units to 6% for the sequenced alternating copolymer poly LG. Erosion followed an inverse trend with the random 50:50 PLGA showing an erosion half-life of 3-4 weeks while poly LG required ca. >10 weeks. Stereosequence was found to play a large role in determining swelling and erosion; stereopure analogs swelled less and were slower to lose mass. Molecular weight loss followed similar trends and increases in dispersity correlated with the onset of significant swelling. The relative proportion of rapidly cleavable G-G linkages relative to G-L/L-G (moderate) and L-L (slow) correlates strongly with the degree of swelling observed and the rate of erosion. The dramatic sequence-dependent variation in swelling, in the absence of a parallel hydrophilicity trend, suggest that osmotic pressure, driven by the differential accumulation of degradation products, plays an important role.

Acylation of arginine in goserelin-loaded PLGA microspheres.

Acylation of peptides is a well-known but unwanted phenomenon in polyester matrices such as poly(d,l-lactic-co-glycolic acid) (PLGA) microspheres used as controlled release formulations. Acylation normally occurs on lysine residues and the N-terminus of the peptide. The purpose of the present work was to assess other possible acylation sites on peptides. Goserelin was used as a model peptide that lacks lysine and a free N-terminus, but contains other nucleophilic residues, i.e. serine, tyrosine and arginine, which potentially can be acylated. Goserelin loaded PLGA microspheres were prepared by a double emulsion solvent evaporation technique. Liquid chromatography ion-trap mass spectrometry (LC-ITMS) was used for determining and monitoring acylation of released goserelin. It is demonstrated that arginine is subjected to acylation with glycolic acid and lactic acid units of PLGA, which was followed by loss of NH3 from the guanidine group to obtain 2-oxazolin-4-one and 5-methyl-2-oxazolin-4-one residues with masses that are 41 and 55Da higher, respectively, than the native goserelin. There was no evidence for acylation of serine and tyrosine in goserelin. Our results demonstrate that beside lysine also acylation of arginine can occur in peptides and proteins that are loaded and released from PLGA matrixes.

Non-specific binding and steric hindrance thresholds for penetration of particulate drug carriers within tumor tissue.

Therapeutic nanoparticles (NPs) approved for clinical use in solid tumor therapy provide only modest improvements in patient survival, in part due to physiological barriers that limit delivery of the particles throughout the entire tumor. Here, we explore the thresholds for NP size and surface poly(ethylene glycol) (PEG) density for penetration within tumor tissue extracellular matrix (ECM). We found that NPs as large as 62nm, but less than 110nm in diameter, diffused rapidly within a tumor ECM preparation (Matrigel) and breast tumor xenograft slices ex vivo. Studies of PEG-density revealed that increasing PEG density enhanced NP diffusion and that PEG density below a critical value led to adhesion of NP to ECM. Non-specific binding of NPs to tumor ECM components was assessed by surface plasmon resonance (SPR), which revealed excellent correlation with the particle diffusion results. Intravital microscopy of NP spread in breast tumor tissue confirmed a significant difference in tumor tissue penetration between the 62 and 110nm PEG-coated NPs, as well as between PEG-coated and uncoated NPs. SPR assays also revealed that Abraxane, an FDA-approved non-PEGylated NP formulation used for cancer therapy, binds to tumor ECM. Our results establish limitations on the size and surface PEG density parameters required to achieve uniform and broad dispersion within tumor tissue and highlight the utility of SPR as a high throughput method to screen NPs for tumor penetration.

Effect of load and temperature on in vitro degradation of poly(glycolide-co-L-lactide) multifilament braids.

The effects of load and temperature on in vitro degradation behaviors of poly(glycolide-co-L-lactide) 90/10 multifilament braids were investigated in phosphate buffer solution at pH 7.4. The property changes of the braids with time were monitored by tensile test, gel permeation chromatography analysis, and scanning electron microscopy. The interrelationships between material properties, time and experimental conditions were explored. The results showed that the polymer braids gradually lost their strength and molecular weight with the increasing in vitro time. While the load levels applied had no effect on the materials, raising temperatures significantly accelerated the degradation. It was found that for a given tensile breaking strength retention (BSR), the dependence of degradation time on temperature could be illustrated by an Arrhenius-type equation, from which the activation energy could be derived. Further analysis indicated that there are well-defined relationships between molecular weight, BSR and breaking strain retention, and these relationships can be illustrated mathematically. Finally, the surface morphology of the fiber showed visible change during the degradation process.

Surface modification of biodegradable polyesters with fatty acid conjugates for improved drug targeting.

We describe a general method for incorporating target ligands into the surface of biocompatible polyester poly(lactic-co-glycolic acid) (PLGA) 50/50 materials using fatty acids. Avidin-fatty acid conjugates were prepared and efficiently incorporated into PLGA. Avidin was chosen as an adaptor protein to facilitate the attachment of a variety of biotinylated ligands. We show that fatty acid preferentially associates with the hydrophobic PLGA matrix, rather than the external aqueous environment, facilitating a prolonged presentation of avidin over several weeks. We successfully applied this approach in both microspheres encapsulating a model protein, bovine serum albumin, and PLGA scaffolds fabricated by a salt-leaching method. Because of its ease, generality and flexibility, this strategy promises widespread utility in modifying the surface of PLGA-based materials for applications in drug delivery and tissue engineering.

