Monitoring Wound Healing with Topically Applied Optical NanoFlare mRNA Nanosensors

An effective wound management strategy needs accurate assessment of wound status throughout the whole healing process. This can be achieved by examining molecular biomarkers including proteins, DNAs, and RNAs. However, existing methods for quantifying these biomarkers such as immunohistochemistry and quantitative polymerase chain reaction are usually laborious, resource-intensive, and disruptive. This article reports the development and utilization of mRNA nanosensors (i.e., NanoFlare) that are topically applied on cutaneous wounds to reveal the healing status through targeted and semi-quantitative examination of the mRNA biomarkers in skin cells. In 2D and 3D in vitro models, the efficacy and efficiency of these nanosensors are demonstrated in revealing the dynamic changes of mRNA biomarkers for different stages of wound development. In mouse models, this platform permits the tracking and identification of wound healing stages and a normal and diabetic wound healing process by wound healing index in real time.

Delivery of Wnt inhibitor WIF1 via engineered polymeric microspheres promotes nerve regeneration after sciatic nerve crush

Injuries within the peripheral nervous system (PNS) lead to sensory and motor deficits, as well as neuropathic pain, which strongly impair the life quality of patients. Although most current PNS injury treatment approaches focus on using growth factors/small molecules to stimulate the regrowth of the injured nerves, these methods neglect another important factor that strongly hinders axon regeneration—the presence of axonal inhibitory molecules. Therefore, this work sought to explore the potential of pathway inhibition in promoting sciatic nerve regeneration. Additionally, the therapeutic window for using pathway inhibitors was uncovered so as to achieve the desired regeneration outcomes. Specifically, we explored the role of Wnt signaling inhibition on PNS regeneration by delivering Wnt inhibitors, sFRP2 and WIF1, after sciatic nerve transection and sciatic nerve crush injuries. Our results demonstrate that WIF1 promoted nerve regeneration ( p < 0.05) after sciatic nerve crush injury. More importantly, we revealed the therapeutic window for the treatment of Wnt inhibitors, which is 1 week post sciatic nerve crush when the non-canonical receptor tyrosine kinase (Ryk) is significantly upregulated.

Ocular Delivery of Predatory Bacteria with Cryomicroneedles Against Eye Infection

The development of potent antibiotic alternatives with rapid bactericidal properties is of great importance in addressing the current antibiotic crisis. One representative example is the topical delivery of predatory bacteria to treat ocular bacterial infections. However, there is a lack of suitable methods for the delivery of predatory bacteria into ocular tissue. This work introduces cryomicroneedles (cryoMN) for the ocular delivery of predatory Bdellovibrio bacteriovorus (B. bacteriovorus) bacteria. The cryoMN patches are prepared by freezing B. bacteriovorus containing a cryoprotectant medium in a microneedle template. The viability of B. bacteriovorus in cryoMNs remains above 80% as found in long-term storage studies, and they successfully impede the growth of gram-negative bacteria in vitro or in a rodent eye infection model. The infection is significantly relieved by nearly six times through 2.5 days of treatment without substantial effects on the cornea thickness and morphology. This approach represents the safe and efficient delivery of new class of antimicrobial armamentarium to otherwise impermeable ocular surface and opens up new avenues for the treatment of ocular surface disorders.

Transdermal delivery of Chinese herbal medicine extract using dissolvable microneedles for hypertrophic scar treatment

Hypertrophic scars are unfavorable skin diseases characterized by excessive collagen deposition. Although systemic treatments exist in clinic to manage hypertrophic scars, they pose significant side effects and tend to lose efficacy over prolonged applications. Traditional Chinese medicine (TCM) offers as a promising candidate to treat pathological scars. A large number of TCMs have been studied to show anti-scarring effect, however, the natural barrier of the skin impedes their penetration, lowering its therapeutic efficacy. Herein, we reported the use of dissolvable hyaluronic acid (HA) microneedles (MNs) as a vehicle to aid the transdermal delivery of therapeutic agent, a model TCM called shikonin for the treatment of hypertrophic scars. Here, shikonin was mixed with HA to make MNs with adequate mechanical strength for skin penetration, making its dosage controllable during the fabrication process. The therapeutic effect of the shikonin HA MNs was studied in vitro using HSFs and then further verified with quantitative reverse transcriptase polymerase chain reaction. Our data suggest that the shikonin HA MNs significantly reduce the viability and proliferation of the HSFs and downregulate the fibrotic-related genes (i.e., TGFβ1, FAP-α and COL1A1). Furthermore, we observed a localized therapeutic effect of the shikonin HA MNs that is beneficial for site-specific treatment.

Nephrotoxicity Assessment with Human Kidney Tubuloids using Spherical Nucleic Acid-Based mRNA Nanoflares

Drug-induced nephrotoxicity represents an important cause of acute kidney injury with associated patient morbidity and mortality and is often responsible for termination of drug development, after extensive resource allocation. We have developed a human kidney tubuloid system that phenocopies, in 3D culture, kidney proximal tubules, a primary injury site of most nephrotoxicants. Traditional end point assays are often performed on 2D cultures of cells that have lost their differentiated phenotype. Herein, we pair a tubuloid system with Nanoflare (NF) mRNA nanosensors to achieve a facile, real-time assessment of drug nephrotoxicity. Using kidney injury molecule-1 (KIM-1) mRNA as a model injury biomarker, we verify NF specificity in engineered and adenovirus-transfected cells and confirm their efficacy to report tubular cell injury by aristolochic acid and cisplatin. The system also facilitates nephrotoxicity screening as demonstrated with 10 representative anticancer moieties. 5-Fluorouracil and paclitaxel induce acute tubular injury, as reflected by an NF signal increase.

