Thiolated Cellulose: A Dual-Acting Mucoadhesive and Permeation-Enhancing Polymer

This study aims to design an anionic, thiolated cellulose derivative and to evaluate its mucoadhesive and permeation-enhancing properties utilizing enoxaparin as a model drug. 2-Mercaptosuccinic acid-modified cellulose (cellulose-mercaptosuccinate) was synthesized by the reaction of cellulose with S-acetylmercaptosuccinic anhydride. The chemical structure of the target compound was confirmed by FTIR and 1H NMR spectroscopy. The thiol content was determined by Ellman's test. The conjugate exhibited 215.5 ± 25 μmol/g of thiol groups and 84 ± 16 μmol/g of disulfide bonds. Because of thiolation, mucoadhesion on porcine intestinal mucosa was 9.6-fold enhanced. The apparent permeability (Papp) of the model dye Lucifer yellow was up to 2.2-fold improved by 0.5% cellulose-mercaptosuccinate on a Caco-2 cell monolayer. Enoxaparin permeation through rat intestinal mucosa increased 2.4-fold in the presence of 0.5% cellulose-mercaptosuccinate compared with the drug in buffer only. In vivo studies in rats showed an oral bioavailability of 8.98% using cellulose-mercaptosuccinate, which was 12.5-fold higher than that of the aqueous solution of the drug. Results of this study show that the modification of cellulose with 2-mercaptosuccinic acid provides mucoadhesive and permeation-enhancing properties, making this thiolated polymer an attractive excipient for oral drug delivery.

PEG vs. zwitterions: How these surface decorations determine cellular uptake of lipid-based nanocarriers

AIM

To evaluate the impact of polyethylene glycol (PEG) and zwitterionic surface decoration of lipid-based nanocarriers (NC) on cellular uptake.

METHODS

Anionic, neutral and cationic zwitterionic lipid-based NCs based on lecithin were compared with conventional PEGylated lipid-based NCs regarding stability in biorelevant fluids, interaction with endosome mimicking membranes, cytocompatibility, cellular uptake and permeation across intestinal mucosa.

RESULTS

PEGylated and zwitterionic lipid-based NCs exhibited a droplet size between 100 and 125 nm with a narrow size distribution. For the PEGylated and zwitterionic lipid-based NCs only minor alterations in size and PDI in fasted state intestinal fluid and mucus containing buffer were observed, demonstrating similar bioinert properties. Erythrocytes interaction studies revealed enhanced endosomal escape properties for zwitterionic lipid-based NCs compared to PEGylated lipid-based NCs. For the zwitterionic lipid-based NCs negligible cytotoxicity on Caco-2 and HEK cells, even in the highest tested concentration of 1 % (v/v) was recorded. The PEGylated lipid-based NCs showed a cell survival of ≥75 % for concentrations ≤0.05 % on Caco-2 and HEK cells, which was considered as non-toxic. For the zwitterionic lipid-based NCs up to 60-fold higher cellular uptake on Caco-2 cells was determined compared to PEGylated lipid-based NCs. For the cationic zwitterionic lipid-based NCs the highest cellular uptake with 58.5 % and 40.0 % in Caco-2 and HEK cells, respectively, was determined. The results were confirmed visually by life cell imaging. Ex-vivo permeation experiments using rat intestinal mucosa demonstrated up to 8.6-fold enhanced permeation of the lipophilic marker coumarin-6 in zwitterionic lipid-based NCs compared to the control. Up to 6.9-fold enhanced permeation of coumarin-6 in neutral zwitterionic lipid-based NCs compared to the PEGylated counterpart was recorded.

CONCLUSION

The replacement of PEG surfactants with zwitterionic surfactants is a promising approach to overcome the drawbacks of conventional PEGylated lipid-based NCs regarding intracellular drug delivery.

Thiolated α-cyclodextrin: The likely smallest drug carrier providing enhanced cellular uptake and endosomal escape

This study aimed to evaluate the effect of thiolated α-cyclodextrin (α-CD-SH) on the cellular uptake of its payload. For this purpose, α-CD was thiolated using phosphorous pentasulfide. Thiolated α-CD was characterized by FT-IR and ¹H NMR spectroscopy, differential scanning calorimetry (DSC), and powder X-ray diffractometry (PXRD). Cytotoxicity of α-CD-SH was evaluated on Caco-2, HEK 293, and MC3T3 cells. Dilauryl fluorescein (DLF) and coumarin-6 (Cou) serving as surrogates for a pharmaceutical payload were incorporated in α-CD-SH, and cellular uptake was analyzed by flow cytometry and confocal microscopy. Endosomal escape was investigated by confocal microscopy and hemolysis assay. Results showed no cytotoxic effect within 3 h, while dose-dependent cytotoxicity was observed within 24 h. The cellular uptake of DLF and Cou was up to 20- and 11-fold enhanced by α-CD-SH compared to native α-CD, respectively. Furthermore, α-CD-SH provided an endosomal escape. According to these results, α-CD-SH is a promising carrier to shuttle drugs into the cytoplasm of target cells.

