Methyl-Branched Liposomes as a Depot for Sustained Drug Delivery.

Inadequate drug loading and control of payload leakage limit the duration of the effect of liposomal drug carriers and may cause toxicity. Here, we report a liposome system as a depot for sustained drug delivery whose design is inspired by the low permeability of Archaeal membranes to protons and solutes. Incorporating methyl-branched phospholipids into lipid bilayers decreased payload diffusion across liposomal membranes, thereby enhancing the drug load capacity by 10-16% and reducing the release of small molecules in the first 24 h by 40-48%. The in vivo impact of this approach was demonstrated by injection at the sciatic nerve. Methyl-branched liposomes encapsulating the anesthetic tetrodotoxin (TTX) achieved markedly prolonged local anesthesia lasting up to 70 h, in comparison to the 16 h achieved with liposomes containing conventional lipids. The present work demonstrates the usefulness of methyl-branched liposomes to enhance liposomal depot systems for sustained drug delivery.

Ablation of Venous Malformations by Photothermal Therapy with Intravenous Gold Nanoshells.

Venous malformations (VMs) consist of hugely enlarged and dysmorphic veins. These lesions cause significant disfigurement, pain, and complications such as bleeding and coagulopathy. Pharmacotherapy for the treatment of VMs has limited efficacy and potentially limiting toxicity. Current treatment for patients with VMs entails life-long pharmacotherapy or surgical procedures. Here we explored whether intravenously administered agents can be used to destroy VMs by photothermal therapy (PTT), using gold nanoshells (AuNSs) that generated heat following irradiation with near-infrared (NIR) light. In a murine model of VMs, intravenous AuNSs accumulated within the VMs. Irradiation of the VMs induced marked regression and even elimination. Nanoparticle-based photothermal therapy can provide effective therapy for VMs, which are otherwise relatively refractory to treatment.

Squaraine Dye-Sensitized Upconversion with Enhanced Stability and Minimized Aggregation-Caused Quenching.

Upconversion nanoparticles (UCNPs) doped with lanthanides have limited brightness due to their small absorption cross section to light. However, using organic sensitizers can significantly enhance their light absorption ability. Unfortunately, the practical application of organic sensitizers has been hindered by poor stability and aggregation-caused quenching (ACQ). To address these issues, we developed a novel squaraine-based dye, SQ-739, for sensitizing upconversion luminescence (UCL). This dye has a maximum absorption at 739 nm, and shows 1 order of magnitude and 2-fold improved chemical- and photostability, compared to the commonly used cyanine-based dye IR-806, respectively. When SQ-739 is used to sensitize UCNPs, the resulting SQ-739-UCNPs exhibit excellent photostability and reduced ACQ in the presence of polar solvents. Moreover, at the single particle level, the SQ-739-UCNPs exhibit a 97-fold increase in UCL emission compared to bare UCNPs. This squaraine dye-based system represents a new design strategy for developing highly stable and efficient NIR upconversion probes.

On-Demand Opioid Effect Reversal with an Injectable Light-Triggered Polymer-Naloxone Conjugate.

Misuse of opioids can lead to a potential lethal overdose. Timely administration of naloxone is critical for survival. Here, we designed a polymer-naloxone conjugate that can provide on-demand phototriggered opioid reversal. Naloxone was attached to the polymer poly(lactic-co-glycolic acid) via a photocleavable coumarin linkage and formulated as injectable nanoparticles. In the absence of irradiation, the formulation did not release naloxone. Upon irradiation with blue (400 nm) light, the nanoparticles released free naloxone, reversing the effect of morphine in mice. Such triggered events could be performed days and weeks after the initial administration of the nanoparticles and could be performed repeatedly.

Polymeric Prodrugs using Dynamic Covalent Chemistry for Prolonged Local Anesthesia.

Depot-type drug delivery systems are designed to deliver drugs at an effective rate over an extended period. Minimizing initial "burst" can also be important, especially with drugs causing systemic toxicity. Both goals are challenging with small hydrophilic molecules. The delivery of molecules such as the ultrapotent local anesthetic tetrodotoxin (TTX) exemplifies both challenges. Toxicity can be mitigated by conjugating TTX to polymers with ester bonds, but the slow ester hydrolysis can result in subtherapeutic TTX release. Here, we developed a prodrug strategy, based on dynamic covalent chemistry utilizing a reversible reaction between the diol TTX and phenylboronic acids. These polymeric prodrugs exhibited TTX encapsulation efficiencies exceeding 90 % and the resulting polymeric nanoparticles showed a range of TTX release rates. In vivo injection of the TTX polymeric prodrugs at the sciatic nerve reduced TTX systemic toxicity and produced nerve block lasting 9.7±2.0 h, in comparison to 1.6±0.6 h from free TTX. This approach could also be used to co-deliver the diol dexamethasone, which prolonged nerve block to 21.8±5.1 h. This work emphasized the usefulness of dynamic covalent chemistry for depot-type drug delivery systems with slow and effective drug release kinetics.

