Posterior eye delivery of angiogenesis-inhibiting RNA nanoparticles via subconjunctival injection

Neovascularization contributes to various posterior eye segment diseases such as age-related macular degeneration and diabetic retinopathy. RNA nanoparticles were demonstrated previously to enter the corneal and retinal cells after subconjunctival injection for ocular delivery. In the present study, antiangiogenic aptamers (anti-vascular endothelial growth factor (VEGF) and anti-angiopoietin-2 (Ang2) aptamers) were conjugated to RNA nanoparticles. The objectives were to investigate the clearance and distribution of these angiogenesis-inhibiting RNA nanoparticles after subconjunctival injection in vivo and their antiangiogenic effects for inhibiting ocular neovascularization in vitro. The results in the whole-body fluorescence imaging study showed that the clearance of RNA nanoparticles was size-dependent with no significant differences between RNA nanoparticles with and without the aptamers except for pRNA-3WJ. The distribution study of RNA nanoparticles by confocal microscopy of the dissected eye tissues in vivo indicated cell internalization of the larger RNA nanoparticles in the retina and retinal pigment epithelium after subconjunctival injection, and the larger nanoparticles with aptamers showed higher levels of cell internalization than those without. In the cell proliferation assay in vitro, RNA nanoparticles with multiple aptamers had higher antiangiogenic effects. With both longer retention time and high antiangiogenic effect, SQR-VEGF-Ang2 could be a promising RNA nanoparticle for posterior eye delivery.

Effect of Receptor Solution in Studies of In Vitro Permeation Test (IVPT)

In Vitro Permeation Test (IVPT) is commonly used to evaluate skin penetration of chemicals and performance of dermatological products. For a permeant with low aqueous solubility, an additive that is expected not to alter the skin barrier can be used in the receptor solution to improve permeant solubility. The objective of this study was to (a) evaluate the effects of these additives in IVPT receptor solution on skin permeability of model permeants and skin electrical resistance and (b) determine the solubility of the permeants in these receptor solutions. Bovine serum albumin (BSA), 2-hydroxypropyl-beta-cyclodextrin (HPCD), ethanol, nonionic surfactant Brij-98, and propylene glycol were the additives, and phosphate buffered saline (PBS) was the control. Steady-state skin permeability coefficients and resistances were determined. The receptor solutions examined in this study did not cause a significant increase in skin permeability or decrease in resistance (less than 40 % changes) except 25 % ethanol. The receptor solution containing 25 % ethanol induced an approximately twofold average increase in skin permeability and reduced skin electrical resistance by approximately threefold. The receptor solution of 2.5 % HPCD provided the highest levels of solubility for the model lipophilic permeants, while 0.2 % Brij-98 and 5 % ethanol showed the lowest solubility enhancement from those in PBS.

Dose-dependent effect on skin permeation of polar and non-polar compounds

The study of the relationship between the amount of drug applied to the skin and fraction of drug absorbed can improve our understanding of finite-dose percutaneous absorption in the development of topical products and risk assessment of hazardous chemical exposure. It has been previously shown that an increase in the dose applied to the skin leads to a decrease in the fraction of drug permeated the skin (dose-dependent effect). The objective of this research was to examine the dose-dependent effect using permeants of varying physiochemical properties. The dose-dependent effect was studied using human epidermal membrane under finite dose conditions in Franz diffusion cell with model permeants at doses ranging from 0.1 to 200 μg. The dose-dependent effect was evident with model permeants caffeine, corticosterone, dexamethasone, and estradiol, consistent with the relationship of decreasing fraction of dose permeated the skin at increasing the applied dose. However, no significant dose-dependent effect was observed for the polar model permeants urea, mannitol, tetraethyl ammonium, and ethylene glycol, suggesting different transport mechanisms for these permeants. It was also found that, at relatively high doses, estradiol, dexamethasone, and corticosterone could increase the permeation of polar and lipophilic permeants, which could counter the dose-dependent effect under the conditions studied.

[Investigation and factor analysis of postoperative surgical site infections in emergency abdominal surgery in China from 2018 to 2021 based on Chinese SSI Surveillance]

Objective: We investigated the incidence of surgical site infection (SSI) following emergency abdominal surgery (EAS) in China and further explored its risk factors, providing a reference for preventing and controlling SSI after EAS. Methods: This was an observational study. Data of patients who had undergone EAS and been enrolled in the Chinese SSI Surveillance Program during 2018-2021were retrospectively analyzed. All included patients had been followed up for 30 days after surgery. The analyzed data consisted of relevant patient characteristics and perioperative clinical data, including preoperative hemoglobin, albumin, and blood glucose concentrations, American Society of Anesthesiologists (ASA) score, grade of surgical incision, intestinal preparation, skin preparation, location of surgical site, approach, and duration. The primary outcome was the incidence of SSI occurring within 30 days following EAS. SSI was defined as both superficial and deep incisional infections and organ/space infections, diagnoses being supported by results of microbiological culture of secretions and pus. Secondary outcomes included 30-day postoperative mortality rates, length of stay in the intensive care unit (ICU), duration of postoperative hospitalization, and associated costs. The patients were classified into two groups, SSI and non-SSI, based on whether an infection had been diagnosed. Univariate and multivariate logistic regression analyses were performed to identify risk factors associated with SSI following EAS. Results: The study cohort comprised 5491 patients who had undergone EAS, comprising 3169 male and 2322 female patients. SSIs were diagnosed in 168 (3.1%) patients after EAS (SSI group); thus, the non-SSI group consisted of 5323 patients. The SSIs comprised superficial incision infections in 69 (41.1%), deep incision infections in 51 (30.4%), and organ or space infections in 48 (28.6%). Cultures of secretions and pus were positive in 115 (68.5%) cases. The most frequently detected organism was Escherichia coli (47/115; 40.9%). There were no significant differences in sex or body mass index between the SSI and non-SSI groups (both P>0.05). However, the proportion of individuals aged 60 years or older was significantly greater in the SSI than in the non-SSI group (49.4% [83/168] vs. 27.5% [1464/5323), χ2=38.604, P<0.001). Compared with the non-SSI group, the SSI group had greater proportions of patients with diabetes (11.9% [20/168] vs. 4.8% [258/5323], χ2=16.878, P<0.001), hypertension (25.6% [43/168] vs. 12.2% [649/5323], χ2=26.562, P<0.001); hemoglobin <110 g/L (27.4% [46/168] vs. 13.1% [697/5323], χ2=28.411, P<0.001), and albuminemia <30 g/L (24.4% [41/168] vs. 5.9% [316/5323], χ2=91.352, P<0.001), and a reduced rate of preoperative skin preparation (66.7% [112/168] vs. 75.9% [4039/5323], χ2=7.491, P=0.006). Furthermore, fewer patients in the SSI group had preoperative ASA scores of between one and two (56.0% [94/168] vs. 88.7% [4724/5323], χ2=162.869, P<0.001) in the non-SSI group. The incidences of contaminated and infected incisions were greater in the SSI group (63.1% [106/168] vs. 38.6% [2056/5323], χ2=40.854, P<0.001). There was a significant difference in surgical site distribution between the SSI and non-SSI groups (small intestine 29.8% [50/168] vs. 10.6% [565/5323], colorectal 26.2% [44/168] vs. 5.6% [298/5 323], and appendix 24.4% [41/168] vs. 65.1% [3465/5323]) χ2=167.897, P<0.001), respectively. There was a significantly lower proportion of laparoscope or robotic surgery in the non-SSI group (24.4 % [41/168] vs. 74.2% [3949/5323], χ2=203.199, P<0.001); the percentage of operations of duration less than 2 hours was significantly lower in the SSI than non-SSI group (35.7% [60/168] vs. 77.4% [4119/5323], χ2=155.487, P<0.001). As to clinical outcomes, there was a higher 30-day postoperative mortality rate (3.0%[5/168] vs. 0.2%[10/5323], χ2=36.807, P<0.001) and higher postoperative ICU occupancy rate (41.7% [70/168] vs. 19.7% [1046/5323], χ2=48.748, P<0.001) in the SSI group. The median length of stay in the ICU (0[2] vs. 0[0] days, U=328597.000, P<0.001), median total length of stay after surgery (16[13] vs. 6[5] days, U=128146.000, P<0.001), and median hospitalization cost (ten thousand yuan, 4.7[4.4] vs. 1.7[1.8], U=175965.000, P<0.001) were all significantly greater in the SSI group. Multivariate logistic regression analysis revealed that the absence of skin preparation before surgery (OR=2.435,95%CI: 1.690-3.508, P<0.001), preoperative albuminemia <30 g/L (OR=1.680, 95%CI: 1.081-2.610, P=0.021), contaminated or infected incisions (OR=3.031, 95%CI: 2.151-4.271, P<0.001), and laparotomy (OR=3.436, 95% CI: 2.123-5.564, P<0.001) were independent risk factors of SSI. Operative duration less than 2 hours (OR=0.465, 95%CI: 0.312-0.695, P<0.001) and ASA score of 1-2 (OR=0.416, 95% CI: 0.289-0.601, P<0.001) were identified as independent protective factors for SSI. Conclusions: It is important to consider the nutritional status in the perioperative period of patients undergoing EAS. Preoperative skin preparation should be conducted and, whenever possible, laparoscope or robot-assisted surgery. Duration of surgery should be as short as possible while maintaining surgery quality and improving patient care.