Influence of electron-beam radiation on the hydrolytic degradation behaviour of poly(lactide-co-glycolide) (PLGA).

The purpose of this study is to examine the effect of electron-beam (e-beam) radiation on the hydrolytic degradation of poly(lactide-co-glycolide) (PLGA) films. PLGA films were irradiated and observed to undergo radiation-induced degradation through chain scission, as observed from a drop in its average molecular weight with radiation dose. Irradiated (5, 10 and 20 Mrad) and non-irradiated (0 Mrad) samples of PLGA were subsequently hydrolytically degraded in phosphate-buffered saline solution at 37.0 degrees C over a span of 12 weeks. It was observed that the natural logarithmic molecular weight (lnMn) of PLGA decreases linearly with hydrolytic degradation time. The rate of water uptake is higher for samples irradiated at higher radiation dose (e.g. 20 Mrad) and subsequently causing an earlier onset of mass loss. It is postulated that the increase in water uptake is due to the presence of more hydrophilic end groups, which results in the formation of microcavities because of an increase in osmotic pressure. A relationship between radiation dose and the rate of hydrolytic degradation of PLGA films, through its molecular weight was also established. This relationship allows a more accurate and precise control of the life span of PLGA through the use of e-beam radiation.

Fabrication of well-defined PLGA scaffolds using novel microembossing and carbon dioxide bonding.

A novel biologically benign technique was developed to produce three-dimensional tissue engineering scaffolds with well-defined structure. Photolithography was used to design and pattern a planar scaffold skeletal structure on a photoresist (SU-8), and a variety of microembossing processes including sacrificial layer embossing and bilayer embossing were developed to transfer the skeletal pattern to the poly(DL-lactide-co-glycolide) substrate as scaffold skeletons. Subcritical carbon dioxide was then introduced to assemble these skeletons to a three-dimensional scaffold at a low temperature. Compared with conventional scaffolds, which have a broad pore size distribution and varying pore geometry, these microfabricated scaffolds have a uniform and well-defined geometry and structure. This uniformity of structural parameters allows for the studies of cell attachment, spreading, and proliferation in scaffolds in a controlled and logical manner. The cytocompatibility of these microfabricated scaffolds was tested by seeding three different cell lines with different morphologies and growth patterns into these scaffolds. All three cell lines attached well to the scaffolds and grew to high densities as observed with scanning electron microscopy. This study demonstrates a controllable method to fabricate tissue scaffolds with a well-defined 3D architecture that can be used to better elucidate the effect of structure parameters such as pore geometry and pore size on tissue growth in 3D scaffolds.

Size and temperature effects on poly(lactic-co-glycolic acid) degradation and microreservoir device performance.

The component materials of controlled-release drug delivery systems are often selected based on their degradation rates. The release time of a drug from a system will strongly depend on the degradation rates of the component polymers. We have observed that some poly(lactic-co-glycolic acid) polymers (PLGA) exhibit degradation rates that depend on the size of the polymer object and the temperature of the surrounding environment. In vitro degradation studies of four different PLGA polymers showed that 150 microm thick membranes degraded more rapidly than 50 microm thick membranes, as characterized by gel permeation chromatography and mass loss measurements. Faster degradation was observed at 37 degrees C than 25 degrees C, and when the saline media was not refreshed. A biodegradable polymeric microreservoir device that we have developed relies on the degradation of polymeric membranes to deliver pulses of molecules from reservoirs on the device. Earlier molecular release was seen from devices having thicker PLGA membranes. Comparison of an in vitro release study from these devices with the degradation study suggests that reservoir membranes rupture and drug release occurs when a membrane threshold molecular weight of 5000-15000 is reached.

Three-dimensional, nano-structured PLGA scaffolds for bladder tissue replacement applications.

In total, approximately 400 million people worldwide suffer from urinary bladder cancer (Nat Biotechnol 17 (1999) 149). When radical cysectomy is required as treatment, a replacement material is clearly necessitated. For this purpose, three-dimensional poly(lactic-co-glycolic acid) (PLGA) scaffolds were constructed using solvent casting and salt leaching processes. These scaffolds were manipulated to possess nano-dimensional surface features by soaking in sodium hydroxide at select concentrations and for various periods of time. Human bladder smooth muscle cells were then seeded onto these nano-dimensional scaffolds; adhesion and longer-term cell growth experiments were performed for either 4 h, or 1, 3, and 5 days, respectively. Additionally, collagen and elastin production was quantified following each experiment. In all cases, control cells were placed in an incubator and subjected to normal atmospheric pressure, while experimental cells were placed in a pressure chamber and subjected to a sustained pressure of 10 cm H(2)O. Results of this study provided evidence that porous, nano-dimensional polymeric scaffolds enhanced cell adhesion and growth, while also promoting increased elastin and collagen production. Moreover, in general, exposure to pressure did not alter cellular adhesion, growth, or extracellular matrix protein production, which suggests that the scaffolds and their resident cells will fair well in the complex mechanical environment of the bladder wall. In combination, these results provide evidence that the nano-dimensional PLGA scaffolds created in this research are promising as the next generation of bladder wall replacement materials.