Concentration Dependent Viscosity of Monoclonal Antibody Solutions: Explaining Experimental Behavior in Terms of Molecular Properties

Purpose

Early identification of monoclonal antibody candidates whose development, as high concentration (≥100 mg/mL) drug products, could prove challenging, due to high viscosity, can help define strategies for candidate engineering and selection.

Methods

Concentration dependent viscosities of 11 proprietary mAbs were measured. Sequence and structural features of the variable (Fv) regions were analyzed to understand viscosity behavior of the mAbs. Coarse-grained molecular simulations of two problematic mAbs were compared with that of a well behaved mAb.

Results

Net charge, ξ-potential and pI of Fv regions were found to correlate with viscosities of highly concentrated antibody solutions. Negative net charges on the Fv regions of two mAbs with poor viscosity behaviors facilitate attractive self-associations, causing them to diffuse slower than a well-behaved mAb with positive net charge on its Fv region. An empirically derived equation that connects aggregation propensity and pI of the Fv region with high concentration viscosity of the whole mAb was developed.

Conclusions

An Fv region-based qualitative screening profile was devised to flag mAb candidates whose development, as high concentration drug products, could prove challenging. This screen can facilitate developability risk assessment and mitigation strategies for antibody based therapeutics via rapid high throughput material-free screening.     

Revealing the WEDM Process Parameters for the Machining of Pure and Heat-Treated Titanium (Ti-6Al-4V) Alloy

Ti-6Al-4V is an alloy that has a high strength-to-weight ratio. It is known as an alpha-beta titanium alloy with excellent corrosion resistance. This alloy has a wide range of applications, e.g., in the aerospace and biomedical industries. Examples of alpha stabilizers are aluminum, oxygen, nitrogen, and carbon, which are added to titanium. Examples of beta stabilizers are titanium–iron, titanium–chromium, and titanium–manganese. Despite the exceptional properties, the processing of this titanium alloy is challenging when using conventional methods as it is quite a hard and tough material. Nonconventional methods are required to create intricate and complex geometries, which are difficult with the traditional methods. The present study focused on machining Ti-6Al-4V using wire electrical discharge machining (WEDM) and conducting numerous experiments to establish the machining parameters. The optimal setting of the machining parameters was predicted using a multiresponse optimization technique. Experiments were planned using the response surface methodology (RSM) technique and analysis of variance (ANOVA) was used to determine the significance and contribution of the input parameters to changes in the output characteristics (cutting speed and surface roughness). The cutting speed obtained during the processing of the annealed titanium alloy using WEDM was quite large as compared to the cutting speed obtained in the case of processing the pure, quenched, and hardened titanium alloys using WEDM. The maximum cutting speed obtained while processing the annealed titanium alloy was 1.75 mm/min.     

Structure-Function Analyses of New SARS-CoV-2 Variants B.1.1.7, B.1.351 and B.1.1.28.1: Clinical,Diagnostic, Therapeutic and Public Health Implications

SARS-CoV-2 (Severe Acute Respiratory Syndrome-Coronavirus 2) has accumulated multiple mutations during its global circulation. Recently, three SARS-CoV-2 lineages, B.1.1.7 (501Y.V1), B.1.351 (501Y.V2) and B.1.1.28.1 (P.1), have emerged in the United Kingdom, South Africa and Brazil, respectively. Here, we have presented global viewpoint on implications of emerging SARS-CoV-2 variants based on structural–function impact of crucial mutations occurring in its spike (S), ORF8 and nucleocapsid (N) proteins. While the N501Y mutation was observed in all three lineages, the 501Y.V1 and P.1 accumulated a different set of mutations in the S protein. The missense mutational effects were predicted through a COVID-19 dedicated resource followed by atomistic molecular dynamics simulations. Current findings indicate that some mutations in the S protein might lead to higher affinity with host receptors and resistance against antibodies, but not all are due to different antibody binding (epitope) regions. Mutations may, however, result in diagnostic tests failures and possible interference with binding of newly identified anti-viral candidates against SARS-CoV-2, likely necessitating roll out of recurring “flu-like shots” annually for tackling COVID-19. The functional relevance of these mutations has been described in terms of modulation of host tropism, antibody resistance, diagnostic sensitivity and therapeutic candidates. Besides global economic losses, post-vaccine reinfections with emerging variants can have significant clinical, therapeutic and public health impacts.     