A novel inclusion complex of oxybenzone with C-methylresorcin[4]arene deters skin permeation

Oxybenzone (OXB), a very widely used sunscreen ingredient has the potential to block both UVA and UVB but can penetrate through skin. Studies have revealed its presence in the blood and urine of most humans, which may lead to long-term health effects. As the confined cavities of macrocycles can alter the physical and chemical properties of encapsulated guests, in this study, we investigated the formation of host-guest complexes between C-methylresorcin[4]arene and OXB. Combined experimental (NMR spectroscopy, UV/vis absorption, and fluorescence spectroscopy) and theoretical investigation confirmed the formation of a weak host-guest complex that had a 1 : 1 stoichiometry. Furthermore, skin permeation testing revealed that complexation by C-methylresorcin[4]arene significantly reduced the skin permeation of OXB which can potentially limit the harmful effects of this organic sunscreen.

Iontophoresis on Porcine and Human Gingiva

PURPOSE

Iontophoresis is a noninvasive method that enhances drug delivery using an electric field. This method can improve drug delivery to the tissues in the oral cavity. The effects of iontophoresis on gingival drug delivery have not been investigated. The objectives of this study were to (a) determine the flux enhancement of model permeants across porcine and human gingiva during iontophoresis, (b) examine the transport mechanisms of gingival iontophoresis, and (c) evaluate the potential of iontophoretically enhanced delivery for three model drugs lidocaine, ketorolac, and chlorhexidine.

METHODS

Passive and iontophoretic fluxes were determined with porcine and human gingiva using a modified Franz diffusion cell and model drugs and permeants. To investigate the transport mechanisms of iontophoresis, the enhancement from the direct-field effect was determined by positively and negatively charged model permeants. The electroosmosis enhancement effect was determined with neutral permeants of different molecular weight. The alteration of the gingival barrier due to electropermeabilization was evaluated using electrical resistance measurements.

RESULTS

Significant flux enhancement was observed during gingival iontophoresis. The direct-field effect was the major mechanism governing the iontophoretic transport of the charged permeants. Electroosmosis was from anode to cathode. The effective pore radius of the iontophoretic transport pathways in the porcine gingiva was ~0.68 nm. Irreversible electropermeabilization was observed after 2 and 4 h of iontophoresis under the conditions studied.

CONCLUSION

Iontophoresis could enhance drug delivery and reduce transport lag time, showing promise for gingival drug delivery.

Permeability of Fresh and Frozen Porcine and Human Gingiva and the Effect of Storage Duration

The gingiva is the target site for some topical drugs, but the permeability of human gingiva has not been systematically evaluated. Pigs are a common animal model for in vitro membrane transport studies. The objectives of this study were to: (a) determine the permeability coefficients of freshly excised human gingiva using model permeants, (b) compare the permeability coefficients of fresh human gingiva with those of fresh porcine gingiva, (c) evaluate the effect of freezing duration on the permeability of porcine gingiva, and (d) compare the permeability coefficients of fresh and cadaver (frozen) human gingiva. A goal was to examine the feasibility of using porcine gingiva as a surrogate for human gingiva. The potential of using frozen tissues in permeability studies of gingiva was also examined. Fresh and frozen porcine gingiva, fresh human gingiva, and frozen cadaver human gingiva were compared in the transport study with model polar and lipophilic permeants. The fresh porcine and human tissues showed similarities in the "permeability coefficient vs. octanol-water distribution coefficient" relationship. The porcine gingiva had a lower permeability than that of the human, with a moderate correlation between the permeability of the fresh porcine and fresh human tissues. The permeability of the porcine tissues for the model polar permeants increased significantly after the tissues were frozen in storage. Moreover, the frozen human cadaver tissue could not be utilized due to the high and indiscriminating permeability of the tissue for the permeants and large tissue sample-to-sample variabilities.

Chitosan capped-gold nanoparticles as skin penetration enhancer for small molecules: A study in porcine skin

Skin is considered one of the most convenient sites for drug administration. The present study evaluated the effect of gold nanoparticles stabilized by chitosan (CS-AuNPs) and citrate ions (Ci-AuNPs) on skin permeation of sodium fluorescein (NaFI) and rhodamine b base (RhB) as small model hydrophilic and lipophilic permeants, respectively. CS-AuNPs and Ci-AuNPs were characterized by transmitted electron microscopy (TEM) and dynamic light scattering (DLS). Skin permeation was investigated using porcine skin with diffusion cells and confocal laser scanning microscopy (CLSM). The CS-AuNPs and Ci-AuNPs were spherical-shaped nanosized particles (38.4±0.7 and 32.2±0.7 nm, respectively). The zeta potential of CS-AuNPs was positive (+30.7±1.2 mV) whereas that of Ci-AuNPs was negative (-60.2±0.4 mV). The skin permeation study revealed that CS-AuNPs could enhance the permeation of NaFI with enhancement ratio (ER) of 38.2±7.5, and the effect was superior to that of Ci-AuNPs. CLSM visualization suggested that skin permeation was enhanced by improving the delivery through the transepidermal pathway. However, the permeability of RhB, a lipophilic molecule, was not significantly affected by CS-AuNPs and Ci-AuNPs. Moreover, CS-AuNPs had no cytotoxic toward human skin fibroblast cells. Therefore, CS-AuNPs are a promising skin permeation enhancer of small polar compounds.

