Biomedical subjects

Daniel S Kohane

Publications and source records attributed to Daniel S Kohane.

30 records · Page 2Linked to original sources

PubMed2004

Injectable microparticle-gel system for prolonged and localized lidocaine release. II. In vivo anesthetic effects.

Current treatment protocols for postoperative pain are beset by either the short duration of the anesthetic effect or requirement of hospitalization of the patients. We reported herein a novel treatment by applying to the surgical site a biodegradable microparticle-gel system for prolonged and localized release of encapsulated anesthetic drugs. In a previous publication, lidocaine-loaded poly(D,L-lactic acid) microspheres were fabricated and their formulations were optimized. In vitro characterization of these lidocaine-loaded microspheres, however, revealed a shortcoming of this system; that is, microspheres tend to fuse physically. Fusion of the microspheres could hinder their clinical applications, as it would clog the needle. In this article, we demonstrated that fabricating microspheres with high molecular weight (approximately 60 KDa) poly(lactic-co-glycolic acid) would increase the glass transition temperature of the microspheres after lidocaine loading, thereby increasing their mechanical stability and eliminating their fusion during storage. Such microspheres containing 31% (w/w) lidocaine in the presence or absence of 25% (w/v) poloxamer 407 gel were then evaluated in vivo by monitoring the sensory and motor functions of the rats after sciatic nerve block, using the previously established hot-plate and weight-bearing testing methods. Results showed that microspheres formulated with poloxamer 407 gel yielded the longest duration of sensory and motor block for a period of approximately 8.5 h, compared to 5 h by microspheres in saline, 5 h by lidocaine in poloxamer 407 gel, and 2 h by lidocaine in saline. This study suggests that the microsphere-gel system containing lidocaine could potentially be applied clinically to the treatment of postoperative pain.

Anesthetics, Local↗

PubMed2004

pH-triggered microparticles for peptide vaccination.

Improving vaccine delivery to human APCs is a way to increase the CTL response to vaccines. We report the use of a novel pH-triggered microparticle that exploits the ability of APCs to cross-present MHC I-restricted Ags that have been engulfed in the low pH environment of the phagosome. A model MHC class I-restricted peptide Ag from the influenza A matrix protein was encapsulated in spray-dried microparticles composed of dipalmitoylphosphatidylcholine and the pH-sensitive polymethacrylate Eudragit E100. Release of the peptide from the particle was triggered by a drop in pH to the acidity normally found in the phagosome. The particles were efficiently phagocytosed by human monocytes and dendritic cells with minimal cellular toxicity and no functional impairment. Encapsulation of the peptide in the microparticles resulted in efficient presentation of the peptide to CD8(+) T cells by human dendritic cells in vitro, and was superior to unencapsulated peptide or peptide encapsulated in an analogous pH-insensitive particle. Vaccination of human HLA-A*0201 transgenic mice with peptide encapsulated in pH-triggering microparticles resulted in priming of CTL responses. These microparticles can be modified to coencapsulate a range of adjuvants along with the Ag of interest. Encapsulation of MHC I epitopes in pH-triggered microparticles increases Ag presentation and may improve CD8(+) T cell priming to peptide vaccines against viruses and cancer.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2004

Effect of excipient composition on the biocompatibility of bupivacaine-containing microparticles at the sciatic nerve.

Microparticulate formulations are often used for experimental prolongation of nerve blockade. Here we examine the effect of excipient composition on the biocompatibility of bupivacaine-containing microparticles. Lipid-protein-sugar particles (LPSPs) composed of 3% (1.3-microm diameter) and 60% (4.7-microm diameter) (w/w) dipalmitoylphosphatidylcholine (DPPC) were produced by spray drying, containing 10% (w/w) bupivacaine. Rat sciatic nerve blocks with 75 mg of particles produced statistically similar durations of sensory nerve block [3% (w/w) DPPC particles: 301 min; 60% (w/w) DPPC particles: 321 min]. Examination of tissues 1 day after injection revealed large particle deposits and acute inflammation in animals that received 60% (w/w) DPPC particles. There were no visible deposits in those that received 3% (w/w) DPPC particles, and microscopic inflammation was reduced. The difference between groups was similar 4 days after injection. Two weeks after injection, there was no particulate mass in either group, and inflammation had largely resolved. In both groups, moderately severe myotoxicity was seen 1 and 4 days after injection but had largely resolved by 2 weeks. In summary, reduction in particles' DPPC content greatly improved biocompatibility without compromising duration of nerve blockade; the improvement was probably attributable to the enhanced rate of particle resorption.

