Agarose Gel: An Overview of the Dermal Filler and a Clinical Experience With 700 Patients

Abstract Background Dermal fillers currently in the market have several advantages and disadvantages over each other. Agarose gel (AG) is a unique material due to its special rheological characteristics and gel-forming capability. Objectives The authors aimed to share their clinical experience on AG for a variety of facial augmentation procedures and its long-term results. Methods The study population consisted of 700 patients (532 females; 168 males) aged 18 to 52 years. Follow-up visits were at 1, 3, 6, 12, and 24 months after the injections. Patient satisfaction was evaluated on a scale from 0 to 10 using a survey and clinical improvement was evaluated using the Global Aesthetic Improvement Scale (GAIS) by 2 independent plastic surgeons before the injection and at 1-year follow-up. Results Eighty-two percent of the patients scored 1 or 2 (exceptional or great improvement) on GAIS. Eighty-five percent of the patients scored 8 or above (very satisfied). Most patients experienced at least 80% persistence of effect at 1-year follow-up. Conclusions AG appears to be suitable for a variety of facial augmentation and contouring applications, as it is safe and has long-lasting favorable cosmetic efficacy. Level of Evidence: 3

In recent years, many materials have been used as tissue fillers, but it would not be correct to acknowledge any of them as ideal fillers.It is important to choose the filler according to its characteristics.A desirable material for injectables should meet several criteria.It must be safe and effective, highly biocompatible, and nonimmunogenic, to avoid any significant inflammatory response.In addition, the biomaterial should possess the ability to retain its form, exhibit a suitable rate of biodegradation at the implant site, and demonstrate longevity.Furthermore, it should facilitate the transportation and preservation of cells or signaling molecules at the site of implantation, while exhibiting minimal potential for intratissue migration.The material should also be affordable and easily storable.[7][8][9][10][11][12][13][14][15][16] Agarose originates from sea algae.It is a saccharide polymer and dissolves into water forms a gel with a threedimensional (3D) porous reticulum.][19][20] There are many fillers on the market with different properties.AG is an option with significant advantages in certain indications.It is a unique material with gel-forming ability and special rheological properties. 19,21,22he important characteristics of this filler to point out are: • AG is nonhydrophilic and it has high G-prime properties which allow the practitioner for accurate injections.It does not have a swelling effect which may disrupt the cosmetic appearance; so that, it is likely to achieve better contour and definition, making the result of the treatment immediately appreciable. 19,23,24 AG does not cause any edema in the surrounding tissues in the mid-term and long-term. 19,23 Due to its slow resorption feature, it remains in place for an extended period of time and this positively affects the clinical result. 23 Due to its nonreticular molecular structure, the probability of migration is very low. 19,23,24 AG is a hydrogel whose consistency is determined by hydrogen bonds between the linear chains.It is nontoxic and it does not contain any reticulating and/or crosslinking agents such as 1,4-butanediol diglycidyl ether or any other chemical agents which are present in HA fillers. 25,26 Being natural absorbable filler, it is completely biodegradable.[23][24][25] AG is currently being used in 45 countries, including Europe.It comes in 4 different concentrations including 1%, 1.5%, 2.5%, and 3.5% agarose in a saline solution.The 2.5% and 3.5% AG fillers also contain 0.4% nonreticulated HA.It is suggested to use higher concentrations for injecting deeper into areas that require more volume, such as the zygoma or chin, while lower concentrations are appropriate for injecting into the more superficial subdermal plane in areas such as marionette or nasolabial lines.Although pain is not seen with slow injection, it is possible to mix with 0.1 to 0.2 mL of 2% lidocaine to prevent the possible discomfort, which means total amount of 1.6 mL of mixture is available.The product is homogenized by transferring it between syringes with Luer-lock fittings, typically 5 to 10 times, until the mixture is uniform.