Oral drug delivery: Influence of mucus on cellular interactions and uptake of lipid-based nanocarriers in Caco-2 cells

This study aimed to investigate the impact of the mucus gel barrier on intestinal mucosal uptake of lipid-based nanocarriers (NCs). Zwitterionic- (ZW), polyglycerol- (PG) and polyethylene glycol- (PEG) surfactant-based o/w nanoemulsions were developed. NCs were assessed regarding their size and zeta potential, stability in biorelevant media and mucus, mucus permeation behavior, cellular interactions and uptake by Caco-2 cells with and without mucus and by a Caco-2/HT29-MTX co-culture. All NCs were in the size range of 178 - 204 nm and exhibited a zeta potential between -4.2 and +1.2 mV. ZW- and PG-NCs demonstrated mucus permeating properties comparable to PEG-NCs. In contrast, ZW- and PG-NCs showed high cellular uptake, whereas limited cellular uptake was observed in case of PEG-NCs. Furthermore, mucus on Caco-2 cells as well as the mucus secreting co-culture had a significant impact on the cellular uptake of all tested NCs. According to these results, ZW- and PG-NCs are advantageous to overcome the mucus and epithelial barrier of the intestinal mucosa. STATEMENT OF SIGNIFICANCE: Within this study the impact of mucus on cellular uptake of lipid-based nanocarriers (NCs) with different surface decorations was investigated. The potential of NCs with zwitterionic-, polyglycerol- and polyethylene glycol-surfactants on their surface to overcome the mucus and epithelial barrier was evaluated. Zwitterionic- and polyglycerol-NCs showed mucus permeating properties similar to PEG-NCs. In contrast, zwitterionic- and polyglycerol-NCs substantially outperformed PEG-NCs in their cellular uptake properties. According to these findings, zwitterionic- and polyglycerol-NCs have the potential to overcome both the mucus and epithelial barrier of the mucosa.

Three generations of thiolated cyclodextrins: A direct comparison of their mucus permeating and mucoadhesive properties

AIM

This study aims to compare the mucus permeating and mucoadhesive properties of three generations of thiolated cyclodextrins (CDs).

METHODS

Free thiol groups of thiolated γ-CDs (CD-SH) were S-protected with 2-mercaptonicotinic acid (MNA), leading to a second generation of thiolated CDs (CD-SS-MNA) and with 2 kDa polyethylene glycol (PEG) bearing a terminal thiol group leading to a third generation of thiolated CDs (CD-SS-PEG). The structure of these thiolated CDs was confirmed and characterized by FT-IR, ¹H NMR and colorimetric assays. Thiolated CDs were evaluated regarding viscosity, mucus diffusion, and mucoadhesion.

RESULTS

The viscosity of the mixture of CD-SH, CD-SS-MNA, or CD-SS-PEG with mucus increased up to 11-, 16-, and 14.1-fold compared to unmodified CD within 3 hours, respectively. Mucus diffusion increased in the following rank order: unprotected CD-SH < CD-SS-MNA < CD-SS-PEG. The residence time of CD-SH, CD-SS-MNA, and CD-SS-PEG on porcine intestine was up to 9.6-, 12.55-, and 11.2-fold prolonged compared to native CD, respectively.

CONCLUSION

According to these results, S-protection of thiolated CDs can be a promising approach to improve their mucus permeating and mucoadhesive properties.

STATEMENT OF SIGNIFICANCE

Three generations of thiolated cyclodextrins (CDs) with different types of thiol ligands have been synthesized to improve mucus interaction. 1^st generation of thiolated CDs was synthesized by converting hydroxyl groups into thiols by reaction with Thiourea. For 2^nd generation, free thiol groups were S-protected by reaction with 2-mercaptonicotinic acid (MNA), resulting in high reactive disulfide bonds. For 3^rd generation, terminally thiolated short PEG chains (2 kDa) were used for S-protection of thiolated CDs. Mucus penetrating properties were found to be increased as follows: 1^st generation < 2^nd generation < 3^rd generation. Furthermore, mucoadhesive properties were improved in the following rank order: 1^st generation < 3^rd generation < 2^nd generation. This study suggests that the S-protection of thiolated CDs can enhance mucus penetrating and mucoadhesive properties.

Biodegradable arginine based steroid-surfactants: Cationic green agents for hydrophobic ion-pairing

The aim of this study was to evaluate the safety and efficacy for hydrophobic ion-pairing of surfactants based on arginine (Arg). The prepared Arg-cholesteryl ester (ACE) and Arg-diosgenyl ester (ADE) were characterized regarding solubility, pKa, critical micellar concentration (CMC), biodegradability as well as membrane- and aquatic toxicity using DOTAP as reference. The ability for hydrophobic ion-pairing was evaluated and the lipophilicity of formed complexes was determined. NMR, FT-IR and MS confirmed successful synthesis of Arg-surfactants. The slightly soluble single-charged Arg-surfactants (pH < pKa₃ (ACE = 10.42 ± 0.52; ADE = 10.38 ± 0.27)) showed CMCs of 27.17 µM for ACE and 35.67 µM for ADE. CMCs of the sparingly soluble double-charged species (pH < pKa₂ (ACE = 5.30 ± 0.20; ADE = 5.55 ± 0.06)) were determined at concentrations of ≥ 250 µM for ACE and ≥ 850 µM for ADE. The enzymatic- and environmental biodegradability was proven by an entire cleavage of Arg-surfactants within 24 h, whereas DOTAP remained stable. Arg-surfactants exhibited lower membrane- (> 2-fold) and aquatic toxicity (> 15-fold) than DOTAP. The complexes formed with Arg-surfactants and insulin showed higher lipophilicity than the DOTAP-complex. According to these results, Arg-surfactants might be a promising safe tool for the delivery of peptide drugs.