Animals↗

PubMed2004

Microparticulate formulations for the controlled release of interleukin-2.

Interleukin 2 (IL-2) is a pleotropic growth factor essential to immune system function. Current methods of administration are limited by the necessity of hospitalization as well as dose-limiting toxicities and side effects. There is also the issue of low therapeutic concentrations at the desired site of action; for instance, in the case of solid tumor treatment. Here we describe the design of controlled-release vehicles for the local administration of IL-2 based on single (SE) and double emulsion (DE) poly(lactic-co-glycolic acid) (PLGA) systems and a newly developed class of spray-dried lipid-protein-sugar systems composed of L-alpha-dipalmitoylphosphatidylcholine (DPPC) and 0.2% Eudragit E 100. All three systems demonstrated the release of therapeutic drug quantities. Totals of 2.0, 0.5, and 2.8 microg of IL-2 (per mg of solid) were encapsulated in the SE, DE, and spray-dried formulations, respectively. The SE and DE released of 30 and 15% of the encapsulated protein, respectively, with delivery of biologically active IL-2 during the first 5 to 10 days. The lipid-protein-sugar-based system demonstrated extended sustained release of biologically active IL-2 for a period of 4 months. These systems provide a potential framework for long-term loco-regional immunotherapeutic treatment regimens.

Animals↗

PubMed2004

Prolongation of sciatic nerve blockade by in situ cross-linked hyaluronic acid.

Controlled release technology has been applied extensively in providing prolonged duration local anesthesia. Here we used modified hyaluronic acids (HAs; hydrazide and aldehyde) that cross-link upon mixing, as the vehicle for bupivacaine. We assessed the formulations' efficacy and biocompatibility in a rat model of sciatic nerve blockade. We found that 2% (w/v) cross-linked HA doubled the duration of block of 0.1%, 0.25%, and 0.5% (w/v) bupivacaine, without a statistically significant increase in myotoxicity. 1% (w/w) cross-linked HA also prolonged nerve block, but unmodified HA, and both modified HAs did not. HA itself was associated with a mild to moderate inflammatory response with macrophages and lymphocytes. Cross-linked HA is an effective and biocompatible vehicle for enhancing local anesthetic efficacy.

Animals↗

PubMed2004

Site 1 sodium channel blockers prolong the duration of sciatic nerve blockade from tricyclic antidepressants.

Many recent reports in the literature address the local anesthetics efficacy of tricyclic antidepressants (TCAs). Here we investigated whether nerve block from TCAs is prolonged by site 1 sodium channel blockers such as tetrodotoxin and saxitoxin, which are known to prolong block from conventional local anesthetics. Tetrodotoxin and saxitoxin greatly prolonged block from TCAs. For example, the median duration of thermal nociceptive blocks for 10 mM amitriptyline, nortriptyline and doxepin were 0, 0, and 124 min; co-injection with 20 microM TTX (median block duration=0), yielded blocks lasting 404, 325, and 697 min, respectively. Co-injection of 12 microM saxitoxin (median block duration=0) with 10 mM amitriptyline resulted in a thermal nociceptive block duration of 373 min. Co-injection of 7.7 mM bupivacaine and 7.7 mM amiptriptyline did not result in block prolongation. Systemic (subcutaneous) delivery of tetrodotoxin or amitriptyline did not result in prolongation of block from the other class of drug injected at the sciatic nerve. In TCA-containing formulations, motor blockade was consistently longer than thermal nociceptive block; motor blockade was also prolonged by tetrodotoxin and saxitoxin. In summary site 1 sodium channel blockers prolong the duration of TCAs via a locally mediated mechanism.

Amitriptyline↗

PubMed2003

Prolonged duration local anesthesia from tetrodotoxin-enhanced local anesthetic microspheres.