Reprogramming of macrophages with macrophage cell membrane-derived nanoghosts

Macrophages can be polarized to M1 or M2 type with pro-inflammatory or anti-inflammatory properties. Nanoparticles have recently been found to be a promising platform to polarize macrophages to desired phenotypes. This article explores the usage of cell membrane-derived nanoparticles (nanoghosts) for reprogramming macrophages. The efficacy and efficiency of this technology are examined via cytokine analysis and immunostaining of the nanoghost-treated cells. We find that several cytokines/chemokines are highly expressed on nanoghosts. In addition, a 2D wound healing model is deployed to reveal their potential application in clinical settings.

Nanodelivery Systems for Topical Management of Skin Disorders

Topical drug delivery has inherent advantages over other administration routes. However, the existence of stratum corneum limits the diffusion to small and lipophilic drugs. Fortunately, the advancement of nanotechnology brings along opportunities to address this challenge. Taking the unique features in size and surface chemistry, nanocarriers such as liposomes, polymeric nanoparticles, gold nanoparticles, and framework nucleic acids have been used to bring drugs across the skin barrier to epidermis and dermis layers. This article reviews the development of these formulations and focuses on their applications in the treatment of skin disorders such as acne, skin inflammation, skin infection, and wound healing. Existing hurdles and further developments are also discussed.

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.

A Double-Layered Microneedle Platform Fabricated through Frozen Spray-Coating

This work reports a frozen spray-coating method for the fabrication of double-layered microneedles (MNs). Taking swellable methacrylated hyaluronic acid (MeHA)-derived MNs as the model, both hydrophobic molecules (Nile red, Cy5) and hydrophilic ones (FITC, FITC-Dextran, Insulin) can be homogeneously coated without impacting the mechanical properties of the original MeHA MNs. The prepared double-layered MNs can execute multiple roles. It is demonstrated that insulin-coated MeHA double-layered MNs allow the effective delivery of the insulin into circulation of mice for controlling the blood glucose level while they also permit the extraction of skin interstitial fluid for the timely analysis of the biomarker (glucose).

Temporal pressure enhanced topical drug delivery through micropore formation

Transdermal drug delivery uses chemical, physical, or biochemical enhancers to cross the skin barrier. However, existing platforms require high doses of chemical enhancers or sophisticated equipment, use fragile biomolecules, or are limited to a certain type of drug. Here, we report an innovative methodology based on temporal pressure to enhance the penetration of all kinds of drugs, from small molecules to proteins and nanoparticles (up to 500 nm). The creation of micropores (~3 μm2) on the epidermal layer through a temporal pressure treatment results in the elevated expression of gap junctions, and reduced expression of occludin tight junctions. A 1 min treatment of 0.28-MPa allows nanoparticles (up to 500 nm) and macromolecules (up to 20 kDa) to reach a depth of 430-μm into the dermal layer. Using, as an example, the delivery of insulin through topical application after the pressure treatment yields up to 80% drop in blood glucose in diabetic mice.

Unraveling Framework Nucleic Acid-Skin Cell Interactions with a Co-Culture System

Framework nucleic acid (FNA) is an emerging drug carrier platform, with its biodegradability and uniform, tunable structures. Recently, its applicability in transdermal drug delivery has been demonstrated, extending the range of applications that are predominantly based on intravenous injection. However, FNA's interaction and impact toward the skin cells are yet to be elucidated. This study employs an optically clear keratinocyte/fibroblast co-culture system to visualize the FNA-skin cell interactions. FNA's influence on these cells is evaluated through polymerase chain reaction analyses and metabolism assays. A size-dependent interaction and cellular internalization on both keratinocytes and fibroblasts is observed, with no adverse effects on cell viability and functions.

Upconversion Nanoparticle Powered Microneedle Patches for Transdermal Delivery of siRNA

Microneedles (MNs) permit the delivery of nucleic acids like small interfering RNA (siRNA) through the stratum corneum and subsequently into the skin tissue. However, skin penetration is only the first step in successful implementation of siRNA therapy. These delivered siRNAs need to be resistant to enzymatic degradation, enter target cells, and escape the endosome-lysosome degradation axis. To address this challenge, this article introduces a nanoparticle-embedding MN system that contains a dissolvable hyaluronic acid (HA) matrix and mesoporous silica-coated upconversion nanoparticles (UCNPs@mSiO₂ ). The mesoporous silica (mSiO₂ ) shell is used to load and protect siRNA while the upconversion nanoparticle (UCNP) core allows the tracking of MN skin penetration and NP diffusion through upconversion luminescence imaging or optical coherence tomography (OCT) imaging. Once inserted into the skin, the HA matrix dissolves and UCNPs@mSiO₂ diffuse in the skin tissue before entering the cells for delivering the loaded genes. As a proof of concept, this system is used to deliver molecular beacons (MBs) and siRNA targeting transforming growth factor-beta type I receptor (TGF-βRI) that is potentially used for abnormal scar treatment.