Characterization of Porcine Gingiva for Drug Absorption

Gingiva or gum is a part of the periodontium that surrounds the tooth. Its main function is to provide an effective barrier to both mechanical trauma and bacterial invasion. Gingiva is the target site for some topical drugs. The most common disease in gingiva is periodontal diseases (gum infections). Understanding the gingiva barrier properties could provide insights into approaches to effective drug delivery for the gingiva. Porcine gingiva was chosen as the model in the present membrane transport study. The permeability coefficients of gingiva were determined using a modified Franz diffusion cell with small diffusional area (0.03 cm2) and 12 model permeants with different physicochemical properties. The influences of edge effect and aqueous boundary layers were not observed in the modified diffusion cell setup for the small pieces of gingiva tissue samples. Lipophilic permeants exhibit higher permeability coefficients than hydrophilic permeants. A correlation was observed between the Log permeability coefficient (Log P) and Log octanol-water distribution coefficient (Log Dow) in the analysis. The permeant molecular weight (MW) was also a factor in the Log P vs. Log Dow relationship. The coefficient of Log Dow in this three-factor relationship (0.42) suggested that the gingiva barrier was less lipophilic than octanol.

Long-Term Antibody Release Polycaprolactone Capsule and the Release Kinetics in Natural and Accelerated Degradation

Although therapy using monoclonal antibodies (mAbs) has been steadily successful over the last 20 years, the means of delivery of mAbs has not been optimized, especially for long-term delivery. Frequent injections or infusions have been the current standard of care. In this study, we have developed a long-term antibody biodegradable implant using a porous polycaprolactone (PCL) capsule. It released bevacizumab (Bev) slowly for 8 months to date. The Bev release kinetics fit a drug release model with experimental data of the diffusion coefficient and partition coefficient through the polymer capsule. Since screening drug release profiles for the long term (>6 months) is time consuming, an accelerated degradation method was used after validating the characteristics of the PCL capsule in natural and accelerated degradation conditions. The correlation of the time period between natural and accelerated degradation was determined. Overall, the study suggests that mAbs can be released from a porous PCL capsule without an effect of the polymer degradation over a long period (∼6 months) and the long-term release kinetics can be determined by the accelerated degradation within 14 days.

Evaluation of in vitro cornea models for quantifying destructive effects of chemicals

In vitro models are available as alternatives for the Draize eye irritation test. However, most of the alternative models are not quantitative nor designed to evaluate the effects of chemicals on the corneal barrier such as those encountered in pharmaceutical and cosmetic products. The objective of the present study was to investigate tissue electrical resistance to provide sensitive in vitro testing of tissue alteration caused by chemicals in pharmaceutical and cosmetic formulations as a potential eye irritation testing approach. The experimental protocols for effective tissue resistance measurements were examined using two in vitro eye models: porcine cornea and EpiCorneal. In these models, a test chemical was applied to the cornea or EpiCorneal tissue for 1 min, and tissue resistances/conductances were measured at 1-60 min after the application. The changes in conductance of the tissues after exposure to the chemicals were shown to provide quantitative evaluations to the influence of the chemicals. A correlation was found between the two in vitro models. The results suggest that these models can provide quantitative in vitro assessments of chemical formulations such as those prepared by eye-irritating chemicals.

Modification of Small Dissolution Chamber System for Long-acting Periodontal Drug Product Evaluation

Conventional dissolution testing methods may not be suitable for long-acting periodontal drug products due to the small volume, slow fluid flow rate, and environment in the periodontal pocket. The objective of this study was to evaluate a 3D-printed small volume flow-through dissolution chamber system (modified from a previous study) for biorelevant and dose-discriminating testing. Three periodontal drug products with different dosage forms were tested: Atridox, Arestin, and PerioChip. Modifications were made to suit the specific characteristics of these dosage forms. No significant differences were observed between the % drug release profiles in vitro and in vivo except for Atridox. The differences observed with Atridox could be related to the exposing surface area of the drug product. Similar differences were observed from this effect in COMSOL model simulations. Overall, the drugs show reasonable in vitro-in vivo correlations (R² ≥ 0.91) with linear regression slopes close to unity. For dose discrimination between 75% and full dosing, significant differences were observed in the drug release data at specific time points of the products (p ≤ 0.05). The present results suggest that a small volume dissolution chamber with slow flow rate could potentially provide biologically relevant and dose-discriminating evaluations for periodontal drug products.

Passive and iontophoretic transport of pramipexole dihydrochloride across human skin microchannels created by microneedles in vitro

Skin microchannels (MCs) created by microneedles (MNs) provide a promising route for enhancing transdermal drug delivery. This study investigated passive and iontophoretic transport of pramipexole dihydrochloride (PXCl) across skin MCs created by polymer MN patches made of 1:2 polymethyl-vinyl-ether-co-maleic acid (PMVEMA) to polyvinyl alcohol (PVA) ratio. Permeation studies were performed in vitro using excised human skin under the conditions of (i) "poke-and-patch" and "poke-and-release" delivery approaches with varying concentration of PXCl in the formulations, (ii) drug-loaded dissolving MN (DMN) and hydrogel-forming MN (HGMN) type patches and (iii) combination of MNs and iontophoresis. The results showed that DMN patch greatly enhanced transdermal delivery of PXCl for both "poke-and-patch" and "poke-and-release" approaches as compared with the conventional delivery method. PXCl flux mainly resulted from the contribution of MC pathway created in skin and increased with increasing drug amounts in the formulations. Compared to DMN patch, HGMN patch provided more linear sustained drug delivery over 72 h. Electromigration was the main mechanism of PXCl iontophoresis through MCs and flux enhancement was found to be larger for HGMN patch than DMN patch. These results demonstrated the potential application of MN patches individually or combined with iontophoresis as an alternative method for PXCl administration.

Effect of Pulsed Direct Current on Iontophoretic Delivery of Pramipexole across Human Epidermal Membrane In Vitro

PURPOSE

Pulsed direct current (PDC) iontophoresis, by allowing skin depolarization, was suggested to provide more efficient ion transport, but the extent of its enhancement effect was unclear. PDC could also offer electric-customized drug delivery. This study examined the effect of PDC iontophoresis on transdermal delivery of pramipexole dihydrochloride (PXCl).

METHODS

Iontophoretic delivery of PXCl across human epidermal membrane from pH 7.0 solution was conducted in vitro using continuous direct current (DC) and 6- and 12-cycle PDC iontophoresis (0.5 mA/cm² and total applied duration of 6 h). Different parameters of PDC iontophoresis were studied, including current density (0.1, 0.2 and 0.5 mA/cm²) and on-off current dosing pattern (1 h/3 h, 0.5 h/3.5 h, and 0.2 h/3.8 h).

RESULTS

Both 6- and 12-cycle PDC iontophoresis protocols provided modulation of the permeation profile but delivered smaller amounts of PXCl (396 and 400 μg/cm², respectively) as compared with continuous DC iontophoresis (482 μg/cm²) at 24 h after 0.5 mA/cm² and 180 mA/cm² × min current dose application. Increasing applied current density from 0.1 to 0.5 mA/cm² increased the PDC iontophoretic flux of PXCl linearly from 5.3 to 14.6 μg/cm²·h (R² = 0.887). Varying the current level and duration but at the same applied current dose (36 mA/cm² × min), the total amount of PXCl delivered by PDC iontophoresis at 24 h was independent of the on-off dosing pattern studied (114-128 μg/cm²).

