Microneedle/nanoencapsulation-mediated transdermal delivery: Mechanistic insights

Efficacy and safety of combined microneedling therapy for androgenic alopecia: A systematic review and meta-analysis of randomized clinical trials

OBJECTIVE

To provide dermatologists with more clinical experience in treating androgenetic alopecia, we evaluated the effect and safety of combined microneedling therapy for androgenetic alopecia.

METHODS

Studies on combined microneedling for hair loss were comprehensively searched by us in PubMed, Excerpta Medica Database, and the Cochrane Library Database. The literature search spanned the period from 2012 to 2022. Inclusion and exclusion criteria were developed, and the literature was screened according to this criteria. The Cochrane Risk of Bias Tool was used to assess the quality of the studies. The researcher applied Revman 5.3 and Stata 15.1 software to analyze the data after extracting information from the data.

RESULTS

Finally, 13 RCTs involving 696 AGA patients were included to compare the clinical effectiveness and adverse events of combined MN therapy with single MN therapy or single drug therapy for AGA. The results of meta-analysis showed as follows: (1) Hair density and diameter changes: The combined MN group was significantly better than any single treatment group, and the differences were statistically significant (MD = 13.36, 95% CI = [8.55, 18.16], Z = 5.45, p < 0.00001; MD = 18.11, 95% CI = [13.70, 22.52], Z = 8.04, p < 0.00001; MD = 13.36, 95% CI = [8.55, 18.16], Z = 5.45, p < 0.00001; MD = 2.50, 95% CI = [0.99, 4.02], Z = 3.23, p = 0.001); (2) the evaluation of satisfaction for efficacy: The doctor satisfaction rating of the combined MN group was significantly higher than that of any single treatment group, with statistical difference (RR = 2.03, 95% CI = [1.62, 2.53], Z = 6.24, p < 0.00001). The difference between the two groups regarding patients satisfaction was not significant (RR = 3.44, 95% CI = [0.67, 17.59], Z = 1.49, p = 0.14). (3) Safety: There was no statistical difference in the incidence of adverse reactions between combination therapy and monotherapy (RR = 0.83, 95% CI = [0.62, 1.12], Z = 1.22, p = 0.22).

CONCLUSION

The combined MN group showed statistically significant improvement in hair density and diameter, and good safety compared with monotherapy.

A Hollow Microneedle Equipped with a Micropillar for Improved Needle Insertion and Injection of Drug Solution

PURPOSE

Hollow-type microneedles (hMNs) are a promising device for the effective administration of drugs into intradermal sites. Complete insertion of the needle into the skin and administration of the drug solution without leakage must be achieved to obtain bioavailability or a constant effect. In the present study, several types of hMN with or without a rounded blunt tip micropillar, which suppresses skin deformation, around a hollow needle, and the effect on successful needle insertion and administration of a drug solution was investigated. Six different types of hMNs with needle lengths of 1000, 1300, and 1500 µm with or without a micropillar were used.

METHODS

Needle insertion and the disposition of a drug in rat skin were investigated. In addition, the displacement-force profile during application of hMNs was also investigated using a texture analyzer with an artificial membrane to examine needle factors affecting successful insertion and administration of a drug solution by comparing with in vivo results.

RESULTS

According to the results with the drug distribution of iodine, hMN1300 with a micropillar was able to successfully inject drug solution into an intradermal site with a high success rate. In addition, the results of displacement-force profiles with an artificial membrane showed that a micropillar can be effective for depth control of the injected solution as well as the prevention of contact between the hMN pedestal and the deformed membrane.

CONCLUSION

In the present study, hMN1300S showed effective solution delivery into an intradermal site. In particular, a micropillar can be effective for depth control of the injected solution as well as preventing contact between the hMN pedestal and the deformed membrane. The obtained results will help in the design and development of hMNs that ensure successful injection of an administered drug.