Charge-Converting Nanoemulsions as Promising Retinal Drug and Gene Delivery Systems

AIM

This study aimed to develop phosphatase-responsive ζ potential converting nanocarriers utilizing polyphosphate-coated cell-penetrating peptide (CPP)-decorated nanoemulsions (NEs) as a novel gene delivery system to retinal cells.

METHODS

Poly-l-lysine (PLL) was first conjugated with oleylamine (OA) only at its carboxylic end to form the amphiphilic PLL-oleylamine (PLOA) conjugate. Afterward, NEs were loaded with PLOA prior to being coated with tripolyphosphate (TPP) to generate PLOA/TPP NEs. A plasmid containing a reporter gene for green fluorescent protein plasmid (pGFP) was complexed with cationic surfactants forming hydrophobic ion pairs that were loaded in the oily core of NEs. Phosphate removal, ζ potential conversion, and cytotoxicity of the system were evaluated. Cellular uptake and transfection efficiency were investigated in 661W photoreceptor-like cells via microscopic analysis, fluorescence spectroscopy, and flow cytometry.

RESULTS

Dephosphorylation of PLOA/TPP NEs triggered by alkaline phosphatase (ALP) resulted in the exposure of positive amine groups on the surface of NE droplets and a notable conversion of the ζ potential from -22.4 to +8.5 mV. Cellular uptake of PLOA/TPP NEs performed on 661W photoreceptor-like cells showed a 3-fold increase compared to control NEs. Furthermore, PLOA/TPP NEs also showed low cytotoxicity and high transfection efficacy with ∼50% of cells transfected.

CONCLUSIONS

Polyphosphate-coated CPP-decorated NEs triggered by ALP could be a promising nanosystem to efficiently deliver drugs and genetic materials to photoreceptor-like cells and other retinal cells for potential treatments of retinal diseases.

Thiolation of non-ionic surfactants for the development of lipid-based mucoadhesive drug delivery systems

The aim of this study was to develop thiolated self-emulsifying drug delivery systems (SEDDS) and nanostructured lipid carriers (NLCs) with improved mucoadhesive properties. Two non-ionic surfactants bearing a short and long PEG chain, namely polyoxyethylene (10) stearyl ether (PSE₁₀) and polyoxyethylene (100) stearyl ether (PSE₁₀₀), were thiolated for the first time by substituting the terminal hydroxyl group with a thiol group. The synthesis was confirmed by FT-IR, NMR and Ellman's test. SEDDS and NLCs containing these thiolated compounds were investigated for size, polydispersity index (PDI) and ζ potential. Subsequently, mucus diffusion studies, rheological evaluations after mixing the nanocarriers with mucus and mucoadhesion studies on porcine intestinal mucosa were performed. All nanocarriers had a size less than 250 nm, a maximum PDI of 0.3 and a ζ potential < -9.0 mV. Mucus diffusion studies resulted in the rank order of increasing diffusivity: PSE₁₀-SH < PSE₁₀₀-SH < PSE₁₀-OH < PSE₁₀₀-OH for NLCs and PSE₁₀-OH < PSE₁₀₀-OH < PSE₁₀₀-SH < PSE₁₀-SH for SEDDS. The mucoadhesive properties and increase in viscosity of SEDDS and NLCs ranked: PSE₁₀₀-OH < PSE₁₀-OH < PSE₁₀₀-SH < PSE₁₀-SH. In addition, the short chain PSE₁₀-SH showed higher mucus interactions than the long chain PSE₁₀₀-SH for both SEDDS and NLCs. The thiolated PSE surfactants appeared to be promising excipients for the design of highly mucoadhesive drug delivery systems.

Chitosan - Polyphosphate nanoparticles for a targeted drug release at the absorption membrane

The aim of this study was to develop nanoparticles (NPs) providing a targeted drug release directly on the epithelium of the intestinal mucosa. NPs were prepared via ionic gelation between cationic chitosan (Cs) and anionic polyphosphate (PP). The resulting NPs were characterized by their size, polydispersity index (PDI) and zeta potential. Isolated and cell-associated intestinal alkaline phosphatase (IAP) was employed to trigger polyphosphate cleavage in Cs-PP NPs which was quantified via malachite green assay. In parallel, the shift in zeta potential was determined. In-vitro drug release studies were performed in Franz diffusion cells with Cs-PP NPs containing rhodamine 123 as model active ingredient. Furthermore, cytotoxicity of Cs-PP NPs was assessed via resazurin assay on Caco-2 cells as well as via hemolysis assay on red blood cells. Cs-PP NPs exhibited an average size of 144.17 ± 10.95 nm and zeta potential of -12.6 ± 0.50 mV. The encapsulation efficiency of rhodamine 123 by Cs-PP NPs was 86.8%. After incubation with isolated IAP for 3 h the polyphosphate of Cs-PP NPs was cleaved to monophosphate and zeta potential raised up to -2.3 ± 0.30 mV. Cs-PP NPs showed a non-toxic profile. Within 3 h, 62.0 ± 10.8% and 14.1 ± 2.2% of total rhodamine 123 was released from Cs-PP NPs upon incubation with isolated as well as porcine intestine derived intestinal alkaline phosphatase (IAP), respectively. According to these results, Cs-PP NPs are promising drug delivery systems to enable a drug targeted release at the absorption membrane.

