Phototriggered Local Anesthesia

Advances in the use of local anesthetic extended-release systems in pain management

Pain management remains among the most common and largely unmet clinical problems today. Local anesthetics play an indispensable role in pain management. The main limitation of traditional local anesthetics is the limited duration of a single injection. To address this problem, catheters are often placed or combined with other drugs in clinical practice to increase the time that local anesthetics act. However, this method does not meet the needs of clinical analgesics. Therefore, many researchers have worked to develop local anesthetic extended-release types that can be administered in a single dose. In recent years, drug extended-release systems have emerged dramatically due to their long duration and efficacy, providing more possibilities for the application of local anesthetics. This paper summarizes the types of local anesthetic drug delivery systems and their clinical applications, discusses them in the context of relevant studies on local anesthetics, and provides a summary and outlook on the development of local anesthetic extended-release agents.

Nanomedicine and voltage-gated sodium channel blockers in pain management: a game changer or a lost cause?

Pain, a complex and debilitating condition affecting millions globally, is a significant concern, especially in the context of post-operative recovery. This comprehensive review explores the complexity of pain and its global impact, emphasizing the modulation of voltage-gated sodium channels (VGSC or NaV channels) as a promising avenue for pain management with the aim of reducing reliance on opioids. The article delves into the role of specific NaV isoforms, particularly NaV 1.7, NaV 1.8, and NaV 1.9, in pain process and discusses the development of sodium channel blockers to target these isoforms precisely. Traditional local anesthetics and selective NaV isoform inhibitors, despite showing varying efficacy in pain management, face challenges in systemic distribution and potential side effects. The review highlights the potential of nanomedicine in improving the delivery of local anesthetics, toxins and selective NaV isoform inhibitors for a targeted and sustained release at the site of pain. This innovative strategy seeks to improve drug bioavailability, minimize systemic exposure, and optimize therapeutic outcomes, holding significant promise for secure pain management and enhancing the quality of life for individuals recovering from surgical procedures or suffering from chronic pain.

Recent advances in stimuli-responsive controlled release systems for neuromodulation

Neuromodulation aims to modulate the signaling activity of neurons or neural networks by the precise delivery of electrical stimuli or chemical agents and is crucial for understanding brain function and treating brain disorders. Conventional approaches, such as direct physical stimulation through electrical or acoustic methods, confront challenges stemming from their invasive nature, dependency on wired power sources, and unstable therapeutic outcomes. The emergence of stimulus-responsive delivery systems harbors the potential to revolutionize neuromodulation strategies through the precise and controlled release of neurochemicals in a specific brain region. This review comprehensively examines the biological barriers controlled release systems may encounter in vivo and the recent advances and applications of these systems in neuromodulation. We elucidate the intricate interplay between the molecular structure of delivery systems and response mechanisms to furnish insights for material selection and design. Additionally, the review contemplates the prospects and challenges associated with these systems in neuromodulation. The overarching objective is to propel the application of neuromodulation technology in analyzing brain functions, treating brain disorders, and providing insightful perspectives for exploiting new systems for biomedical applications.

Nanotechnology-based delivery systems to overcome drug resistance in cancer

Cancer nanomedicine is defined as the application of nanotechnology and nanomaterials for the formulation of cancer therapeutics that can overcome the impediments and restrictions of traditional chemotherapeutics. Multidrug resistance (MDR) in cancer cells can be defined as a decrease or abrogation in the efficacy of anticancer drugs that have different molecular structures and mechanisms of action and is one of the primary causes of therapeutic failure. There have been successes in the development of cancer nanomedicine to overcome MDR; however, relatively few of these formulations have been approved by the United States Food and Drug Administration for the treatment of cancer. This is primarily due to the paucity of knowledge about nanotechnology and the fundamental biology of cancer cells. Here, we discuss the advances, types of nanomedicines, and the challenges regarding the translation of in vitro to in vivo results and their relevance to effective therapies.

Aromatized liposomes for sustained drug delivery

Insufficient drug loading and leakage of payload remain major challenges in designing liposome-based drug delivery systems. These phenomena can limit duration of effect and cause toxicity. Targeting the rate-limiting step in drug release from liposomes, we modify (aromatized) them to have aromatic groups within their lipid bilayers. Aromatized liposomes are designed with synthetic phospholipids with aromatic groups covalently conjugated onto acyl chains. The optimized aromatized liposome increases drug loading and significantly decreases the burst release of a broad range of payloads (small molecules and macromolecules, different degrees of hydrophilicity) and extends their duration of release. Aromatized liposomes encapsulating the anesthetic tetrodotoxin (TTX) achieve markedly prolonged effect and decreased toxicity in an application where liposomes are used clinically: local anesthesia, even though TTX is a hydrophilic small molecule which is typically difficult to encapsulate. Aromatization of lipid bilayers can improve the performance of liposomal drug delivery systems.

Emerging Anesthetic Nanomedicines: Current State and Challenges

Anesthetics, which include both local and general varieties, are a unique class of drugs widely utilized in clinical surgery to alleviate pain and promote relaxation in patients. Although numerous anesthetics and their traditional formulations are available in the market, only a select few exhibit excellent anesthetic properties that meet clinical requirements. The main challenges are the potential toxic and adverse effects of anesthetics, as well as the presence of the blood-brain barrier (BBB), which makes it difficult for most general anesthetics to effectively penetrate to the brain. Loading anesthetics onto nanocarriers as anesthetic nanomedicines might address these challenges and improve anesthesia effectiveness, reduce toxic and adverse effects, while significantly enhance the efficiency of general anesthetics passing through the BBB. Consequently, anesthetic nanomedicines play a crucial role in the field of anesthesia. Despite their significance, research on anesthetic nanomedicines is still in its infancy, especially when compared to other types of nanomedicines in terms of depth and breadth. Although local anesthetic nanomedicines have received considerable attention and essentially meet clinical needs, there are few reported instances of nanomedicines for general anesthetics. Given the extensive usage of anesthetics and the many of them need for improved performance, emerging anesthetic nanomedicines face both unparalleled opportunities and considerable challenges in terms of theory and technology. Thus, a comprehensive summary with systematic analyses of anesthetic nanomedicines is urgently required. This review provides a comprehensive summary of the classification, properties, and research status of anesthetic nanomedicines, along with an exploration of their opportunities and challenges. In addition, future research directions and development prospects are discussed. It is hoped that researchers from diverse disciplines will collaborate to study anesthetic nanomedicines and develop them as a valuable anesthetic dosage form for clinical surgery.