There is interest in developing prolonged duration local anesthesics. Here we examine whether tetrodotoxin (TTX) can be used to prolong the block from bupivacaine microspheres with and without dexamethasone. Rats received sciatic nerve blocks with 75 mg of microspheres containing 0.05% (w/w) TTX, 50% (w/w) bupivacaine and/or 0.05% (w/w) dexamethasone. 0.1% (w/w) TTX microspheres were also tested. The carrier fluid contained 1:100,000 epinephrine. Nociceptive and motor blockade of the hindpaw were quantified. Nerves and adjacent muscles were harvested 2 weeks after injection for histological assessment by light microscopy. The median nociceptive block duration in hours from the microsphere groups were: bupivacaine=6.2, 0.05% TTX=0, bupivacaine+TTX=35.3, bupivacaine+dexamethasone=31.3, TTX+dexamethasone=8.1, TTX+bupivacaine+dexamethasone=221.7. Some animals receiving particles containing 0.05% TTX had deficits in the uninjected extremity; all animals receiving 0.1% (w/w) TTX particles died. Pockets of particles were associated with localized inflammation, and all samples showed some evidence of myotoxicity in the vicinity of the injection. The nerves themselves appeared intact. In summary, coencapsulation of TTX in controlled release devices containing bupivacaine and dexamethasone resulted in very prolonged nerve blocks. As formulated here, this preparation had a narrow margin of safety. While the myotoxicity appears consistent with the well-known reversible myotoxicity associated with local anesthetics, its long-term significance remains to be established.

Anesthetics, Local↗

PubMed2003

pH-triggered release of macromolecules from spray-dried polymethacrylate microparticles.

PURPOSE: pH-triggered microparticles release their therapeutic payloads at acidic pH (e.g., in the phagosome), making intracellular drug delivery more efficient. Here we modify lipid-based microparticles that are safe and efficacious in nerve and brain and are potentially inhalable, making them pH-triggerable by incorporating an acid-soluble polymethacrylate, Eudragit E100 (E100). METHODS: Microparticles were produced by spray-drying and characterized by electron microscopy, Coulter counting, density measurement, and release kinetics of fluorescently labeled proteins. In addition, biocompatibility and cellular uptake were observed in rats. RESULTS: Microparticles were spheroids 3 to 5 microm in diameter with densities of 0.12 to 0.25 g/L. Microparticles with 20% (w/w) or more E100 demonstrated slow release of fluorescently labeled proteins at pH 7.4 but rapid release at pH 5. pH-triggerability was maintained for over 2 weeks in solution. Protein loadings of 0.2-20% (w/w) were pH-triggerable. Histologic examination of particles in rat connective tissue near nerve and muscle demonstrated biocompatibility aside from muscle edema in the cell layers adjacent to the particles and a localized inflammatory reaction with macrophages laden with microparticles. CONCLUSIONS: Microparticles containing E100 were pH-triggerable for many days and were taken up by macrophages, suggesting that they may be useful for intracellular drug delivery.

Acrylates↗

PubMed2002

Lipid-sugar particles for intracranial drug delivery: safety and biocompatibility.

Controlled release of drugs to specific locales in the brain has engendered considerable interest. Here we evaluate the safety and biocompatibility of 6-microm diameter particles composed of dipalmitoylphosphatidylcholine and chondroitin sulfate A, when delivered into the cerebral parenchyma and ventricles, and in the case of intravascular injection. Some particles were loaded with fluorescein-labeled albumin to facilitate detection. Particles placed in medium with cultured murine primary cortical neurons did not increase cell death at concentrations as high as 4 mg/ml. When particles (100 microg in 2 microl) were placed stereotactically in the striatum and lateral ventricles, there was no histological evidence on hematoxylin-eosin stained sections of tissue injury outside of the needle track in any animal 3, 7, and 14 days after injection (n=6 each), and no inflammation. Ventricular size was not significantly different between animals given intraventricular injections of particles and albumin solution at those time points (n=4 each). Intracarotid injection of particles at concentrations of 0.2 and 1 mg/ml (n=4 each) did not affect relative cerebral blood flow, and there were no embolic events on histology. In one animal in the group injected with 5 mg/ml (n=3), there was a profound decrease in rCBF, with patchy emboli on histology. These novel biodegradable particles are biocompatible in and around the brain, and may be safe for intracranial sustained drug delivery either in the parenchyma or into the CSF.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2002

Biocompatibility of lipid-protein-sugar particles containing bupivacaine in the epineurium.