CONCLUSIONS

The results indicate that PDC iontophoresis can benefit transdermal delivery of PXCl in terms of controlling its permeation but does not enhance iontophoretic transport compared to continuous DC iontophoresis under the conditions studied.

Effect of pH on Iontophoretic Transport of Pramipexole Dihydrochloride across Human Epidermal Membrane

PURPOSE

Drugs with higher molecular charges generally show higher flux enhancement when electromigration is the main mechanism in transdermal iontophoresis. This study evaluated the effect of decreasing the formulation pH to increase the positive charges of pramipexole dihydrochloride (PXCl) on its iontophoretic transport across skin.

METHODS

In vitro transdermal iontophoresis of PXCl in buffer solution isotonized with either sodium chloride or mannitol were performed in a pH range of 3.0-7.0. Experiments of iontophoresis under symmetric condition with respect to donor and receiver pH and passive transport of the drugs after pretreatment with iontophoresis were conducted to investigate the transport mechanism involved.

RESULTS

Iontophoretic permeation of PXCl was pH-dependent in drug solution isotonized with mannitol. The iontophoretic flux of PXCl with valence z = +2 at pH 3.0 was half of that of PXCl with z = +1 at pH 7.0. The results suggest that the decrease in PXCl delivery at higher valence at pH 3 was mainly due to pH-dependent selectivity of PX ion permeation across the skin and not electroosmosis.

CONCLUSIONS

Skin permselectivity is a significant factor for iontophoretic transport of PXCl, and reducing formulation pH to increase the positive charges on PX ions did not enhance PXCl delivery.

Laser-Activated Drug Implant for Controlled Release to the Posterior Segment of the Eye

To treat chronic posterior eye diseases, frequent intravitreal injections or sustained-release drug implants are the current standard of care. Sustained-release drug implants often involve burst release of the drugs and the dosage from the implants cannot be controlled after implantation, which may lead to local side effects. The present study attempts to develop a dosage-controllable drug delivery implant that consists of a nanoporous biodegradable PLGA capsule and light-activated liposomes. Controllable drug release from the implant was achieved using a pulsed near-infrared (NIR) laser both in vitro and in vivo. The in vitro drug release kinetics from two different initial dose implants, 1000 and 500 μg, was analyzed by fitting zero-order and first-order kinetics, as well as the Korsmeyer-Peppas and Higuchi models. The 1000 and 500 μg implants fit the first-order and zero-order kinetics model, respectively, the best. The multiple drug releases in the vitreous were determined by an in vivo fluorimeter, which was consistent with the in vitro data. The dose released was also clinically relevant. Histology and optical and ultrasound imaging data showed no abnormality in the eyes received implant treatment, suggesting that the drug delivery system was safe to the retina. This on-demand dose-controllable drug delivery system could be potentially used for long-term posterior eye disease treatment to avoid frequent invasive injections.

[Clinical characteristics of recurrent appendicitis]

Objective: To analyze clinical characteristics of recurrent appendicitis. Methods: A retrospective cohort study was carried out. Clinical data of patients who underwent appendectomy due to acute appendicitis confirmed by pathology in the Affiliated Hospital of Qingdao University from January 2011 to December 2015 were analyzed retrospectively. Exclusion criteria: (1) age of less than 18 years;(2) chronic appendicitis; (3) periappendiceal abscess; (4) appendiceal mucocele or mucinous neoplasms; (5) appendiceal neuroendocrine tumors or cancers; (6) appendicitis during pregnancy; (7) concurrent AIDS, hematological disease, autoimmune disease, inflammatory bowel disease or advanced cancer; (8) other simultaneous surgery. A total of 373 patients were enrolled the study. These patients were divided into the recurrent group (133 cases) and the first episode group (240 cases) according to the previous history of antibiotic therapy for acute appendicitis. The prevalence of recurrent appendicitis was calculated, and the clinical characteristics were analyzed, including gender, age, comorbidities and preoperative CT images. Results: Of 373 patients, 209 were male and 164 were female, with a median age of 42 (18 to 88) years. Median recurrent time of the recurrent group was 4 (1 to 60) months. Compared to the first episode group, the recurrent group had higher proportion of age <50 years [71.4% (95/133) vs. 57.5% (138/240), χ(2)=7.081, P=0.008], higher proportion of concurrent diabetes [13.5% (18/133) vs. 5.4% (13/240), χ(2)=7.399, P=0.007], shorter onset time [(41.7±13.6) hours vs. (59.4±56.2) hours, t=-3.286, P=0.001], lower proportion of abdominal tension and rebound pain [57.9% (77/133) vs. 66.7% (160/240), χ(2)=5.065, P=0.024], lower score of modified Alvarado score [(5.6±1.9) point vs. (6.1±1.9) point, t=-2.417, P=0.016], lower WBC count [(10.5±4.6) ×10(9)/L vs. (11.5±4.5)×10(9)/L, t=-1.190, P=0.047], higher percentage of lymphocyte [(19.4±14.7)% vs. (16.1±13.3)%, t=2.069, P=0.039]. In the recurrent group, ratio of length of removed appendix ≥7 cm was higher as compared with the first episode group [44.4% (59/133) vs. 32.9% (79/240), χ(2)=4.808, P=0.028], while the ratio of complicated appendicitis was significantly lower [8.3% (11/133) vs. 22.9% (55/240), χ(2)=10.823, P=0.001]. CT images were available in 129 patients, intraluminal appendicoliths was found in 19 of 50 patients (38%) in the recurrent group, while in 16 of 79 patients (20.3%) in the first episode group, and there was statistically significant difference between the two groups (χ(2)=4.880, P=0.027). Conclusions: Clinical characteristics of recurrent acute appendicitis include age less than 50 years, concurrent diabetes, short onset time, less abdominal tension or rebound pain, low modified Alvarado score, low WBC count, high percentage of lymphocyte, appendix length longer than 7 cm, non-complicated appendicitis and intraluminal appendicoliths.

Patterns of COVID-19 on computed tomography imaging

PURPOSE

As the designated tertiary referral centre for infectious diseases in Hong Kong, our hospital received the city's first group of patients diagnosed with coronavirus disease 2019 (COVID-19). Herein, we studied the earliest patients admitted to our centre in order to clarify the typical radiological findings, particularly computed tomography (CT) findings, associated with COVID-19.

METHODS

From 22 January 2020 to 29 February 2020, 19 patients with confirmed COVID-19 underwent high-resolution or conventional CT scans of the thorax in our centre. The CT imaging findings of these patients with confirmed COVID-19 in Hong Kong were reviewed in this study.

RESULTS

Ground-glass opacities (GGO) with peripheral subpleural distribution were found in all patients (100%). No specific zonal predominance was observed. All lobes were involved in 16 (84.2%) patients, focal subsegmental consolidations were observed in 14 (73.7%) patients, and interlobular septal thickening was present in 12 (63.2%) patients. No mediastinal lymph node enlargement, centrilobular nodule, or pleural effusion was detected in any of the patients. Other imaging features present in several patients include bronchial dilatation, bronchial wall thickening, and crazy-paving patterns.