Materials for Controlled Release of Local Anesthetics

Controlled release systems for prolonged duration local anesthesia have long been an area of research interest, and now are entering clinical practice, in part driven by the opioid epidemic. We discuss the design considerations and material properties of systems for controlled release of local anesthetics, from relatively simple systems to covalent binding of drugs to materials and delivery triggered by external stimuli.

Examining Silver Deposition Pathways onto Gold Nanorods with Liquid-Phase Transmission Electron Microscopy

Liquid-phase transmission electron microscopy (LP-TEM) enables one to directly visualize the formation of plasmonic nanoparticles and their postsynthetic modification, but the relative contributions of plasmonic hot electrons and radiolysis to metal precursor reduction remain unclear. Here we show silver deposition onto plasmonic gold nanorods (AuNRs) during LP-TEM is dominated by water radiolysis-induced chemical reduction. Silver was observed with LP-TEM to form bipyramidal shells at higher surfactant coverage and tip-preferential lobes at lower surfactant coverage. Ex situ silver photodeposition formed nanometer-thick shells on AuNRs with preferential deposition in inter-rod gaps, while chemical reduction deposited silver at AuNR tips at low surfactant coverage and formed pyramidal shells at higher surfactant coverage, consistent with LP-TEM. Silver deposition locations during LP-TEM were inconsistent with simulated near-field enhancement and hot electron generation hot spots. Collectively, the results indicate chemical reduction dominated during LP-TEM, indicating observation of plasmonic hot electron-induced photoreduction will necessitate suppression of radiolysis.

Responsive Nanostructure for Targeted Drug Delivery

Currently, intelligent, responsive biomaterials have been widely explored, considering the fact that responsive biomaterials provide controlled and predictable results in various biomedical systems. Responsive nanostructures undergo reversible or irreversible changes in the presence of a stimulus, and that stimuli can be temperature, a magnetic field, ultrasound, pH, humidity, pressure, light, electric field, etc. Different types of stimuli being used in drug delivery shall be explained here. Recent research progress in the design, development and applications of biomaterials comprising responsive nanostructures is also described here. More emphasis will be given on the various nanostructures explored for the smart stimuli responsive drug delivery at the target site such as wound healing, cancer therapy, inflammation, and pain management in order to achieve the improved efficacy and sustainability with the lowest side effects. However, it is still a big challenge to develop well-defined responsive nanostructures with ordered output; thus, challenges faced during the design and development of these nanostructures shall also be included in this article. Clinical perspectives and applicability of the responsive nanostructures in the targeted drug delivery shall be discussed here.

Lipid-Based Intelligent Vehicle Capabilitized with Physical and Physiological Activation

Intelligent drug delivery system based on "stimulus-response" mode emerging a promising perspective in next generation lipid-based nanoparticle. Here, we classify signal sources into physical and physiological stimulation according to their origin. The physical signals include temperature, ultrasound, and electromagnetic wave, while physiological signals involve pH, redox condition, and associated proteins. We first summarize external physical response from three main points about efficiency, particle state, and on-demand release. Afterwards, we describe how to design drug delivery using the physiological environment in vivo and present different current application methods. Lastly, we draw a vision of possible future development.

Micro- and nanocarriers for pain alleviation

Acute or chronic pain is a major source of impairment in quality of life and affects a substantial part of the population. To date, pain is alleviated by a limited range of treatments with significant toxicity, increased risk of misuse and inconsistent efficacy, owing, in part, to lack of specificity and/or unfavorable pharmacokinetic properties. Thanks to the unique properties of nanoscaled drug carriers, nanomedicine may enhance drug biodistribution and targeting, thus contributing to improved bioavailability and lower off-target toxicity. After a brief overview of the current situation and the main critical issues regarding pain alleviation, this review will examine the most advanced approaches using nanomedicine of each drug class, from the preclinical stage to approved nanomedicines.

NIR Light-Triggered Quantitative Pulsed Drug Release

Quantitative drug release is important for improving therapeutic efficiency and avoiding side effects. While using long-term delivery system for repeated therapies, it is indispensable but challenging to accurately control the drug dosing. Here, a photocleavable prodrug loaded hydrogel is proposed for near infrared (NIR) light-triggered quantitative pulsed drug release. IR783, a commercially available NIR fluorescent dye, is conjugated with methyl honokiol (mHNK) to give a photocleavable IR783-mHNK prodrug. Injectable glycol chitosan (GC) hydrogel is chosen as a reservoir, in which IR783-mHNK can be efficiently loaded via electrostatic and hydrophobic interactions. Upon 680 nm light-emitting diode (LED) light irradiation, IR783-mHNK cleaves and mHNK is released. Notably, it is found that IR783-mHNK presents synchronous photocleavage-fluorescence bleaching phenomenon. The released amount of mHNK is visible by measuring the residual fluorescent intensity of hydrogel. Quantitative drug release is achieved by controlling irradiation duration and the drug release process is visible by fluorescence imaging. The prodrug-loaded hydrogel shows good stability, minimum leakage and efficient light responsibility both in vitro and in vivo. After light triggering, monitorable quantitative mHNK release and on-demand sleep-promotiing effect are verified in mice without toxicities.