Design of nanostructured lipid carriers and solid lipid nanoparticles for enhanced cellular uptake

In this study PEG-free and zeta potential changing lipid-based nanocarriers providing enhanced cellular uptake were developed. Nanostructured lipid carriers (NLC), consisting of paraffin wax, caprylic/ capric triglyceride, cetyltrimethylammoniumchloride and either soy lecithin or polyglycerol-4 laurate and solid lipid nanoparticles (SLN) with the same composition but without the liquid lipid content were developed. All formulations exposed a positive surface charge and were then coated with the polyphosphate Graham's salt. Phosphate release from these formulations was evaluated by incubation with intestinal alkaline phosphatase as well as on a Caco-2 monolayer and zeta potentials were measured. Additionally, cellular uptake studies were performed. Within 5 h, a remarkable amount of phosphate was released from all formulations incubated with intestinal alkaline phosphatase. Enzymatically induced phosphate release with intestinal alkaline phosphatase led to a zeta potential shift up to Δ 26 mV. Results of phosphate release and zeta potential change were confirmed on Caco-2 cells. Cellular uptake studies on Caco-2 cells showed an up to 5.6-times higher uptake compared to cells with inhibited phosphatase. According to these results, polyphosphate coating is a powerful tool to obtain lipid-based nanocarriers for enhanced cellular uptake.

SEDDS-loaded mucoadhesive fiber patches for advanced oromucosal delivery of poorly soluble drugs

To date, buccal administration of lipophilic drugs is still a major challenge due to their poor solubility in saliva and limited penetration into mucosal tissues. To overcome these limitations, we developed electrospun patches combining the benefits of mucoadhesive fibers and self-emulsifying drug delivery systems (SEDDS). The fiber system comprises a combination of mucoadhesive thiolated polyacrylic acid fibers and SEDDS-loaded fibers fabricated by parallel electrospinning. The resulting mucoadhesive electrospun SEDDS patches were systemically investigated for fiber characteristics, self-emulsification, mucoadhesion, drug penetration into porcine buccal tissue and biocompatibility. The patches showed high encapsulation efficiency for SEDDS without causing fiber defects or leakage. SEDDS incorporation enhanced the spinning process and reduced the fiber diameter and fiber size distribution. Hydration-dependent self-emulsification provided a controlled release of curcumin being encapsulated in nano-scaled o/w emulsion for over 3 h. Due to the thiolated polyacrylic acid fibers, the buccal residence time of patches was 200-fold prolonged. Further, they promoted a significantly increased drug penetration into buccal tissue compared to fiber patches without SEDDS. Finally, biocompatibility and improved therapeutic effects of curcumin-loaded patches on human keratinocytes and fibroblasts were confirmed. Mucoadhesive electrospun SEDDS patches represent a promising approach to overcome current challenges in the oromucosal delivery of lipophilic drugs to unlock their full therapeutic potential.

Digestion of lipid excipients and lipid-based nanocarriers by pancreatic lipase and pancreatin

The digestion behaviour of lipid-based nanocarriers (LNC) has a great impact on their oral drug delivery properties. In this study, various excipients including surfactants, glycerides and waxes, as well as various drug-delivery systems, namely self-emulsifying drug delivery systems (SEDDS), solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) were examined via the pH-stat lipolysis model. Lipolysis experiments with lipase and pancreatin revealed the highest release of fatty acids for medium chain glycerides, followed by long chain glycerides and surfactants. Waxes appeared to be poor substrates with a maximum digestion of up to 10% within 60 min. Within the group of surfactants, the enzymatic cleavage decreased in the following order: glycerol monostearate > polyoxyethylene (20) sorbitan monostearate > PEG-35 castor oil > sorbitan monostearate. After digestion experiments of the excipients, SEDDS, SLN and NLC with sizes between 30 and 300 nm were prepared. The size of almost all formulations was increasing during lipolysis and levelled off after approximately 15 min except for the SLN and NLC consisting of cetyl palmitate. SEDDS exceeded 6000 nm after some minutes and were almost completely hydrolysed by pancreatin. No significant difference was observed between comparable SLN and NLC but surfactant choice and selection of the lipid component had an impact on digestion. SLN and NLC with cetyl palmitate were only digested by 5% whereas particles with glyceryl distearate were decomposed by 40-80% within 60 min. Additionally, the digestion of the same SLN or NLC, only differing in the surfactant, was higher for SLN/NLC containing polyoxyethylene (20) sorbitan monostearate than PEG-35 castor oil. This observation might be explained by the higher PEG content of PEG-35 castor oil causing a more pronounced steric hindrance for the access of lipase. Generally, digestion experiments performed with pancreatin resulted in a higher digestion compared to lipase. According to these results, the digestion behaviour of LNC depends on both, the type of nanocarrier and on the excipients used for them.