Recent progress in PLGA-based microneedle-mediated transdermal drug and vaccine delivery

Microneedles (MNs) have recently been found to have applications in drug, vitamin, protein and vaccine delivery. Polymeric MN arrays continue to attract increasing attention due to their capability to bypass the skin's stratum corneum (SC) barrier with minimal invasiveness. These carriers can achieve the targeted intradermal delivery of drugs and vaccines and improve their transdermal delivery level. As a nontoxic FDA-approved copolymer, polylactic glycolic acid (PLGA) has good biocompatibility and biodegradability. Currently, PLGA-based MNs have a noticeable tendency to be utilized as a delivery system. This study focuses on the most recent advances in PLGA-based MNs. Both PLGA nanoparticle-based MNs and PLGA matrix-based MNs, created for the delivery of vaccines, drugs, proteins and other therapeutic agents, are discussed. The paper also discusses the various types of MNs and their potential applications. Finally, the prospects and challenges of PLGA-based MNs are reviewed.

Preparation and Evaluation of Liposomes and Niosomes Containing Total Ginsenosides for Anti-Photoaging Therapy

Ginsenosides are the principal bioactive compounds of ginseng. Total ginsenosides (GS) contain a variety of saponin monomers, which have potent anti-photoaging activity and improve the skin barrier function. To enhance the efficiency of GS transdermal absorption, GS liposomes (GSLs) and GS niosomes (GSNs) were formulated as delivery vehicles. Based on the clarified and optimized formulation process, GSL and GSN were prepared. The structure, cumulative transmittance, skin retention, total transmittance, and bioactivity of GSLs and GSNs were characterized. GSL and GSN were shown to inhibit lipid peroxidation and increase the contents of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) in human keratinocytes (HaCaTs). In addition, HaCAT cell migration, proliferation, and GS cellular uptake were significantly increased. The therapeutic effects of GSL and GSN were also evaluated in a rat model of photoaging. Histopathological changes were assessed in rat skin treated with GSL, GSN, or GS by hematoxylin–eosin (H&amp;E) and aldehyde fuchsine staining. Malondialdehyde (MDA), SOD, GSH-Px, matrix metalloproteinases (MMPs), interleukin-6 (IL-6), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) expression levels were determined. Results indicated that the optimal formulation of GSL used soybean lecithin (SPC) as the phospholipid, with a lipid–drug ratio of 1:0.4 and a phospholipid–cholesterol ratio of 1:3.5. The optimal temperature for the preparation process of GSN by ethanol injection was 65°C, with a ratio of the organic phase to aqueous phase of 1:9. It was demonstrated that the cumulative release rate, skin retention rate, and total transmission rate of GSL-7 at 24 h were higher than those of GSN-4 and GS. GSL-7 significantly inhibited skin lipid peroxidation caused by ultraviolet (UV) radiation. In addition, GSL-7 reduced the contents of MMPs and inflammatory cytokines in skin tissue. In conclusion, GSL-7 may reduce skin aging caused by UV radiation and contribute to skin tissue repair.

Particle Size Effect of Curcumin Nanocrystals on Transdermal and Transfollicular Penetration by Hyaluronic Acid-Dissolving Microneedle Delivery

Microneedles are one promising penetration enhancement vehicle to overcome the stratum corneum skin barrier, which hampers the penetration of drug nanocrystals by transdermal delivery. In order to clarify the particle size effect of nanocrystals on transdermal delivery, 60 nm, 120 nm, and 480 nm curcumin nanocrystals were fabricated and incorporated into dissolving hyaluronic acid polysaccharide microneedles. The microneedles showed good mechanical strength with 1.4 N/needle, possessing the ability to insert into the skin. The passive permeation results showed that the smaller particle size of 60 nm curcumin nanocrystals diffused faster and deeper than the larger 120 nm and 480 nm curcumin nanocrystals with size-dependent diffusion behaviors. Thereafter, higher concentration gradients and overlap diffusional coronas also formed in the skin layers by the smaller-particle-size nanocrystals. Furthermore, the diffusion rate of the smaller particle size of curcumin nanocrystals to the hair follicle was also higher than that of the larger curcumin nanocrystals. In conclusion, the particle sizes of curcumin nanocrystals influenced the transdermal and transfollicular penetration in deeper skin layers

Comparison Study of the Effects of Cationic Liposomes on Delivery across 3D Skin Tissue and Whitening Effects in Pigmented 3D Skin