Near-infrared triggered ropivacaine liposomal gel for adjustable and prolonged local anaesthesia

Local analgesics effectively allow patients to relieve postoperative pain and reduce the need for inhaled general anesthetics or opioids. Compared with other similar long-acting local anesthetics, ropivacaine (Rop) is widely used due to its potential to minimize cardiotoxicity. However, the relatively short duration of Rop efficacy, which lasts for several hours after injection, is considered insufficient for long-term acute and chronic pain treatment. At present, repeated injections or indwelling catheters are used to achieve long-term drug delivery, which can easily cause infection and inflammation. To achieve externally controllable analgesia for a prolonged time, we prepared near-infrared (NIR)-responsive Rop liposomes (Rop@Lip) containing photosensitizers PdPC(OBu)₈ and unsaturated phospholipid DLPC. The particle size of the Rop@Lip was 234.73 ± 5.21 nm, the PDI was 0.42 ± 0.02, and the drug encapsulation rate was 94.62 ± 1.1%. The release of Rop was highly NIR-dependent in vitro and in vivo. To ensure that the liposomes reside around the nerve for an extended period, we next designed an in situ gel with chitosan (CS) and β-sodium glycerophosphate (β-GP) to form a liposomal gel (Lip/Gel). This Lip/Gel composite drug delivery system could be retained in vivo for 10 d, reduce the side effects caused by drug overdose, and prolong the duration of efficacy. In summary, the NIR-responsive Rop composite drug delivery system generated in this paper can effectively solve the shortcomings of traditional local injections, reduce the toxicity and side effects of free Rop, and provide a basis for a light-responsive delivery system of analgesic drugs.

New peripheral nerve blocks and local anesthetics

PURPOSE OF REVIEW

To describe current developed regional blocks, their indications and clinical use. Furthermore, describe new local anesthetics recently introduced and the new agents in pipeline.

RECENT FINDINGS

There are multiple new blocks recently developed with the introduction of ultrasound to regional anesthesia and studies demonstrate effect in different surgical procedures. However, majority of the studies do not compare with gold standard and are relatively small to change clinical practice. Some of these blocks are: erector spinae plane block, infiltration between the popliteal artery and capsule of the posterior knee, pectoral nerve blocks, quadratus lumborum and transversus abdominis plane block. New local anesthetics and adjuvants have been developed in recent years. However, the studies with even with the oldest one introduced Exparel is currently questioned, large future studies are needed to determine efficacy and safety profile and compared with conventional local anesthetics.

SUMMARY

New regional block techniques and new local anesthetics have been introduced recently. However, the efficacy/safety and comparison to conventional techniques and local anesthetics are still needed. Future studies must focus on prolonging analgesia with least invasive regional technique and compare new local anesthetics with current ones.

Learning from natural design for local anesthetic delivery

There is a sizeable but unfilled need for drug delivery systems that prolong the duration of action and reduce the systemic toxicity of local anesthetics. Inspired by the interactions of anesthetics with their natural binding sites on sodium channels, Ji et al. designed self-assembled nanostructures that achieve specific delivery and sustained release of anesthetics.

An injectable mesoporous silica-based analgesic delivery system prolongs the duration of sciatic nerve block in mice with minimal toxicity

The major limitation of traditional local anesthetics is the finite duration of a single injection. The present study developed two kinds of novel injectable anesthetic nanocomposites based on mesoporous silica, and evaluated their long-lasting analgesic effect and biosafety. The nanoparticulate carriers, mesoporous silica nanoparticles (MSNs) and mesoporous silica-coated gold nanorods (GNR@MSN), were firstly constructed using the oil-water biphase reaction approach and then ropivacaine (RPC), a local anesthetic, was loaded into the mesoporous carriers by vacuum suction. Transmission electron microscopic images showed the well-ordered mesoporous structure for drug loading. RPC-loaded MSNs and RPC-loaded GNR@MSN exhibited a sustained-release pattern in vitro, and the latter also showed a controlled-release manner triggered by near-infrared (NIR) irradiation. RPC-loaded MSNs and RPC-loaded GNR@MSN caused an initial sensory blockade in mice that lasted for 6 h, almost 2.5 folds of that from free RPC solution. Furthermore, upon NIR irradiation, the latter induced three additional periods of the blockade. Neither of them showed motor nerve block, which may be due to the sustained release manner. The low myotoxicity and low neurotoxicity of the two nanocomposites were presented both in vitro and in vivo. These results demonstrate the potential of the mesoporous silica-based analgesic nanocomposites in effectively controlling postoperative pain, maybe RPC-loaded MSNs for moderate pain and RPC-loaded GNR@MSN for severe pain. STATEMENT OF SIGNIFICANCE: Adequate postoperative analgesia helps early functional exercise after surgery and accelerates rapid recovery, while uncontrolled postoperative pain probably develops chronic post-surgical pain that impacts the life quality of patients for a long time. However, postoperative pain management is still a challenge. The current treatment drugs are always accompanied by some side effects due to their systemic effect. Opioids have risks of addiction and respiratory depression, and nonsteroidal anti-inflammatory drugs can lead to gastrointestinal reaction. Therefore, the long-lasting local anesthetic formulation with good biocompatibility is the most promising solution to manage post-surgical pain. The present study developed novel injectable anesthetic nanocomposites based on mesoporous silica, providing long-lasting pain relief in mice with minimal toxicity.

Hybrid thermoresponsive nanoparticles containing drug nanocrystals for NIR-triggered remote release

The on-demand administration of anaesthetic drugs can be a promising alternative for chronic pain management. To further improve the efficacy of drug delivery vectors, high drug loadings combined with a spatiotemporal control on the release can not only relief the pain according to patient's needs, but also improve the drawbacks of conventional burst release delivery systems. In this study, a hybrid nanomaterial was developed by loading bupivacaine nanocrystals (BNCs) into oligo(ethylene glycol) methyl ether methacrylate (OEGMA)-based thermoresponsive nanogels and coupling them to NIR-absorbing biodegradable copper sulphide nanoparticles (CuS NPs). Those CuS NPs were surface modified with polyelectrolytes using layer-by-layer techniques to be efficiently attached to the surface of nanogels by means of supramolecular interactions. The encapsulation of bupivacaine in the form of nanocrystals allowed to achieve CuS@BNC-nanogels having drug loadings as high as 65.5 wt%. The nanocrystals acted as long-lasting drug reservoirs, leading to an elevated localized drug content, which was useful for their application in prolonged pain relief. The CuS@BNC-nanogels exhibited favorable photothermal transducing properties upon NIR-light irradiation. The photothermal effect granted by the CuS NPs triggered the nano-crystallized drug release to be boosted by the collapse of the thermoresponsive nanogels upon heating. Remote control was achieved for on-demand release at a specific time and place, indicating their potential use as an externally activated triggerable drug-delivery system. Furthermore, cell viability tests and flow cytometry analysis were performed showing satisfactory cytocompatibility in the dose-ranging study having a subcytotoxic concentration of 0.05 mg/mL for CuS@BNC-nanogels. This remotely activated nanoplatform is a promising strategy for long-lasting controlled analgesia and a potential alternative for clinical pain management.