Synthesis and evaluation of sulfosuccinate-based surfactants as counterions for hydrophobic ion pairing

Hydrophobic ion pairing is a promising strategy to raise the lipophilic character of therapeutic peptides and proteins. In past studies, docusate, an all-purpose surfactant with a dialkyl sulfosuccinate structure, showed highest potential as hydrophobic counterion. Being originally not purposed for hydrophobic ion pairing, it is likely still far away from the perfect counterion. Thus, within this study, docusate analogues with various linear and branched alkyl residues were synthesized to derive systematic insights into which hydrophobic tail is most advantageous for hydrophobic ion pairing, as well as to identify lead counterions that form complexes with superior hydrophobicity. The successful synthesis of the target compounds was confirmed by FT-IR, ¹H-NMR, and ¹³C-NMR. In a screening with the model protein hemoglobin, monostearyl sulfosuccinate, dioleyl sulfosuccinate, and bis(isotridecyl) sulfosuccinate were identified as lead counterions. Their potential was further evaluated with the peptides and proteins vancomycin, insulin, and horseradish peroxidase. Dioleyl sulfosuccinate and bis(isotridecyl) sulfosuccinate significantly increased the hydrophobicity of the tested peptides and proteins determined as logP or lipophilicity determined as solubility in 1-octanol, respectively, in comparison to the gold standard docusate. Dioleyl sulfosuccinate provided an up to 8.3-fold higher partition coefficient and up to 26.5-fold higher solubility in 1-octanol than docusate, whereas bis(isotridecyl) sulfosuccinate resulted in an up to 6.7-fold improvement in the partition coefficient and up to 44.0-fold higher solubility in 1-octanol. The conjugation of highly lipophilic alkyl tails to the polar sulfosuccinate head group allows the design of promising counterions for hydrophobic ion pairing. STATEMENT OF SIGNIFICANCE: Hydrophobic ion pairing enables efficient incorporation of hydrophilic molecules into lipid-based formulations by forming complexes with hydrophobic counterions. Docusate, a sulfosuccinate with two branched alkyl tails, has shown highest potential as anionic hydrophobic counterion. As it was originally not purposed for hydrophobic ion pairing, its structure is likely still far away from the perfect counterion. To improve its properties, analogues of docusate with various alkyl tails were synthesized in the present study. The investigation of different alkyl residues allowed to derive systematic insights into which tail structures are most favorable for hydrophobic ion pairing. Moreover, the lead counterions dioleyl sulfosuccinate and bis(isotridecyl) sulfosuccinate bearing highly lipophilic alkyl tails provided a significant improvement in the hydrophobicity of the resulting complexes.

Emerging technologies to increase gastrointestinal transit times of drug delivery systems

Apart from already established technologies to increase gastrointestinal transit times, including devices rapidly increasing in size once they have reached the stomach in order to retard the passage through the pylorus, formulations that float on gastric fluids and mucoadhesive drug delivery systems adhering to the gastrointestinal mucosa, there are new technologies emerging that might be game changing. They include mucus permeating nanocarriers that are able to diffuse deeply into the mucus gel layer of the gastric and intestinal mucosa remaining there for a prolonged time period (i), charge-converting nanocarriers that shift their zeta potential from negative to positive within the mucus gel layer providing strong ionic bonds with anionic mucus glycoproteins (ii) and thiolated nanocarriers and cyclodextrins form even covalent bonds with cysteine-rich subdomains of mucus glycoproteins (iii). Within this review we will provide an overview about these emerging new technologies and will critically discuss their potential and shortcomings.

Thiolated pectins: In vitro and ex vivo evaluation of three generations of thiomers

In recent decades, three generations of thiomers have been developed with the main purpose of obtaining enhanced interactions with mucosal tissues. Therefore, many different types of thiolated ligands have been generated and attached to polymeric backbones. The aim of this study was to synthesize all three generations of thiomers and to directly compare their properties regarding mucus penetration and mucoadhesion. Starting from pectin, the unprotected thiomer pectin-cysteine (Pec-Cys), the preactivated S-protected thiomer pectin-cysteine-mercaptonicotinic acid (Pec-Cys-MNA) and the less reactive S-protected thiomer pectin-cysteine-glutathione (Pec-Cys-GSH) were synthesized and characterised by FT-IR, NMR, and colorimetric studies. The polymers were evaluated regarding their cytotoxicity, swelling behaviour, viscosity after mixing with mucus, mucus diffusion, penetration into mucosa, and mucoadhesion. The amount of the three ligands (Cys, Cys-MNA and Cys-GSH) bound to the polymer was determined to be in the range of 193-196 µmol/g. All polymers showed no cytotoxicity. Viscosity of the mixture of Pec-Cys-MNA and Pec-Cys-GSH with mucus increased 21.5- and 26.7-fold, respectively, compared to the unmodified polymer within 3 hours. Swelling, mucoadhesion, interpenetration and mucus diffusion were increased in the following rank order: Pec-Cys < Pec-Cys-MNA < Pec-Cys-GSH. Results of mucoadhesion study indicated a 7.4 and 8.1-fold increase of Pec-Cys-MNA and Pec-Cys-GSH, respectively, compared to the unmodified polymer. As the less reactive S-protected thiomer exhibited higher mucoadhesive properties than the other thiomers, this study provides evidence for the superior mucoadhesion of 3^rd generation thiomers. STATEMENT OF SIGNIFICANCE: Three generations of thiolated polymers have been developed bearing different types of thiol ligands with the main purpose of enhancing mucus interactions. In this study, all generations were synthesized on the polymeric backbone of pectin for the first time to directly compare their mucus penetrating and mucoadhesive properties. 1^st generation exhibited covalently bound L-cysteine moieties. For 2^nd generation, thiols of cysteines were S-protected with 2-mercaptonicotinic acid (MNA), resulting in high reactive disulfide bonds. 3^rd generation was synthesized by a thiol/disulfide exchange of glutathione with MNA, producing a less reactive disulfide bond. Mucus penetrating and mucoadhesive properties were found to be increased as follows: 1^st generation < 2^nd generation < 3^rd generation. According to these results, the thiomer of 3^rd generation represents a promising excipient with strong mucoadhesion.