Charged phospholipids are employed to formulate liposomes with different surface charges to enhance the permeation of active ingredients through epidermal layers. Although 3D skin tissue is widely employed as an alternative to permeation studies using animal skin, only a small number of studies have compared the difference between these skin models. Liposomal delivery strategies are investigated herein, through 3D skin tissue based on their surface charges. Cationic, anionic, and neutral liposomes are formulated and their size, zeta-potential, and morphology are characterized using dynamic light scattering and cryogenic-transmission electron microscopy (cryo-TEM). A Franz diffusion cell is employed to determine the delivery efficiency of various liposomes, where all liposomes do not exhibit any recognizable difference of permeation through the synthetic membrane. When the fluorescence liposomes are applied to 3D skin, considerable fluorescence intensity is observed at the stratum cornea and epithelium layers. Compared to other liposomes, cationic liposomes exhibit the highest fluorescence intensity, suggesting the enhanced permeation of liposomes through the 3D skin layers. Finally, the ability of niacinamide (NA)-incorporated liposomes to suppress melanin transfer in pigmented 3D skin is examined, where cationic liposomes exhibit the highest degree of whitening effects.

Microneedle Technology: An Insight into Recent Advancements and Future Trends in Drug and Vaccine Delivery

Over the last decade, microneedle (MN) induced microporation multifunctional approaches to enhance the delivery of drugs through the skin. MN technology included micron-sized needles to create microchannels into the Stratum corneum of skin, the most significant protective layer. Delivery of drugs and vaccines through the transdermal route is an alternative route for hypodermic and oral. It overcomes the problems associated with gastrointestinal along with drug deterioration. It is affordable, noninvasive, painless, simple, and self-administered techniques that provide prolonged release of drugs to enhance patient compliance. The MN delivery focused on biopharmaceuticals like proteins or peptides. The novel concepts have drawn interest in using these techniques in tandem with other enhancement approaches. This review article discussed the latest advancements in MN technology. It emphasized types of MNs, methodology, mechanisms, strategies for delivery of several drugs and vaccines, and significant challenges in the marketing of biopharmaceuticals. Furthermore, relevant U.S. patents and clinical trials based on MNs are also accentuated. Therefore, MN techniques will play a pivotal role in promoting clinical applications and innovative research for scientists and researchers working in the pharmaceutical field.

Advances in Antimicrobial Microneedle Patches for Combating Infections

Skin infections caused by bacteria, viruses and fungi are difficult to treat by conventional topical administration because of poor drug penetration across the stratum corneum. This results in low bioavailability of drugs to the infection site, as well as the lack of prolonged release. Emerging antimicrobial transdermal and ocular microneedle patches have become promising medical devices for the delivery of various antibacterial, antifungal, and antiviral therapeutics. In the present review, skin anatomy and its barriers along with skin infection are discussed. Potential strategies for designing antimicrobial microneedles and their targeted therapy are outlined. Finally, biosensing microneedle patches associated with personalized drug therapy and selective toxicity toward specific microbial species are discussed.

Advancement of Lipid-Based Nanocarriers and Combination Application with Physical Penetration Technique

On account of the advantages of transdermal delivery and the application situation of transcutaneous technology in transdermal delivery, the article critically comments on nanosystems as permeation enhancement model. Nanosystems possess great potential for transcutaneous drug delivery. This review focuses on recent advances in lipid-based nanocarriers, including liposome, transfersomes, ethosomes, nanoemulsions, solid lipid nanoparticles, nanostructured lipid carriers and combination application of the lipid-based nanocarriers with microneedle, iontophoresis, electroporation and sonophoresis in the field for the development of the transdermal drug delivery system. We attempted to give an overview of lipid-based nanocarriers with the aim to improve transdermal and dermal drug delivery. A special focus is given to the nanocarrier composition, characteristic and interaction mechanisms through the skin. Recent combination applications of lipid-based nanocarriers with the physical penetration technology demonstrate the superiority of the combined use of nanocarriers and physical methods in drug penetration enhancement compared to their single use. In the future, lipidbased nanocarriers will play a greater role in the field of transdermal and dermal drug delivery.