Transdermal delivery of small interfering RNAs with topically applied mesoporous silica nanoparticles for facile skin cancer treatment

Small interfering RNA (siRNA) is a promising tool for the treatment of skin disorders including skin squamous cell carcinoma (SCC). This article develops a topical formulation for the transdermal delivery of siRNA. The formulation is built on mesoporous silica nanoparticles (MSNPs) with a loading capacity of 1.4 μg of oligonucleotide per mg of MSNPs. Cell experiments are employed to study the functionality of the formulation including the cellular uptake, the qualitative and quantitative detection of specific gene biomarkers. The clinical potential of this system is examined by topically delivering siRNA targeting TGFβR-1 (TGFβR-1) to the SCC in a mouse xenograft model. In comparison to the controls, MSNPs containing TGFβR-1 siRNA show a 2-fold suppression of TGFβR-1.

Framework Nucleic Acids: A Paradigm Shift in Transdermal Drug Delivery

Transdermal drug delivery (TDD) provides a direct drug administration route bypassing gastrointestinal and liver metabolism. Until now, topical nanocarriers responsible for efficient TDD are predominantly polymeric or lipid based. The size-dependent skin penetration ability of framework nucleic acids (FNAs) has recently been reported, along with their efficacy in delivering doxorubicin for skin melanoma therapy. This commentary is to highlight the paradigm shift of nucleic acid delivery from being a cargo moiety to serving as a drug carrier instead. Further development directions to maximize the potential of FNAs for TDD are also discussed.

Abnormal scar identification with spherical-nucleic-acid technology

The accurate diagnosis of scar type and severity relies on histopathology of biopsied tissue, which is invasive and time-consuming, causes discomfort and may exacerbate scarring. Here, we show that imaging nanoprobes for the live-cell detection of intracellular messenger RNA (mRNA) (also known as NanoFlares) enable measurements of the expression of connective tissue growth factor (CTGF) as a visual indicator of hypertrophic scars and keloids. During cell culture, NanoFlares enabled the distinction of hypertrophic and keloidal fibroblasts from normal fibroblasts, and the detection of changes in CTGF expression resulting from the regulatory effects of transforming growth factor-β (TGF-β) agonists and TGF-β antagonists. We also applied the NanoFlares topically to the skin of live mice and rabbits, and to ex vivo human skin models. Transepidermal penetration of the NanoFlares enabled the visual and spectroscopic quantification of underlying abnormal fibroblasts on the basis of CTGF mRNA expression. Our proof-of-concept studies of topically applied NanoFlare technology as a means of biopsy-free scar diagnosis may eventually inform therapeutic decisions on the basis of the mRNA-expression patterns of skin disorders.

Framework nucleic acids as programmable carrier for transdermal drug delivery

DNA nanostructures are promising drug carriers with their intrinsic biocompatibility, uniformity and versatility. However, rapid serum disintegration leads to low bioavailability at targeted sites following systemic administration, hindering their biomedical applications. Here we demonstrate transdermal delivery of framework nucleic acids (FNAs) through topical applications. By designing FNAs with distinct shapes and sizes, we interrogate their penetration on mice and human skin explant. Skin histology reveals size-dependent penetration, with FNAs ≤75 nm effectively reaching dermis layer. 17 nm-tetrahedral FNAs show greatest penetration to 350 µm from skin periphery. Importantly, structural integrity is maintained during the skin penetration. Employing a mouse melanoma model, topical application of doxorubicin-loaded FNAs accommodates ≥2-fold improvement in drug accumulation and tumor inhibition relative to topically-applied free doxorubicin, or doxorubicin loaded in liposomes and polymeric nanoparticles. Programmable penetration with minimal systemic biodistribution underlines FNA potential as localized transdermal drug delivery carriers.

Oligonucleotide Molecular Sprinkler for Intracellular Detection and Spontaneous Regulation of mRNA for Theranostics of Scar Fibroblasts

Early diagnosis and timely intervention are key for the successful treatment of skin diseases like abnormal scars. This study introduces a nucleic-acid-based probe (i.e., molecular sprinkler) for the diagnosis and spontaneous regulation of the abnormal expression of fibrosis-related mRNA in scar-derived skin fibroblasts. Using mRNA encoding connective tissue growth factor (CTGF) as the model gene, a probe with three oligonucleotides is constructed, including a recognition sequence complementary to the CTGF mRNA, a siRNA against transforming growth factor receptor I (TGFβRI) as the CTGF mRNA suppressor, and a connecting sequence. The probe can detect CTGF mRNA with a limit of 10 × 10^-9 m and distinguishes scar fibroblasts from normal ones in both 2D and 3D environments. Two days after transfection, the siRNA released from the probe reduces the expression of TGFβRI and, consequently, decreases the cellular expression of CTGF mRNA (up to 70%). This dual-role probe presents opportunities to monitor the TGF- β signaling pathway, screen for drugs that target the CTGF pathway, and determine the role of inhibition of the CTGF pathway in therapeutic efficacy.