In Vitro Investigation of Thiolated Chitosan Derivatives as Mucoadhesive Coating Materials for Solid Lipid Nanoparticles

In the present study, chitosan (CS) was thiolated by introducing l-cysteine via amide bond formation. Free thiol groups were protected with highly reactive 6-mercaptonicotinic acid (6-MNA) and less-reactive l-cysteine, respectively, via thiol/disulfide-exchange reactions. Unmodified CS, l-cysteine-modified thiolated CS (CS-Cys), 6-MNA-S-protected thiolated CS (CS-Cys-MNA), and l-cysteine-S-protected thiolated CS (CS-Cys-Cys) were applied as coating materials to solid lipid nanoparticles (SLN). The strength of mucus interaction followed the rank order plain < CS < CS-Cys-Cys < CS-Cys < CS-Cys-MNA, whereas mucus diffusion followed the rank order CS-Cys < CS-Cys-Cys < CS < CS-Cys-MNA < plain. In accordance with lower reactivity, CS-Cys-Cys-coated SLN were immobilized to a lower extent than CS-Cys-coated SLN, while CS-Cys-MNA-coated SLN dissociated from their coating material resulting in a similar diffusion behavior as plain SLN. Consequently, CS-Cys-Cys-coated SLN and CS-Cys-MNA-coated SLN showed the highest retention on porcine intestinal mucosa by enabling a synergism of efficient mucus diffusion and strong mucoadhesion.

Nanostructured Lipid Carriers (NLCs) for Oral Peptide Drug Delivery: About the Impact of Surface Decoration

This study was aimed to evaluate the impact of surfactants used for nanostructured lipid carriers (NLCs) to provide enzymatic protection for incorporated peptides. Insulin as a model peptide was ion paired with sodium dodecyl sulfate to improve its lipophilicity. Three NLC formulations containing polyethylene glycol ester (PEG-ester), polyethylene glycol ether (PEG-ether), and polyglycerol ester (PG-ester) surfactants were prepared by solvent diffusion method. NLCs were characterized regarding particle size, polydispersity index, and zeta potential. Biocompatibility of NLCs was assessed on Caco-2 cells via resazurin assay. In vitro lipolysis study was performed using a standard lipid digestion method. Proteolytic studies were performed in simulated gastric fluid containing pepsin and simulated intestinal fluid containing pancreatin. Lipophilicity of insulin in terms of log Poctanol/water was improved from -1.8 to 2.1. NLCs were in the size range of 64-217 nm with a polydispersity index of 0.2-0.5 and exhibited a negative surface charge. PG-ester NLCs were non-cytotoxic up to a concentration of 0.5%, PEG-ester NLCs up to a concentration of 0.25% and PEG-ether NLC up to a concentration of 0.125% (w/v). The lipolysis study showed the release of >90%, 70%, and 10% of free fatty acids from PEG-ester, PG-ester, and PEG-ether NLCs, respectively. Proteolysis results revealed the highest protective effect of PEG-ether NLCs followed by PG-ester and PEG-ester NLCs for incorporated insulin complex. Findings suggest that NLCs bearing substructures less susceptible to degrading enzymes on their surface can provide higher protection for incorporated peptides toward gastrointestinal proteases.

Thiolated cyclodextrins: Mucoadhesive and permeation enhancing excipients for ocular drug delivery

Thiolated β-cyclodextrin (β-CD) has the potential to enhance mucoadhesive and permeation enhancing properties on ocular mucosa. Thiolated β-CD was synthesized via replacement of all primary hydroxyl groups on β-CD backbone by halogen followed by substitution with thiol groups. The structure was confirmed by FT-IR and ¹H NMR spectroscopy. Thiolated CD was characterized for hemolytic effect, ocular irritation, solubility enhancement, viscoelastic behavior and mucoadhesive properties. Moreover, the permeation enhancing effect of thiolated oligomer on different ocular tissues including conjunctiva, sclera and cornea was evaluated with sodium fluorescein (Na-Flu) as a marker. Thiolated β-CD displayed 5360 ± 412 µmol/g thiol groups. The newly synthesized oligomer did not show any hemolytic effect on red blood cells at a concentration of 0.5% (m/v) for an incubation period of 3 h and minimal corneal irritation effects without any inflammation within 72 h. Thiolated β-CD exhibited a 5.3-fold improved aqueous solubility as compared to the unmodified β-CD. Thiolated oligomer (0.5% m/v) enhanced the viscosity of mucus up to 6.2-fold within 4 h and provided a 26-fold prolonged ocular residence time due to mucoadhesion. Moreover, 0.5% (m/v) thiolated β-CD enhanced the permeation of Na-Flu 9.6-, 7.1- and 5.3-fold on conjunctiva, sclera and cornea, respectively. Based on these findings, thiolated β-CD might be a promising auxiliary agent for ocular drug delivery.

