Simulated skin model for in vitro evaluation of insertion performance of microneedles: design, development, and application verification.

Microneedles, as a new efficient and safe transdermal drug delivery technology, has a wide range of applications in drug delivery, vaccination, medical cosmetology, and diagnostics. The degree of microneedles penetration into the skin determines the reliability of the delivery dose, but its evaluation is not yet well-established, which is one of the major constraints in the commercialization of microneedles. In this paper, a novel visual simulated skin model was developed with reference to the physical properties of real skin. The simulated skin model was well-designed and its prescription was optimized to make the thickness, hardness, elasticity, and other parameters close to those of real skin. It not only meets the need to assess the degree of insertion of microneedles but also provides a visual observation of the insertion state of microneedles.

Immune cell receptor-specific nanoparticles as a potent adjuvant for nasal split influenza vaccine delivery.

Mucosal delivery systems have gained much attention as effective way for antigen delivery that induces both systemic and mucosal immunity. However, mucosal vaccination faces the challenges of mucus barrier and effective antigen uptake and presentation. In particular, split, subunit and recombinant protein vaccines that do not have an intact pathogen structure lack the efficiency to stimulate mucosal immunity. In this study, poly (lactic acid-co-glycolic acid-polyethylene glycol) (PLGA-PEG) block copolymers were modified by mannose to form a PLGA-PEG-Man conjugate (mannose modified PLGA-PEG), which were characterized. The novel nanoparticles (NPs) prepared with this material had a particle size of about 150 nm and a zeta potential of -15 mV, and possessed ideal mucus permeability, immune cell targeting, stability and low toxicity. Finally, PLGA-PEG-Man nanoparticles (PLGA-PEG-Man NPs) were successfully applied for intranasal delivery of split influenza vaccine in rat for the first time, which triggered strong systemic and mucosal immune responses. These studies suggest that PLGA-PEG-Man NPs could function as competitive potential nano-adjuvants to address the challenge of inefficient mucosal delivery of non-allopathogenic antigens.

Coated Porous Microneedles for Effective Intradermal Immunization with Split Influenza Vaccine.

In order to alleviate the pain associated with subcutaneous injections, microneedles (MNs) are gaining increasing attention as a novel transdermal drug delivery modality. Among them, porous microneedles (pMNs) are particularly suitable for the delivery of drugs and vaccines whose activity is sensitive to the microneedle preparation process. They can carry drugs actively to achieve an effective load and deliver drugs into the skin. In this study, the biocompatible cellulose acetate (CA) microporous MNs with a large pore size of 1.13 µm ± 0.45 and a high porosity of 74.8% ± 2.8% were prepared by using a safe nonsolvent-induced phase separation (NIPS) method. The MN patches prepared after adsorption of appropriate concentrations of split influenza vaccine fully met the dose loading requirements. A biocompatible carboxymethyl cellulose (CMC) solution was used in the pMN coating to strengthen their mechanical properties, with an average maximum stress of 32.89 N, and to act as a medium for the dispersion of an adjuvant in the coating layer. The influenza vaccine adsorbed in the micropore and the adjuvant dispersed in the coating were released intradermally to exert synergistic effects with different release patterns and rates. The coated pMNs induced an efficient immune response in Wistar rats with a hemagglutination inhibition (HI) titer of ≥1024, which was comparable to that of intramuscular injection. The research is organized around the goal of engineering exploration of innovative technologies, suggesting that pMNs have a tantalizing prospect for future applications. It opens up the possibility of eventually obtaining a simple, easy-to-use, and efficient application technology for the prevention of global epidemics like influenza.

Porous Microneedles for Therapy and Diagnosis: Fabrication and Challenges.

The use of microneedles (MNs), an innovative transdermal technology, enables efficient, convenient, painless, and controlled-release drug delivery. Porous microneedles (pMNs), special MNs with abundant interconnected pores that can produce capillary action, are gaining increasing attention as a novel MNs technology. pMNs can actively adsorb bioactive ingredients from solutions of drugs or vaccines for in vivo delivery or from interstitial skin fluids (ISFs) for wearable and point-of-care testing (POCT) products. Different pore sizes and porosities of pMNs can be achieved with different materials and preparation processes, which makes the application of pMNs adaptable to multiple scenarios. In addition, easier and faster detection will be accomplished by the smart combination of pMNs with other detection technologies. This paper aims to summarize the recent research progress of pMNs, focusing on the influence of various materials and their corresponding preparation methods on its structure and function display, discussing the key issues and looking forward to the future development.

Bioimaging of Dissolvable Microneedle Arrays: Challenges and Opportunities.

The emergence of microneedle arrays (MNAs) as a novel, simple, and minimally invasive administration approach largely addresses the challenges of traditional drug delivery. In particular, the dissolvable MNAs act as a promising, multifarious, and well-controlled platform for micro-nanotransport in medical research and cosmetic formulation applications. The effective delivery mostly depends on the behavior of the MNAs penetrated into the body, and accurate assessment is urgently needed. Advanced imaging technologies offer high sensitivity and resolution visualization of cross-scale, multidimensional, and multiparameter information, which can be used as an important aid for the evaluation and development of new MNAs. The combination of MNA technology and imaging can generate considerable new knowledge in a cost-effective manner with regards to the pharmacokinetics and bioavailability of active substances for the treatment of various diseases. In addition, noninvasive imaging techniques allow rapid, receptive assessment of transdermal penetration and drug deposition in various tissues, which could greatly facilitate the translation of experimental MNAs into clinical application. Relying on the recent promising development of bioimaging, this review is aimed at summarizing the current status, challenges, and future perspective on in vivo assessment of MNA drug delivery by various imaging technologies.