Fused Deposition Modeling 3D Printing: Test Platforms for Evaluating Post-Fabrication Chemical Modifications and In-Vitro Biological Properties

3D printing is attracting considerable interest for its capacity to produce prototypes and small production runs rapidly. Fused deposit modeling (FDM) was used to produce polyvalent test plates for investigation of the physical, chemical, and in-vitro biological properties of printed materials. The polyvalent test plates (PVTPs) are poly-lactic acid cylinders, 14 mm in diameter and 3 mm in height. The polymer ester backbone was surface modified by a series of ramified and linear oligoamines to increase its hydrophilicity and introduce a positive charge. The chemical modification was verified by FT-IR spectroscopy, showing the introduction of amide and amine functions, and contact angle measurements confirmed increased hydrophilicity. Morphology studies (SEM, optical microscopy) indicated that the modification of PVTP possessed a planar morphology with small pits. Positron annihilation lifetime spectroscopy demonstrated that the polymeric free volume decreased on modification. An MTT-based prolonged cytotoxicity test using Caco-2 cells showed that the PVTPs are non-toxic at the cellular level. The presence of surface oligoamines on the PVTPs reduced biofilm formation by Candida albicans SC5314 significantly. The results demonstrate that 3D printed objects may be modified at their surface by a simple amidation reaction, resulting in a reduced propensity for biofilm colonization and cellular toxicity.

Design, formulation and evaluation of novel dissolving microarray patches containing a long-acting rilpivirine nanosuspension

One means of combating the spread of human immunodeficiency virus (HIV) is through the delivery of long-acting, antiretroviral (ARV) drugs for prevention and treatment. The development of a discreet, self-administered and self-disabling delivery vehicle to deliver such ARV drugs could obviate compliance issues with daily oral regimens. Alternatives in development, such as long-acting intramuscular (IM) injections, require regular access to health care facilities and disposal facilities for sharps. Consequently, this proof of concept study was developed to evaluate the use of dissolving microarray patches (MAPs) containing a long-acting (LA) nanosuspension of the candidate ARV drug, rilpivirine (RPV). MAPs were mechanically strong and penetrated skin in vitro, delivering RPV intradermally. In in vivo studies, the mean plasma concentration of RPV in rats (431 ng/ml at the Day 7 time point) was approximately ten-fold greater than the trough concentration observed after a single-dose in previous clinical studies. These results are the first to indicate, by the determination of relative exposures between IM and MAP administration, that larger multi-array dissolving MAPs could potentially be used to effectively deliver human doses of RPV LA. Importantly, RPV was also detected in the lymph nodes, indicating the potential to deliver this ARV agent into one of the primary sites of HIV replication over extended durations. These MAPs could potentially improve patient acceptability and adherence to HIV prevention and treatment regimens and combat instances of needle-stick injury and the transmission of blood-borne diseases, which would have far-reaching benefits, particularly to those in the developing world.

Mini-Review: Assessing the Potential Impact of Microneedle Technologies on Home Healthcare Applications

The increasing devolution of healthcare towards community care has meant that the management of many conditions is conducted within the home either by community nurses or by the patients themselves. The administration of medicines within home healthcare scenarios can however be problematic—especially when considering the delivery of medicines through injection. The possibility of needlestick injury (NSI) has become an ever-present hazard within healthcare settings, with a significant proportion of percutaneous injuries occurring during the handling and disposal of the needle. The emergence of transdermal microneedle systems, however, offers a potentially revolutionary advance and could dramatically improve safety—particularly within home healthcare where there are mounting concerns over the use and disposal of sharps. A mini-review of the advantages proffered by microneedle drug delivery technologies is presented and the potential impact on delivery of medicines within the home is critically appraised.

Combined use of nanocarriers and physical methods for percutaneous penetration enhancement

Dermal and transdermal drug delivery (due to its non-invasiveness, avoidance of the first-pass metabolism, controlling the rate of drug input over a prolonged time, etc.) have gained significant acceptance. Several methods are employed to overcome the permeability barrier of the skin, improving drug penetration into/through skin. Among chemical penetration enhancement methods, nanocarriers have been extensively studied. When applied alone, nanocarriers mostly deliver drugs to skin and can be used to treat skin diseases. To achieve effective transdermal drug delivery, nanocarriers should be applied with physical methods, as they act synergistically in enhancing drug penetration. This review describes combined use of frequently used nanocarriers (liposomes, novel elastic vesicles, lipid-based and polymer-based nanoparticles and dendrimers) with the most efficient physical methods (microneedles, iontophoresis, ultrasound and electroporation) and demonstrates superiority of the combined use of nanocarriers and physical methods in drug penetration enhancement compared to their single use.