Delivery of local anaesthetics by a self-assembled supramolecular system mimicking their interactions with a sodium channel

Site-1 sodium channel blockers (S1SCBs) act as potent local anaesthetics, but they can cause severe systemic toxicity. Delivery systems can be used to reduce the toxicity, but the hydrophilicity of S1SCBs makes their encapsulation challenging. Here, we report a self-assembling delivery system for S1SCBs whose design is inspired by the specific interactions of S1SCBs with two peptide sequences on the sodium channel. Specifically, the peptides were modified with hydrophobic domains so that they could assemble into nanofibres that facilitated specific binding with the S1SCBs tetrodotoxin, saxitoxin and dicarbamoyl saxitoxin. Injection of S1SCB-carrying nanofibres at the sciatic nerves of rats led to prolonged nerve blockade and to reduced systemic toxicity, with benign local-tissue reaction. The strategy of mimicking a molecular binding site via supramolecular interactions may be applicable more broadly to the design of drug delivery systems for receptor-mediated drugs.

From Poison to Promise: The Evolution of Tetrodotoxin and Its Potential as a Therapeutic

Tetrodotoxin (TTX) is a potent neurotoxin that was first identified in pufferfish but has since been isolated from an array of taxa that host TTX-producing bacteria. However, determining its origin, ecosystem roles, and biomedical applications has challenged researchers for decades. Recognized as a poison and for its lethal effects on humans when ingested, TTX is primarily a powerful sodium channel inhibitor that targets voltage-gated sodium channels, including six of the nine mammalian isoforms. Although lethal doses for humans range from 1.5-2.0 mg TTX (blood level 9 ng/mL), when it is administered at levels far below LD₅₀, TTX exhibits therapeutic properties, especially to treat cancer-related pain, neuropathic pain, and visceral pain. Furthermore, TTX can potentially treat a variety of medical ailments, including heroin and cocaine withdrawal symptoms, spinal cord injuries, brain trauma, and some kinds of tumors. Here, we (i) describe the perplexing evolution and ecology of tetrodotoxin, (ii) review its mechanisms and modes of action, and (iii) offer an overview of the numerous ways it may be applied as a therapeutic. There is much to be explored in these three areas, and we offer ideas for future research that combine evolutionary biology with therapeutics. The TTX system holds great promise as a therapeutic and understanding the origin and chemical ecology of TTX as a poison will only improve its general benefit to humanity.

Applications of capillary action in drug delivery

Contrary to the fact that capillary action is ubiquitous in our daily lives, its role in drug delivery has not attracted attention. Therefore, its application in medicine and disease treatment has not been actively developed. This perspective begins by reviewing the principles, advantages, and limitations of the three existing drug delivery strategies: non-covalent interaction, cavity loading, and covalent conjugation. Then, we discussed the principle of capillary action in drug delivery and the influencing factors that determine its performance. To illustrate the advantages of capillary action over existing drug delivery strategies and how the capillary action could potentially address the shortcomings of the existing drug delivery strategies, we described five examples of using capillary action to design drug delivery platforms for disease treatment: marker pen for topical and transdermal drug delivery, microneedle patch with a sponge container for pulsatile drug delivery, core-shell scaffold for sustained release of growth factors, oral bolus for insulin delivery to the esophagus, and semi-hollow floating ball for intravesical and gastroprotective drug delivery. Each of the five drug delivery platforms exhibits certain unique functions that existing drug delivery technologies cannot easily achieve, hence expected to solve specific practical medical problems that are not satisfactorily resolved. As people pay more attention to capillary action and develop more drug delivery platforms, more unique functions and characteristics of capillary action in drug delivery will be explored. Thus, capillary action could become an important choice for drug delivery systems to improve therapeutic drug efficacy, treat diseases, and improve human health.

Nanogels with High Loading of Anesthetic Nanocrystals for Extended Duration of Sciatic Nerve Block

The development of thermoresponsive nanogels loaded with nanocrystals of the local anesthetic bupivacaine nanocrystals (BNCs) for prolonged peripheral nerve pain relief is reported here. BNCs were prepared using the antisolvent precipitation method from the hydrophobic form of bupivacaine (bupivacaine free base). The as-prepared BNCs were used stand-alone or encapsulated in temperature-responsive poly(ethylene glycol) methyl ether methacrylate (OEGMA)-based nanogels, resulting in bupivacaine NC-loaded nanogels (BNC-nanogels) of monodisperse size. The synthesis protocol has rendered high drug loadings (i.e., 93.8 ± 1.5 and 84.8 ± 1.2 wt % for the NC and BNC-nanogels, respectively) and fast drug dissolution kinetics in the resulting composite material. In vivo tests demonstrated the efficacy of the formulation along with an extended duration of sciatic nerve block in murine models of more than 8 h with a formulation containing only 2 mg of the local anesthetic thanks to the thermoresponsive character of the polymer, which, at body temperature, becomes hydrophobic and acts as a diffusion barrier for the encapsulated drug nanocrystals. The hydrophobicity of the encapsulated bupivacaine free base probably facilitates its pass through cell membranes and also binds strongly to their hydrophobic lipid bilayer, thereby protecting molecules from diffusion to extracellular media and to the bloodstream, reducing their clearance. When using BNC-nanogels, the duration of the anesthetic blockage lasted twice as long as compared to the effect of just BNCs or a conventional bupivacaine hydrochloride solution both containing equivalent amounts of the free drug. Results of the in vivo tests showed enough sensory nerve block to potentially relieve pain, but still having mobility in the limb, which enables motor function when required. The BNC-nanogels presented minimal toxicity in the in vivo study due to their sustained drug release and excellent biocompatibility. The encapsulation of nano-sized crystals of bupivacaine provides a prolonged regional anesthesia with reduced toxicity, which could be advantageous in the management of chronic pain.