Functional Imaging with Nucleic-Acid-Based Sensors: Technology, Application and Future Healthcare Prospects

Timely monitoring and assessment of human health plays a crucial role in maintaining the wellbeing of our advancing society. In addition to medical tools and devices, suitable probe agents are crucial to assist such monitoring, either in passive or active ways (i.e., sensors) through inducible signals. In this review we highlight recent developments in activatable optical sensors based on nucleic acids. Sensing mechanisms and bio-applications of these nucleic acid sensors in ex vivo assays, intracellular or in vivo settings are described. In addition, we discuss the limitations of these sensors and how nanotechnology can complement/enhance sensor properties to promote translation into clinical applications.

Molecular Beacon Gold Nanosensors for Leucine-Rich Alpha-2-Glycoprotein-1 Detection in Pathological Angiogenesis

Leucine-rich alpha-2-glycoprotein-1 (Lrg1) is an emerging biomarker for angiogenesis. Its expression in ocular tissues is up-regulated in both human patients with proliferative diabetic retinopathy and rodent models of pathological angiogenesis. However, there is no existing sensor that allows visualization and monitoring of Lrg1 expression noninvasively and in real time. Herein, we report a nucleic acid-gold nanorod-based nanosensor for the noninvasive monitoring of cellular Lrg1 expression in angiogenesis. Specifically, this platform is constructed by covalently conjugating molecular beacons onto gold nanorods, which prequench the fluorophores on the molecular beacons. Upon intracellular entry and endosomal escape, the complexes interact with cellular Lrg1 mRNA through hybridization of the loop area of the molecular beacons. This complexation distances the fluorophores from nanorod and restores the prequenched fluorescence. The reliability of this platform is confirmed by examining the increased Lrg1 expression in migrating keratinocytes and the Lrg1 gene changes in different postnatal stages of mouse retinal vasculature growth in the mouse retina model.

Graphene Materials in Antimicrobial Nanomedicine: Current Status and Future Perspectives

Graphene materials (GMs), such as graphene, graphene oxide (GO), reduced GO (rGO), and graphene quantum dots (GQDs), are rapidly emerging as a new class of broad-spectrum antimicrobial agents. This report describes their state-of-the-art and potential future covering both fundamental aspects and biomedical applications. First, the current understanding of the antimicrobial mechanisms of GMs is illustrated, and the complex picture of underlying structure-property-activity relationships is sketched. Next, the different modes of utilization of antimicrobial GMs are explained, which include their use as colloidal dispersions, surface coatings, and photothermal/photodynamic therapy agents. Due to their practical relevance, the examples where GMs function as synergistic agents or release platforms for metal ions and/or antibiotic drugs are also discussed. Later, the applicability of GMs in the design of wound dressings, infection-protective coatings, and antibiotic-like formulations ("nanoantibiotics") is assessed. Notably, to support our assessments, the existing clinical applications of conventional carbon materials are also evaluated. Finally, the key hurdles of the field are highlighted, and several possible directions for future investigations are proposed. We hope that the roadmap provided here will encourage researchers to tackle remaining challenges toward clinical translation of promising research findings and help realize the potential of GMs in antimicrobial nanomedicine.

Abnormal scar identification with spherical-nucleic-acid technology

The accurate diagnosis of scar type and severity relies on histopathology of biopsied tissue, which is invasive and time-consuming, causes discomfort and may exacerbate scarring. Here, we show that imaging nanoprobes for the live-cell detection of intracellular messenger RNA (mRNA) (also known as NanoFlares) enable measurements of the expression of connective tissue growth factor (CTGF) as a visual indicator of hypertrophic scars and keloids. During cell culture, NanoFlares enabled the distinction of hypertrophic and keloidal fibroblasts from normal fibroblasts, and the detection of changes in CTGF expression resulting from the regulatory effects of transforming growth factor-β (TGF-β) agonists and TGF-β antagonists. We also applied the NanoFlares topically to the skin of live mice and rabbits, and to ex vivo human skin models. Transepidermal penetration of the NanoFlares enabled the visual and spectroscopic quantification of underlying abnormal fibroblasts on the basis of CTGF mRNA expression. Our proof-of-concept studies of topically applied NanoFlare technology as a means of biopsy-free scar diagnosis may eventually inform therapeutic decisions on the basis of the mRNA-expression patterns of skin disorders.

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.

A Concise Review of Gold Nanoparticles-Based Photo-Responsive Liposomes for Controlled Drug Delivery

The focus of drug delivery is shifting toward smart drug carriers that release the cargo in response to a change in the microenvironment due to an internal or external trigger. As the most clinically successful nanosystem, liposomes naturally come under the spotlight of this trend. This review summarizes the latest development about the design and construction of photo-responsive liposomes with gold nanoparticles for the controlled drug release. Alongside, we overview the mechanism involved in this process and the representative applications.

