Real-Time Imaging of Dynamic Cell Reprogramming with Nanosensors.

Cellular reprogramming, the process by which somatic cells regain pluripotency, is relevant in many disease modeling, therapeutic, and drug discovery applications. Molecular evaluation of reprogramming (e.g., polymerase chain reaction, immunostaining) is typically disruptive, and only provides snapshots of phenotypic traits. Gene reporter constructs facilitate live-cell evaluation but is labor intensive and may risk insertional mutagenesis during viral transfection. Herein, the utilization of a non-integrative nanosensor is demonstrated to visualize key reprogramming events in situ within live cells. Principally based on sustained intracellular release of encapsulated molecular probes, nanosensors successfully monitored mesenchymal-epithelial transition, pluripotency acquisition, and transdifferentiation events. Tracking the dynamic expression of four pivotal biomarkers (i.e., THY1, E-CADHERIN, OCT4, and GATA4 mRNA), nanosensor signal showed great agreement with polymerase chain reaction and gene reporter imaging (R2 > 0.9). Overall, such facile, versatile nanosensor enables real-time monitoring of low-frequency reprogramming events, thereby useful for high-throughput assessment, optimization, and biomarker-specific cell enrichment.

Cryomicroneedles for transdermal cell delivery.

Cell therapies for the treatment of skin disorders could benefit from simple, safe and efficient technology for the transdermal delivery of therapeutic cells. Conventional cell delivery by hypodermic-needle injection is associated with poor patient compliance, requires trained personnel, generates waste and has non-negligible risks of injury and infection. Here, we report the design and proof-of-concept application of cryogenic microneedle patches for the transdermal delivery of living cells. The microneedles are fabricated by stepwise cryogenic micromoulding of cryogenic medium with pre-suspended cells, and can be easily inserted into porcine skin and dissolve after deployment of the cells. In mice, cells delivered by the cryomicroneedles retained their viability and proliferative capability. In mice with subcutaneous melanoma tumours, the delivery of ovalbumin-pulsed dendritic cells via the cryomicroneedles elicited higher antigen-specific immune responses and led to slower tumour growth than intravenous and subcutaneous injections of the cells. Biocompatible cryomicroneedles may facilitate minimally invasive cell delivery for a range of cell therapies.

A self-adhesive microneedle patch with drug loading capability through swelling effect.

Microneedles (MNs) offer a rapid method of transdermal drug delivery through penetration of the stratum corneum. However, commercial translation has been limited by fabrication techniques unique to each drug. Herein, a broadly applicable platform is explored by drug-loading via swelling effect of a hydrogel MN patch. A range of small molecule hydrophilic, hydrophobic, and biomacromolecule therapeutics demonstrate successful loading and burst release from hydrogel MNs fabricated from methacrylated hyaluronic acid (MeHA). The post-fabrication drug loading process allows MeHA MN patches with drug loadings of 10 µg cm-2. Additional post-fabrication processes are explored with dendrimer bioadhesives that increase work of adhesion, ensuring stable fixation on skin, and allow for additional drug loading strategies.

Osmosis-Powered Hydrogel Microneedles for Microliters of Skin Interstitial Fluid Extraction within Minutes.

Hydrogel microneedle patch enables the extraction of skin interstitial fluid (ISF) through in situ swelling in a minimally invasive manner without assistance of mechano-chemical peripherals. However, existing hydrogel microneedles require tens of minutes with multistep process to collect sufficient volume (1 mL) for effective analysis. This study introduces an osmolyte-powered hydrogel microneedle patch that can extract ISF three times faster than the existing platforms and provide in situ analysis of extracted biomarkers. The microneedle patch is composed of osmolytes (i.e., maltose) and hydrogel (i.e., methacrylated hyaluronic acid). During the extraction process, the osmolytes dissolve in the matrix and provide the osmotic pressure that increases the diffusion of ISF from skin to the hydrogel matrix. A patch with 100 microneedles can extract 7.90 µL of ISF from pig skin ex vivo and 3.82 µL of ISF from mouse skin in vivo within 3 min, whereas the control (i.e., hydrogel microneedle without osmolytes) requires >10 min to achieve similar results. The extracted ISF allows the quantification of biomarkers such as glucose and/or drugs such as insulin in vivo. Through the integration with the electronic glucose sensors, the whole system permits the direct and rapid analysis of the extracted glucose.

In Situ Generation of Zinc Oxide Nanobushes on Microneedles as Antibacterial Coating.

This paper introduces a facile and scalable method to generate a layer of antibacterial coating on microneedles. The antibacterial coating (i.e., zinc oxide nanobushes) is generated on the surface of gold-coated polystyrene microneedles using the hydrothermal growth method. The antimicrobial property is examined using the agar diffusion test with both gram-positive and gram-negative bacteria.