Targeting drug delivery with light: A highly focused approach

Light is a uniquely powerful tool for controlling molecular events in biology. No other external input (e.g., heat, ultrasound, magnetic field) can be so tightly focused or so highly regulated as a clinical laser. Drug delivery vehicles that can be photonically activated have been developed across many platforms, from the simplest "caging" of therapeutics in a prodrug form, to more complex micelles and circulating liposomes that improve drug uptake and efficacy, to large-scale hydrogel platforms that can be used to protect and deliver macromolecular agents including full-length proteins. In this Review, we discuss recent innovations in photosensitive drug delivery and highlight future opportunities to engineer and exploit such light-responsive technologies in the clinical setting.

Ultrahigh Penetration and Retention of Graphene Quantum Dot Mesoporous Silica Nanohybrids for Image Guided Tumor Regression

So far, near-infrared (NIR) light responsive nanostructures have been well-defined in cancer nanomedicine. However, poor penetration and retention in tumors are the limiting factors. Here, we report the ultrahigh penetration and retention of carbanosilica (graphene quantum dots, GQDs embedded mesoporous silica) in solid tumors. After NIR light exposure, quick (0.5 h) emission from the tumor area is observed that is further retained up to a week (tested up to 10 days) with a single dose administration of nanohybrids. Emissive and photothermally active GQDs and porous silica shell (about 31% drug loading) make carbanosilica a promising nanotheranostic agent exhibiting 68.75% tumor shrinking compared to without NIR light exposure (34.48%). Generated heat (∼52 °C) alters the permeability of tumor enhancing the accumulation of nanotheranostics into the tumor environment. Successive tumor imaging ensures the prolonged follow-up of image guided tumor regression due to synergistic therapeutic effect of nanohybrids.

Keeping Nanomedicine on Target

A principal purpose of targeting or triggering is to improve the active agents’ therapeutic indices by preferentially increasing their concentrations at the desired site of effect.

Light: A Magical Tool for Controlled Drug Delivery

Light is a particularly appealing tool for on-demand drug delivery due to its noninvasive nature, ease of application and exquisite temporal and spatial control. Great progress has been achieved in the development of novel light-driven drug delivery strategies with both breadth and depth. Light-controlled drug delivery platforms can be generally categorized into three groups: photochemical, photothermal, and photoisomerization-mediated therapies. Various advanced materials, such as metal nanoparticles, metal sulfides and oxides, metal-organic frameworks, carbon nanomaterials, upconversion nanoparticles, semiconductor nanoparticles, stimuli-responsive micelles, polymer- and liposome-based nanoparticles have been applied for light-stimulated drug delivery. In view of the increasing interest in on-demand targeted drug delivery, we review the development of light-responsive systems with a focus on recent advances, key limitations, and future directions.

Recent Progress in Bioconjugation Strategies for Liposome-Mediated Drug Delivery

In nanoparticle (NP)-mediated drug delivery, liposomes are the most widely used drug carrier, and the only NP system currently approved by the FDA for clinical use, owing to their advantageous physicochemical properties and excellent biocompatibility. Recent advances in liposome technology have been focused on bioconjugation strategies to improve drug loading, targeting, and overall efficacy. In this review, we highlight recent literature reports (covering the last five years) focused on bioconjugation strategies for the enhancement of liposome-mediated drug delivery. These advances encompass the improvement of drug loading/incorporation and the specific targeting of liposomes to the site of interest/drug action. We conclude with a section highlighting the role of bioconjugation strategies in liposome systems currently being evaluated for clinical use and a forward-looking discussion of the field of liposomal drug delivery.

Near-infrared triggered on-demand local anesthesia using a jammed microgels system

To conveniently modulate the degree of local analgesia in response to changes in patients' needs and level of activity, a NIR-activated drug delivery system based on jammed microgels was introduced in the present study to realize on-demand local anesthesia. Chemically cross-linked gelatin microgels (5-15 μm) containing N-isopropylacrylamide (NIPAM), methylallyl polyethylene glycol (APEG) and graphene oxide (GOs) were fabricated through emulsion. After the in situ free radical polymerization, the physical network was formed, producing microgels with double networks (DN microgels). The DN microgels exhibited thermosensitive properties. The copolymerization of APEG resulted in the increase of lower critical solution temperature (LCST) of microgels. The maximum volume shrinkage ratio of DN microgels (NIPAM40 + APEG60) increased with the increase of the content of physical cross-linking network. The DN microgels also exhibited NIR-responsive ability. Under the NIR irradiance of 272 mW/cm², the temperature of DN microgels with 3 mg/mL GOs reached 40 °C within 60 s, resulting in the volume shrinkage of 14%. Ropivacaine release from DN microgels could be effectively triggered by NIR irradiation in vitro. After centrifugation, a jammed microgels system was produced where microgels packed densely, displaying shear-thinning behavior for achieving injection. The jammed DN microgels carrying ropivacaine were injected subcutaneously into rat footpad. NIR irradiation produced on-demand and repeated infiltration anesthesia in the rat footpad. The jammed DN microgels system thus was beneficial in the management of pain.

Polymer Nanocomposite Microactuators for On-Demand Chemical Release via High-Frequency Magnetic Field Excitation

On-demand delivery of substances has been demonstrated for various applications in the fields of chemistry and biomedical engineering. Single-pulse release profile has been shown previously for micro/nanoparticles in different form factors. However, to obtain a sustained release, a pulsatile release profile is needed. Here, we demonstrate such a release profile from polymer magnetic nanocomposite microspheres loaded with chemicals. By exciting the microactuators with AC magnetic fields, we could achieve up to 61% cumulative release over a five-day period. One of the main advantages of using a magnetic stimulus is that the properties of the environment (e.g., transparency, density, and depth) in which the particles are located do not affect the performance. The operating magnitude of the magnetic field used in this work is safe and does not interact with any nonmetallic materials. The proposed approach can potentially be used in microchemistry, drug delivery, lab-on-chip, and microrobots for drug delivery.