Microneedle-mediated transdermal delivery of nanostructured lipid carriers for alkaloids from Aconitum sinomontanum

A combination method using microneedle (MN) pretreatment and nanostructured lipid carriers (NLCs) was developed to improve the transdermal delivery of therapeutics. The MN treatment of the skin and co-administration of NLCs loaded with total alkaloids isolated from Aconitum sinomontanum (AAS-NLCs) significantly increased the skin permeation of the drugs. Fluorescence imaging confirmed that MNs could provide microchannels penetrating the stratum corneum, and delivery of NLCs through the channels led to their deeper permeation. In vivo studies showed that combination of AAS-NLCs with MNs (AAS-NLCs-MN) in transdermal delivery could improve the bioavailability and maintain stable drug concentrations in the blood. Moreover, AAS-NLCs-MN showed benefits in eliminating paw swelling, decreasing inflammation and pain, and regulating immune function in adjuvant arthritis rats. After administration of AAS-NLCs-MN, no skin irritation was observed in rabbits, and electrocardiograms of rats showed improved arrhythmia. These results indicated that the dual approach combining MN insertion and NLCs has the potential to provide safe transdermal delivery and to improve the therapeutic efficacy through sustained release of AAS.

PLGA-loaded nanomedicines in melanoma treatment: Future prospect for efficient drug delivery

Current treatment methods for melanoma have some limitations such as less target-specific action, severe side effects and resistance to drugs. Significant progress has been made in exploring novel drug delivery systems based on suitable biochemical mechanisms using nanoparticles ranging from 10 to 400 nm for drug delivery and imaging, utilizing their enhanced penetration and retention properties. Poly-lactide-co-glycolide (PLGA), a copolymer of poly-lactic acid and poly-glycolic acid, provides an ideally suited performance-based design for better penetration into skin cells, thereby having a greater potential for the treatment of melanoma. Moreover, encapsulation protects the drug from deactivation by biological reactions and interactions with biomolecules, ensuring successful delivery and bioavailability for effective treatment. Controlled and sustained delivery of drugs across the skin barrier that otherwise prohibits entry of larger molecules can be successfully made with adequately stable biocompatible nanocarriers such as PLGA for taking drugs through the small cutaneous pores permitting targeted deposition and prolonged drug action. PLGA is now being extensively used in photodynamic therapy and targeted therapy through modulation of signal proteins and drug-DNA interactions. Recent advances made on these nanomedicines and their advantages in the treatment of skin melanoma are highlighted and discussed in this review.

Efficient delivery of nanoparticles to deep skin layers using dissolvable microneedles with an extended-length design

Dissolvable microneedles with an extended-length design can efficiently deliver NPs to the deep skin layers and prolong the skin retention time of NPs up to 5 days.

Polylactic acid (PLA) controlled delivery carriers for biomedical applications

Polylactic acid (PLA) and its copolymers have a long history of safety in humans and an extensive range of applications. PLA is biocompatible, biodegradable by hydrolysis and enzymatic activity, has a large range of mechanical and physical properties that can be engineered appropriately to suit multiple applications, and has low immunogenicity. Formulations containing PLA have also been Food and Drug Administration (FDA)-approved for multiple applications making PLA suitable for expedited clinical translatability. These biomaterials can be fashioned into sutures, scaffolds, cell carriers, drug delivery systems, and a myriad of fabrications. PLA has been the focus of a multitude of preclinical and clinical testing. Three-dimensional printing has expanded the possibilities of biomedical engineering and has enabled the fabrication of a myriad of platforms for an extensive variety of applications. PLA has been widely used as temporary extracellular matrices in tissue engineering. At the other end of the spectrum, PLA's application as drug-loaded nanoparticle drug carriers, such as liposomes, polymeric nanoparticles, dendrimers, and micelles, can encapsulate otherwise toxic hydrophobic anti-tumor drugs and evade systemic toxicities. The clinical translation of these technologies from preclinical experimental settings is an ever-evolving field with incremental advancements. In this review, some of the biomedical applications of PLA and its copolymers are highlighted and briefly summarized.