CONCLUSIONS

Peripheral subpleural GGO without zonal predominance in the absence of centrilobular nodule, pleural effusion, and lymph node enlargement were consistent findings in patients with confirmed COVID-19. The observed radiological patterns on CT scans can help identify COVID-19 and assess affected patients in the context of the ongoing outbreak.

Evaluation of Heat Effects on Fentanyl Transdermal Delivery Systems Using In Vitro Permeation and In Vitro Release Methods

Experimental conditions that could impact the evaluation of heat effects on transdermal delivery systems (TDS) using an in vitro permeation test (IVPT) and in vitro release testing (IVRT) were examined. Fentanyl was the model TDS. IVPT was performed using Franz diffusion cell, heating lamp, and human skin with seven heat application regimens. IVRT setup was similar to IVPT, without using skin. Dissolution study was conducted in a modified dissolution chamber. The activation energy of skin permeation for fentanyl was determined using aqueous solution of fentanyl. In IVPT, the increase of temperature from 32 °C to 42 °C resulted in a 2-fold increase in flux for fentanyl TDS, consistent with the activation energy determined. The magnitude of flux increase was affected by the heat exposure onset time and duration: higher flux was observed when heat was applied earlier or following sustained heat application. Heat induced flux increases could not be observed when inadequate sampling time points were used, suggesting the importance of optimizing sampling time points. Drug release from TDS evaluated using IVRT was fast and the skin was the rate-limiting barrier for TDS fentanyl delivery under elevated temperature.

Evaluation of Heat Effects on Transdermal Nicotine Delivery In Vitro and In Silico Using Heat-Enhanced Transport Model Analysis

A combined experimental and computational model approach was developed to assess heat effects on drug delivery from transdermal delivery systems (TDSs) in vitro and nicotine was the model drug. A Franz diffusion cell system was modified to allow close control of skin temperature when heat was applied from an infrared lamp in vitro. The effects of different heat application regimens on nicotine fluxes from two commercial TDSs across human cadaver skin were determined. Results were interpreted in terms of transport parameters estimated using a computational heat and mass transport model. Steady-state skin surface temperature was obtained rapidly after heat application. Increasing skin surface temperature from 32 to 42°C resulted in an approximately 2-fold increase in average nicotine flux for both TDSs, with maximum flux observed during early heat application. ANOVA statistical analyses of the in vitro permeation data identified TDS differences, further evidenced by the need for a two-layer model to describe one of the TDSs. Activation energies associated with these data suggest similar temperature effects on nicotine transport across the skin despite TDS design differences. Model simulations based on data obtained from continuous heat application were able to predict system response to intermittent heat application, as shown by the agreement between the simulation results and experimental data of nicotine fluxes under four different heat application regimens. The combination of in vitro permeation testing and a computational model provided a parameter-based heat and mass transport approach to evaluate heat effects on nicotine TDS delivery.

Modeling Temperature-Dependent Dermal Absorption and Clearance for Transdermal and Topical Drug Applications

A computational model was developed to better understand the impact of elevated skin temperatures on transdermal drug delivery and dermal clearance. A simultaneous heat and mass transport model with emphasis on transdermal delivery system (TDS) applications was developed to address transient and steady-state temperature effects on dermal absorption. The model was tested using representative data from nicotine TDS applied to human skin either in vitro or in vivo. The approximately 2-fold increase of nicotine absorption with a 10°C increase in skin surface temperature was consistent with a 50-65 kJ/mol activation energy for diffusion in the stratum corneum, with this layer serving as the primary barrier for nicotine absorption. Incorporation of a dermal clearance component into the model revealed efficient removal of nicotine via the dermal capillaries at both normal and elevated temperatures. Two-compartment pharmacokinetic simulations yielded systemic drug concentrations consistent with the human pharmacokinetic data. Both in vitro skin permeation and in vivo pharmacokinetics of nicotine delivered from a marketed TDS under normal and elevated temperatures can be satisfactorily described by a simultaneous heat and mass transfer computational model incorporating realistic skin barrier properties and dermal clearance components.

Size-Exclusive Nanoporous Biodegradable PLGA Capsules for Drug Delivery Implants and In Vivo Stability in the Posterior Segment

The current standard of care for posterior segment eye diseases, such as neovascular age-related macular degeneration, diabetic macular edema, is frequent intravitreal injections or sustained-release drug implants. Intravitreal injections have a low incidence of serious complications such as retinal detachment, endophthalmitis, iatrogenic traumatic cataract, or iridocyclitis and injection-site reactions. However, there is a significant burden to the patient, the patient's family, and the health system because current intravitreal therapies require between every 4 and 12 week administration over many years. Drug implants have side effects due to the burst release of the drugs, and their release cannot be easily controlled after implantation. We have developed a size-exclusive nanoporous biodegradable PLGA capsule for dosage-controllable drug delivery implants. We have optimized the nanoporous structure by tuning the ratio between porogen and high molecular weight PLGA and tested the stability against passive leakage of the liposomal drug (1-2 μm) and the safety in vivo rabbit eyes for 6 months. Our results suggest that PLGA implants made of the nanoporous PLGA sheet can selectively release drug molecules, keeping the liposomal drug inside. In addition, the implant was biocompatible, causing no inflammation and foreign body response when implanted for 6 months. Overall, the implant shows great potential for on-demand dose-controllable drug release applications.

Transscleral Iontophoresis for Noninvasive Ocular Drug Delivery of Macromolecules

Purpose: The objectives were to investigate the effect of transscleral iontophoresis of macromolecules in vitro and in vivo, to study the importance of electroosmosis on macromolecules of low charge to mass ratio, and to evaluate transscleral iontophoresis efficacy in a choroidal neovascularization (CNV) animal model. Methods: Through in vitro transport experiments, the permeability coefficients of macromolecules [eg, immunoglobulin G (IgG), dextran 70 kDa] were determined under different conditions. The effect of ionic strength formulations and iontophoretic conditions was studied on the distribution of IgG and bevacizumab into the eye in vivo. Magnetic resonance imaging (MRI) was utilized to evaluate in vivo real time distribution of gadolinium-labeled albumin (Galbumin) following iontophoresis. The efficacy between no treatment, intravitreal injection (IVT), and iontophoresis of bevacizumab on a CNV model of subretinal injection of adeno-associated virus encoding human VEGF-165 was investigated. Results: The permeability data suggested a significant effect of ionic strength on the iontophoretic transport of macromolecules. Transscleral iontophoresis of IgG at 4 mA with a low ionic strength formulation was about 600 times greater than passive diffusion and 14-fold over a conventional formulation in vitro. Approximately 0.6 mg of bevacizumab can be delivered into the rabbit eye in vivo with a 20-min treatment of iontophoresis. MRI showed that Galbumin was in the posterior tissues after iontophoresis. In the CNV model, the iontophoresis and IVT methods of bevacizumab delayed retinal neovascularization by 4 and 8 weeks, respectively. Conclusions: Transscleral iontophoresis is capable of delivering macromolecule drugs through the conjunctiva and sclera, eventually exposing the retina/choroid to the drugs.