METHODS
A variety of facial augmentation applications using AG dermal filler (Algeness Advanced Aesthetic Technologies; Brookline, MA) were performed on patients between February 2020 and February 2022 at our clinic.Patients over the age of 18 were selected to be eligible for inclusion and required that patients have facial soft-tissue deficiency.
The study excluded patients who had received permanent implants or previous soft-tissue augmentation, as well as those with a known allergy to fillers, recurring skin disease, history of connective tissue disease, or active infection at the time of the study.Bezmialem Vakif University institutional review board approved the study protocol.Also, this study adhered to the guidelines of the Declaration of Helsinki.Written consent was obtained from all patients, allowing the use and analysis of their data.

Areas of Treatment and Procedure
The senior author conducted each procedure in the office.After the injection was administered, the treated area was subjected to gentle massage, and the patients were closely monitored for any adverse reactions.On average, the treatment duration was 20 min.
The primary areas treated were chin, nasolabial area, temple, zygoma, and nose.The most commonly treated site was the zygoma (188 patients).AG was administered with a 23 G blunt tip rigid cannula or 27 G 13 mm needle provided by the manufacturer.The precise technique, injection volumes, and concentrations used varied.Generally, a linear threading, small boluses, and big boluses techniques were used.Injection planes were the supraperiosteal, subdermal, and/or subsuperficial musculoaponeurotic system (SMAS) planes, depending on the area being augmented.Since the migration feature of AG is low, linear threading technique is applied to avoid lump  Buhsem and Kirazoglu formation especially in soft tissue and subdermal applications (Table 1).Example of injection techniques and instructions can be seen in Videos 1 and 2.

Patient Follow-up and Evaluation
Follow-up visits were at 1, 3, 6, 12, and 24 months after the injections.All patients were followed up >2 years.
Standardized digital photography was used and taken before the treatment and at the follow-up visits.To assess patient satisfaction, a survey was conducted.The clinical improvement was evaluated using the Global Aesthetic Improvement Scale (GAIS) by 2 independent plastic surgeons.The assessments were performed before the injection and at a 1-year follow-up (as presented in Table 2).Additionally, patients were monitored after the injection for any complications or the need for revisional "touch-up" procedures.Touch-ups were performed 2 to 4 weeks after the initial procedure.

Statistical Analysis
A descriptive analysis was conducted.Categorical data were presented as numbers and percentages, and numerical data were presented with mean, median, and minimum-maximum values.Statistical analyses were performed using SPSS version 21.0 for Windows (SPSS Inc., Chicago, IL).

Study Population
The study population consisted of 700 patients with the ratio of 532 females:168 males and ages ranging from 18 to 52 years.

Follow-up
The average follow-up time was 16 months ranging from 12 to 24 months.

Efficacy
All patients were effectively treated, as indicated by the study's results.Clinical evaluation scores were recorded before the injections and at the 1-year follow-up.Prior to treatment, the average score on the GAIS was 1.6 out of 5, whereas after a year, it improved to 1.8 out of 5. Additionally, 82% of the patients (574 out of 700) had exceptional or great improvement, scoring 1 or 2 on the GAIS.The mean score for patient satisfaction was 4.4 out of 10 before the injection and 8.2 out of 10 after a year, with 85% of patients (595 out of 700) reporting high levels of satisfaction with a score of 8 or above.Further details can be found in Table 3.

Duration
At the 1-year follow-up, patients exhibited a minimum of 80% persistence of effect, irrespective of the treatment site.However, after 1.5 years, the outcome varied depending on several factors, such as age, depth of depression, location, and tissue thickness.Figures 2 through 6 showcase the results of patients who were treated with AG at our practice.

Safety
All patients had experienced mild erythema and edema at the injection site at the end of the procedures that resolved spontaneously within 24 h.Although some patients experienced mild discomfort during the injection, it was easily overcame by slower injections.Regarding long-term follow-ups, 1 chin augmentation patient had an infection  localized to the area augmented.All of the patients had taken Cefuroxime 500 mg treatment, one of them was drained, all fully recovered without any sequela.A total of 5 lumps were identified during the follow-ups.All of them were invisible but palpable.Over time, lumps gradually disappeared along with the filler without any specific intervention.Lastly, 3 migration-displacement events were encountered.All migration cases were noticed during injection and corrected with adequate massage and molding immediately.No other serious adverse events or major complications, such as vascular injections, nodules, granulomas, or other complications were reported at any time point (Table 4).