The Influence of Solid Microneedles on the Transdermal Delivery of Selected Antiepileptic Drugs

The aim of this project was to examine the effect of microneedle rollers on the percutaneous penetration of tiagabine hydrochloride and carbamazepine across porcine skin in vitro. Liquid chromatography-mass spectrometric analysis was carried out using an Agilent 1200 Series HPLC system coupled to an Agilent G1969A TOF-MS system. Transdermal flux values of the drugs were determined from the steady-state portion of the cumulative amount versus time curves. Following twelve hours of microneedle roller application, there was a 6.74-fold increase in the percutaneous penetration of tiagabine hydrochloride (86.42 ± 25.66 µg/cm²/h) compared to passive delivery (12.83 ± 6.30 µg/cm²/h). For carbamazepine in 20% ethanol, passive transdermal flux of 7.85 ± 0.60 µg/cm²/h was observed compared to 10.85 ± 0.11 µg/cm²/h after microneedle treatment. Carbamazepine reconstituted in 30% ethanol resulted in only a 1.19-fold increase in drug permeation across porcine skin (36.73 ± 1.83 µg/cm²/h versus 30.74 ± 1.32 µg/cm²/h). Differences in flux values of untreated and microneedle-treated porcine skin using solid microneedles for the transdermal delivery of tiagabine were statistically significant. Although there were 1.38- and 1.19-fold increases in transdermal flux values of carbamazepine when applied as 20% and 30% ethanol solutions across microneedle-treated porcine skin, respectively, the increases were not statistically significant.

On the interaction of alginate-based core-shell nanocarriers with keratinocytes in vitro

Calcium alginate nanocarriers (CaANCs) were developed as a potential tool for delivery of hydrophobic active molecules such as pharmaceutical and cosmetic active ingredients. In this study, we focused on interactions between CaANCs and keratinocytes in culture and examined toxicity, internalization and drug release. Prior to cellular interactions, cryogenic transmission electron microscopy images showed that CaANCs appear as regular, spherical and dense particles, giving evidence of the surface gelation of CaANCs. Their size, around 200nm, was stable under tested conditions (temperature, culture media, presence of serum and presence of encapsulated dye), and their toxicity on keratinocytes was very low. Flow cytometry assays showed that CaANCs are internalized into keratinocytes by endocytosis with a predominant implication of the caveolae-mediated route. Förster resonance energy transfer (FRET) demonstrated that after a 2h contact, the release of CaANC contents in the cytoplasm of keratinocytes was almost complete. The endocytosis of CaANCs by a lysosome-free pathway, and the rapid release of their contents inside keratinocytes, will allow vectorized molecules to fully exhibit their pharmacological or cosmetic activity.

Microneedles: A New Frontier in Nanomedicine Delivery

This review aims to concisely chart the development of two individual research fields, namely nanomedicines, with specific emphasis on nanoparticles (NP) and microparticles (MP), and microneedle (MN) technologies, which have, in the recent past, been exploited in combinatorial approaches for the efficient delivery of a variety of medicinal agents across the skin. This is an emerging and exciting area of pharmaceutical sciences research within the remit of transdermal drug delivery and as such will undoubtedly continue to grow with the emergence of new formulation and fabrication methodologies for particles and MN. Firstly, the fundamental aspects of skin architecture and structure are outlined, with particular reference to their influence on NP and MP penetration. Following on from this, a variety of different particles are described, as are the diverse range of MN modalities currently under development. The review concludes by highlighting some of the novel delivery systems which have been described in the literature exploiting these two approaches and directs the reader towards emerging uses for nanomedicines in combination with MN.

Flexible PEGDA-based microneedle patches with detachable PVP–CD arrowheads for transdermal drug delivery

A polymer-based microneedle patch with drug-loaded and detachable arrowhead tips for transdermal drug delivery.