Strategies to Obtain Encapsulation and Controlled Release of Small Hydrophilic Molecules

The therapeutic effect of small hydrophilic molecules is limited by the rapid clearance from the systemic circulation or a local site of administration. The unsuitable pharmacokinetics and biodistribution can be improved by encapsulating them in drug delivery systems. However, the high-water solubility, very hydrophilic nature, and low molecular weight make it difficult to encapsulate small hydrophilic molecules in many drug delivery systems. In this mini-review, we highlight three strategies to efficiently encapsulate small hydrophilic molecules and achieve controlled release: physical encapsulation in micro/nanocapsules, physical adsorption via electronic interactions, and covalent conjugation. The principles, advantages, and disadvantages of each strategy are discussed. This review paper could be a guide for scientists, engineers, and medical doctors who want to improve the therapeutic efficacy of small hydrophilic drugs.

Light-triggered release of conventional local anesthetics from a macromolecular prodrug for on-demand local anesthesia

An on-demand anesthetic that would only take effect when needed and where the intensity of anesthesia could be easily adjustable according to patients' needs would be highly desirable. Here, we design and synthesize a macromolecular prodrug (P407-CM-T) in which the local anesthetic tetracaine (T) is attached to the polymer poloxamer 407 (P407) via a photo-cleavable coumarin linkage (CM). P407-CM-T solution is an injectable liquid at room temperature and gels near body temperature. The macromolecular prodrug has no anesthetic effect itself unless irradiated with a low-power blue light emitting diode (LED), resulting in local anesthesia. By adjusting the intensity and duration of irradiation, the anesthetic effect can be modulated. Local anesthesia can be repeatedly triggered.

Effect of Laser Irradiation on Reversibility and Drug Release of Light-Activatable Drug-Encapsulated Liposomes

Although several studies have demonstrated repetitive drug release using light-activatable liposomes, inconsistent drug release at each activation limits widespread usage. Here, we report reversible plasmonic material-coated encapsulated liposomes for proportional controlled delivery of methotrexate (MTX), which is a common drug for cancer and autoimmune diseases, using repetitive laser irradiation. Our results suggest a proportional increase in total drug release after repetitive laser irradiation. We hypothesize that the drug is released via "melted" lipid bilayers when the plasmonic materials on the liposome surface are heated by laser irradiation followed by reversible formation of the liposome. To evaluate our hypothesis, the number density of liposomes after laser irradiation was measured using single-particle (liposome) collision experiments at an ultramicroelectrode. Collisional frequency data suggest that the number density of liposomes remains unaltered even after 60 s of laser irradiation at 1.1 and 1.8 W, indicating that the liposome structure is reversible. The results were further compared with gold nanorod-coated nanodroplets where drug is released via irreversible phase transition. In contrast to what was observed with the liposome particles, the number density of the nanodroplets decreased with increasing laser irradiation duration. The structure reversibility of our liposome particles may be responsible for repetitive drug release with laser heating. We also studied the temperature rise in the lipid bilayer by incorporating polymerized 10,12-pentacosadiynoic acid (PCDA) in the lipid composition. The red shift in the UV-vis spectrum due to the structural change in PCDA lipids after laser irradiation indicates a rise in temperature above 75 °C, which is also above the chain-melting temperature of the main lipid used in the liposomes. All these results indicate that drug is released from the light-activatable liposomes due to reversible nanostructural alteration in the lipid bilayer by plasmonic resonance heating. The liposomes have potential to be a drug carrier for dose-controlled repetitive drug delivery.

Light-triggered nanoparticles for pain management

Introduction: Recent technological progress in pain management includes patient´s stratification depending on their disease subtype, prognosis, risk, or treatment response using data analysis and genetic testing in order to select the most appropriate drug for each group. A spatiotemporal control on the release of the selected anesthetic drug is also desirable in order to minimize side effects and to provide the patient with the appropriate dose above the therapeutic threshold and below the maximum desirable concentration. Light can be used non-invasively as an exogenous trigger to allow multiple drug administrations with precise spatiotemporal control. By controlling light fluence/irradiance, pulse structure, and duration of the irradiation drug release kinetics can be controlled in a pulsatile manner to release totally or partially the drug loaded into particulate carriers.Areas covered: Recent advances in the field of light-triggered nanoparticles used in pain management specially those studies which include preclinical models are reviewed.Expert opinion: Two decades later after the first light-sensitive drug delivery systems reported still several limitations hinder their clinical translation. Additional efforts should be undertaken to understand the nanoparticles biological fate, to satisfy their large-scale production, and to facilitate the technology to apply this therapeutic approach at a low cost.

Recent advances in porphyrin-based nanocomposites for effective targeted imaging and therapy

Porphyrins are organic compounds that continue to attract much theoretical interest, and have been called the "pigments of life". They have a wide role in photodynamic and sonodynamic therapy, along with uses in magnetic resonance, fluorescence and photoacoustic imaging. There is a vast range of porphyrins that have been isolated or designed, but few of them have real clinical applications. Due to the hydrophobic properties of porphyrins, and their tendency to aggregate by stacking of the planar molecules they are difficult to work with in aqueous media. Therefore encapsulating them in nanoparticles (NPs) or attachment to various delivery vehicles have been used to improve delivery characteristics. Porphyrins can be used in a composite designed material with properties that allow specific targeting, immune tolerance, extended tissue lifetime and improved hydrophilicity. Drug delivery, healing and repairing of damaged organs, and cancer theranostics are some of the medical uses of porphyrin-based nanocomposites covered in this review.

Advances of Nano-Structured Extended-Release Local Anesthetics

Extended-release local anesthetics (LAs) have drawn increasing attention with their promising role in improving analgesia and reducing adverse events of LAs. Nano-structured carriers such as liposomes and polymersomes optimally meet the demands of/for extended-release, and have been utilized in drug delivery over decades and showed satisfactory results with extended-release. Based on mature technology of liposomes, EXPAREL, the first approved liposomal LA loaded with bupivacaine, has seen its success in an extended-release form. At the same time, polymersomes has advances over liposomes with complementary profiles, which inspires the emergence of hybrid carriers. This article summarized the recent research successes on nano-structured extended-release LAs, of which liposomal and polymeric are mainstream systems. Furthermore, with continual optimization, drug delivery systems carry properties beyond simple transportation, such as specificity and responsiveness. In the near future, we may achieve targeted delivery and controlled-release properties to satisfy various analgesic requirements.