Enhancement of Trans-Tympanic Drug Delivery by Pharmacological Induction of Inflammation.

Drug delivery directly across the tympanic membrane (TM) could eliminate systemic exposure to antibiotics prescribed for otitis media, the most common reason for pediatricians to prescribe antibiotics. Here, we hypothesized that inducing inflammation of the TM could enhance drug flux across the TM. We demonstrated that the flux of ciprofloxacin across the TM was greatly increased by treatment with the proinflammatory agent histamine. That enhancement was blocked by concurrent treatment with blockers of histamine receptor 1. Treatment of the TM with histamine was able to enhance drug flux sufficiently to eradicate otitis media in vivo in chinchillas, but only if the histamine was applied prior to treatment with antibiotics.

Reprogramming the microenvironment with tumor-selective angiotensin blockers enhances cancer immunotherapy.

Cancer-associated fibroblasts (CAFs) can either suppress or support T lymphocyte activity, suggesting that CAFs may be reprogrammable to an immunosupportive state. Angiotensin receptor blockers (ARBs) convert myofibroblast CAFs to a quiescent state, but whether ARBs can reprogram CAFs to promote T lymphocyte activity and enhance immunotherapy is unknown. Moreover, ARB doses are limited by systemic adverse effects such as hypotension due to the importance of angiotensin signaling outside tumors. To enhance the efficacy and specificity of ARBs in cancer with the goal of revealing their effects on antitumor immunity, we developed ARB nanoconjugates that preferentially accumulate and act in tumors. We created a diverse library of hundreds of acid-degradable polymers and chemically linked ARBs to the polymer most sensitive to tumor pH. These tumor microenvironment-activated ARBs (TMA-ARBs) remain intact and inactive in circulation while achieving high concentrations in tumors, wherein they break down to active ARBs. This tumor-preferential activity enhances the CAF-reprogramming effects of ARBs while eliminating blood pressure-lowering effects. Notably, TMA-ARBs alleviate immunosuppression and improve T lymphocyte activity, enabling dramatically improved responses to immune-checkpoint blockers in mice with primary as well as metastatic breast cancer.

Synergy in Nanomedicine: What It Is Not, and What It Might Be.

Interactions between nanoformulations delivering two or more drugs-or a drug and some other therapeutic modality-are often described as synergistic. In fact, synergy is a specific term of art, with important therapeutic implications. The term is often misused in the nanoscience literature. Here we discuss what synergy is and an approach to demonstrating it rigorously.

Targeting Nanoparticles to Bioengineered Human Vascular Networks.

Pharmacotherapy of vascular anomalies has limited efficacy and potentially limiting toxicity. Targeted nanoparticle (NP) drug delivery systems have the potential to accumulate within tissues where the vasculature is impaired, potentially leading to high drug levels (increased efficacy) in the diseased tissue and less in off-target sites (less toxicity). Here, we investigate whether NPs can be used to enhance drug delivery to bioengineered human vascular networks (hVNs) that are a model of human vascular anomalies. We demonstrate that intravenously injected phototargeted NPs enhanced accumulation of NPs and the drug within hVNs. With phototargeting we demonstrate 17 times more NP accumulation within hVNs than was detected in hVNs without phototargeting. With phototargeting there was 10-fold more NP accumulation within hVNs than in any other organ. Phototargeting resulted in a 6-fold increase in drug accumulation (doxorubicin) within hVNs in comparison to animals injected with the free drug. Nanoparticulate approaches have the potential to markedly improve drug delivery to vascular anomalies.

Drug Delivery across Barriers to the Middle and Inner Ear.

The prevalence of ear disorders has spurred efforts to develop drug delivery systems to treat these conditions. Here, recent advances in drug delivery systems that access the ear through the tympanic membrane (TM) are reviewed. Such methods are either non-invasive (placed on the surface of the TM), or invasive (placed in the middle ear, ideally on the round window [RW]). The major hurdles to otic drug delivery are identified and highlighted the representative examples of drug delivery systems used for drug delivery across the TM to the middle and (crossing the RW also) inner ear.

