Drug delivery with topically applied nanoparticles: science fiction or reality.

The efficacy of topically applied drugs is determined by their action mechanism and their potential capacity of passing the skin barrier. Nanoparticles are assumed to be efficient carrier systems for drug delivery through the skin barrier. For flexible nanoparticles like liposomes, this effect has been well demonstrated. The penetration properties of solid nanoparticles are currently under intensive investigation. The crucial advantage of nanoparticles over non-particulate substances is their capability to penetrate deeply into the hair follicles where they can be stored for several days. There is no evidence, yet, that solid particles ≥40 nm are capable of passing through the healthy skin barrier. Therefore and in spite of the long-standing research efforts in this field, commercially available solid nanoparticle-based products for drug delivery through the healthy skin are still missing. Nevertheless, the prospects for the clinical use of nanoparticles in drug delivery are tremendous. They can be designed as transport systems delivering drugs efficiently into the hair follicles in the vicinity of specific target structures. Once deposited at these structures, specific signals might trigger the release of the drugs and exert their effects on the target cells. In this article, examples of such triggered drug release are presented.

Geometric Flow Control Lateral Flow Immunoassay Devices (GFC-LFIDs): A New Dimension to Enhance Analytical Performance.

The nitrocellulose (NC) membrane based lateral flow immunoassay device (LFID) is one of the most important and widely used biosensor platforms for point-of-care (PoC) diagnostics. However, the analytical performance of LFID has limitations and its optimization is restricted to the bioassay chemistry, the membrane porosity, and the choice of biolabel system. These bottom neck technical issues resulted from the fact that the conventional LFID design principle has not evolved for many years, which limited the LFID for advanced biosensor applications. Here we introduce a new dimension for LFID design and optimization based on geometric flow control (GFC) of NC membranes, leading to highly sensitive GFC-LFID. This novel approach enables comprehensive flow control via different membrane geometric features such as the width (w) and the length (l) of a constriction, as well as its input angle (θ 1) and output angle (θ 2). The GFC-LFID (w=0.5 mm, l=7 mm, θ 1 = 60°, θ 2 = 45°) attained a 10-fold increase in sensitivity for detection of interleukin-6 (IL-6), compared with conventional LFID, whereas reducing by 10-fold the antibody consumption. The GFC-LFID detects IL-6 over a linear range of 0.1-10 ng/mL with a limit of detection (LoD) of 29 pg/mL, which even outperforms some commercial IL-6 LFIDs. Such significant improvement is attained by pure geometric control of the NC membrane, without additives, that only relaying on a simple high throughput laser ablation procedure suitable for integration on regular large-scale manufacturing of GFC-LFIDs. Our new development on GFC-LFID with the combination of facile scalable fabrication process, tailored flow control, improved analytical performance, and reduced antibodies consumption is likely to have a significant impact on new design concept for the LFID industry.

Integrating printed microfluidics with silicon photomultipliers for miniaturised and highly sensitive ATP bioluminescence detection.

Bioluminescence has been widely used for important biosensing applications such as the measurement of adenosine triphosphate (ATP), the energy unit in biological systems and an indicator of vital processes. The current technology for detection is mainly based on large equipment such as readers and imaging systems, which require intensive and time-consuming procedures. A miniaturised bioluminescence sensing system, which would allow sensitive and continuous monitoring of ATP, with an integrated and low-cost disposable microfluidic chamber for handling of biological samples, is highly desirable. Here, we report the design, fabrication and testing of 3D printed microfluidics chips coupled with silicon photomultipliers (SiPMs) for high sensitive real-time ATP detection. The 3D microfluidic chip reduces reactant consumption and facilitates solution delivery close to the SiPM to increase the detection efficiency. Our system detects ATP with a limit of detection (LoD) of 8nM and an analytical dynamic range between 15nM and 1µM, showing a stability error of 3%, and a reproducibility error below of 20%. We demonstrate the dynamic monitoring of ATP in a continuous-flow system exhibiting a fast response time, ~4s, and a full recovery to the baseline level within 17s. Moreover, the SiPM-based bioluminescence sensing system shows a similar analytical dynamic range for ATP detection to that of a full-size PerkinElmer laboratory luminescence reader.

Correction: W.C. Mak, et al. Controlled Delivery of Human Cells by Temperature Responsive Microcapsules. J. Funct. Biomater. 2015, 6, 439-453.

Recently, we found a mistake in Figure 4D in our previously published paper[...].