Influence of skin furrows on tape stripping in characterizing the depth of skin penetration

The stratum corneum (SC), the outermost layer of the skin and its major barrier for penetration, contains furrows of different depths on its surface. The presence of these furrows might lead to erroneous interpretation of the results in skin permeation studies using tape stripping, in which the material trapped in the furrows removed by the tapes representing different layers of the SC might be interpreted as material penetrating within these layers. The present objective was to investigate the effect of skin furrows on tape stripping results. Non-penetrating fluorescent materials were topically applied to split-thickness human and full-thickness porcine skin samples. Tape stripping was applied, and the tapes were assessed by fluorescence microscopy and quantitative analyses. The microscopy images were assessed visually to determine the presence of the applied material in the furrows. The penetration depth of the material was examined and the fluorescence content and pattern in each tape were analyzed. The results suggested that skin furrows could be important in the first 10 tapes, affecting the quantification of materials in the SC, particularly in permeation studies of materials with low penetration into the SC. Depending on the properties of the materials, skin rinsing could reduce the impact of furrows.

Compatibility of Melphalan in Iodinated Contrast Media

Melphalan is used in selective ophthalmic artery infusion chemotherapy. In the procedure to catheterize the ophthalmic artery in selective ophthalmic artery infusion chemotherapy, the microcatheter is usually filled with an iodinated contrast medium. It is not known whether mixing of iodinated contrast medium with melphalan solutions promotes precipitation of melphalan during selective ophthalmic artery infusion chemotherapy. The objective of the present study was to examine the compatibility of melphalan and iodinated contrast medium. In the experiments, melphalan solutions were prepared with and without iodinated contrast medium (iohexol 300 mg Iodine/mL or ioversol 74%). Melphalan solution of clinically relevant concentration (0.45 mg/mL) in the absence of iodinated contrast medium was evaluated as a reference. The 0.45-mg/mL melphalan solution was diluted with iodinated contrast medium at 1:9 and 1:1 ratios to form solutions comprising iodinated contrast medium at 10% or 50% (v/v), and each was evaluated. The formation of particles was examined using filtration (pore size 0.45 µm) followed by high-performance liquid chromatography at four quarterly time intervals (15 min, 30 min, 45 min, and 60 min) over a 1-hour period after solution preparation. High-performance liquid chromatography analysis of microfiltered solutions did not reveal evidence of melphalan crystal formation over a 60-minute period for the solutions studied. The filtration studies suggest that mixing of the iodinated contrast medium with melphalan solutions does not result in significant melphalan precipitation.

Dissolution Chamber for Small Drug Delivery System in the Periodontal Pocket

Existing dissolution chambers have relatively large volume compared to the size of the periodontal pocket. A small volume dissolution method that simulates the physiological release environment for periodontal drug delivery is needed. The objectives were to construct a small, more physiologically relevant, dissolution chamber and investigate the properties of the new dissolution chamber for the assessment of sustained drug release systems in periodontal delivery. Flow-through dissolution chambers were constructed using three-dimensional (3D) printing. Drug release experiments were performed using the dissolution chamber and a commercially available long-acting periodontal insert product, PerioChip®. Similar experiments were performed under more traditional larger volume bulk solution conditions for comparison. Computer simulations and experimental results showed that drug clearance from the dissolution chamber was fast compared to drug release from the periodontal product. Drug clearance from the flow-through dissolution chamber and drug release from the sustained release product in the chamber were related to the dissolution medium flow rate and chamber volume. Drug release in the flow-through chamber was slower than that observed in bulk solution, but approached it when the medium flow rate increased. The presence of trypsin in the dissolution medium enhanced drug release from the product. A flow-through dissolution system was constructed that could evaluate drug release from a sustained release product in a small dimension environment by modifying the flow rate and composition of the dissolution medium.

In Vitro Penetration of Petrolatum in Stratum Corneum from Bodywash Formulation

Petrolatum is a mixture of hydrocarbons that is widely used as a moisturizer. It is incorporated in bodywash formulations to help hydrate and maintain healthy skin appearance. The aim of this study was to investigate skin deposition and penetration of petrolatum from an experimental bodywash system consisting of petrolatum in vitro. Experiments were performed using cadaver split-thickness skin and Franz diffusion cells. Radiolabeled ¹⁴C-dotriacontane (C₃₂-alkane) was used as a model permeant for petrolatum. The bodywash was applied on the skin and subsequently rinsed. At predetermined time points, the skin was wiped to remove the residual material on the surface, and tape-stripping was performed. Petrolatum was observed to deposit from the bodywash when applied on split-thickness skin with simulated rinsing. Petrolatum then penetrated into the stratum corneum and was detected at the depth of 12 tape-stripping and in the epidermis. The bodywash formulation could provide significant deposition and penetration of petrolatum into the stratum corneum at 1-72 hours postapplication.

Influencing factors on gelatin matrix for chlorhexidine delivery

OBJECTIVE

The objective was to evaluate the influencing factors in the fabrication of gelatin matrix (gelatin chips) for drug delivery. The attributes affecting drug release characteristics of the gelatin products were examined.

SIGNIFICANCE

Understanding the attributes that affect drug release from gelatin matrix could provide the knowledge base for the development, manufacturing, and performance evaluation of gelatin-based drug products for sustained drug delivery.

METHODS

Chlorhexidine (CHX) was the model drug in the gelatin-product testing. The gelatin products were fabricated by two methods: a single-pot mixing of all the components and a two-step gelatin crosslinking followed by drug loading. Different gelatin types (Type A porcine and Type B bovine), glutaraldehyde (GTA) crosslinking conditions, glycerin concentration, and CHX concentration in drug loading and loading time were used to fabricate the products. The cumulative amounts of CHX release from the gelatin products were determined using in vitro release testing (IVRT).

RESULTS

The attributes affecting CHX release from the gelatin products were gelatin type, GTA crosslinking, and CHX loading concentration. The fabrication methods (two-step method of gelatin crosslinking and drug loading by equilibration vs. direct mixing of the components) also affected CHX release. Other attributes such as glycerin and CHX loading time did not show significant effects on drug release under the conditions studied. In addition, the results in the two IVRT methods employed in this study were comparable.

CONCLUSION

Gelatin products of qualitative (Q1) and quantitative (Q2) differences could lead to different drug release behaviors. Drug release was also affected by the ingredient mixing steps during gelatin chip fabrication.

Skin Permeation Enhancement in Aqueous Solution: Correlation With Equilibrium Enhancer Concentration and Octanol/Water Partition Coefficient

The effectiveness of skin penetration enhancers and the enhancer concentration required for effective skin permeation enhancement are difficult to predict. A comprehensive quantitative structure-enhancement relationship of chemical penetration enhancers for skin permeation is not currently available. The present study (a) investigated the relationship between skin permeation enhancement and chemical enhancer concentration and (b) examined a simple quantitative structure-enhancement relationship for predicting skin permeation enhancement to guide enhancer formulation development. In the present analysis, data from previous skin permeation studies that used the symmetric/equilibrium configuration and skin parallel pathway model were summarized to determine the relationship between enhancement factor and enhancer concentration. Under the equilibrium conditions, semilogarithmic linear relationships between enhancement factor (E) and enhancer aqueous concentration (C) were observed and an enhancer potency parameter (α) was defined. A correlation between the potency parameter α and enhancer octanol/water partition coefficient (Koct) was obtained. The enhancement factor relationship was derived: Log E = 0.32 ∙ C ∙ Koct. The results suggest that a "threshold" of (C ∙ Koct) > 0.5 M is required to induce effective skin permeation enhancement under these conditions. Consistent with the analyses in previous studies, the data suggest that octanol represents the skin barrier microenvironment for the penetration enhancers.