The effect of temporal manipulation of transforming growth factor beta 3 and fibroblast growth factor 2 on the derivation of proliferative chondrocytes from mensenchymal stem cells-A study monitored by quantitative reverse transcription polymerase chain reaction and molecular beacon based nanosensors

Proliferative chondrocytes are critical to realize regeneration of damaged epiphyseal growth plate. However, acquiring autologous replacement cells involves highly invasive procedures and often results in limited cell quantity. Mesenchymal stem cells (MSCs) are a potential source of chondrogenic cells for the treatment of cartilage disorders and injuries. The temporal effect of transforming growth factor beta 3 (TGFβ3) and fibroblast growth factor 2 (FGF2) on the derivation of proliferative chondrocytes from MSCs in three-dimensional agarose was investigated by manipulating the duration of TGFβ3 and FGF2 treatment. The differentiation process was monitored by quantitative reverse transcription polymerase chain reaction (qRT-PCR) as well as nanosensors containing two molecular beacons that target critical biomarkers for proliferative chondrocytes (i.e., collagen type-II messenger ribonucleic acid [mRNA] and Ki67 mRNA). The molecular beacon-based nanosensors were found to be comparable to qRT-PCR in measuring mRNA expression and thus providing a noninvasive mean to screen and monitor culture samples. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 895-904, 2018.

Nitric Oxide Nanosensors for Predicting the Development of Osteoarthritis in Rat Model

Osteoarthritis (OA) is a chronic arthritic disease that causes the overproduction of inflammatory factors such as nitric oxide (NO). This study develops a NO nanosensor to predict the OA development. The nanosensor is synthesized by encapsulating the NO sensing molecules (i.e., 4-amino-5-methylamino-2',7'-difluorofluorescein Diaminofluorescein-FM (DAF-FM)) within the biodegradable poly(lactic-co-glycolic acid) nanoparticles. In vitro, the nanosensor allows the monitoring of the NO release in interleukin-1β-stimulated chondrocytes and the alleviated effect of N^G-monomethyl-l-arginine (a NO inhibitor) and andrographolide (an anti-inflammatory agent). In the rat OA model, it permits the quantification of NO level in joint fluid. The proposed NO nanosensor may facilitate a noninvasive and real-time evaluation of the OA development.

Improvement of endothelial progenitor outgrowth cell (EPOC)-mediated vascularization in gelatin-based hydrogels through pore size manipulation

In addition to chemical compositions, physical properties of scaffolds, such as pore size, can also influence vascularization within the scaffolds. A larger pore has been shown to improve host vascular tissue invasion into scaffolds. However, the influence of pore sizes on vascularization by endothelial cells directly encapsulated in hydrogels remains unknown. In this study, micro-cavitary hydrogels with different pore sizes were created in gelatin-methacrylate hydrogels with dissolvable gelatin microspheres (MS) varying in sizes. The effect of pore sizes on vascular network formation by endothelial progenitor outgrowth cells (EPOCs) encapsulated in hydrogels was then investigated both in vitro and in vivo. When cultured in vitro, vascular networks were formed around pore structures in micro-cavitary hydrogels. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro. When implantation in vivo, functional connections between encapsulated EPOCs and host vasculature micro-cavitary hydrogels were established. Vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones.

STATEMENT OF SIGNIFICANCE

This study reveals that the optimal pore size for hydrogel vascularization in vitro and in vivo is different. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro, while vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones.

Peptide delivery with poly(ethylene glycol) diacrylate microneedles through swelling effect

Transdermal delivery of therapeutic biomolecules (including peptides) can avoid enzymatic digestion that occurs in the oral route. (Polyethylene glycol) diacrylate (PEGDA)-based microneedles, with good biocompatibility, are easily fabricated through photo-polymerization with a precisely controlled structure. It has successfully been used for the transdermal delivery of small molecule drugs such as 5-fluorouracil. However, the delivery of peptide-based therapeutics using this platform is seldom reported. This is because of the potential damage to the peptide during the photo-polymerization process of PEGDA. Herein, we introduce a method to load PEGDA microneedles with peptides without compromising peptide potency. Using gap junction inhibitor (Gap 26) as an example, the peptide was loaded into PEGDA microneedles through the swelling effect of PEGDA in the aqueous solution. The peptide-loaded microneedles were applied to a keloid scar model and exhibited inhibition expression of collagen I, a predominant marker of keloid scar, demonstrating its potential therapeutic effects.

Near-infrared light-responsive liposomal contrast agent for photoacoustic imaging and drug release applications

Photoacoustic imaging has become an emerging tool for theranostic applications. Not only does it help in <italic<in vivo</italic<, noninvasive imaging of biological structures at depths but it can also be used for drug release and therapeutic applications. We explore near-infrared light-sensitive liposomes coated with gold nanostars (AuNSs) for both imaging and drug release applications using a photoacoustic imaging system. Being amphiphilic, the liposomes lipid bilayer and the aqueous core enable encapsulation of both hydrophobic and hydrophilic drugs. The AuNSs on the surface of the liposomes act as photon absorbers due to their intrinsic surface plasmon resonance. Upon excitation by laser light at specific wavelength, AuNSs facilitate rapid release of the contents encapsulated in the liposomes due to local heating and pressure wave formation (photoacoustic wave). Herein, we describe the design and optimization of the AuNSs-coated liposomes and demonstrate the release of both hydrophobic and hydrophilic model drugs (paclitaxel and calcein, respectively) through laser excitation at near-infrared wavelength. The use of AuNSs-coated liposomes as contrast agents for photoacoustic imaging is also explored with tissue phantom experiments. In comparison to blood, the AuNSs-coated liposomes have better contrast (approximately two times) at 2-cm imaging depth.