Light-activated doxorubicin-encapsulated perfluorocarbon nanodroplets for on-demand drug delivery in an in vitro angiogenesis model: Comparison between perfluoropentane and perfluorohexane

Phase-transition perfluorocarbon (PFC) nanodroplets have been developed for on-demand drug delivery carriers with external triggers such as ultrasound or laser irradiation techniques. Although various perfluorocarbons, including perfluoropentane (C₅F₁₂) and perfluorohexane (C₆F₁₄), have been investigated for their theranostic use, comparison of the phase-transition efficiency, the drug delivery efficacy by light activation, and physical properties of the PFC nanodroplets have not been reported. We have synthesized gold nanorod-coated doxorubicin-encapsulated perfluorocarbon nanodroplets using perfluoropentane and perfluorohexane as light-activated on-demand drug delivery carriers, called PF5 and PF6, respectively. When gold nanorods on the perfluorocarbon nanodroplets resonate with a laser wavelength, plasmonic heat generated on the gold nanorods vaporizes the nanodroplets to gas bubbles (phase-transition), and releases the encapsulated drug from the nanodroplet core. Overall, the nanodroplet size, drug encapsulation efficiency, number density, and cytotoxicity were similar between PF5 and PF6. However, the long-term stability against passive phase-transition or coalescence in physiological conditions and the phase-transition efficiency were different from each other. PF6 was better in long-term stability but showed lower phase-transition than PF5. The lower phase-transition of PF6 might have led to lower drug delivery efficiency compared to PF5. This is probably because PF6 has higher temperature thresholds required for phase-transition due to its higher boiling point. The study demonstrated feasibility of the light-activated nanodroplets for on-demand targeted nanotherapy, which suppresses the development of angiogenesis.

Combination of light-driven co-delivery of chemodrugs and plasmonic-induced heat for cancer therapeutics using hybrid protein nanocapsules

BACKGROUND

Improving the water solubility of hydrophobic drugs, increasing their accumulation in tumor tissue and allowing their simultaneous action by different pathways are essential issues for a successful chemotherapeutic activity in cancer treatment. Considering potential clinical application in the future, it will be promising to achieve such purposes by developing new biocompatible hybrid nanocarriers with multimodal therapeutic activity.

RESULTS

We designed and characterised a hybrid nanocarrier based on human serum albumin/chitosan nanoparticles (HSA/chitosan NPs) able to encapsulate free docetaxel (DTX) and doxorubicin-modified gold nanorods (DOXO-GNRs) to simultaneously exploit the complementary chemotherapeutic activities of both antineoplasic compounds together with the plasmonic optical properties of the embedded GNRs for plasmonic-based photothermal therapy (PPTT). DOXO was assembled onto GNR surfaces following a layer-by-layer (LbL) coating strategy, which allowed to partially control its release quasi-independently release regarding DTX under the use of near infrared (NIR)-light laser stimulation of GNRs. In vitro cytotoxicity experiments using triple negative breast MDA-MB-231 cancer cells showed that the developed dual drug encapsulation approach produces a strong synergistic toxic effect to tumoral cells compared to the administration of the combined free drugs; additionally, PPTT enhances the cytostatic efficacy allowing cell toxicities close to 90% after a single low irradiation dose and keeping apoptosis as the main cell death mechanism.

CONCLUSIONS

This work demonstrates that by means of a rational design, a single hybrid nanoconstruct can simultaneously supply complementary therapeutic strategies to treat tumors and, in particular, metastatic breast cancers with good results making use of its stimuli-responsiveness as well as its inherent physico-chemical properties.

Delivery of Local Anesthesia: Current Strategies, Safety, and Future Prospects

BACKGROUND

The systemic administration of anesthesia is associated with severe and undesirable side effects such as sedation, vomiting, nausea, allergies, respiratory problems, and neutrophil dysfunction. With the increase in the procedures of limb surgery, cosmetics, facial, skin, and cancer reconstruction, the demand for local anesthesia has increased multifold during the last one decade. Therefore, novel, safe, and cost-effective methods are being developed to deliver local anesthetics by the surgeons.

METHOD

To prepare a comprehensive research report on anesthesia, we performed a structured literature search of bibliographic databases for peer-reviewed articles published recently. The studies of different articles were summarized and a deductive qualitative and quantitative data analysis was applied. Subsequently, a comprehensive summary of the analysis was used to frame this review article with ample examples.

RESULTS

A thorough analysis of the reports suggested that there have been tremendous developments of synthesizing nanoparticle-based local anesthesia drugs. The active targeting ability of nanoparticle-based drug delivery strategy can further help to deliver the desired anesthetic drug locally. It was also found that different local anesthetic drugs are developed into liposome form and show better efficacy in patients receiving anesthesia.

CONCLUSION

The findings of this review article endorse that safe delivery of anesthesia drugs are essential for the safety of patients. Further, nanotechnology-based strategies are extremely useful for targeted delivery of anesthetic drugs at the required dose without affecting the neighboring tissues.

Polymer-tetrodotoxin conjugates to induce prolonged duration local anesthesia with minimal toxicity

There is clinical and scientific interest in developing local anesthetics with prolonged durations of effect from single injections. The need for such is highlighted by the current opioid epidemic. Site 1 sodium channel blockers such as tetrodotoxin (TTX) are extremely potent, and can provide very long nerve blocks but the duration is limited by the associated systemic toxicity. Here we report a system where slow release of TTX conjugated to a biocompatible and biodegradable polymer, poly(triol dicarboxylic acid)-co-poly(ethylene glycol) (TDP), is achieved by hydrolysis of ester linkages. Nerve block by the released TTX is enhanced by administration in a carrier with chemical permeation enhancer (CPE) properties. TTX release can be adjusted by tuning the hydrophilicity of the TDP polymer backbone. In vivo, 1.0–80.0 µg of TTX released from these polymers produced a range of durations of nerve block, from several hours to 3 days, with minimal systemic or local toxicity.