DISCUSSION
Owing to its characteristics, AG is a biocompatible material that can be used in various preclinical and clinical applications.15][16][17][18][19][20][27][28][29][30][31][32] Hydrogels are a versatile material that can be employed for developing both 3D scaffolding and injectable systems.The synthesis of hydrogels can be tailored to impart specific geometric, physical, and chemical properties to meet the requirements of the target tissue.4][35] It has also been extensively researched for drug delivery applications, wherein it is utilized for controlled release of pharmacological substances, and as a carrier for cells and drugs. 34,36,37garose has a wide range of applications in tissue engineering, including its use as a temporary scaffold for growth factors and bony cells.][40][41] It is also used in different applications in various areas: in microbiology as culture media, in pharmaceuticals and phytotherapy applications as thickeners, as a laxative, a defense for the mucous membranes of the gastrointestinal tract. 25Agar has been employed in the food industry as a stabilizer, thickener, humectant, surface finisher, and flavoring agent.It is considered a safe ingredient and complies with the specifications of the Food Chemicals Codex. 42G can be utilized as an alternative treatment option for several functional disorders in the head and neck region, as an example of its clinical applications.It has been used for the management of periprosthetic leaks after total laryngectomy and for the prevention of recurrent aspiration pneumonia.In addition, promising functional indications with long-term outcomes have been observed in the treatment of unilateral vocal cord paralysis using AG. 43s the face and neck age, the loss of bone and fat volume, formation of wrinkles, and reduction in elastin and collagen can manifest.Moreover, congenital or acquired deformities in the facial features, nose, ears, lips, and scars may require aesthetic intervention for correction.In these cases, AG can be used as the primary choice due to its reshaping and molding properties.
2][3] Considering its structural properties, nonhydrophilic AG can be used in the supraperiosteal plane in the radix and nasal spine without causing undesirable swelling. 44Linear retrograde injection is the recommended injection technique in AG applications, as intradermal and big bolus injections can cause palpability and lump formation.However, serial small bolus injection has been found to give good results if it is over the supraperiosteum or subSMAS.Given the persistency of the fillers, according to the studies with a 2-year follow-up, 3.5% AG fillers indicated for radix and nasal spine could last up to 18 months which is comparable to other fillers currently on the market. 4,44s individual's age deepening of the nasolabial folds is a common occurrence.To address this issue, AG can be injected in Ristow's space, below the ala of the nose and the elevator muscle of the lower lip, using higher density preparations such as AG 2.5% or 3.5%.However, care must be taken during injection to avoid inadvertent spread  of the product from the fibrous lip subcutis to the softer cheek subcutis, which can result in unwanted nasolabial fullness.To prevent this, lateral compression of the cheek can be applied during injection.This technique can also help to prevent the injectable from spreading intraarterially. 11,43andibular and chin volumization can augment, refine, and improve the definition of the entire face.AG 2.5% or 3.5% can be used supraperiosteally using small boluses and linear retrograde technique. 43he zygomatic region can be treated with AG 2.5% or 3.5% supraperiosteally.It is important to inject the filler slowly and to mold it carefully after injection to ensure proper shaping. 43n cases of depression, the temple can be successfully treated with AG 2.5% or 3.5%.Placing AG deep in the temporalis muscle can help avoid the superficial temporal artery, which is a major blood vessel located on the surface of the temple.Injection can be performed supraperiosteally using big bolus injection into the area defined. 43n a study, a concentration of 2.5% wt AG was proposed for lip augmentation in 62 patients, resulting in immediate clinical improvement that lasted for 5 months. 19We have been used AG and HA fillers in a hybrid combination for nonsurgical rhinoplasty procedures to 32 patients in 2 years period which yielded very good and durable results. 44In another study, It has been shown that 3.5% AG can last up to 12 months or even longer to 16 months. 4egarding their comparable durations, 3 to 5 months of duration can be expected for 1% AG.Four to 8 months are typical for 1.5% and 2.5% AG, while longer durations of up to 12 to 18 months can be seen with 3.5% AG fillers. 4,19,44mmediately after AG injections, some erythema, swelling and tenderness may occur at the injection site.These findings are temporary and will resolve within a few hours or a few days. 456][47] Precautions should be taken to minimize the risk of embolization, such as lifting the skin and applying pressure to important vessel origins during needle insertion, using linear threading technique and aspirating for 5 s before the insertion. 11,43,44It is also crucial to be aware of the facial anatomy and key vessels, such as the angular artery around the nasolabial fold, and to respect the recommended tissue layer around the zygomatic region to avoid key vessels. 43o far, there have been no cases of intravascular injection complications associated with the use of AG fillers reported in the literature.In the event of any complications, hyaluronidase can be added to the treatment procedure in particulate fillers, since noncross-linked HA is present in the preparations at concentrations of 2.5% and 3.5%. 44,48e kindly do not recommend injecting AG intradermally in a bolus fashion to avoid palpability of macrophage conglomerates constitute lump formation.Posttreatment massage is important and should be considered to decrease the risk of palpability, especially when injecting to thin skin areas such as lips or nose. 19,22,44omplications and major side effects such as abscesses, inflammatory nodules and granulomas may occur after injectables.However, no such case has yet been reported regarding AG injections. 43,44Lumps may also form due to the low migration effect of AG when big bolus injections are administered.Therefore, the application method is of great importance.
Our experience with AG showed it to be a safe and versatile injectable soft-tissue filler.To our knowledge, this is the largest clinical study to date on AG in facial aesthetic procedures.The limitation of the presented study is that it is not a double-blind comparative study.We are pleased  with the low incidence of adverse events with high patient satisfaction rates.In an earlier study we performed, 90.6% of 32 patients reported very satisfied with their results following the treatment. 44