Thermo-rheological responsive microcapsules for time-dependent controlled release of human mesenchymal stromal cells.

Human mesenchymal stromal cells (hMSCs) are adult-source cells that have been extensively evaluated for cell-based therapies. hMSCs delivered by intravascular injection have been reported to accumulate at the sites of injury to promote tissue repair and can also be employed as vectors for the delivery of therapeutic genes. However, the full potential of hMSCs remains limited as the cells are lost after injection due to anoikis and the adverse pathologic environment. Encapsulation of cells has been proposed as a means of increasing cell viability. However, controlling the release of therapeutic cells over time to target tissue still remains a challenge today. Here, we report the design and development of thermo-rheological responsive hydrogels that allow for precise, time dependent controlled-release of hMSCs. The encapsulated hMSCs retained good viability from 76% to 87% dependent upon the hydrogel compositions. We demonstrated the design of different blended hydrogel composites with modulated strength (S parameter) and looseness of hydrogel networks (N parameter) to control the release of hMSCs from thermo-responsive hydrogel capsules. We further showed the feasibility for controlled-release of encapsulated hMSCs within 3D matrix scaffolds. We reported for the first time by a systematic analysis that there is a direct correlation between the thermo-rheological properties associated with the degradation of the hydrogel composite and the cell release kinetics. This work therefore provides new insights into the further development of smart carrier systems for stem cell therapy.

Biosensor for rapid determination of 3-hydroxybutyrate using bi-enzyme system.

A bi-enzyme-based Clark electrode was developed for the determination of 3-hydroxybutyrate. This sensor is based on the specific dehydrogenation by 3-hydroxybutyrate dehydrogenase (HBDH, E.C. 1.1.1.30) in combination with salicylate hydroxylase (SHL E.C. 1.14.13.1). The enzymes were entrapped by a poly(carbamoyl) sulfonate (PCS) hydrogel on a Teflon membrane. The principle of the determination scheme is as follows: the specific detecting enzyme, HBDH, catalyses the specific dehydrogenation of 3-hydroxybutyrate consuming NAD(+). The products, NADH, initiate the irreversible decarboxylation and the hydroxylation of salicylate by SHL in the presence of oxygen. SHL forces the equilibrium of dehydrogenation of 3-hydroxybutyrate by HBDH to the product side by consuming NADH. Dissolved oxygen acts as an essential material for SHL during its enzymatic reactions. This results in a detectable signal due to the SHL-enzymatic consumptions of dissolved oxygen in the measurement of 3-hydroxybutyrate. Interferences from different amino acids and electroactive substances were found to be minimal due to the specificity of HBDH and the application of a Teflon membrane. The sensor has a fast response (2s) and short recovery time (2 min) with a linear range between 8 and 800 microM 3-hydroxybutyrate and a detection limit of 3.9 microM. A good agreement (R(2)=0.9925) with theoretical calculation was obtained in spiked serum sample measurements.

Triggered release of model drug from AuNP-doped BSA nanocarriers in hair follicles using IRA radiation.

Recent advances in the field of dermatotherapy have resulted in research efforts focusing on the use of particle-based drug delivery systems for the stimuli-responsive release of drugs in the skin and skin appendages, i.e. hair follicles and sebaceous glands. However, effective and innocuous trigger mechanisms which result in the release of the drugs from the nanocarriers upon reaching the target structures are still lacking. For the first time, the present study demonstrated the photo-activated release of the model drug fluorescein isothiocyanate (FITC) from topically applied gold nanoparticle-doped bovine serum albumin (AuNPs-doped BSA) particles (approx. 545nm) using water-filtered infrared A (IRA) radiation in the hair follicles of an ex vivo porcine skin model. The IRA radiation-induced plasmonic heating of the AuNPs results in the partial decomposition or opening of the albumin particles and release the model drug, while control particles without AuNPs show insignificant release. The results demonstrate the feasibility of using IRA radiation to induce release of encapsulated drugs from plasmonic nanocarriers for the targeting of follicular structures. However, the risk of radiation-induced skin damage subsequent to repeated applications of high infrared dosages may be significant. Future studies should aim at determining the suitability of lower infrared A dosages, such as for medical treatment regimens which may necessitate repeated exposure to therapeutics. STATEMENT OF SIGNIFICANCE: Follicular targeting using nanocarriers is of increasing importance in the prophylaxis and treatment of dermatological or other diseases. For the first time, the present study demonstrated the photo-activated release of the model drug fluorescein isothiocyanate (FITC) from topically applied gold nanoparticle-doped bovine serum albumin (AuNPs-doped BSA) particles using water-filtered infrared A (IRA) radiation in the hair follicles of an ex vivo porcine skin model. The results demonstrate the feasibility of using wIRA radiation to induce release of encapsulated drugs for the targeting of follicular structures, and provide a new vision on the development of optically addressable delivery systems for controlled release of drugs in the skin and skin appendages, i.e. hair follicles and sebaceous glands.