Enhancement of the Mechanical and Drug-Releasing Properties of Poloxamer 407 Hydrogels with Casein.

PURPOSE: Topical therapy of local disease (e.g. skin) is advantageous over oral therapy since there is less systemic drug distribution (so fewer side-effects), no first-pass effect, etc. However, patient compliance with topical therapy can be poor as it may require many applications a day and can last months. Here we propose a topical controlled release formulation with thermoresponsive gelation at body temperature and improved adhesiveness, making it easier to remain in contact with the body. METHODS: The formulation contains two excipients, poloxamer 407 (P407) and casein. Casein can modify the properties of the hydrogel through molecular entanglement. In addition, tissue reaction and drug release profile were evaluated. RESULTS: Changes in casein concentration affected adhesive strength, viscosity, mechanical properties and drug release, presumably by hydrophobic interactions between casein and P407. Two different concentrations of P407 were tested with two different concentrations of casein. Formulations containing 5% and 10% casein released 80% of model drug in 48 h, while formulations without casein released the same fraction in around 24 h hours. Formulations with 10% casein had almost twice the adhesive strength of those without casein. CONCLUSIONS: Addition of casein modified the mechanical properties and drug release rate of the hydrogel. There was no inflammation or injury after brief exposure in vivo.

Dually Enzyme- and Acid-Triggered Self-Immolative Ketal Glycoside Nanoparticles for Effective Cancer Prodrug Monotherapy.

The use of glycoside prodrugs is a promising strategy for developing new targeted medicines for chemotherapy. However, the in vivo utility of such prodrugs is hindered by insufficient activation and the lack of convenient synthetic methods. We have developed an innovative strategy for synthesizing ketal glycoside prodrugs that are unique in being activated by a dual enzyme- and acid-triggered self-immolative mechanism. Amphiphilic glucosyl acetone-based ketal-linked etoposide glycoside prodrug isomers were synthesized and fabricated into excipient-free nanoparticles for effective cancer prodrug monotherapy. Hydrolysis of the glycosidic linkage or the ketal linkage triggered hydrolysis of the other linkage, which resulted in spontaneous self-immolative hydrolysis of the prodrugs. Nanoparticles of the prodrug isomer that was the most labile in a lysosome-mimicking environment displayed high intratumoral accumulation and strong antitumor activity in an A549 xenograft mouse model. Our strategy may be useful for the development of stimulus-responsive self-immolative prodrugs and their nanomedicines.

Transcytosis of Nanomedicine for Tumor Penetration.

The diffusion of nanomedicines used to treat tumors is severely hindered by the microenvironment, which is a challenge that has emerged as a bottleneck for the effective outcome of nanotherapies. Classical strategies for enhancing tumor penetration rely on passive movement in the extracellular matrix (ECM). Here, we demonstrate that nanomedicine also penetrates tumor lesions via an active trans-cell transportation process. This process was discovered by directly observing the movement of nanoparticles between cells, evaluating the intracellular trafficking pathway of nanoparticles via Rab protein labeling, comparing endocytosis-exocytosis between nanoparticles administered with inhibitors, and correlating the transcytosis process with the micro-CT distribution of nanomedicines. We also demonstrated that enhanced tumor penetration promotes the therapeutic efficacy of a photodynamic therapeutic nanomedicine. Our research thus suggests that transcytosis could be an important positive factor for designing cancer nanomedicines.

A Simple, Yet Multifunctional, Nanoformulation for Eradicating Tumors and Preventing Recurrence with Safely Low Administration Dose.

Designing simple-structured nanomedicine without lacking key functionalities, thereby avoiding incomplete damage or relapse of tumor with the administration of a safe dose, is pivotal for successful cancer nanotherapy. We herein presented a nanomedicine of photodynamic therapy (PDT) that simply assembled amphiphilic macromolecules of poly-l-lysine conjugating with photosensitizers onto hydrophobic upconverting nanoparticles. We demonstrated that the nanoformulation, despite its simple structure and synthesis, simultaneously possesses multiple features, including substantial payload of photosensitizers, avid cellular internalization both in vitro and in vivo, efficient diffusion and broad distribution in tumor lesion, and potent fatality for cancer stem cells that are refractory to other therapy modalities. Because of the combination of these functionalities, the tumors in mice were eradicated and no relapse was observed after at least 40 days, just with an extremely low intraperitoneal injection dose of 5.6 mg/kg. Our results suggested a strategy for designing multifunctional nanomedicines with simple construct and efficacious therapeutic response and presented the promising potential of PDT for a radical cure of cancer.