CONCLUSIONS
Beginning with aesthetic indications, reaching functional disorder treatments, the indications of AG have expanded considerably thanks to its unique features over the years.The contouring ability makes AG a good lifting and shaping tool.Knowing how to use it, which danger zones to avoid, and to manage potential complications paves the way for optimal clinical outcomes.In conclusion, AG dermal filler is suitable for various facial augmentation and contouring applications, as it is safe and has long-lasting favorable cosmetic efficacy.

Figure 1 .
Figure 1.(A) Chemical structure of agarose.(B) The 3D structure of the AG, with pores of different size, observed by scanning electron microscope.

Figure 2 .Figure A 47
Figure 2. (A, C) Preprocedure and (B, D) 2 years postprocedure results of a 26-year-old female can be seen after 1.4 mL of 3.5% AG injection supraperiosteally to chin.Follow-up images showing the remaining clinical effects can be seen 2 years after the initial treatment.

Figure 4 .
Figure 4.A 28-year-old male patient (A, C) prior to treatment and (B, D) 2 years after initial injection and 1-month touch-up treatment of 0.7 mL of %3.5 mL AG to radix and nasal spine each, combined with HA filler to tip and supratip area.

Figure
Figure (A, C) Preprocedure and (B, D) 2 years postprocedure results of 22-year-old female patient can be seen after 1.4 mL of 3.5% AG injection to each zygoma on the supraperiosteal plane.A total of 2.8 mL of 3.5% AG filler was used in the procedure.

Figure A 34
Figure A 34-year-old female patient (A) prior to treatment of nasolabial area and smile lines and (B) 18 months after the injection of 2.1 mL of 2.5% AG to each side can be seen.The procedure was performed on subdermal plane using linear threading technique with a 23 G cannula.

Table 2 .
Global Aesthetic Improvement Scale Assessment

Table 3 .
Patient Satisfaction Scores and GAIS ResultsShowing Two Independent Plastic Surgeons' Objective Clinical Evaluation Scores After Injection

Table 4 .
Complications of AG Dermal Filler Applications in Our Study