Decisive Diagnosis of Seronegative Polyarthritis by 3-phase Bone Scintigraphy

Inflammatory joint disease is mainly diagnosed on grounds of clinical investigation, laboratory testing (acute phase reactants), and radiography. Radionuclide imaging has recently been added to the armamentarium of clinician. This case report points out the role of three-phase bone scan and HIG (human immunoglobulin) scan in the discovery of the inflammatory nature of polyarthralgia in a young woman with equivocal clinical and laboratory results. In the aim of diagnosing arthritis early in its course scintigraphy proved to be superior to conventional radiography. It also allows more discriminating selection of subsequent X-ray examination to limit radiation exposure.

Targeted diagnostic magnetic nanoparticles for medical imaging of pancreatic cancer

Highly aggressive cancer types such as pancreatic cancer possess a mortality rate of up to 80% within the first 6months after diagnosis. To reduce this high mortality rate, more sensitive diagnostic tools allowing an early stage medical imaging of even very small tumours are needed. For this purpose, magnetic, biodegradable nanoparticles prepared using recombinant human serum albumin (rHSA) and incorporated iron oxide (maghemite, γ-Fe2O3) nanoparticles were developed. Galectin-1 has been chosen as target receptor as this protein is upregulated in pancreatic cancer and its precursor lesions but not in healthy pancreatic tissue nor in pancreatitis. Tissue plasminogen activator derived peptides (t-PA-ligands), that have a high affinity to galectin-1 have been chosen as target moieties and were covalently attached onto the nanoparticle surface. Improved targeting and imaging properties were shown in mice using single photon emission computed tomography-computer tomography (SPECT-CT), a handheld gamma camera, and magnetic resonance imaging (MRI).

New approaches in nuclear medicine for early diagnosis of Alzheimer's disease

Dementia, Alzheimer's disease (AD) being the most common cause of it, is a major and growing medical and social problem, particularly in the advanced age, with the highest rate in the population over 75 y. Recent sophisticated therapeutic measures require more sensitive diagnostic tests to recognize early stages of the disease. In this paper, the current neuronuclear imaging literature is reviewed with regard to early and differential diagnosis of dementia. Functional imaging with single photon emission computed tomography (SPECT) and positron emission tomography (PET) could provide the clinician with additional information complementary to morphological assessments, thus contributing to achieve a more adequate diagnosis, and also with information regarding prodromal stages of AD.

Ultrasonic imaging of sheet metal forming

With sheet metal hydroforming, a sheet metal is formed by a liquid medium under high pressure (up to 1000 bar) and a cavity contour (die). As the exact state of forming is of interest, an ultrasonic imaging system is under development. The task is to determine the geometry of a sheet metal contour with respect to the original (before forming) and the final (die) state of the sheet metal. For this purpose, two different contour reconstruction algorithms were designed, tested and compared. With the reconstruction results it will be possible to determine the optimal distribution of transmitters and receivers in the ultrasonic transducer matrix. Experiments were conducted with one pair of transducers (unfocussed, center frequency 2 MHz) and a three axis stepper motor set-up. For each experimental set of data, the contour was reconstructed with both SAFT reconstruction algorithms. Both algorithms incorporate a priori information such as original and final contour and maximal axial dislocation of the sheet metal. The results for both algorithms are compared and the relative mean error in axial direction is 0.30% and 0.48%.

Metabolic impairment of brain metabolism in patients with Lewy body dementia

A reliable assessment of dementia is essential for a differentiated treatment. Recent studies have demonstrated a poor accuracy of clinical criteria for diagnosis of Lewy body dementia. Diffuse Lewy body disease (LBD) is the second most common cause of senile degenerative dementia and is characterized histologically by the occurrence of Lewy bodies in allocortical, neocortical and subcortical structures. Seven male patients (mean age 81 years) with clinically suspected diffuse LBD were investigated with 18F-fluorodeoxyglucose (FDG)-PET using a Siemens ECAT-ART PET-scanner. The 18F-FDG-PET showed a diffuse glucose hypometabolism in the entire cerebral cortex with relative sparing of the primary sensory-motor cortex in all patients. This diffuse metabolic impairment in the entire cortex with relative sparing of central region seems to be a typical pattern for LBD, distinct from Alzheimer's disease.

[New design concept to improve medical application software]

Up to now, there has been no software model available that adequately addresses the growing importance of flexibility in using different information tools. Based on Java, Jini technology provides distributed and therefore robust software architecture. In case of an application crash, Jini is able to minimize the damage by adding functions that reverse the effects of the crash. Owing to increasing user mobility, it is necessary to be able to receive location-independent information. The growing use of powerful telecommunications suggests the application of 'wireless application protocol' (WAP) mobile telephones also for medical purposes. This paper presents the application of these new software trends (Jini and wireless application protocol).