Fluorescent Poly(glycerol-co-sebacate) Acrylate Nanoparticles for Stem Cell Labeling and Longitudinal Tracking

The stable presence of fluorophores within the biocompatible and biodegradable elastomer poly(glycerol-co-sebacate) acrylate (PGSA) is critical for monitoring the transplantation, performance, and degradation of the polymers in vivo. However, current methods such as physically entrapping the fluorophores in the polymer matrix or providing a fluorescent coating suffer from rapid leakage of fluorophores. Covalent conjugation of fluorophores with the polymers and the subsequent core-cross-linking are proposed here to address this challenge. Taking rhodamine as the model dye and PGSA nanoparticles (NPs) as the model platform, we successfully showed that the synthesized rhodamine-conjugated PGSA (PGSAR) NPs only released less than 30% rhodamine at day 28, whereas complete release of dye occurred for rhodamine-encapsulated PGSA (PGSA-p-R) NPs at day 7 and 57.49% rhodamine was released out for the un-cross-linked PGSAR NPs at day 28. More excitingly, PGSAR NPs showed a strong quantum yield enhancement (26.24-fold) of the fluorophores, which was due to the hydrophobic environment within PGSAR NPs and the restricted rotation of (6-diethylamino-3H-xanthen-3-ylidene) diethyl group in rhodamine after the conjugation and core-cross-linking. The stable presence of dye in the NPs and enhanced fluorescence allowed a longitudinal tracking of stem cells both in vitro and in vivo for at least 28 days.

Real-time and non-invasive monitoring of embryonic stem cell survival during the development of embryoid bodies with smart nanosensor

Embryonic stem cells (ESCs)-derived embryoid body (EB) is a powerful model for the study of early embryonic development and the discovery of therapeutics for tissue regeneration. This article reports a smart nanosensor platform for labeling and tracking the survival and distribution of ESCs during the EB development in a real-time and non-invasive way. Compared with the cell tracker (i.e. DiO) and the green fluorescent protein (GFP), nanosensors provide the homogenous and highly-efficient ESC labeling. Following the internalization, intracellular nanosensors gradually release the non-fluorescent molecules that become fluorescent only in viable cells. This allows a continuous monitoring of ESC survival and distribution during the process of EB formation. Finally, we confirm that nanosensor labeling does not cause the significant influences to biological properties of the ESCs and EBs.

STATEMENT OF SIGNIFICANCE

The distribution pattern of viable embryonic stem cells (ESCs) within embryoid body (EB) is closely related with the maturation of EBs. Noninvasive and real-time monitoring of viable ESC distribution in EBs would allow researchers to optimize the culturing condition in time during the EB development and to select the suitable EBs for subsequent applications.

Near-infrared light-sensitive liposomes for enhanced plasmid DNA transfection

Near‐infrared (NIR) light‐responsive liposomes are attractive carriers for targeted and controlled drug delivery to the superficial organ or tissue (e.g., skin). This work describes the development of NIR‐responsive liposomes by incorporating gold nanostars within liposomes composed of Phospholipon 90 g and cholesterol. Following cellular delivery, photothermal effect around the gold nanostar upon NIR stimulation induces microcavitation and liposome phase transition which consequently triggers the release of encapsulated molecules. Taking GFP plasmid as an example, we demonstrate enhanced gene transfection into fibroblasts following NIR treatment.

Microfluidic Buffer Exchange for Interference-free Micro/Nanoparticle Cell Engineering

Engineering cells with active-ingredient-loaded micro/nanoparticles (NPs) is becoming an increasingly popular method to enhance native therapeutic properties, enable bio imaging and control cell phenotype. A critical yet inadequately addressed issue is the significant number of particles that remain unbound after cell labeling which cannot be readily removed by conventional centrifugation. This leads to an increase in bio imaging background noise and can impart transformative effects onto neighboring non-target cells. In this protocol, we present an inertial microfluidics-based buffer exchange strategy termed as Dean Flow Fractionation (DFF) to efficiently separate labeled cells from free NPs in a high throughput manner. The developed spiral microdevice facilitates continuous collection (>90% cell recovery) of purified cells (THP-1 and MSCs) suspended in new buffer solution, while achieving >95% depletion of unbound fluorescent dye or dye-loaded NPs (silica or PLGA). This single-step, size-based cell purification strategy enables high cell processing throughput (10(6) cells/min) and is highly useful for large-volume cell purification of micro/nanoparticle engineered cells to achieve interference-free clinical application.

Layer-by-Layer 3D Constructs of Fibroblasts in Hydrogel for Examining Transdermal Penetration Capability of Nanoparticles

Nanoparticles are emerging transdermal delivery systems. Their size and surface properties determine their efficacy and efficiency to penetrate through the skin layers. This work utilizes three-dimensional (3D) bioprinting technology to generate a simplified artificial skin model to rapidly screen nanoparticles for their transdermal penetration ability. Specifically, this model is built through layer-by-layer alternate printing of blank collagen hydrogel and fibroblasts. Through controlling valve on-time, the spacing between printing lines could be accurately tuned, which could enable modulation of cell infiltration in the future. To confirm the effectiveness of this platform, a 3D construct with one layer of fibroblasts sandwiched between two layers of collagen hydrogel is used to screen silica nanoparticles with different surface charges for their penetration ability, with positively charged nanoparticles demonstrating deeper penetration, consistent with the observation from an existing study involving living skin tissue.

