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Cavitation, the formation and collapse of vapor-filled bubbles, poses a problem in spring-driven autoinjectors (AIs). It occurs when the syringe accelerates abruptly during activation, causing pressure fluctuations within the liquid. These bubbles expand and then collapse, generating shock waves that can harm both the device and the drug molecules. This issue stems from the syringe's sudden acceleration when the driving rod hits the plunger. To better understand cavitation in AIs, we explore how design factors like drive spring force, air gap size, and fluid viscosity affect its likelihood and severity. We use a dynamic model for spring-driven autoinjectors to predict and analyze the factors contributing to cavitation initiation and severity. This model predicts the motion of AI components, such as the displacement and velocity of the syringe barrel, and allows us to investigate pressure wave propagation and the subsequent dynamics of cavitation under various operating conditions. We investigated different air gap heights (from 1 to 4 mm), drive spring forces (from 8 to 30 N), and drug solution viscosities (from 1 to 18 cp) to assess cavitation inception based on operational parameters. Results reveal that AI dynamics and cavitation onset and severity strongly depend upon AI operating parameters, namely drive spring force and air gap height. The maximum syringe acceleration increases with spring stiffness and decreases with air gap height; increases in air gap height prolong the time interval of syringe acceleration but diminish the maximum syringe acceleration. From actuation to injection, air gap pressure peaks twice, first due to impact with the rod/plunger and secondly due to the deacceleration event upon injection. The maximum air gap pressure increases with spring stiffness and decreases with air gap height. Results show that maximum cavitation bubble radii and collapse-driven extension rates occur with higher driver spring forces, smaller air gap heights, and less viscous solutions. A cavitation criterion is developed for cavitation in autoinjectors that concludes that cavitation in autoinjectors depends on the peak syringe acceleration., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Understanding the interface motion and hydrodynamic shear induced by the liquid sloshing during the insertion stage of an autoinjector can help improve drug product administration. We perform experiments to investigate the interfacial motion and hydrodynamic shear due to the acceleration and deceleration of syringes. The goal is to explore the role of fluid properties, air gap size, and syringe acceleration on the interface dynamics caused by autoinjector activation. We used a simplified autoinjector platform to record the syringe and liquid motion without any view obstruction. Water and silicone oil with the same viscosity are used as the model fluids. Particle Image Velocimetry (PIV) is employed to measure the velocity field. Simultaneous shadowgraph visualization captures the air entrainment. Our in-house PIV and image processing algorithms are used to quantify the hydrodynamic stress and interfacial area to investigate the effects of various autoinjector design parameters and fluid types on liquid sloshing. The results indicate that reducing the air gap volume and syringe acceleration/deceleration mitigate the interface area and effective shear. Moreover, the interfacial area and induced hydrodynamic stress decrease with the Fr=U/aD, where U is the interface velocity, a is the maximum syringe acceleration, and D is the syringe diameter., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: Cavitation is an undesired phenomenon that may occur in certain types of autoinjectors (AIs). Cavitation happens because of rapid changes of pressure in a liquid, leading to the formation of small vapor-filled cavities, which upon collapsing, can generate an intense shock wave that may damage the device container and the protein drug molecules. Cavitation occurs in the AI because of the syringe-drug relative displacement as a result of the syringe's sudden acceleration during needle insertion and the ensuing pressure drop at the bottom of the container. Therefore, it's crucial to analyze the potential effect of cavitation on AI. The goal of the current study is to investigate the effects of syringe and AI design parameters such as air gap size, syringe filling volume, fluid viscosity, and drive spring force (syringe acceleration) on the risk and severity of cavitation., Methods: A model autoinjector platform is built to record the syringe and cavitation dynamics which we use to estimate the cavitation intensity in terms of extension rate and to study the effects of design parameters on the severity of cavitation., Results: Our results show the generation of an intense shock wave and a high extension rate upon cavitation collapse. The induced extension rate increases with syringe acceleration and filling volume and decreases with viscosity and air gap size., Conclusion: The most severe cavitation occurred in an AI device with the larger drive spring force and the syringe of a smaller air gap size filled with a less viscous fluid and a larger filling volume., (© 2022. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Liquid perfluorocarbon-based nanodroplets are stable enough to be used in extravascular imaging, but provide limited contrast enhancement due to their small size, incompressible core, and small acoustic impedance mismatch with biological fluids. Here we show a novel approach to overcoming this limitation by using a heating-cooling cycle, which we will refer to as thermal modulation (TM), to induce echogenicity of otherwise stable but poorly echogenic nanodroplets without triggering a transient phase shift. We apply thermal modulation to high-boiling point tetradecafluorohexane (TDFH) nanodroplets stabilized with a bovine serum albumin (BSA) shell. BSA-TDFH nanodroplets with an average diameter under 300 nanometers showed an 11.9 ± 5.4 mean fold increase in echogenicity on the B-mode and a 13.9 ± 6.9 increase on the nonlinear contrast (NLC) mode after thermal modulation. Once activated, the particles maintained their enhanced echogenicity ( p < 0.001) for at least 13 h while retaining their nanoscale size. Our data indicate that thermally modulated nanodroplets can potentially serve as theranostic agents or sensors for various applications of contrast-enhanced ultrasound.