Sentinel lymph node detection with large human serum albumin colloid particles in breast cancer

Detection of metastatic involvement of lymph nodes is essential for management and prognostic evaluation in breast cancer patients. The success of lymphatic mapping depends on identifying the sentinel lymph node(s) draining the primary tumour. However, when mapping is performed with a radiocolloidal agent, the number of hot lymph nodes varies with the agent and its size, among other factors. In this study, we evaluated prospectively the detection rate of sentinel lymph nodes in breast cancer when injecting large particles (100-600 nm) of human serum albumin colloids (Senti-Scint). In 128 consecutive breast cancer patients without palpable lymph nodes, pre-operative static lymphoscintigraphic mapping of the breast was performed after subcutaneous injection of 15 MBq of the radiocolloid. Lymphoscintigrahic results were compared with intra-operative surgical gamma detection probe and blue dye mapping data. Pre-operative lymphoscintigraphy and surgical gamma detection probe both correctly detected 203 sentinel lymph nodes in 122/128 patients (95%), while blue dye mapping showed only 183 sentinel lymph nodes in 82% of the patients. Only one or two sentinel lymph nodes were identified in each patient, which allowed the surgeon easily to find the sentinel lymph node(s) intra-operatively. In conclusion, lymphoscintigraphy with large particles of human serum albumin colloids is a helpful and reliable procedure for the surgical management of breast cancer.

[Determination of therapy management in rectal carcinoma by staging with 18-FDG-PET]

The curative treatment of carcinoma of the rectum in the early stage of the disease is radical local surgery. If there is a solitary liver metastasis, resection is also a curative treatment. This report describes a female patient with rectal carcinoma, in whom a solitary liver metastasis in the left lobe was diagnosed only by FDG-PET and verified at surgery. This case report demonstrates the potential role of FDG-PET even for primary staging in detecting occult hepatic and extrahepatic metastases, thus significantly influencing the therapeutic management and prognosis of these patients.

Regional cerebral blood flow in patients suffering from post-traumatic stress disorder

OBJECTIVE

The aim of the study was to determine whether regional cerebral blood flow in survivors of torture suffering from post-traumatic stress disorder (PTSD) differed significantly from that in healthy controls.

METHOD

We examined the cerebral regional distribution of 99m-technetium-hexamethylpropyleneamineoxime (HMPAO) using single photon emission computed tomography (SPECT) in 8 patients and in 8 healthy controls. A semi-quantitative analysis was performed in which symmetrical regions of interest (ROI) were drawn in all subjects.

RESULTS

Regional blood flow was markedly more heterogeneous in patients suffering from PTSD than in healthy controls. The differences are significant.

CONCLUSION

Severe psychological trauma induced by torture can cause neurobiologic alterations that may contribute, even years after the original trauma, to a number of complaints commonly expressed by patients suffering from PTSD.

Distributed nuclear medicine applications using World Wide Web and Java technology

At present, medical applications applying World Wide Web (WWW) technology are mainly used to view static images and to retrieve some information. The Java platform is a relative new way of computing, especially designed for network computing and distributed applications which enables interactive connection between user and information via the WWW. The Java 2 Software Development Kit (SDK) including Java2D API, Java Remote Method Invocation (RMI) technology, Object Serialization and the Java Advanced Imaging (JAI) extension was used to achieve a robust, platform independent and network centric solution. Medical image processing software based on this technology is presented and adequate performance capability of Java is demonstrated by an iterative reconstruction algorithm for single photon emission computerized tomography (SPECT).

Scintimammography enhances negative predictive value of non-invasive pre-operative assessment of breast lesions

AIMS

The aim of this study was to develop a criterion with a high negative predictive value for the evaluation of breast lesions. We aimed to determine the value of combining three non-invasive tests, mammography (MM), ultrasonography (USS) and 99mTc-methoxyisobutylisonitrite (99mTc-MIBI) scintimammography (scinti-MM).

METHODS

We included 94 consecutive patients with suspected lesions detected by mammography or on physical examination. MM, USS and scinti-MM were performed no more than 4 weeks prior to excisional biopsy in all patients. We then compared the biopsy results with a score calculated for each patient, derived from the results of the three tests, which we termed 'mamma malignancy index' (MMI).

RESULTS

Each of the three exams yielded a score ranging from 0 to 2, with 0 representing an almost certainly benign lesion, 1 an indeterminate finding and 2 a likely malignant lesion, and hence giving a total score ranging from 0 to 6. The biopsy results showed that the lesions in 64 patients were benign. Forty-nine (77%) of these patients had received an MMI score of 0 or 1. The negative predictive value for malignancy in patients with a score less than 2 was 100%.

CONCLUSIONS

Since the smallest detected lesion was 9 mm in diameter, we conclude that MMI may be a highly useful diagnostic tool in the delineation of breast lesions > or =1 cm which should not be routinely referred for biopsy but may be followed non-invasively. Although fine needle aspiration has limitations, we would recommend it as a less invasive method to evaluate suspected lesions smaller than 1 cm.

A Jini service to reconstruct tomographic data

Distributed computing that uses dynamic networks will change the way we work and communicate thanks to the interaction of devices and services, that are automatically added and removed from the network as needed. The Jini technology, which is built atop the Java programming language, provides a homogenous view of the network and extends the ability of code to migrate in Java. This software design model simplifies the configuration and access to hardware devices and software services in a network. Thus, it becomes possible to execute new services without pre-installing software on client machines. This new programming paradigm is especially important in medical applications, where the reliable transmission of information is essential. This paper demonstrates how single photon emission computerized tomography data can be iteratively reconstructed using a Jini service.