New Strategies in Cancer Nanomedicine.

We review recent progress in cancer nanomedicine, including stimulus-responsive drug delivery systems and nanoparticles responding to light for phototherapy or tumor imaging. In addition, several new strategies to improve the circulation of nanoparticles in vivo, tumor penetration, and tumor targeting are discussed. The application of nanomedicine in cancer immunology, a relatively new type of cancer therapy, is also highlighted.

Transtympanic Delivery of Local Anesthetics for Pain in Acute Otitis Media.

Acute otitis media (AOM) commonly causes pain and distress in children. Existing analgesic ototopical drops have limited effectiveness due to the impermeable nature of the tympanic membrane. We developed a local drug delivery system to provide sustained pain relief in patients with AOM, achieved by applying a single dose of a hydrogel formulation onto the tympanic membrane. Successful drug delivery across intact tympanic membranes was demonstrated using the amino-amide anesthetic, bupivacaine, and a highly potent site 1 sodium channel blocker anesthetic, tetrodotoxin. The chemical permeation enhancers incorporated in the delivery system increased the permeability of the tympanic membrane to the anesthetics considerably. The drug levels measured using a previously developed ex vivo model reflect the potential for highly effective local anesthesia.

The Duration of Nerve Block from Local Anesthetic Formulations in Male and Female Rats.

PURPOSE: It is unknown whether there are sex differences in response to free or encapsulated local anesthetics. METHODS: We examined nerve block duration and toxicity following peripheral nerve blockade in male and female rats. We studied the local anesthetic bupivacaine (free or encapsulated) as well as tetrodotoxin, which acts on a different site of the same voltage-gated channel. RESULTS: Sensory nerve blockade was 158.5 [139-190] minutes (median [interquartile range]) (males) compared to 173 [134-171] minutes (females) (p = 0.702) following bupivacaine injection, N = 8 male, 8 female. Motor nerve blockade was 157 [141-171] minutes (males) compared to 172 [146-320] minutes (females) (p = 0.2786). Micellar bupivacaine (N = 8 male, 8 female) resulted in sensory nerve blockade of 266 [227-320] minutes (males) compared to 285 [239-344] minutes (females) (p = 0.6427). Motor nerve blockade was 264 [251-264] minutes (males) compared to 287 [262-287] minutes (females) (p = 0.3823). Liposomal bupivacaine (N = 8 male, 8 female) resulted in sensory nerve blockade of 240 [207-277] minutes (males) compared to 289 [204-348] minutes (females) (p = 0.1654). Motor nerve blockade was 266 [237-372] minutes (males) compared to 317 [251-356] minutes (females) (p = 0.6671). Following tetrodotoxin injection (N = 12 male,12 female) sensory nerve blockade was 54.8 [5-117] minutes (males) compared to 54 [14-71] minutes (females) (p = 0.6422). Motor nerve blockade was 72 [40-112] minutes (males) compared to 64 [32-143] minutes (females) (p = 0.971). CONCLUSIONS: We found no statistically significant sex differences associated with the formulations tested. In both sexes, durations of nerve block were similar between micellar and liposomal bupivacaine formulations, despite the micellar formulation containing less drug.

Quantile Regression and Its Applications: A Primer for Anesthesiologists.

Multivariable regression analysis is a powerful statistical tool in biomedical research with numerous applications. While linear regression can be used to model the expected value (ie, mean) of a continuous outcome given the covariates in the model, quantile regression can be used to compare the entire distribution of a continuous response or a specific quantile of the response between groups. The advantage of the quantile regression methodology is that it allows for understanding relationships between variables outside of the conditional mean of the response; it is useful for understanding an outcome at its various quantiles and comparing groups or levels of an exposure on those quantiles. We present quantile regression in a 3-step approach: determining that quantile regression is desired, fitting the quantile regression model, and interpreting the model results. We then apply our quantile regression analysis approach using 2 illustrative examples from the 2015 American College of Surgeons National Surgical Quality Improvement Program Pediatric database, and 1 example utilizing data on duration of sensory block in rats.