Investigation of dual-bend serpentine/spiral waveguides coupled to a microchannel system for competent,evanescent-wave-absorption-based,on-chip,biological-/chemical-sensing applications

U or C-shaped waveguides, coupled to analyte microchannels, have been shown to be very responsive to evanescent-wave-absorption-based sensing. However, due to only having a single C-bend length, for analyte interaction in earlier devices, there was always an opportunity to advance their evanescent-absorbance sensitivity, by including multiple C-bend structures (interfaced with the analyte microchannel system) in the device design. To achieve this objective, two different types of waveguide probes (having a different orientation of two C-bends), i.e. S-bend and spiral-bend, were theoretically analyzed and further, experimentally tested for their comparative sensitivity to evanescent wave absorption, in this pioneering study. A novel single-step fabrication procedure (using an SU-8 photoresist), was executed to fabricate these waveguide structures interfaced (both at their inner and outer bend surfaces) with a microchannel system, along with fiber-to-waveguide coupler structures. Experimentally, the sensitivity of the S-bend waveguides was found to be ∼25% higher compared to that of spiral waveguides of similar dimensions, which corroborated the results from numerical modeling. Compared to our earlier embedded C-bend waveguides, the overall evanescent-wave-absorption-based detection sensitivity of the embedded spiral and S-bend waveguides were found to be improved by ∼7.5 times and ∼9 times respectively. Finally, these devices were found to be ideally suited for more sensitive biological-, as well as, chemical-sensing applications, provided a suitable surface alteration process is performed to these waveguide probes. Further, the proposed device has a possible capability for: facile continuous (real-time) analysis, a fixed sample volume interaction, and control over the evaporation of analyte samples introduced in to the device.

The reported device is a versatile sensing-platform, with high sensitivity, for any chemical/biological-sensing applications, if suitable surface adaptation is first performed to the microchannel-system-embedded duel-bend waveguide-probe.     

Pancreatic ascites and Pleural Effusion in Children: Clinical Profile,Management and Outcomes

BackgroundPancreatic ascites (PA) and pleural effusion (PPE) are rarely encountered in children. They develop due to disruption of the pancreatic duct (PD) or leakage from an associated pancreatic fluid collection (PFC). The literature on childhood PA/PPE and its management is scarce.MethodsA retrospective review of children with PA/PPE diagnosed and managed at our center over the last 4 years was performed. The clinical, biochemical, radiological and management profiles were analyzed. Conservative management included nil per oral, octreotide and drainage using either percutaneous catheter or repeated paracentesis. Endotherapy included endoscopic retrograde cholangiopancreatography (ERCP) and transpapillary stenting.ResultsOf the 214 children with pancreatitis, 15 (7%) had PA/PPE. Median age was 9 years with a third under 2 years. Median ascitic fluid amylase was 8840 U/L and all had elevated protein (>2.5 g/dl) and low serum ascites-albumin gradient ascites (<1.1). While PA/PPE was the first manifestation of underlying chronic pancreatitis (CP) in 10 children (67%), trauma was seen in 4 (26%) and hypertriglyceridemia in 1 (7%). On imaging, PD disruption could be identified in 10 (67%) children. ERCP and stenting was done in 10 children. Conservative management alone (n = 4) and endotherapy (n = 10) was successful in 93% with only one requiring surgery. The younger children (n = 4), were managed conservatively and only 1 of them required surgery. Resolution of PA/PPE was achieved in all with no recurrences.ConclusionsConservative management and ERCP plus transpapillary stenting results in resolution of majority of pediatric PA/PPE. Children presenting with PA/PPE needs to be evaluated for CP.