Nanosensors for Continuous and Noninvasive Monitoring of Mesenchymal Stem Cell Osteogenic Differentiation

Assessing mesenchymal stem cell (MSC) differentiation status is crucial to verify therapeutic efficacy and optimize treatment procedures. Currently, this involves destructive methods including antibody-based protein detection and polymerase chain reaction gene analysis, or laborious and technically challenging genetic reporters. Development of noninvasive methods for real-time differentiation status assessment can greatly benefit MSC-based therapies. This report introduces a nanoparticle-based sensing platform that encapsulates two molecular beacon (MB) probes within the same biodegradable polymeric nanoparticles. One MB targets housekeeping gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH) as an internal reference, while another detects alkaline phosphatase (ALP), a functional biomarker. Following internalization, MBs are gradually released as the nanoparticle degrades. GAPDH MBs provide a stable reference signal throughout the monitoring period (18 days) regardless of differentiation induction. Meanwhile, ALP mRNA undergoes well-defined dynamics with peak expression observed during early stages of osteogenic differentiation. By normalizing ALP-MB signal with GAPDH-MB, changes in ALP expression can be monitored, to noninvasively validate osteogenic differentiation. As proof-of-concept, a dual-colored nanosensor is applied to validate MSC osteogenesis on 2D culture and polycaprolactone films containing osteo-inductive tricalcium phospate.

Smart Magnetic Nanosensors Synthesized through Layer-by-Layer Deposition of Molecular Beacons for Noninvasive and Longitudinal Monitoring of Cellular mRNA

Noninvasive and longitudinal monitoring of gene expression in living cells is essential for understanding and monitoring cellular activities. Herein, a smart magnetic nanosensor is constructed for the real-time, noninvasive, and longitudinal monitoring of cellular mRNA expression through the layer-by-layer deposition of molecular beacons (MBs) and polyethylenimine on the iron oxide nanoparticles. The loading of MBs, responsible for the signal intensity and the tracking time, was easily tuned with the number of layers incorporated. The idea was first demonstrated with the magnetic nanosensors for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA, which was efficiently internalized into the cells under the influence of magnetic field. This nanosensor allowed the continuous monitoring of the cellular GAPDH mRNA expression for 1 month. Then this platform was further utilized to incorporate two kinds of MBs for alkaline phosphatase (ALP) and GAPDH mRNAs, respectively. The multifunctional nanosensors permitted the simultaneous monitoring of the reference gene (GAPDH mRNA) and the early osteogenic differentiation marker (ALP mRNA) expression. When the fluorescence signal ratio between ALP mRNA MBs and GAPDH mRNA MBs was taken, the dynamic osteogenic differentiation process of MSCs was accurately monitored.

Synergism of Water Shock and a Biocompatible Block Copolymer Potentiates the Antibacterial Activity of Graphene Oxide

Graphene oxide (GO) is promising in the fight against pathogenic bacteria. However, the antibacterial activity of pristine GO is relatively low and concern over human cytotoxicity further limits its potential. This study demonstrates a general approach to address both issues. The developed approach synergistically combines the water shock treatment (i.e., a sudden decrease in environmental salinity) and the use of a biocompatible block copolymer (Pluronic F-127) as a synergist co-agent. Hypoosmotic stress induced by water shock makes gram-negative pathogens more susceptible to GO. Pluronic forms highly stable nanoassemblies with GO (Pluronic-GO) that can populate around bacterial envelopes favoring the interactions between GO and bacteria. The antibacterial activity of GO at a low concentration (50 μg mL(-1) ) increases from <30% to virtually complete killing (>99%) when complemented with water shock and Pluronic (5 mg mL(-1) ) at ≈2-2.5 h of exposure. Results suggest that the enhanced dispersion of GO and the osmotic pressure generated on bacterial envelopes by polymers together potentiate GO. Pluronic also significantly suppresses the toxicity of GO toward human fibroblast cells. Fundamentally, the results highlight the crucial role of physicochemical milieu in the antibacterial activity of GO. The demonstrated strategy has potentials for daily-life bacterial disinfection applications, as hypotonic Pluronic-GO mixture is both safe and effective.

A Nanoparticle-based Sensor Platform for Cell Tracking and Status/Function Assessment

Nanoparticles are increasingly popular choices for labeling and tracking cells in biomedical applications such as cell therapy. However, all current types of nanoparticles fail to provide real-time, noninvasive monitoring of cell status and functions while often generating false positive signals. Herein, a nanosensor platform to track the real-time expression of specific biomarkers that correlate with cell status and functions is reported. Nanosensors are synthesized by encapsulating various sensor molecules within biodegradable polymeric nanoparticles. Upon intracellular entry, nanosensors reside within the cell cytoplasm, serving as a depot to continuously release sensor molecules for up to 30 days. In the absence of the target biomarkers, the released sensor molecules remain 'Off'. When the biomarker(s) is expressed, a detectable signal is generated (On). As a proof-of-concept, three nanosensor formulations were synthesized to monitor cell viability, secretion of nitric oxide, and β-actin mRNA expression.