In vitro skin penetration of petrolatum and soybean oil and effects of glyceryl monooleate

OBJECTIVES

Petrolatum and soybean oil are common ingredients incorporated in topical skin formulations for skin protection and moisturization. However, the stratum corneum (SC) penetration kinetics of these two cosmetic ingredients has not been systematically studied. Glyceryl monooleate (GlyMOle) has been shown to enhance skin penetration of various compounds. It was hypothesized that GlyMOle could enhance skin penetration of petrolatum and soybean oil. This study aimed to examine the in vitro skin penetration of petrolatum and soybean oil in the presence or absence of GlyMOle.

METHODS

Skin permeation experiments were conducted using the in vitro Franz diffusion cell model with split-thickness human skin and human epidermal membrane (HEM). The effect of permeant dose and the kinetics of permeant penetration were examined with and without GlyMOle in vitro.

RESULTS

Petrolatum and soybean oil were found to permeate across HEM, and no effect of GlyMOle on skin permeation into the receptor chamber was observed. GlyMOle enhanced the penetration of petrolatum into the split-thickness skin at 50 μg dose (petrolatum:GlyMOle, 49 : 1, w/w). However, no effect of GlyMOle on petrolatum penetration was observed at 200 μg dose (of the same petrolatum:GlyMOle ratio), indicating a dose-dependent effect. GlyMOle at the level used in the study did not enhance the penetration of soybean oil with 50 and 200 μg doses at any timepoints.

CONCLUSION

GlyMOle was a skin penetration enhancer for petrolatum under the in vitro conditions identified in this study.

Transepidermal water loss and skin conductance as barrier integrity tests

In vitro skin permeation studies are commonly used in the risk assessment of toxic compound skin exposure. The present study examined the utility of transepidermal water loss (TEWL) and electrical conductance as barrier integrity tests before skin permeation studies in vitro using a large number of skin samples and fentanyl. TEWL and conductance of the skin samples were measured before the permeation experiments in Franz diffusion cells in vitro with a vapometer and low voltage application, respectively. The data were analyzed based on the in vitro permeation results and in vivo skin absorption information from the transdermal fentanyl product labels. The results showed poor correlations between TEWL and electrical conductance for the skin samples. Weak correlations between fentanyl delivery rate (flux x area) and TEWL and skin conductance were observed. For comparison, TEWL and conductance were also examined after skin perturbation with a syringe needle, and both TEWL and conductance values of the skin samples increased after the perturbation. The data suggest that either TEWL of 10 g/m²/h or skin conductance of 0.07 mS/cm² can be used as exclusion criteria in skin integrity testing to remove skin samples with high permeabilities under the in vitro conditions studied.

Transscleral passive and iontophoretic transport: theory and analysis

INTRODUCTION

The sclera is considered the 'static barrier,' a main barrier for transscleral drug delivery. The characterization of passive and iontophoretic transport across the sclera in vitro is the first step toward our ability to predict transscleral drug delivery. Although previous studies have investigated this topic, the quantitative structure permeation relationships (QSPR) for passive and iontophoretic transscleral transport are not available.

AREAS COVERED

This review evaluated previous results of transscleral passive and iontophoretic transport in vitro and examined QSPR for transscleral permeation of small permeants and macromolecules. Passive permeation data in the literature were compared with respective to the animal species employed in the studies. Data variability was investigated. Electrotransport theory and the mechanisms of iontophoresis were reviewed and used to analyze the iontophoresis data.

EXPERT OPINION

QSPR was examined for passive transscleral permeation, showing correlations between logarithm of permeability coefficient and logarithm of molecular weight. Potential causes of data variability were proposed. QSPR were established for electroosmosis using the molecular weight of neutral permeants and for iontophoresis enhancement using the molecular weight and charge of ionic permeants. However, QSPR for charged macromolecules were empirical; iontophoretic flux enhancement was significantly smaller than Nernst-Planck model prediction due to complicating factors.

Prolonged and localized sweat stimulation by iontophoretic delivery of the slowly-metabolized cholinergic agent carbachol

BACKGROUND

Continuous non-invasive sampling and sensing of multiple classes of analytes could revolutionize medical diagnostics and wearable technologies, but also remains highly elusive because of the many confounding factors for candidate biofluids such as interstitial fluid, tears, saliva, and sweat. Eccrine sweat biosensing has seen a recent surge in demonstrations of wearable sampling and sensing devices. However, for subjects at rest, access to eccrine sweat is highly limited and unpredictable compared to saliva and tears.

OBJECTIVE

Reported here is a prolonged and localized sweat stimulation by iontophoretic delivery of the slowly-metabolized nicotinic cholinergic agonist carbachol.

METHODS

Presented here are detailed measurements of natural baseline sweat rates across multiple days, confirming a clear need for localized sweat stimulation. Iontophoresis was performed with either carbachol or pilocarpine in order to stimulate sweat in subjects at rest. Furthermore, improved methods of quantifying sweat generation rates (nL/min/gland) are demonstrated.

RESULTS

In-vivo testing reveals that carbachol stimulation can surpass a major goal of 24-h sweat access, in some cases providing more than an order of magnitude longer duration than stimulation with commonly-used pilocarpine. Also demonstrated is reduction of the traditional iontophoretic dosage for sweat stimulation (<5.25-42mC/cm²). This increases the viability of repeated dosing as demonstrated herein, and for carbachol is as much as 100-1000X less than used for other applications.

CONCLUSION

This work is not only significant for wearable sweat biosensing technology, but could also have broader impact for those studying topical skin products, antiperspirants, textiles and medical adhesives, nerve disorders, the effects of perspiration on skin-health, skin related diseases such as idiopathic pure sudomotor failure and hyperhidrosis, and other skin- and perspiration-related applications.

Magnetization reversal and magnetic interactions in anisotropic Nd-Dy-Fe-Co-B/MgO/α-Fe disks and multilayers

We report on a field induced domain evolutionary procedure in the anisotropic Nd-Dy-Fe-Co-B/MgO/Fe multilayers by using first-order-reversal-curves and magnetic force microscopy. Different reversal behaviors and domain sizes are found in well coupled and decoupled multilayers by changing the thickness of the spacer layer. The competition between dipolar magnetostatic energy and Zeeman energy is evaluated by in-field observation throughout nucleation and annihilation processes. In addition, lithography-patterned arrays of soft Fe disks onto a continuous Nd-Dy-Fe-Co-B hard-magnetic layer are designed. By decreasing the applied field, it is found that magnetization orientations of the Fe disk and Nd-Dy-Fe-Co-B layer are aligned parallel. In the decoupled disk, although the out-of-plane magnetization orientations are observed, the orientation of the domains in the Fe disk is random. Furthermore, it is found that a stronger anisotropy of the Nd-Dy-Fe-Co-B layer decreases the interaction length. Our results provide a new understanding of anisotropic nanocomposite magnets with long-ranged magnetic interactions.

Characterization of Temperature Profiles in Skin and Transdermal Delivery System When Exposed to Temperature Gradients In Vivo and In Vitro

PURPOSE

Performance of a transdermal delivery system (TDS) can be affected by exposure to elevated temperature, which can lead to unintended safety issues. This study investigated TDS and skin temperatures and their relationship in vivo, characterized the effective thermal resistance of skin, and identified the in vitro diffusion cell conditions that would correlate with in vivo observations.