Effect of formulation variables on preparation of celecoxib loaded polylactide-co-glycolide nanoparticles

Polymer based nanoparticle formulations have been shown to increase drug bioavailability and/or reduce drug adverse effects. Nonsteroidal anti-inflammatory drugs (e.g. celecoxib) reduce prostaglandin synthesis and cause side effects such as gastrointestinal and renal complications. The aim of this study was to formulate celecoxib entrapped poly lactide-co-glycolide based nanoparticles through a solvent evaporation process using didodecyldimethylammonium bromide or poly vinyl alcohol as stabilizer. Nanoparticles were characterized for zeta potential, particle size, entrapment efficiency, and morphology. Effects of stabilizer concentration (0.1, 0.25, 0.5, and 1% w/v), drug amount (5, 10, 15, and 20 mg), and emulsifier (lecithin) on nanoparticle characterization were examined for formula optimization. The use of 0.1, 0.25, and 0.5% w/v didodecyldimethylammonium bromide resulted in a more than 5-fold increase in zeta potential and a more than 1.5-fold increase in entrapment efficiency with a reduction in particle size over 35%, when compared to stabilizer free formulation. Nanoparticle formulations were also highly influenced by emulsifier and drug amount. Using 0.25% w/v didodecyldimethylammonium bromide NP formulations, peak zeta potential was achieved using 15 mg celecoxib with emulsifier (17.15±0.36 mV) and 20 mg celecoxib without emulsifier (25.00±0.18 mV). Peak NP size reduction and entrapment efficiency was achieved using 5 mg celecoxib formulations with (70.87±1.24 nm and 95.55±0.66%, respectively) and without (92.97±0.51 nm and 95.93±0.27%, respectively) emulsifier. In conclusion, formulations using 5 mg celecoxib with 0.25% w/v didodecyldimethylammonium bromide concentrations produced nanoparticles exhibiting enhanced size reduction and entrapment efficiency. Furthermore, emulsifier free formulations demonstrated improved zeta potential when compared to formulations containing emulsifier (p<0.01). Therefore, our results suggest the use of emulsifier free 5 mg celecoxib drug formulations containing 0.25% w/v didodecyldimethylammonium bromide for production of polymeric NPs that demonstrate enhanced zeta potential, small particle size, and high entrapment efficiency.

Solid-phase microextraction/gas chromatography-mass spectrometry method optimization for characterization of surface adsorption forces of nanoparticles

A complete characterization of the different physico-chemical properties of nanoparticles (NPs) is necessary for the evaluation of their impact on health and environment. Among these properties, the surface characterization of the nanomaterial is the least developed and in many cases limited to the measurement of surface composition and zetapotential. The biological surface adsorption index approach (BSAI) for characterization of surface adsorption properties of NPs has recently been introduced (Xia et al. Nat Nanotechnol 5:671–675, 2010; Xia et al. ACS Nano 5(11):9074–9081, 2011). The BSAI approach offers in principle the possibility to characterize the different interaction forces exerted between a NP's surface and an organic—and by extension biological—entity. The present work further develops the BSAI approach and optimizes a solid-phase microextraction gas chromatography–mass spectrometry (SPME/GC-MS) method which, as an outcome, gives a better-defined quantification of the adsorption properties on NPs. We investigated the various aspects of the SPME/GC-MS method, including kinetics of adsorption of probe compounds on SPME fiber, kinetic of adsorption of probe compounds on NP's surface, and optimization of NP's concentration. The optimized conditions were then tested on 33 probe compounds and on Au NPs (15 nm) and SiO₂ NPs (50 nm). The procedure allowed the identification of three compounds adsorbed by silica NPs and nine compounds by Au NPs, with equilibrium times which varied between 30 min and 12 h. Adsorption coefficients of 4.66 ± 0.23 and 4.44 ± 0.26 were calculated for 1-methylnaphtalene and biphenyl, compared to literature values of 4.89 and 5.18, respectively. The results demonstrated that the detailed optimization of the SPME/GC-MS method under various conditions is a critical factor and a prerequisite to the application of the BSAI approach as a tool to characterize surface adsorption properties of NPs and therefore to draw any further conclusions on their potential impact on health.

Graphical Abstract