Interference-free Micro/nanoparticle Cell Engineering by Use of High-Throughput Microfluidic Separation

Engineering cells with active-ingredient-loaded micro/nanoparticles is becoming increasingly popular for imaging and therapeutic applications. A critical yet inadequately addressed issue during its implementation concerns the significant number of particles that remain unbound following the engineering process, which inadvertently generate signals and impart transformative effects onto neighboring nontarget cells. Here we demonstrate that those unbound micro/nanoparticles remaining in solution can be efficiently separated from the particle-labeled cells by implementing a fast, continuous, and high-throughput Dean flow fractionation (DFF) microfluidic device. As proof-of-concept, we applied the DFF microfluidic device for buffer exchange to sort labeled suspension cells (THP-1) from unbound fluorescent dye and dye-loaded micro/nanoparticles. Compared to conventional centrifugation, the depletion efficiency of free dyes or particles was improved 20-fold and the mislabeling of nontarget bystander cells by free particles was minimized. The microfluidic device was adapted to further accommodate heterogeneous-sized mesenchymal stem cells (MSCs). Complete removal of unbound nanoparticles using DFF led to the usage of engineered MSCs without exerting off-target transformative effects on the functional properties of neighboring endothelial cells. Apart from its effectiveness in removing free particles, this strategy is also efficient and scalable. It could continuously process cell solutions with concentrations up to 10(7) cells·mL(-1) (cell densities commonly encountered during cell therapy) without observable loss of performance. Successful implementation of this technology is expected to pave the way for interference-free clinical application of micro/nanoparticle engineered cells.

Molecular beacon-loaded polymeric nanoparticles for non-invasive imaging of mRNA expression

Assessment of intracellular mRNA expression is invaluable for understanding cellular signaling activities, identifying disease stages, and monitoring the gene expression pattern of therapeutic cells during their culture, expansion and/or differentiation process. Previous methods suffer from the need to disrupt the biological samples to perform polymerase chain reaction analysis which can be laborious, fragmented and destructive. Herein, we develop a mRNA nanosensor based on the sustained release of mRNA-specific molecular beacons (probes that fluoresce upon hybridization) from the biodegradable poly(d,l-lactide-co-glycolide) nanoparticles. Post cellular internalization, the particles gradually degrade and release the encapsulated probes which are initially weakly fluorescent. When the released probes meet and hybridize with target mRNA, they restore pre-quenched fluorescence. By virtue of quantifying the fluorescence intensity, we can estimate the cellular mRNA expression. As a case study, β-actin mRNA expression in mesenchymal stem cells cultured on a 3D matrix was monitored and compared with those cultured on a 2D plate for one week. Critically, the observed expression profile shows a great correlation with the established quantitative polymerase chain reaction analysis.

Aptamer technology for tracking cells' status & function

In fields such as cancer biology and regenerative medicine, obtaining information regarding cell bio-distribution, tropism, status, and other cellular functions are highly desired. Understanding cancer behaviors including metastasis is important for developing effective cancer treatments, while assessing the fate of therapeutic cells following implantation is critical to validate the efficacy and efficiency of the therapy. For visualization purposes with medical imaging modalities (e.g. magnetic resonance imaging), cells can be labeled with contrast agents (e.g. iron-oxide nanoparticles), which allows their identification from the surrounding environment. Despite the success of revealing cell biodistribution in vivo, most of the existing agents do not provide information about the status and functions of cells following transplantation. The emergence of aptamers, single-stranded RNA or DNA oligonucleotides of 15 to 60 bases in length, is a promising solution to address this need. When aptamers bind specifically to their cognate molecules, they undergo conformational changes which can be transduced into a change of imaging contrast (e.g. optical, magnetic resonance). Thus by monitoring this signal change, researchers can obtain information about the expression of the target molecules (e.g. mRNA, surface markers, cell metabolites), which offer clues regarding cell status/function in a non-invasive manner. In this review, we summarize recent efforts to utilize aptamers as biosensors for monitoring the status and function of transplanted cells. We focus on cancer cell tracking for cancer study, stem cell tracking for regenerative medicine, and immune cell (e.g. dendritic cells) tracking for immune therapy.

Aptamer technology for tracking cells' status & function

In fields such as cancer biology and regenerative medicine, obtaining information regarding cell bio-distribution, tropism, status, and other cellular functions are highly desired. Understanding cancer behaviors including metastasis is important for developing effective cancer treatments, while assessing the fate of therapeutic cells following implantation is critical to validate the efficacy and efficiency of the therapy. For visualization purposes with medical imaging modalities (e.g. magnetic resonance imaging), cells can be labeled with contrast agents (e.g. iron-oxide nanoparticles), which allows their identification from the surrounding environment. Despite the success of revealing cell biodistribution in vivo, most of the existing agents do not provide information about the status and functions of cells following transplantation. The emergence of aptamers, single-stranded RNA or DNA oligonucleotides of 15 to 60 bases in length, is a promising solution to address this need. When aptamers bind specifically to their cognate molecules, they undergo conformational changes which can be transduced into a change of imaging contrast (e.g. optical, magnetic resonance). Thus by monitoring this signal change, researchers can obtain information about the expression of the target molecules (e.g. mRNA, surface markers, cell metabolites), which offer clues regarding cell status/function in a non-invasive manner. In this review, we summarize recent efforts to utilize aptamers as biosensors for monitoring the status and function of transplanted cells. We focus on cancer cell tracking for cancer study, stem cell tracking for regenerative medicine, and immune cell (e.g. dendritic cells) tracking for immune therapy.