Objective: Autoinjectors are a convenient and efficient way to self-administer subcutaneous injections of biopharmaceuticals. Differences in device mechanical design can affect the autoinjector functionality and performance. This study investigates the performance differences of two single-spring-actuated autoinjectors. Methods: We compare the performance between Emgality (120 mg/mL) and Aimovig (140 mg/mL) autoinjector devices from an engineering point of view at two test conditions: room (25 C[Formula: see text]) and storage (5 C[Formula: see text]) temperatures. We employ a novel experimental procedure to simultaneously acquire the force and acoustic signals during operation, and high-speed imaging during the needle insertion and drug injection. Results: We perform 18 quantitative comparisons between Emgality and Aimovig, and we observe that 14 of these have statistically significant differences. For both test conditions, Emgality requires an 8 N activation force while Aimovig requires 14 N activation force, and the needle of Emgality has an insertion depth of 5 mm while Aimovig has an insertion depth of 7 mm. The injection speeds are significantly affected by temperature. Emgality has an injection speed of 0.40 mL/s and 0.28 mL/s at room and storage temperature condition, respectively; while Aimovig has an injection speed of 0.24 mL/s and 0.16 mL/s at those conditions. Lastly, confirmation "click" sound of Emgality occurs 0.75-1.53 s after dose completion, while in Aimovig, the confirmation "click" sound occurs 0.26-0.46 s before dose completion. Conclusions: This study revealed performance differences between Emgality and Aimovig autoinjector devices, despite the fact that the delivery principle of these single-spring-actuated autoinjectors are the same. These differences may result in different risk of intramuscular injection and premature device removal, both of which need to be further verified in clinical trials.

Stromelysin has been proposed to play a major role in the pathologic degradation of diseased cartilage of osteoarthritis and rheumatoid arthritis patients. A truncated, recombinant form of this enzyme, with the sequence Phe83 to Thr260 (mSL-t), has been expressed and purified from E. coli to investigate its biochemical and biophysical properties, and to develop inhibitors for arthritis treatment. LC/ESI-MS technique was utilized for the characterization of mSL-t. The mass spectra of mSL-t showed the presence of a number of different protein components in addition to the full-length mSL-t form. We have demonstrated that protein degradation arose from autolysis. Molecular weights determined by LC/ESI-MS of these autolysis products allowed for the identification of new autolytic sites in mSL-t. Furthermore, two strategies were undertaken to prepare mSL-t free of degradation products. These include preparation of a mutant form of the enzyme in which Arg163 was substituted for Leu163 and purification of mSL-t using affinity chromatography. The LC/ESI-MS data of the mutant protein confirmed the Leu to Arg mutation. The affinity-purified material showed only one LC peak in the LC/MS chromatograms, and the mass spectrum of the peak identified only the intact protein, demonstrating that the full-length protein has been successfully separated from the autodegradation products and further autolysis of the enzyme has been prevented.

Liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS), tandem mass spectrometry with on-line liquid chromatography (LC/ESI-MS/MS) and high-resolution mass spectrometry with liquid secondary ionization (LSI-MS) were utilized to identify the modified amino acids in peptides and proteins formed during oxidation with performic acid. The procedure of protein oxidation was chosen to assist in protein unfolding by oxidizing the cystines to cysteic acids to allow for more complete proteolytic digestion and to create additional cleavage sites for endoproteinase Asp-N. Investigation of the Asp-N peptide map of oxidized superoxide dismutase (SOD) by LC/ESI-MS revealed that an expected proteolytic fragment of the protein was missing. In its place, two peptides with molecular weights 66 and 100 higher than that calculated for the missing peptide were observed. To identify the modified amino acids in the unexpected peptides, a model peptide with some amino acid similarities (tyrosine, arginine, methionine, lysine) to the missing peptide was chosen and was subjected to similar oxidation and enzymatic digestion steps, conditions, and reactions. After oxidation and digestion, the model peptide (TAP; sequence, Ac-MDKVLNRY) showed three major peaks in LC/MS. The peptides in the three peaks were identified as the unmodified peptide and two peptides whose molecular weights were 66 and 100 higher than that of TAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Human fibroblast collagenase belongs to a family of matrix metalloproteinases which have been implicated in a number of connective tissue disorders ranging from rheumatoid arthritis to tumor invasion. To examine the active site of this enzyme by biophysical studies, a 19 kDa recombinant truncated mature collagenase (mCL-t) was prepared. Electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) mass spectrometry have been utilized for the characterization of mCL-t. The molecular weights measured by these techniques identified the presence of two closely related protein components separated by approximately 100 Da. Edman sequence analysis demonstrated that the two protein components differ from each other by an amino terminal valine, consistent with the mass spectrometric data. In addition, the molecular weight of mCL-t determined by mass spectrometry did not agree with that calculated from the reported sequence. To identify the origin of this discrepancy, the DNA sequence of the mCL-t clone was examined. Several differences were noted between the DNA sequence of mCL-t and the published collagenase gene sequence. When these differences were taken into account, the measured molecular weights were found to be in good agreement with that calculated for the modified sequence. In separate experiments, both ESI and MALDI mass spectrometry have been used to determine molecular weights of mCL-t samples enriched with stable isotopes 15N and (15N + 13C). The measured molecular weights demonstrated a 97% (15N) and 99% (15N + 13C) incorporation of labeled isotopes in the two samples.

Clonidine, an antihypertensive drug, binds to alpha 2-adrenergic and imidazoline receptors. The endogenous ligand for imidazoline receptors may be a clonidine-displacing substance, a small molecule isolated from bovine brain. This clonidine-displacing substance was purified and determined by mass spectroscopy to be agmatine (decarboxylated arginine), heretofore not detected in brain. Agmatine binds to alpha 2-adrenergic and imidazoline receptors and stimulates release of catecholamines from adrenal chromaffin cells. Its biosynthetic enzyme, arginine decarboxylase, is present in brain. Agmatine, locally synthesized, is an endogenous agonist at imidazoline receptors, a noncatecholamine ligand at alpha 2-adrenergic receptors and may act as a neurotransmitter.

The previously reported reaction of tolazamide with nitrite, under physiological conditions, to form N-nitrosohexamethyleneimine and surprisingly, N-nitrosopiperidine was confirmed. By using the six-membered ring analogue of tolazamide, 1-(piperidyl)-3-(p-tolylsulfonyl)urea, which yields the corresponding N-nitrosopiperidine and N-nitrosopyrrolidine, the present study shows that an unusual ring contraction occurs, excising the carbon alpha to the nitrogen.

Tolazamide, an antidiabetic drug, was found to produce N-nitrosohexamethyleneimine (NHM) upon exposure to an oxidizing agent and in the absence of a nitrosating agent. The oxidizing agents were either hydrogen peroxide or oxygen.

o-Hydroxyhippuric acid (HHA) is formed in liver during the process of detoxication of salicylic acid which arises from either salicylic-containing dietary vegetables or hydrolysis of aspirin. Recently, HHA has also been shown as one of the so-called 'uremic toxins'. By derivatization of HHA with o-phthaldialdehyde (OPA), the resulting fluorescent product can easily be measured with the limit of measurement somewhere below 3 pmol on high performance liquid chromatography. Using the method described, an approximately 85% recovery of added HHA in human sera was obtained. This analytical system is now being employed to determine the concentration of HHA in human sera of uremic patients. Determination of HHA content in human uremic patients is very important, since uremia is associated with defective binding of many acidic drugs to serum protein(s) and HHA replaces these drugs by tightly binding to these proteins. This could potentially affect the therapeutic effectiveness of various pharmacologic agents.