Novel lipid-protein-sugar particles (LPSPs) are potentially biocompatible because they are composed of naturally occurring ingredients and their expected tissue dwell times are relatively short. In this research, we used histological sections to study tissue reaction to LPSPs (4.4-microm median diameter) when used for sciatic nerve block in the rat. As a reference, we compared LPSPs to 60-microm median diameter poly(lactic-co-glycolic) acid (PLGA) microspheres (110,000 MW PLGA, glycolic/lactic ratio 65:35). Four days after injection, both particle types produced acute inflammation within the confines of the injectate, inflammation in adjacent tissues, and myotoxicity. Bupivacaine-free particles did not display myotoxicity, and inflammation in adjacent tissues was reduced. At 2 weeks, inflammation from LPSPs had almost disappeared, whereas PLGA microspheres had a foreign-body giant cell reaction until at least 8 weeks after injection. In contrast, 3.6-microm median diameter, 20,000-MW PLGA microspheres produced a primarily histiocytic reaction 2 weeks after injection. In summary, the LPSPs and PLGA microspheres studied herein have excellent biocompatibility, but tissue reaction to the former is of much shorter duration. Myotoxicity and inflammation of surrounding tissue is largely attributed to bupivacaine. Foreign-body giant cells may be attributed to particle size rather than a specific reaction to PLGA.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2002

Effectiveness of muscimol-containing microparticles against pilocarpine-induced focal seizures.

PURPOSE: To investigate the efficacy of in situ lipid-protein-sugar particles (LPSPs) in mitigating the epileptogenic and histologic effects of intrahippocampal pilocarpine in rats. METHODS: LPSPs with and without muscimol were produced by spray-drying, sized by Coulter counter, and muscimol content determined by high-pressure liquid chromatography (HLPC). Particles, free muscimol or saline, were injected into the hippocampi of Sprague-Dawley rats before 40 mM pilocarpine, and seizure activity was scored. The trajectories of behavioral scores between groups were compared with two-way repeated measures analysis of variance. Animals were killed after 2 weeks. Brain sections were stained (Timm and thionin) and scored. RESULTS: LPSPs were 4 to 5 microm in diameter, and contained 0 or 2% (wt/wt) muscimol. In vitro, muscimol was released over a 5-day period. Intrahippocampal injections of normal saline and blank LPSPs did not deter seizure activity from pilocarpine. The rise of the trajectory in behavior scores in animals given LPSPs containing 5 microg muscimol was significantly slower than in those receiving saline, blank particles, or 5 microg of unencapsulated muscimol. There was less apparent neuronal injury and CA3 and supragranular mossy fiber sprouting in hippocampi of animals receiving muscimol-containing particles than in animals that did not receive muscimol. Hippocampi of animals that received 5 microg of encapsulated muscimol showed less supragranular sprouting than did those receiving 5 microg of unencapsulated muscimol, but showed no difference in cell loss or CA3 sprouting. CONCLUSIONS: Focally delivered biodegradable microparticles loaded with muscimol are effective in reducing seizure activity from pilocarpine in animals and mitigate the histologic effects.

Animals↗

PubMedDate not supplied

Local anesthetics inhibit uterine activity in vitro. Possible application on preterm labor prevention and treatment.

OBJECTIVE: Analysis of the effects of local anesthetics upon the gravid uterus. METHODS: Isolated strips of pregnant-rat myometrium were placed within tissue baths. Muscular activity was then recorded by a force transducer, at cumulative concentrations of either procaine, lidocaine, or ropivacaine. RESULTS: The effects of myometrial activity were non-monotonic. At lower concentrations, an increase in contraction frequency was noted, concomitant with a depression in amplitude. As the concentrations increased, both amplitude and frequency were depressed until, eventually, activity was abolished. CONCLUSIONS: Local anesthetics administered in situ consistently inhibit or completely arrest overall myometrial activity. These agents may prove clinically useful in preterm labor management, if administered locally to the myometrium via suitable slow release drug delivery systems, warranting further trials in vivo.

Amides↗