Kawasaki disease in Hong Kong, 1994 to 2000.

OBJECTIVE: To describe the epidemiology, clinical characteristics, and management of Kawasaki disease in children in Hong Kong. DESIGN: Retrospective survey of medical records from July 1994 to June 1997, and prospective data collection from July 1997 to June 2000. SETTING: Hospitals with a paediatric unit in Hong Kong. PATIENTS: Patients diagnosed with Kawasaki disease between July 1994 and June 2000 in public hospitals in Hong Kong. MAIN OUTCOME MEASURES: Incidence of Kawasaki disease and coronary artery aneurysm rates. RESULTS: A total of 696 cases of Kawasaki disease were reported. There were 435 (62.5%) boys and 261 (37.5%) girls giving a male to female ratio of 1.7:1. The age ranged from 1 month to 15 years 5 months with a median of 1.7 years. Infants (<1 year) constituted the largest group of patients (223, 32.0%) and overall, 638 (91.7%) were younger than 5 years. Skin rash, conjunctivitis, and oral signs were among the principal clinical features present in over 80% of cases. Prominent cervical lymph nodes larger than 1.5 cm were less commonly found (24%). Coronary artery aneurysms or ectasia were present in 15.7% (109/696), 8.5% (59/696), and 5.0% (35/696) of patients at 2, 4, and 8 weeks, respectively. The incidence of Kawasaki disease per 100,000 children under 5 years was significantly higher in the prospective study period than in the retrospective period (39 vs 26, P<0.001). CONCLUSION: The incidence of Kawasaki disease is high in Hong Kong and is 39 per 100,000 children below 5 years of age. The coronary artery aneurysm prevalence is 5%. Intravenous gamma-globulin and high-dose aspirin is the mainstay of treatment.

Controlled Delivery of Human Cells by Temperature Responsive Microcapsules.

Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line-human umbilical vein endothelial cells (HUVECs). While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation.

Biofunctionalized indigo-nanoparticles as biolabels for the generation of precipitated visible signal in immunodipsticks.

A novel class of organic nanoparticles as biolabels that can generate an instant visible signal was applied to immunodipsticks. A new principle for signal generation based on hydrolysis of colourless signal precursor molecules to produce coloured signal molecules followed by signal precipitation and localization was demonstrated. The nanoparticle biolabels were applied to sandwich immunoassays for the detection of mouse immunoglobulin G (M IgG). In the presence of M IgG, a nanoparticle-immunocomplex was formed and bound on the test zone immobilized with goat anti M IgG (Gt α M IgG). A blue line was developed on the test zone upon the addition of a signal developing reagent. An optical signal could be simply assessed using naked eyes or quantified using a reading device. The lowest visible signal that could be observed using naked eyes was found to be 1.25 µg L(-1) M IgG. The nanoparticle biolabel also showed a better sensitivity (signal-to-noise ratio) compared with the conventional colloidal gold biolabel. This novel class of organic nanoparticles offers an alternative biolabel system for the development of point-of-care immunodipsticks.

Nanoscale surface engineered living cells with extended substrate spectrum.

We report on cell surface engineering of living microorganisms by using Layer-by-Layer (LbL) technology to extend the substrate spectrum. The yeast Arxula adeninivorans LS3 (Arxula) was employed as a model organism and biological template. By using LbL technology, Arxula cells were encapsulated by polyelectrolyte and enzyme layers. The biological activity of the Arxula was retained after the encapsulation process. The polymeric capsule surrounding the Arxula provides a stable interface for surface engineering of living cells. LbL of polyelectrolytes followed by an enzyme layer of lactate oxidase were assembled. The outer enzyme layer provides an additional biological function for Arxula to convert the unfavourable substrate lactate into the favourable substrate pyruvate, thus extending the substrate spectrum of the organism. Moreover, capsule stability and enzyme conjugate stability of the surface engineered Arxula were studied.