[Study on In Vitro Degradation of Oxidized Regenerated Cellulose Absorbable Hemostatic Products].

OBJECTIVE: To study the in vitro degradation of oxidized regenerated cellulose absorbable hemostatic products. METHODS: The morphology of the oxidized regenerated cellulose hemostatic products before and after degradation was observed by FTIR and SEM. The degradation products were determined by GPC and HILIC-ELSD. RESULTS: In the initial stage of degradation, there was a great change in morphology. GPC determined its degradation end point was 10 d; it was determined that its degradation products contained glucose (0.13%) and cellobiose (0.17%) and other components. CONCLUSIONS: A method was established for determining the end point of degradation of oxidized regenerated cellulose, which provided a new idea and reference for the study of the degradation end point.

Application of composite dissolving microneedles with high drug loading ratio for rapid local anesthesia.

We report a type of dissolving microneedles (DMNs) which was made of composite matrix materials of hydroxypropyl methyl cellulose (HPMC) and poly(methylvinylether­co­maleic anhydride) (PMVE/MA copolymer, Gantrez S-97), and was successfully loaded with lidocaine hydrochloride. The weight of lidocaine hydrochloride loaded in the microneedles tip was 70% of the weight of the whole tip. The content was 3.43 ±â€¯0.12 mg in weight, which was determined by high performance liquid chromatography (HPLC). The results for mechanical test showed that these microneedles were able to penetrate into the skin of the experimental animals, that was proved using organic staining, texture analyzer and histological examination. The fracture force of the microneedles was 5.442 ±â€¯0.412 N, which was much higher than the one required for the skin penetration. The DMNs with lidocaine hydrochloride could be dissolved inside of the rat skin in 5 min. The onset time would be faster (in <5 min) when it was applied to the guinea pig model, in comparing with a commercially available anesthesia cream that had an onset time for 100 min. However, the efficacy of the DMNs for the local anesthesia only lasted for 16 min. It was shorter than that of the commercially available anesthesia cream with which the efficacy could last for about 130 min. After the DMNs was packaged under the vacuum and dark condition, it was stable for 3 months under the condition of a temperature of 40 ±â€¯2 °C and a humidity of 75 ±â€¯5%. The result of the experiment for the safety evaluation showed that the microneedles were non-irritating and non-allergenic to the skin. In conclusion, the DMNs with lidocaine hydrochloride could be safely administered to the skin with a quick onset time for the local anesthesia.

Preparative separation and purification of two highly polar alkaloids derived from Semen Strychni extracted with dichloromethane by high-speed countercurrent chromatography.

Brucine chloromethochloride and strychnine chloromethochloride, the two chloromethochloride derivatives formed during the extraction of Semen Strychni in which dichloromethane was used as the extracting solvent, were isolated and purified by high-speed countercurrent chromatography for the first time. The two-phase solvent system composed of chloroform/methanol/0.3 mol/L hydrochloric acid (4:3:2, v/v/v) was selected for separation. From 300 mg of the crude extracts, 56.2 mg of brucine chloromethochloride and 60.2 mg of strychnine chloromethochloride were obtained with the purity of 99.78 and 96.99%, respectively, and the structures were confirmed by mass spectrometry, 1 H, 13 C, and two-dimensional NMR spectroscopy. The results indicated that the present method is a powerful technology for large-scale isolation of alkaloids from Semen Strychni.

[Research of Determining Complete Degradation Time in Vitro Based on Cellulose Absorbable Hemostatic Products].

To develop a method for determining complete degradation time of solublehemostatic products in vitro with accuracy, high speed and effectiveness, the current weight loss method originated from GB/T 16886 serial standards was optimized by using dialysis bag combined with assay of reducing sugar. The degradation was carried out with 3% hydrogen peroxide solution, at 37℃, 150 rpm. The dialysis bags were taken out in the 3rd, 6th, 8th, 10th and 14th day, vacuum drying folowed by percentage of weight loss testing. Cumulative content of reducing sugar in degradation solution out of dialysis bag was determined simultaneously. The correlation analysis was performed by SPSS 22.0 equipped with Pearson Correlation Coeffi cient. The correlation coeffi cient between percentage of weight loss and cumulative content of reducing sugar was 0.957, which ilustrated high correlation with each other. Hence dialysis bag combined with assay of reducing sugar is capable of evaluating the degradation endpoint of soluble hemostatic products in vitro. The method also provides a way for the evaluation of degradation of other degradable biomaterials in vitro.

A fusion protein of conotoxin MVIIA and thioredoxin expressed in Escherichia coli has significant analgesic activity.

omega-Conotoxin MVIIA (CTX MVIIA) is a potent and selective blocker of the N-type voltage-sensitive calcium channel in neurons. Its analgesic and neuroprotective effects may prove useful in treatment of severe pains and ischemia. In this paper, we report that a fusion form of CTX MVIIA with thioredoxin (Trx) has analgesic function. The DNA fragments were chemically synthesized and ligated to form the DNA sequence encoding CTX MVIIA. The synthetic gene was then cloned into the expression vector pET-32a(+) and the fusion protein Trx-CTX MVIIA containing 6x His-tag was purified by one-step metal chelated affinity chromatography (MCAC). The purity of final product was over 95% determined by HPLC and the yield of the fusion protein was approximately 40 mg/L. The analgesic function was detected by using mouse hot-plate assay. After intracranially administering fusion protein with the dose of 0.6 mg/kg, marked analgesia was observed. The analgesic effects (elevated pain thresholds) were dose-dependent and the biological half-life of the fusion toxin was approximately 1.6 h.