METHODS

Experiments were performed in humans and in Franz diffusion cells with human cadaver skin to record skin and TDS temperatures at room temperature and with exposure to a heat flux. Skin temperatures were regulated with two methods: a heating lamp in vivo and in vitro, or thermostatic control of the receiver chamber in vitro.

RESULTS

In vivo basal skin temperatures beneath TDS at different anatomical sites were not statistically different. The maximum tolerable skin surface temperature was approximately 42-43°C in vivo. The temperature difference between skin surface and TDS surface increased with increasing temperature, or with increasing TDS thermal resistance in vivo and in vitro.

CONCLUSIONS

Based on the effective thermal resistance of skin in vivo and in vitro, the heating lamp method is an adequate in vitro method. However, the in vitro-in vivo correlation of temperature could be affected by the thermal boundary layer in the receiver chamber.

Understanding the formidable nail barrier: A review of the nail microstructure, composition and diseases

The topical treatment of nail fungal infections has been a focal point of nail research in the past few decades as it offers a much safer and focused alternative to conventional oral therapy. Although the current focus remains on exploring the ways of enhancing permeation through the formidable nail barrier, the understanding of the nail microstructure and composition is far from complete. This article reviews our current understanding of the nail microstructure, composition and diseases. A few of the parameters affecting the nail permeability and potential causes of the recurrence of fungal nail infection are also discussed.

Heat effects on drug delivery across human skin

INTRODUCTION

Exposure to heat can impact the clinical efficacy and/or safety of transdermal and topical drug products. Understanding these heat effects and designing meaningful in vitro and in vivo methods to study them are of significant value to the development and evaluation of drug products dosed to the skin.

AREAS COVERED

This review provides an overview of the underlying mechanisms and the observed effects of heat on the skin and on transdermal/topical drug delivery, thermoregulation and heat tolerability. The designs of several in vitro and in vivo heat effect studies and their results are reviewed.

EXPERT OPINION

There is substantial evidence that elevated temperature can increase transdermal/topical drug delivery. However, in vitro and in vivo methods reported in the literature to study heat effects of transdermal/topical drug products have utilized inconsistent study conditions, and in vitro models require better characterization. Appropriate study designs and controls remain to be identified, and further research is warranted to evaluate in vitro-in vivo correlations and the ability of in vitro models to predict in vivo effects. The physicochemical and pharmacological properties of the drug(s) and the drug product, as well as dermal clearance and heat gradients may require careful consideration.

Size and Charge Dependence of Ion Transport in Human Nail Plate

The electrical properties of human nail plate are poorly characterized yet are a key determinate of the potential to treat nail diseases, such as onychomycosis, using iontophoresis. To address this deficiency, molar conductivities of 17 electrolytes comprising 12 ionic species were determined in hydrated human nail plate in vitro. Cation transport numbers across the nail for 11 of these electrolytes were determined by the electromotive force method. Effective ionic mobilities and diffusivities at infinite dilution for all ionic species were determined by regression analysis. The ratios of diffusivities in nail to those in solution were found to correlate inversely with the hydrodynamic radii of the ions according to a power law relationship having an exponent of -1.75 ± 0.27, a substantially steeper size dependence than observed for similar experiments in skin. Effective diffusivities of cations in nail were 3-fold higher than those of comparably sized anions. These results reflect the strong size and charge selectivity of the nail plate for ionic conduction and diffusion. The analysis implies that efficient transungual iontophoretic delivery of ionized drugs having radii upward of 5 Å (molecular weight, ca. ≥ 340 Da) will require chemical or mechanical alteration of the nail plate.

Periocular Tissue Concentrations of Propranolol after Ocular Instillation of a Gel-Forming Solution

BACKGROUND

The aim of this study was to determine the concentrations of propranolol in periocular tissues and plasma after ocular instillation of 0.5% propranolol gel-forming solution (GFS) as compared to 0.5% propranolol non-gelforming solution (non-GFS) for potential use in the treatment of periocular capillary hemangiomas.

METHODS

A GFS prepared in 1% sodium alginate or a non-GFS in phosphatebuffered saline was instilled into the eyes of rabbits. At predetermined time intervals after dosing, blood was withdrawn, rabbits were euthanized, and periocular tissues were dissected.

RESULTS

Ocular instillation of the GFS resulted in higher concentrations of propranolol in the outer layers of both the upper and lower eyelids (in the range of 9.9-36.9 μg/g) and maintained higher levels of propranolol in these tissues for 24 h after dosing, as compared to the ocular instillation of the non-GFS (in the range of 3.4-15.1 μg/g). While the concentrations of propranolol in the other periocular tissues were generally similar for GFS and non-GFS at 1 h after dosing, the concentrations of propranolol in the extraocular muscles and periocular fat were higher for GFS than those for non-GFS between 4-24 h after dosing. Lower level of propranolol in plasma was observed at 1 h with GFS as compared with non-GFS.

CONCLUSION

The use of the propranolol gel-forming solution can prolong drug retention on the ocular surface and increase its distribution to the outer layers of the eyelids while decreasing systemic exposure to the drug.

Characterization of novel nitrate reductase-deficient mutants for transgenic Dunaliella salina systems

The aim of the present study was to isolate and characterize novel nitrate reductase (NR)-deficient mutants, which may be useful for the transgenic manipulation of Dunaliella salina. Three NR-deficient mutants of D. salina, J-1, J-2, and J-3, were successfully isolated by screening for chlorate resistance after chemical mutagenesis with ethylnitrosourea. NR activity was not detected in the mutants and the expression of NR mRNA was significantly decreased. Growth analysis of D. salina strains grown in media containing different nitrogen sources revealed that these mutants were capable of utilizing nitrite and urea, but not nitrate as a nitrogen source, indicating that these mutants are indeed NR-deficient. Mutation analysis of NR cDNA sequences revealed that there were 11 point mutations shared by the J-1, J-2, and J-3 mutants. Furthermore, the results of the functional complementation experiment showed that NR activity of transformant T-1 derived from J-1 was recovered to 48.1 % of that of the wild-type D. salina. The findings of the present study indicate that nitrate may be used as a selective agent rather than antibiotics or herbicides for the isolated NR-deficient mutants in future transgenic D. salina systems.

Diffusion of uncharged solutes through human nail plate

Passive diffusion data for uncharged solutes in hydrated human nail plate are collected and compared to the predictions of two theories for diffusion of uncharged solutes in dense keratin matrices. Quantitative agreement between the experimental data and the theories examined is poor. Concerns with both the experiments and the theories are identified and discussed. It is evident from the analysis that magnitude of the experimental nail permeability data may be questioned, as may the extrapolation procedures used to estimate the properties of dense fiber arrays from more dilute systems. Despite these caveats, it can be inferred that the microstructure of the nail plate is more complex than that assumed in the described models. The influence of residual lipids is implicated. More rigorous experiments and theoretical analysis of mass transport in the nail plate system are warranted. Successful completion of these tasks could lead not only to better predictions of transungual drug delivery, but also to better models of skin permeability, if hydrated nail plate can indeed serve as a model for the corneocyte phase of (partially hydrated) stratum corneum.