There is interest in developing long-lasting local anaesthetics for a range of applications. Here, the authors report on the application of tetrodotoxin conjugated to amphiphilic biodegradable polymer to reduce systemic toxicity, achieve sustained release and investigate application as a local anaesthetic.

Ultrasound/Acidity-Triggered and Nanoparticle-Enabled Analgesia

Local anesthetics have been extensively employed to treat postoperative pain, but they generally suffer from short acting duration and potential neurotoxicity under high local concentrations, which require the controlled and sustained releasing patterns of treatment drugs. In this work, it is reported, for the first time, the construction of hollow mesoporous organosilica nanoparticles (HMONs)-based nanoplatforms for localized delivery and controlled/sustained release of loaded ropivacaine for local anesthetics, which can be repeatedly triggered by either external ultrasound irradiation or acidity triggering to release the payload, causing on-demand and long-lasting analgesia. Based on the in vivo mouse model of incision pain, the controlled and sustained release of ropivacaine achieves more than six hours of continuous analgesia, which is almost three times longer as compared to single free ropivacaine injection. The low neurotoxicity and high biocompatibility of HMONs for nanoparticle-enabled analgesia are also demonstrated both in vitro and in vivo. This designed/constructed HMONs-based nanoplatform provides a potential methodology for clinical pain management via on-demand and long-lasting pain relief.

Nano-engineered microcapsules boost the treatment of persistent pain

Persistent pain remains a major health issue: common treatments relying on either repeated local injections or systemic drug administration are prone to concomitant side-effects. It is thought that an alternative could be a multifunctional cargo system to deliver medicine to the target site and release it over a prolonged time window. We nano-engineered microcapsules equipped with adjustable cargo release properties and encapsulated the sodium-channel blocker QX-314 using the layer-by-layer (LbL) technology. First, we employed single-cell electrophysiology to establish in vitro that microcapsule application can dampen neuronal excitability in a controlled fashion. Secondly, we used two-photon excitation imaging to monitor and adjust long-lasting release of encapsulated cargo in target tissue in situ. Finally, we explored an established peripheral inflammation model in rodents to find that a single local injection of QX-314-containing microcapsules could provide robust pain relief lasting for over a week. This was accompanied by a recovery of the locomotive deficit and the amelioration of anxiety in animals with persistent inflammation. Post hoc immunohistology confirmed biodegradation of microcapsules over a period of several weeks. The overall remedial effect lasted 10-20 times longer than that of a single focal drug injection. It depended on the QX-314 encapsulation levels, involved TRPV1-channel-dependent cell permeability of QX-314, and showed no detectable side-effects. Our data suggest that nano-engineered encapsulation provides local drug delivery suitable for prolonged pain relief, which could be highly advantageous compared to existing treatments.

A biodegradable fluorescent nanohybrid for photo-driven tumor diagnosis and tumor growth inhibition

Specific targeting and phototriggered therapy in mouse model have recently emerged as the starting point of cancer theragnosis. Herein, we report a bioresponsive and degradable nanohybrid, a liposomal nanohybrid decorated with red emissive carbon dots, for localized tumor imaging and light-mediated tumor growth inhibition. Unsaturated carbon dots (C-dots) anchored to liposomes convert near-infrared (NIR) light into heat and also produce reactive oxygen species (ROS), demonstrating the capability of phototriggered cancer cell death and tumor regression. The photothermal and oxidative damage of breast tumor by the nonmetallic nanohybrid has also been demonstrated. Designed nanoparticles show excellent aqueous dispersibility, biocompatibility, light irradiated enhanced cellular uptake, release of reactive oxygen species, prolonged and specific tumor binding ability and good photothermal response (62 °C in 5 minutes). Safe and localized irradiation of 808 nm light demonstrates significant tumor growth inhibition and bioresponsive degradation of the fluorescent nanohybrid without affecting the surrounding healthy tissues.

Addressing the Issue of Tetrodotoxin Targeting

This review is devoted to the medical application of tetrodotoxin (TTX), a potent non-protein specific blocker of voltage-gated sodium (NaV) channels. The selectivity of action, lack of affinity with the heart muscle NaV channels, and the inability to penetrate the blood–brain barrier make this toxin an attractive candidate for anesthetic and analgesic drug design. The efficacy of TTX was shown in neuropathic, acute and inflammatory pain models. The main emphasis of the review is on studies focused on the improvement of TTX efficacy and safety in conjunction with additional substances and drug delivery systems. A significant improvement in the effectiveness of the toxin was demonstrated when used in tandem with vasoconstrictors, local anesthetics and chemical permeation enhancers, with the best results obtained with the encapsulation of TTX in microparticles and liposomes conjugated to gold nanorods.

Long-acting liposomal corneal anesthetics

Eye drops producing long-acting ocular anesthesia would be desirable for corneal pain management. Here we present liposome-based formulations to achieve very long ocular anesthetic effect after a single eye drop instillation. The liposomes were functionalized with succinyl-Concanavalin A (sConA-Lip), which can bind corneal glycan moieties, to significantly prolong the dwell time of liposomes on the cornea. sConA-Lip were loaded with tetrodotoxin and dexmedetomidine (sConA-Lip/TD), and provided sustained release for both. A single topical instillation of sConA-Lip/TD on the cornea could achieve 105 min of complete analgesia and 608 min of partial analgesia, which was significantly longer than analgesia with proparacaine, tetrodotoxin/dexmedetomidine solution or unmodified liposomes containing tetrodotoxin and dexmedetomidine. sConA-Lip/TD were not cytotoxic in vitro to human corneal limbal epithelial cells or corneal keratocytes. Topical administration of sConA-Lip/TD provided prolonged corneal anesthesia without delaying corneal wound healing. Such a formulation may be useful for the management of acute surgical and nonsurgical corneal pain, or for treatment of other ocular surface diseases.